Initial push

author: info@mode42.com <info@mode42.com> 2026-08-07 18:25:13 +0000
committer: info@mode42.com <info@mode42.com> 2026-08-07 18:25:13 +0000
commit: 04d965d67a7264a1c7c211494aebda1953df7603 (patch)
tree: 0ebd700a6e219f84a26a656f4bee8778bc75da7b /stacks
208 files changed, 28137 insertions, 0 deletions
diff --git a/stacks/crdop/.github/workflows/build.yml b/stacks/crdop/.github/workflows/build.yml
new file mode 100644
index 0000000..a9d6465
--- /dev/null
+++ b/stacks/crdop/.github/workflows/build.yml
@@ -0,0 +1,54 @@
+name: Build
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  linux-gcc:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install deps
+        run: sudo apt-get update && sudo apt-get install -y build-essential cmake libasound2-dev pkg-config libcmocka-dev
+      - name: Build and test
+        run: |
+          chmod +x scripts/*.sh
+          CRDOP_BUILD_TESTS=ON CRDOP_RUN_TESTS=ON ./scripts/build-crdop.sh
+
+  linux-clang:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install deps
+        run: sudo apt-get update && sudo apt-get install -y clang cmake libasound2-dev pkg-config libcmocka-dev
+      - name: Build and test (Clang)
+        run: |
+          chmod +x scripts/*.sh
+          CC=clang CRDOP_BUILD_TESTS=ON CRDOP_RUN_TESTS=ON ./scripts/build-crdop.sh
+
+  linux-aarch64-cross:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install cross toolchain
+        run: sudo apt-get update && sudo apt-get install -y cmake gcc-aarch64-linux-gnu libasound2-dev:arm64 pkg-config
+      - name: Cross-build ARM64
+        run: |
+          chmod +x scripts/*.sh
+          CRDOP_TOOLCHAIN=aarch64-linux-gnu ./scripts/build-crdop.sh
+
+  windows-cross:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install MinGW
+        run: sudo apt-get update && sudo apt-get install -y cmake mingw-w64
+      - name: Cross-build Windows x64
+        run: |
+          chmod +x scripts/*.sh
+          CRDOP_TOOLCHAIN=x86_64-w64-mingw32 ./scripts/build-crdop.sh
+      - name: Verify exe
+        run: test -x build/crdopc.exe
diff --git a/stacks/crdop/.gitignore b/stacks/crdop/.gitignore
new file mode 100644
index 0000000..715a31d
--- /dev/null
+++ b/stacks/crdop/.gitignore
@@ -0,0 +1,13 @@
+build/
+build-*/
+*.o
+*.a
+*.so
+*.exe
+*.log
+.DS_Store
+vendor/ardopcf/
+vendor/ardopcf/.crdop-patches-applied
+
+# vault/agent — never ship
+AGENT-INDEX.md
diff --git a/stacks/crdop/CMakeLists.txt b/stacks/crdop/CMakeLists.txt
new file mode 100644
index 0000000..27ab174
--- /dev/null
+++ b/stacks/crdop/CMakeLists.txt
@@ -0,0 +1,55 @@
+cmake_minimum_required(VERSION 3.16)
+# Product label CRDOP-CUR999 (pre-release until v0.5). CMake project() requires a
+# numeric VERSION; 0.0.999 is the build-time fallback. Human-facing strings live
+# in VERSION (CUR999) and include/crdop/version.h (CRDOP-CUR999 / CUR999).
+project(crdop VERSION 0.0.999 LANGUAGES C)
+
+set(CMAKE_C_STANDARD 17)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
+include(GNUInstallDirs)
+
+if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
+    set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)
+endif()
+
+option(CRDOP_VENDOR_ARDOPCF
+       "Dev-only: build legacy ARDOP (ardopcf) vendor — OFF by default; never installed in MAX25 releases"
+       OFF)
+
+set(CRDOP_ROOT "${CMAKE_CURRENT_SOURCE_DIR}")
+set(VENDOR_DIR "${CRDOP_ROOT}/vendor/ardopcf")
+
+function(crdop_install_scaffold)
+    install(FILES
+        "${CRDOP_ROOT}/share/crdop.ini.example"
+        "${CRDOP_ROOT}/share/crdop-dual.ini.example"
+        "${CRDOP_ROOT}/share/crdop-amateur.ini.example"
+        "${CRDOP_ROOT}/share/crdop.freebsd.ini.example"
+        DESTINATION ${CMAKE_INSTALL_DATADIR}/crdop
+    )
+    install(FILES "${CRDOP_ROOT}/VERSION" DESTINATION ${CMAKE_INSTALL_DATADIR}/crdop)
+    install(PROGRAMS "${CRDOP_ROOT}/scripts/crdopc"
+            DESTINATION ${CMAKE_INSTALL_BINDIR} RENAME crdop)
+    install(PROGRAMS
+        "${CRDOP_ROOT}/tools/max25-signal-sniffer"
+        "${CRDOP_ROOT}/tools/audio-dummyd"
+        DESTINATION ${CMAKE_INSTALL_BINDIR}
+    )
+    install(DIRECTORY "${CRDOP_ROOT}/lib/"
+            DESTINATION ${CMAKE_INSTALL_DATADIR}/crdop/lib
+            FILES_MATCHING PATTERN "*.py")
+endfunction()
+
+if(CRDOP_VENDOR_ARDOPCF AND EXISTS "${VENDOR_DIR}/Makefile")
+    include("${CRDOP_ROOT}/cmake/CRDOPVendorArdopcf.cmake")
+    crdop_install_scaffold()
+    message(STATUS "CRDOP ${PROJECT_VERSION} → crdopc (legacy vendor/ardopcf)")
+elseif(CRDOP_VENDOR_ARDOPCF)
+    message(WARNING "CRDOP: CRDOP_VENDOR_ARDOPCF=ON but vendor/ardopcf missing — scaffold only")
+    crdop_install_scaffold()
+    message(STATUS "CRDOP: scaffold only (native modem in development)")
+else()
+    crdop_install_scaffold()
+    message(STATUS "CRDOP: scaffold only (native Eigenentwicklung; -DCRDOP_VENDOR_ARDOPCF=ON for legacy vendor build)")
+endif()
diff --git a/stacks/crdop/LICENSE b/stacks/crdop/LICENSE
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index 0000000..3488377
--- /dev/null
+++ b/stacks/crdop/LICENSE
@@ -0,0 +1,22 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ CRDOP (MAX25-SoftModem) — subproject of MainAX25-Stack (MAX25-Stack)
+ Copyright (C) 2026 ngteq
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+---
+
+Full license text: [../../LICENSE](../../LICENSE) (repository root).
diff --git a/stacks/crdop/NOTICE.md b/stacks/crdop/NOTICE.md
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index 0000000..43c302f
--- /dev/null
+++ b/stacks/crdop/NOTICE.md
@@ -0,0 +1,9 @@
+# Third-party notices
+
+**CRDOP (MAX25-SoftModem)** — Copyright (c) 2026 ngteq, **GNU GPL v3** ([LICENSE](LICENSE), [../../LICENSE](../../LICENSE))
+
+In-house sound-card modem subproject of MainAX25-Stack. Sound-card based; kernel ALSA via MAX25 sound-proxy. Project rule: [docs/CRDOP.md](../../docs/CRDOP.md).
+
+Operators must comply with local radio regulations.
+
+Third-party **ARDOP** host software (optional, separate from CRDOP): [plugins/external/ardop/README.md](../../plugins/external/ardop/README.md).
diff --git a/stacks/crdop/README.md b/stacks/crdop/README.md
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index 0000000..aeb701d
--- /dev/null
+++ b/stacks/crdop/README.md
@@ -0,0 +1,36 @@
+# CRDOP — MAX25-SoftModem
+
+**CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`).
+
+Sound-card software modem subproject of MAX25-Stack.
+
+**Stack version:** MAX25-Stack **v1.0.0** · **Dev track:** `CUR999` in `$SRC/stacks/crdop/VERSION`.
+
+**Canonical project rule:** [docs/CRDOP.md](../../docs/CRDOP.md)  
+**License:** GNU GPL v3 — [LICENSE](LICENSE)
+
+## Summary
+
+| | |
+|---|---|
+| Type | MAX25-Stack **subproject** (`stacks/crdop/`) |
+| Interface | Sound card IN/OUT → kernel ALSA → MAX25 sound-proxy |
+| Goal | **AX.25 / KISS / TNC / modem compatible** software modem |
+| Mission | **Hardware solutions** (primary) + **pure software** on computers |
+| Build | Default ON (`MAX25_BUILD_CRDOP=ON`) |
+
+Read [docs/CRDOP.md](../../docs/CRDOP.md) before changing modem, audio, or plugin code.
+
+## Technical docs
+
+**Index:** [docs/INDEX.md](docs/INDEX.md)
+
+| Doc | Topic |
+|-----|--------|
+| [docs/MAX25-USAGE.md](docs/MAX25-USAGE.md) | MAX25-Stack operator guide |
+| [docs/DEVELOPER.md](docs/DEVELOPER.md) | Source tree, modules, tests |
+| [docs/HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md) | Generic radio interface spec |
+| [docs/SOFTMODEM.md](docs/SOFTMODEM.md) | Baud, duplex, acoustic AX.25 |
+| [docs/AUDIO-ARCHITECTURE.md](docs/AUDIO-ARCHITECTURE.md) | Kernel ALSA only, no PulseAudio |
+| [docs/CONFIG.md](docs/CONFIG.md) | INI / launcher |
+| [ROADMAP.md](ROADMAP.md) | P0/P1/P2 milestones |
diff --git a/stacks/crdop/ROADMAP.md b/stacks/crdop/ROADMAP.md
new file mode 100644
index 0000000..0ae1aa4
--- /dev/null
+++ b/stacks/crdop/ROADMAP.md
@@ -0,0 +1,445 @@
+# MAX25-SoftModem (CRDOP) — development roadmap
+
+> **Static rule:** **CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`). Authoritative everywhere CRDOP is named in MAX25-Stack.
+
+**Stack version:** MAX25-Stack **v1.0.0** · **Dev track:** `CUR999` in `$SRC/stacks/crdop/VERSION`
+
+**Stack dependency:** CRDOP sources live in `stacks/crdop/` and are **standalone-capable** in principle, but **MAX25-Stack is required for integration** (build, `max25d`, INI, operator tooling) until **CRDOP-v1.0.0** (or later) marks a mature standalone release. Current stack product: **MAX25-Stack-v1.0.0**.
+
+**Nature:** MAX25 in-house development — open development and test program for the kernel-ALSA sound-card modem. CRDOP is the standard modem; ARDOP is a separate optional plugin.
+
+**Research synthesis:** 2026-07-13 — modem and integration priorities synthesized into this ROADMAP and linked in-repo docs below. **No duplicate re-copy** of external notes into this tree.
+
+---
+
+## Protocol taxonomy (research catalog)
+
+| Class | Description | CRDOP relation |
+|-------|-------------|----------------|
+| **A** | Classic AX.25 packet (HDLC, frequency-toggle line code) | **P0/P1/P2 targets** — 1200 AFSK, G3RUH, 300 HF |
+| **B** | AX.25 + FEC extension | **Reference** — FX.25 informs FEC block design |
+| **C** | New L2 (not AX.25 on-air) | **Reference** — IL2P lessons (no bit-stuffing, RS FEC) |
+| **D** | HF/VHF data modems (Winlink ecosystem) | **Out of scope** on-air — separate ARDOP-plugin registry |
+| **E** | Keyboard/chat modes (PSK31, RTTY, …) | **Out of scope** — boundary only |
+
+---
+
+## MAX25-Stack integration (until CRDOP-v1.0.0+)
+
+| Topic | Policy |
+|-------|--------|
+| **Source tree** | All CRDOP sources in `stacks/crdop/` — standalone CMake possible; **operator integration via MAX25-Stack** until mature **CRDOP-v1.0.0** (or later) |
+| **Build** | `MAX25_BUILD_CRDOP=ON` default — installs launcher, `lib/`, tools, INI |
+| **Daemon** | `max25d` → `CrdopTcpBackend` / `AudioDummyBackend` — see [docs/MAX25-USAGE.md](docs/MAX25-USAGE.md) |
+| **AX.25 runtime** | Native `ax25_codec.py` in MAX25 — no libax25 bundle in releases |
+| **HyBBX** | External consumer — serial ownership boundary; CRDOP via host TCP attach |
+| **Docs entry** | [docs/INDEX.md](docs/INDEX.md) · project rule [docs/CRDOP.md](../../docs/CRDOP.md) |
+
+HyBBX boundary: [docs/HYBBX.md](../../docs/HYBBX.md) · [docs/PLUGINS-DEVICE-MODEL.md](../../docs/PLUGINS-DEVICE-MODEL.md)
+
+---
+
+## MAX25-Stack DEV-Level gate
+
+> Stack DEV-Levels are approximate (*ca.*) — see [docs/V2.0.0-SCOPE.md](../../docs/V2.0.0-SCOPE.md#dev-levels-roadmap-stack-wide). CRDOP modulation milestones (P0/P1/P2 below) are **subproject delivery** labels, not stack DEV-Levels.
+
+**DEV-Level 1 (*ca.* current — stack priority):** modular TCP/IP + Linux/FreeBSD platform compat. CRDOP work in DEV-Level 1 is **minimal/native only** — existing backend, bench DSP, enough OSS path for FreeBSD TCP/IP hub. **Do not expand CRDOP scope** ahead of DEV-Level 1.
+
+**DEV-Level 4 (*ca.*):** CRDOP expansion (OSS polish, G3RUH, acoustic validation, hardware docs). Modulation milestones below remain valid but are **scheduled for DEV-Level 4** unless required to unblock DEV-Level 1 platform work.
+
+**WebSocket** is **DEV-Level 3** — separate from CRDOP expansion.
+
+Stack roadmap: [docs/V2.0.0-SCOPE.md](../../docs/V2.0.0-SCOPE.md#dev-levels-roadmap-stack-wide).
+
+---
+
+## Current phase: development and test
+
+| Area | Status |
+|------|--------|
+| MAX25-Stack standard build/install (`MAX25_BUILD_CRDOP=ON`) | **Done** |
+| `max25d` `crdop-tcp` backend + offline tests | **Done** |
+| INI scaffold, launcher (`scripts/crdopc`), HyBBX attach examples | **Done** |
+| Native modem DSP — 1200 baud Bell 202 AFSK (`stacks/crdop/lib/`) | **In progress** |
+| Acoustic AX.25 validation vs reference 1200 AFSK paths | **In progress** |
+| Half- and full-duplex operator paths + FEC strategy | **In progress** |
+| Open hardware interface documentation | **In progress** |
+| G3RUH 9600–19200 (direct FSK rig path) | **Planned** (DEV-Level 4 / P1) |
+| 300 baud HF AFSK | **Optional** (P2) |
+| Speeds >19200 baud | **Out of scope** |
+
+---
+
+## Modulation priority matrix
+
+Synthesized from research catalog — implementation order for CRDOP native DSP.
+
+| Priority | Mode | Modulation | Baud | RF path | Bands | CRDOP target |
+|----------|------|------------|------|---------|-------|--------------|
+| **P0** | AX.25 Packet | **AFSK Bell 202** (1200/2200 Hz) | **1200** | Audio AFSK (Mic/Spkr/Line) | **CB, VHF/UHF** | **Primary on-air** |
+| **P0** | FEC + duplex profiles | Short frames, frequent TX | 1200 | same | CB, VHF | **Strategy** (see below) |
+| **P1** | AX.25 Packet | **G3RUH FSK/GMSK** (scrambled baseband) | **9600–19200** | **Direct FSK** (varactor + discriminator) | VHF/UHF backbone | **Hard max 19200** |
+| **P2** | AX.25 Packet | AFSK/FSK tone pairs | **300** | SSB audio (USB/LSB) | HF | **Optional** |
+| — | 2400/4800 AFSK | V.26/V.27 class | 2400–4800 | Audio | VHF | Low priority incremental |
+| 📋 | FX.25 / IL2P | FEC wrappers / new L2 | 1200+ | Audio or FSK PHY | VHF/HF | **Reference only** — inform FEC design |
+| ❌ | VARA / PACTOR / WINMOR | Proprietary DSP | various | Audio / SSB / hardware | HF/VHF/CB | **Out of scope** |
+| 📋 | ARDOP | 4FSK/PSK/QAM Winlink modes | adaptiv | Soundcard SSB | HF/VHF | **Separate plugin** — not CRDOP |
+
+**Rule:** CRDOP on-air goal is **AX.25-compatible PHY + framing** at P0/P1/P2. Winlink-class protocols (VARA, PACTOR, ARDOP OTA) are **not** CRDOP targets.
+
+---
+
+## RF path matrix
+
+What CRDOP implements per physical interface — hardware choice drives baud ceiling.
+
+| RF path | Connection | Practical max baud | CB | Amateur (VHF/UHF) | Amateur (HF) | CRDOP milestone |
+|---------|------------|-------------------|-----|-------------------|--------------|-----------------|
+| **Audio AFSK** | Mic IN / Speaker OUT / Line | ~4800 theory; **1200 field** | ✅ K24/K25 | ✅ APRS, digipeater access | — | **P0 bench–on-air** |
+| **Audio wide** | Line, de-emphasis off | up to ~9600 (difficult) | rare | experimental | — | not primary |
+| **Direct FSK** | Varactor TX + FM discriminator RX | **9600–19200** | ❌ | ✅ backbone, sat | ❌ | **P1** (DEV-Level 4) |
+| **SSB audio** | USB/LSB suppressed carrier | **300** packet; kHz-BW modes separate | ❌ | 10 m APRS exception | ✅ | **P2 optional** |
+
+**CB note:** 9600+ G3RUH requires direct RF modulation and wide IF — standard CB FM rigs are **not** 9k6-ready. CRDOP does **not** target high baud on 27 MHz.
+
+---
+
+## Band context
+
+### CB (27 MHz CEPT)
+
+| Item | Detail |
+|------|--------|
+| **Primary channel** | **K24** (27.235 MHz) — Packet QSO, APRS-like traffic |
+| **Net / forward** | **K25** (27.245 MHz) — nets, data traffic; proprietary FM-narrow DSP modes appear in practice (reference only — not CRDOP OTA) |
+| **Legal (brief)** | EN 300 433 / ECC (11)03 — voice service primary; FM max **4 W** ERP typical; **data tolerated or explicit** on K24/K25 in several EU administrations. Operator responsibility. |
+| **CRDOP mode** | **1200 AFSK Bell 202**, half-duplex, `persist=255`, short UI frames |
+| **Why not 9600+** | CB rigs lack direct FSK port and wide-IF path; FM voice channel ≈3 kHz — fits 1200/2200 Hz, not G3RUH |
+
+### VHF/UHF (2 m, 70 cm, …)
+
+| Application | Baud | Modulation | CRDOP |
+|-------------|------|------------|-------|
+| **APRS**, packet BBS, digipeater **access** | 1200 | AFSK Bell 202 | **P0** — acoustic/line |
+| Digipeater **backbone**, satellite | 9600–19200 | G3RUH FSK | **P1** — requires data-port radio |
+| IL2P | 1200/2400 | BPSK/QPSK audio | 📋 reference |
+| FX.25 | 1200+ | AX.25 + RS FEC wrapper | 📋 reference for FEC block sizing |
+
+### HF (160 m – 10 m)
+
+| Item | Detail |
+|------|--------|
+| **Standard packet** | **300 baud** AFSK/FSK, **200 Hz shift** |
+| **Common tone pairs** | 1600/1800 Hz (common default), 2110/2310 Hz, others — dial frequency must match pair |
+| **10 m exception** | 1200 AFSK on FM/USB for APRS — same PHY as VHF |
+| **Winlink boundary** | Proprietary HF mail modems = **separate protocol ecosystems** — not CRDOP OTA goals |
+| **CRDOP** | **P2 optional** — 300 bd after P0/P1 stable; SSB USB/LSB audio path |
+
+### Satellite / space (reference)
+
+| Application | Baud | Modulation | CRDOP |
+|-------------|------|------------|-------|
+| Legacy FM packet | 1200 | AFSK Bell 202 | P0 PHY same |
+| Pacsat / wide-IF links | 9600–38400+ | G3RUH FSK/GMSK | P1 extended; >19200 out of scope |
+
+---
+
+## Layer model
+
+CRDOP splits **host integration** from **on-air PHY**. Code mapping to `stacks/crdop/lib/`:
+
+```
+Application (APRS, BBS, HyBBX, max25-terminal)
+    ↓
+AX.25 v2.0 (UI / I-frames)          ← stacks/daemon/ax25_codec.py
+    ↓
+HDLC + frequency-toggle + CRC-16    ← hdlc_codec.py (+ bell202_line_code.py)
+    ↓
+Modem PHY (AFSK / future G3RUH)    ← afsk_modulator.py, afsk_demodulator.py
+    ↓
+MAX25 sound-proxy → kernel ALSA     ← sound_proxy.py (+ include/crdop/sound_proxy.h scaffold)
+    ↓
+Radio (FM audio / direct FSK / SSB)
+```
+
+| Layer | Responsibility | Module / tool |
+|-------|----------------|---------------|
+| **L2 AX.25** | Addresses, UI body, FCS semantics | `ax25_codec.py` (daemon), used by `acoustic_engine.py` |
+| **Framing** | HDLC flags `0x7E`, bit-stuffing, CRC-16-CCITT | `hdlc_codec.py` |
+| **Line code** | Bell 202 frequency-toggle (bit 0 → tone change) | `bell202_line_code.py` |
+| **PHY 1200** | Continuous-phase AFSK 1200/2200 Hz, Goertzel demod | `afsk_modulator.py`, `afsk_demodulator.py` |
+| **PHY 9k6+** | G3RUH scrambler + FSK — **not yet in lib/** | planned P1 (DEV-Level 4) |
+| **PHY 300 HF** | 200 Hz shift tone pairs — **not yet in lib/** | planned P2 optional |
+| **Audio I/O** | ALSA capture/playback, no PulseAudio | `sound_proxy.py` |
+| **Bench integration** | Loopback encode/decode, sniffer | `acoustic_engine.py` |
+| **Host TCP** | M25-family ctrl + KISS-semantics data | `m25_host_protocol.py` → `audio-dummyd` |
+| **Operator tools** | Sniff, calibrate mark/space | `tools/max25-signal-sniffer` |
+
+**Host vs on-air:** `m25_host_protocol.py` carries AX.25 UI **without** HDLC on the data port; `acoustic_engine.encode_ax25_ui()` builds full on-air HDLC + AFSK. Do not confuse MAX25 TCP host with ARDOP FEC/ARQ wire modes.
+
+---
+
+## FEC, duplex & retransmission strategy
+
+**Leitprinzip:** *Lieber öfter senden als oft lange.*
+
+Packet on CB/VHF (poor SNR, QRM, half-duplex collisions) favours **short UI frames** and **frequent repetition** over long payloads and heavy block FEC.
+
+### Half-duplex (CB default)
+
+| Aspect | Strategy |
+|--------|----------|
+| Channel access | CSMA + persist — CB: **`persist=255`** |
+| TX slot | Short UI frames; minimal but stable TXDELAY/TXTAIL |
+| FEC | Shorter codewords; optional 2–3 repeats vs one large block |
+| Retransmit | Application/beacon: **send more often** with small payloads (≤128 B info) |
+| PTT | Explicit — VOX off on CB |
+| INI | `duplex = half`, `EXTRADELAY 150` (CB profile) |
+
+### Full-duplex
+
+| Aspect | Strategy |
+|--------|----------|
+| Channel | Simultaneous TX/RX — no CSMA |
+| FEC | Stronger codes possible when bandwidth allows |
+| Audio | Echo suppression / separate paths — full-duplex sound card |
+| INI | `duplex = full`, `EXTRADELAY 0` |
+
+### FEC layers
+
+| Level | Mechanism | CRDOP status |
+|-------|-----------|--------------|
+| **L1 modem** | CRC-16-CCITT (mandatory), preamble sync | **Done** in `hdlc_codec.py` |
+| **L1 optional** | Lightweight FEC for short blocks | **Planned** — offline AWGN simulator |
+| **L2 AX.25** | UI = no ARQ; I-frames = host may ARQ | Host policy |
+| **Application** | Frequent beacons, staggered dual-TNC | HyBBX / max25d INI |
+| **Reference** | FX.25 (RS wrapper), IL2P (new L2) | Inform design; not mandatory on-air |
+
+### FEC design takeaways (see [docs/FEC-SPEC.md](docs/FEC-SPEC.md))
+
+| Source | Lesson for CRDOP |
+|--------|------------------|
+| **FX.25** | Reed-Solomon FEC **wrapper** around AX.25 — backward-compatible idea; AX.25 bit-stuffing weakens naive FEC |
+| **IL2P** | Eliminates bit-stuffing; packet-sync LFSR scramble; RS FEC — **reference** for future optional L2, not P0 on-air |
+| **Operator** | UI frames have no L2-ARQ — reliability via **short payloads + frequent TX** before heavy block FEC |
+| **VARA / IL2P DSP** | Multi-stage FEC and adaptive rate — **reference for DSP strategy only**, not protocol target |
+
+### Host-protocol alignment
+
+| Component | Status |
+|-----------|--------|
+| Spec | **[HOST-PROTOCOL-SPEC.md](docs/HOST-PROTOCOL-SPEC.md)** — frozen v1.0.0 |
+| `max25d CrdopTcpBackend` (default) | `PROTOCOLMODE KISS`, `[CRDOP AX25 UI …]` display |
+| `m25_host_protocol.py` | Defaults **8515/8516** — matches `crdopc` INI |
+| `audio-dummyd` bench | Same ports via CLI; `audio-dummy` max25d **host** mode may use **8520** when :8515 busy |
+
+---
+
+## Implementation status (`stacks/crdop/lib/`)
+
+Honest mapping — 2026-07-13.
+
+| Component | File / tool | Status | Notes |
+|-----------|-------------|--------|-------|
+| Bell 202 line code | `bell202_line_code.py` | **Done** | Mark 1200 / Space 2200; frequency-toggle encode/decode |
+| Line code tests | `test_bell202_line_code.py` | **Done** | Round-trip unit tests |
+| AFSK modulator | `afsk_modulator.py` | **Done** | Continuous-phase PCM @ 48 kHz default |
+| AFSK demodulator | `afsk_demodulator.py` | **Done** | Per-symbol Goertzel demod |
+| HDLC + CRC | `hdlc_codec.py` | **Done** | Flags, bit-stuff, CRC-16 via `ax25_crc` |
+| Sound-proxy (Python) | `sound_proxy.py` | **In progress** | `arecord`/`aplay` subprocess path; C header scaffold separate |
+| Acoustic bench engine | `acoustic_engine.py` | **In progress** | Full loopback UI→HDLC→AFSK→demod→parse; RF path not closed |
+| M25 host protocol | `m25_host_protocol.py` | **In progress** | TCP ctrl/data for bench; port alignment with `max25d` pending |
+| `audio-dummyd` | `tools/audio-dummyd.py` | **In progress** | M25 host + `AcousticEngine`; default launcher target |
+| `max25-signal-sniffer` | `tools/max25-signal-sniffer.py` | **In progress** | ALSA/WAV/loopback Bell 202 analysis |
+| G3RUH 9600–19200 | — | **Planned** | No module yet; direct FSK radio required |
+| 300 HF AFSK | — | **Planned** | Optional P2 |
+| FEC codec (short blocks) | — | **Planned** | Offline inject-bit-error tests first |
+| `speed_baud` INI → launcher | — | **Not implemented** | Research gap |
+| Native C `crdopc` DSP binary | `include/crdop/` | **Scaffold** | Python lib leads; C port follows validation |
+| RF automated CI | — | **Planned** | Manual acoustic/TNC tests today |
+
+---
+
+## Milestones — modulation delivery (P0 / P1 / P2)
+
+> CRDOP subproject milestones — distinct from stack [DEV-Levels](../../docs/V2.0.0-SCOPE.md#dev-levels-roadmap-stack-wide). P0/P1/P2 work lands primarily in **DEV-Level 4** except bench/minimal path in DEV-Level 1.
+
+### P0 bench — Acoustic bench (current)
+
+**Goal:** Prove Bell 202 + HDLC + AX.25 UI in software loopback and ALSA bench — no RF required.
+
+| Deliverable | Status |
+|-------------|--------|
+| `bell202_line_code` + `afsk_*` + `hdlc_codec` unit path | Done |
+| `acoustic_engine.loopback_self_test()` | Done |
+| `max25-signal-sniffer --loopback` | In progress |
+| `audio-dummyd` + `audio-dummy` max25d device | In progress |
+| Document acceptable sound cards (community list) | Planned |
+| Host protocol single definition (launcher ↔ max25d) | Planned |
+
+**Exit criteria:** Stable loopback decode; sniffer reports AX.25 UI from generated PCM; `test_crdop_backend.py` green.
+
+### P0 on-air — CB/VHF 1200 on-air
+
+**Goal:** Field-validated 1200 AFSK interoperable with standard AX.25 packet peers on CB and VHF APRS-class paths.
+
+| Deliverable | Status |
+|-------------|--------|
+| Acoustic and line-level coupling validation | In progress |
+| Line interface to FM rig (CB channels) | Planned |
+| Half-duplex PTT timing in INI + launcher | In progress |
+| FEC strategy: short frames, beacon stagger | In progress |
+| Hardware interface guide (generic spec) | In progress — [docs/HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md) |
+| Decode parity vs reference 1200 AFSK captures | Planned |
+
+**Exit criteria:** Verified AX.25 UI exchange with at least one reference 1200 AFSK path (acoustic or line-level).
+
+### P1 — G3RUH 9600–19200
+
+**Goal:** Direct-FSK VHF/UHF backbone rates up to **19200 baud** hard maximum.
+
+| Deliverable | Status |
+|-------------|--------|
+| G3RUH scrambler + FSK mod/demod module | Planned |
+| Data-port radio integration docs | Planned |
+| Wide-IF rig requirements checklist | Planned |
+| Loopback with recorded IQ/baseband fixtures | Planned |
+
+**Prerequisite:** P0 on-air stable; radio with suitable data port and wide-IF path for direct FSK.
+
+**Exit criteria:** Scrambler-compatible exchange with G3RUH reference captures or peer at 9600 minimum.
+
+### P2 — HF 300 baud (optional)
+
+**Goal:** SSB USB/LSB 300 bd packet — 1600/1800 Hz pair first.
+
+| Deliverable | Status |
+|-------------|--------|
+| 300 bd demod/mod (200 Hz shift) | Planned |
+| Tone-pair INI selection | Planned |
+| HF dial-frequency calculator notes | Planned |
+
+**Scope:** Optional; does not block CRDOP-v0.5 if deferred.
+
+---
+
+## Validation targets (generic)
+
+Interop validation uses **reference signal classes**, not product endorsements.
+
+| Reference class | Mode | Interface | CRDOP milestone |
+|-----------------|------|-----------|-----------------|
+| **1200 AFSK hardware modem** | Bell 202 | Serial KISS or acoustic | P0 bench–on-air |
+| **Kernel bit-bang modem** | 1200 AFSK | Parallel/serial | P0 bench tone reference |
+| **Mobile KISS → audio** | 1200 AFSK | Bluetooth/audio bridge | P0 on-air mobile |
+| **G3RUH FSK modem** | 4800–19200 | Direct FSK data port | P1 golden reference |
+| **Multi-mode HF TNC** | 300 HF + 1200 VHF | Multi-mode serial | P2 optional |
+| **Sound-card reference decoder** | 300–9600+ | ALSA | Software decode parity (1200) |
+
+Open-hardware documentation: [docs/HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md). Audio QA: [docs/SOUNDCARD-QUALIFICATION.md](docs/SOUNDCARD-QUALIFICATION.md).
+
+---
+
+## Technical goals (unchanged intent)
+
+1. **1200 baud Bell 202** — reference AX.25 AFSK; primary on-air target (P0).
+2. **Acoustic compatibility** — verifiable against standard 1200 AFSK tone paths.
+3. **Hardware modem parity** — sound IN/OUT + radio usable like serial/KISS hardware in `max25d`.
+4. **Documented DIY hardware** — generic interface spec for builders ([HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md)).
+5. **Good sound card enforcement** — kernel ALSA direct; MAX25 sound-proxy API; requirements scale with baud.
+6. **G3RUH to 19200** — incremental after 1200 stable (P1).
+7. **FEC via operator strategy** — frequent short sends before heavy on-air FEC (P0).
+
+---
+
+## Not in MAX25 releases
+
+| Item | Policy |
+|------|--------|
+| `vendor/ardopcf` dev tree | Local dev only (`CRDOP_VENDOR_ARDOPCF=ON`); not in release install |
+| **libax25 / ax25-tools / ax25-apps** bundles | Reference tarballs only — not shipped as CRDOP dependency |
+| VARA / PACTOR / WINMOR implementations | Out of scope |
+| Speeds **>19200 baud** | Out of scope (current phase) |
+
+---
+
+## Next release checklist (CRDOP-v0.5 target)
+
+- [ ] Loopback + acoustic bench test automation in CI
+- [ ] Published acceptable sound-card list (community + lab)
+- [ ] Native `crdopc` / `audio-dummyd` path unified in default build
+- [ ] Field validation on CB reference channel (K24)
+- [ ] Hardware interface guide — [docs/HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md)
+- [ ] Host protocol alignment (`m25_host_protocol` ↔ `max25d` backend)
+- [ ] `speed_baud` INI wired to launcher
+
+---
+
+## Research synthesis (document map)
+
+Synthesis **2026-07-13** — topics below are covered in this ROADMAP and in-repo CRDOP docs. Site-specific operator INI and lab hardware runbooks stay outside this tree.
+
+| Source topic | Synthesized in this ROADMAP |
+|----------------|----------------------------|
+| `reference/modems-packet-radio/MASTER-SOLUTIONS-CATALOG.md` | Taxonomy, baud table, RF matrix, CRDOP priorities |
+| `cb-packet-solutions.md` | CB band context, K24/K25, legal, 1200-only rationale |
+| `amateur-vhf-uhf-solutions.md` | VHF/UHF table, APRS, G3RUH backbone |
+| `amateur-hf-packet-solutions.md` | HF 300 bd, Winlink boundary |
+| `l2-fec-protocols.md` | FEC layers, FX.25/IL2P takeaways |
+| `modern-softmodems.md` | Class D out-of-scope, decision matrix (generic) |
+| `bell-202-afsk-1200.md` | P0 PHY parameters, P0 bench–on-air |
+| `g3ruh-fsk-9600-19200.md` | P1 direct FSK, DEV-Level 4 |
+| `hf-300-baud-afsk.md` | P2 tone pairs, SSB path |
+| `nrzi-hdlc-ax25-layers.md` | Layer model + `lib/` mapping |
+| `MODULATION-REFERENCE.md` | Modulation priority matrix |
+| `soundcard-requirements.md` | ALSA requirements, baud scaling |
+| `acoustic-coupling-hardware.md` | → [HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md) |
+| `projects/max25-stack/2026-07-13-crdop-development-master.md` | Product scope, MAX25 integration |
+| `projects/max25-stack/2026-07-13-crdop-fec-duplex-strategy.md` | FEC/duplex section |
+| `reference/2026-07-12-cb-eu-packet.md` | CB legal/channel detail |
+| `reference/2026-07-12-packet-radio-fundamentals.md` | Background — no CRDOP code impact |
+| `reference/2026-07-12-modems-linux.md` | Linux sound-modem landscape — reference |
+| `reference/2026-07-12-linux-ax25-ecosystem.md` | Kernel AX.25 deprecation context |
+| `projects/integration/2026-07-12-max25-hybbx-boundary-final.md` | HyBBX attach / serial ownership |
+| `DEVELOPMENT.md` (operator P0–P2) | Parallel to stack release — see [docs/DEVELOPER.md](docs/DEVELOPER.md) |
+
+**Not in CRDOP tree:** site TNC hardware runbooks, production INI, serial acceptance logs — operator-local only.
+
+### Scenario → CRDOP mode (generic, from research)
+
+| Scenario | CRDOP mode |
+|----------|------------|
+| CB packet QSO (FM audio) | **P0** — 1200 AFSK AX.25 |
+| CB net with heavy QRM | **P0** + short-frame FEC strategy; proprietary FM-narrow DSP = separate protocol |
+| VHF APRS / digipeater access | **P0** — 1200 AFSK |
+| VHF/UHF backbone | **P1** — G3RUH direct FSK (≤19200) |
+| HF packet 300 bd | **P2** optional |
+| HF mail / Winlink-class | **Out of scope** — separate protocols |
+| MAX25 RF broadcast / soft-modem path | **P0** target — native CRDOP in stack |
+
+---
+
+## In-repo technical docs
+
+| Document | Topic |
+|----------|--------|
+| [docs/INDEX.md](docs/INDEX.md) | Documentation index |
+| [docs/SOFTMODEM.md](docs/SOFTMODEM.md) | Product definition |
+| [docs/MAX25-USAGE.md](docs/MAX25-USAGE.md) | MAX25-Stack operator guide |
+| [docs/DEVELOPER.md](docs/DEVELOPER.md) | Developer guide |
+| [docs/HARDWARE-INTERFACE.md](docs/HARDWARE-INTERFACE.md) | Generic radio interface spec |
+| [docs/LICENSE-USAGE.md](docs/LICENSE-USAGE.md) | GPLv3 private + commercial |
+| [docs/HOST-PROTOCOL-SPEC.md](../stacks/crdop/docs/HOST-PROTOCOL-SPEC.md) | M25 host wire (frozen) |
+| [docs/ACOUSTIC-TEST-PROTOCOL.md](../stacks/crdop/docs/ACOUSTIC-TEST-PROTOCOL.md) | P0 bench |
+| [docs/FEC-SPEC.md](../stacks/crdop/docs/FEC-SPEC.md) | FEC/duplex parameters |
+| [docs/SOUNDCARD-QUALIFICATION.md](../stacks/crdop/docs/SOUNDCARD-QUALIFICATION.md) | Audio interface QA |
+| [docs/G3RUH-DESIGN.md](../stacks/crdop/docs/G3RUH-DESIGN.md) | P1 — 9600–19200 direct FSK |
+| [docs/CRDOP.md](../../docs/CRDOP.md) | Static project rule |
+| [docs/AUDIO-ARCHITECTURE.md](docs/AUDIO-ARCHITECTURE.md) | Kernel ALSA, sound-proxy |
+| [docs/PROTOCOL.md](docs/PROTOCOL.md) | Host TCP interface |
+| [docs/CONFIG.md](docs/CONFIG.md) | INI keys |
+
+---
+
+*Roadmap synthesized 2026-07-13 from modem catalog and MAX25 integration notes. Update when DEV-Level gates close or modulation priorities change.*
+.*
diff --git a/stacks/crdop/VERSION b/stacks/crdop/VERSION
new file mode 100644
index 0000000..2f5e876
--- /dev/null
+++ b/stacks/crdop/VERSION
@@ -0,0 +1 @@
+CUR999
diff --git a/stacks/crdop/cmake/CRDOPCompiler.cmake b/stacks/crdop/cmake/CRDOPCompiler.cmake
new file mode 100644
index 0000000..e1aab37
--- /dev/null
+++ b/stacks/crdop/cmake/CRDOPCompiler.cmake
@@ -0,0 +1,37 @@
+# CRDOP compiler detection and warning flags (GCC, Clang, MSVC)
+
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    set(CRDOP_COMPILER "gcc")
+elseif(CMAKE_C_COMPILER_ID MATCHES "Clang|AppleClang")
+    set(CRDOP_COMPILER "clang")
+elseif(MSVC)
+    set(CRDOP_COMPILER "msvc")
+else()
+    set(CRDOP_COMPILER "${CMAKE_C_COMPILER_ID}")
+endif()
+
+message(STATUS "CRDOP compiler=${CRDOP_COMPILER} (${CMAKE_C_COMPILER_ID} ${CMAKE_C_COMPILER_VERSION})")
+
+function(crdop_set_compile_options target)
+    if(MSVC)
+        target_compile_options(${target} PRIVATE /W3 /utf-8)
+    else()
+        target_compile_options(${target} PRIVATE -Wall -Wextra -Wno-unused-parameter)
+        if(CRDOP_COMPILER STREQUAL "clang")
+            target_compile_options(${target} PRIVATE
+                -Wno-gnu-zero-variadic-macro-arguments
+                -Wno-deprecated-non-prototype
+            )
+        endif()
+        if(CMAKE_BUILD_TYPE STREQUAL "Release")
+            target_compile_options(${target} PRIVATE -O2)
+        endif()
+    endif()
+endfunction()
+
+include(CheckLinkerFlag)
+if(NOT WIN32 AND NOT APPLE)
+    check_linker_flag(C "-Wl,--wrap=malloc" CRDOP_LINKER_SUPPORTS_WRAP)
+else()
+    set(CRDOP_LINKER_SUPPORTS_WRAP FALSE)
+endif()
diff --git a/stacks/crdop/cmake/CRDOPPlatform.cmake b/stacks/crdop/cmake/CRDOPPlatform.cmake
new file mode 100644
index 0000000..9d78683
--- /dev/null
+++ b/stacks/crdop/cmake/CRDOPPlatform.cmake
@@ -0,0 +1,71 @@
+# CRDOP platform / architecture detection (standalone project)
+#
+# Tested: Linux, *BSD, Windows, macOS — GCC and Clang/LLVM
+
+if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64)$")
+    set(CRDOP_ARCH "aarch64")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv7|armv7l|arm)$")
+    set(CRDOP_ARCH "arm32")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(i[3-6]86)$")
+    set(CRDOP_ARCH "x86")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64)$")
+    set(CRDOP_ARCH "x86_64")
+else()
+    set(CRDOP_ARCH "${CMAKE_SYSTEM_PROCESSOR}")
+endif()
+
+set(CRDOP_PLATFORM_INCLUDES "")
+set(CRDOP_PLATFORM_LIBS "")
+set(CRDOP_PLATFORM_SOURCES "")
+
+if(WIN32)
+    set(CRDOP_PLATFORM "windows")
+    set(CRDOP_PLATFORM_SOURCES
+        src/windows/Waveout.c
+        lib/hid/hid.c
+    )
+    set(CRDOP_PLATFORM_LIBS wsock32 winmm setupapi ws2_32)
+elseif(APPLE)
+    set(CRDOP_PLATFORM "darwin")
+    set(CRDOP_PLATFORM_SOURCES
+        src/linux/ALSASound.c
+        src/linux/LinSerial.c
+        src/darwin/alsa_shim.c
+    )
+    list(APPEND CRDOP_PLATFORM_INCLUDES "${VENDOR_DIR}/src")
+    find_library(CRDOP_COREAUDIO_LIB CoreAudio REQUIRED)
+    find_library(CRDOP_AUDIOTOOLBOX_LIB AudioToolbox REQUIRED)
+    find_library(CRDOP_COREFOUNDATION_LIB CoreFoundation REQUIRED)
+    set(CRDOP_PLATFORM_LIBS
+        ${CRDOP_COREAUDIO_LIB}
+        ${CRDOP_AUDIOTOOLBOX_LIB}
+        ${CRDOP_COREFOUNDATION_LIB}
+        pthread m
+    )
+elseif(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
+    set(CRDOP_PLATFORM "freebsd-oss")
+    set(CRDOP_PLATFORM_SOURCES
+        src/linux/LinSerial.c
+    )
+    set(CRDOP_PLATFORM_LIBS pthread m)
+elseif(CMAKE_SYSTEM_NAME MATCHES "OpenBSD|NetBSD|DragonFly")
+    set(CRDOP_PLATFORM "bsd-oss")
+    set(CRDOP_PLATFORM_SOURCES
+        src/linux/LinSerial.c
+    )
+    set(CRDOP_PLATFORM_LIBS pthread m)
+elseif(UNIX)
+    set(CRDOP_PLATFORM "linux")
+    set(CRDOP_PLATFORM_SOURCES
+        src/linux/ALSASound.c
+        src/linux/LinSerial.c
+    )
+    find_package(PkgConfig REQUIRED)
+    pkg_check_modules(ALSA REQUIRED alsa)
+    set(CRDOP_PLATFORM_INCLUDES ${ALSA_INCLUDE_DIRS})
+    set(CRDOP_PLATFORM_LIBS ${ALSA_LIBRARIES} rt pthread m)
+else()
+    message(FATAL_ERROR "CRDOP: unsupported system ${CMAKE_SYSTEM_NAME}")
+endif()
+
+message(STATUS "CRDOP platform=${CRDOP_PLATFORM} arch=${CRDOP_ARCH} system=${CMAKE_SYSTEM_NAME}")
diff --git a/stacks/crdop/cmake/CRDOPTests.cmake b/stacks/crdop/cmake/CRDOPTests.cmake
new file mode 100644
index 0000000..64b6b48
--- /dev/null
+++ b/stacks/crdop/cmake/CRDOPTests.cmake
@@ -0,0 +1,104 @@
+# Upstream ardopcf cmocka unit tests (Unix + GNU/Clang ld --wrap)
+
+option(CRDOP_BUILD_TESTS "Build and register upstream ardopcf unit tests" OFF)
+
+if(NOT CRDOP_BUILD_TESTS)
+    return()
+endif()
+
+if(WIN32 OR APPLE)
+    message(STATUS "CRDOP_BUILD_TESTS: skipped on ${CRDOP_PLATFORM} (cmocka/--wrap needs Unix GNU or lld linker)")
+    return()
+endif()
+
+find_package(PkgConfig QUIET)
+if(PkgConfig_FOUND)
+    pkg_check_modules(CMOCKA QUIET cmocka)
+endif()
+
+if(NOT CMOCKA_FOUND)
+    find_path(CMOCKA_INCLUDE_DIR cmocka.h)
+    find_library(CMOCKA_LIBRARY cmocka)
+    if(CMOCKA_INCLUDE_DIR AND CMOCKA_LIBRARY)
+        set(CMOCKA_FOUND TRUE)
+        set(CMOCKA_INCLUDE_DIRS "${CMOCKA_INCLUDE_DIR}")
+        set(CMOCKA_LIBRARIES "${CMOCKA_LIBRARY}")
+    endif()
+endif()
+
+if(NOT CMOCKA_FOUND)
+    message(WARNING "CRDOP_BUILD_TESTS: libcmocka not found — install cmocka dev package (see docs/BUILD.md)")
+    return()
+endif()
+
+if(NOT CRDOP_LINKER_SUPPORTS_WRAP)
+    message(WARNING "CRDOP_BUILD_TESTS: linker does not support --wrap; unit tests disabled")
+    return()
+endif()
+
+enable_testing()
+
+set(CRDOP_VENDOR_TEST_DIR "${VENDOR_DIR}/test/ardop")
+set(CRDOP_VENDOR_TEST_COMMON
+    "${CRDOP_VENDOR_TEST_DIR}/setup.c"
+)
+
+function(crdop_add_vendor_test name)
+    cmake_parse_arguments(ARG "" "" "SOURCES;WRAP" ${ARGN})
+    set(test_src "${CRDOP_VENDOR_TEST_DIR}/test_${name}.c")
+    if(NOT EXISTS "${test_src}")
+        message(FATAL_ERROR "CRDOP test source missing: ${test_src}")
+    endif()
+
+    set(sources "${test_src}" ${CRDOP_VENDOR_TEST_COMMON})
+    if(ARG_SOURCES)
+        foreach(rel IN LISTS ARG_SOURCES)
+            list(APPEND sources "${VENDOR_DIR}/${rel}")
+        endforeach()
+    endif()
+
+    add_executable(crdop_test_${name} ${sources})
+    crdop_set_compile_options(crdop_test_${name})
+
+    target_include_directories(crdop_test_${name} PRIVATE
+        "${CRDOP_ROOT}/include"
+        "${VENDOR_DIR}/src"
+        "${VENDOR_DIR}/lib"
+        ${CRDOP_PLATFORM_INCLUDES}
+    )
+
+    if(ARG_SOURCES)
+        target_link_libraries(crdop_test_${name} PRIVATE m pthread)
+        if(CRDOP_PLATFORM STREQUAL "linux")
+            target_link_libraries(crdop_test_${name} PRIVATE rt)
+        endif()
+    else()
+        target_link_libraries(crdop_test_${name} PRIVATE ardopcf_vendor)
+    endif()
+
+    target_link_libraries(crdop_test_${name} PRIVATE ${CMOCKA_LIBRARIES})
+    target_include_directories(crdop_test_${name} PRIVATE ${CMOCKA_INCLUDE_DIRS})
+
+    if(ARG_WRAP)
+        foreach(sym IN LISTS ARG_WRAP)
+            target_link_options(crdop_test_${name} PRIVATE "-Wl,--wrap=${sym}")
+        endforeach()
+    endif()
+
+    add_test(NAME crdop_test_${name} COMMAND crdop_test_${name})
+endfunction()
+
+crdop_add_vendor_test(ARDOPCommon)
+crdop_add_vendor_test(HostInterface)
+crdop_add_vendor_test(Locator)
+crdop_add_vendor_test(Packed6)
+crdop_add_vendor_test(StationId)
+crdop_add_vendor_test(log
+    SOURCES
+        src/common/log_file.c
+        src/common/log.c
+    WRAP
+        fopen fclose fwrite fflush freopen
+)
+
+message(STATUS "CRDOP_BUILD_TESTS: registered upstream ardopcf cmocka tests")
diff --git a/stacks/crdop/cmake/CRDOPVendorArdopcf.cmake b/stacks/crdop/cmake/CRDOPVendorArdopcf.cmake
new file mode 100644
index 0000000..e82c605
--- /dev/null
+++ b/stacks/crdop/cmake/CRDOPVendorArdopcf.cmake
@@ -0,0 +1,127 @@
+# Legacy vendor/ardopcf build (opt-in only; not shipped in MAX25 v1).
+
+include("${CRDOP_ROOT}/cmake/CRDOPCompiler.cmake")
+include("${CRDOP_ROOT}/cmake/CRDOPPlatform.cmake")
+
+option(CRDOP_BUILD_TESTS "Build upstream ardopcf cmocka unit tests" OFF)
+
+set(CRDOP_VENDOR_COMMON
+    lib/rawhid/rawhid.c
+    lib/rockliff/rrs.c
+    lib/ws_server/ws_server.c
+    src/common/ARDOPC.c
+    src/common/ARDOPCommon.c
+    src/common/ardopSampleArrays.c
+    src/common/ARQ.c
+    src/common/BusyDetect.c
+    src/common/FEC.c
+    src/common/FFT.c
+    src/common/HostInterface.c
+    src/common/Locator.c
+    src/common/log_file.c
+    src/common/log.c
+    src/common/Modulate.c
+    src/common/Packed6.c
+    src/common/RXO.c
+    src/common/sdft.c
+    src/common/SoundInput.c
+    src/common/StationId.c
+    src/common/TCPHostInterface.c
+    src/common/txframe.c
+    src/common/wav.c
+    src/common/Webgui.c
+    src/common/noise.c
+    src/common/ardopcf.c
+)
+
+set(CRDOP_VENDOR_SRCS "")
+foreach(rel IN LISTS CRDOP_VENDOR_COMMON CRDOP_PLATFORM_SOURCES)
+    list(APPEND CRDOP_VENDOR_SRCS "${VENDOR_DIR}/${rel}")
+endforeach()
+
+set(TXT2C "${CMAKE_BINARY_DIR}/txt2c")
+add_executable(txt2c "${VENDOR_DIR}/lib/txt2c/txt2c.c")
+crdop_set_compile_options(txt2c)
+set_target_properties(txt2c PROPERTIES RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}")
+
+set(WEBGUI_HTML_C "${CMAKE_BINARY_DIR}/gen-webgui.html.c")
+set(WEBGUI_JS_C "${CMAKE_BINARY_DIR}/gen-webgui.js.c")
+add_custom_command(
+    OUTPUT "${WEBGUI_HTML_C}"
+    COMMAND txt2c "${VENDOR_DIR}/webgui/webgui.html" "${WEBGUI_HTML_C}" webgui_html
+    DEPENDS txt2c "${VENDOR_DIR}/webgui/webgui.html"
+    COMMENT "Embedding webgui.html"
+)
+add_custom_command(
+    OUTPUT "${WEBGUI_JS_C}"
+    COMMAND txt2c "${VENDOR_DIR}/webgui/webgui.js" "${WEBGUI_JS_C}" webgui_js
+    DEPENDS txt2c "${VENDOR_DIR}/webgui/webgui.js"
+    COMMENT "Embedding webgui.js"
+)
+
+add_library(ardopcf_vendor_objs OBJECT
+    ${CRDOP_VENDOR_SRCS}
+    "${WEBGUI_HTML_C}"
+    "${WEBGUI_JS_C}"
+)
+
+target_include_directories(ardopcf_vendor_objs PRIVATE
+    "${CRDOP_ROOT}/include"
+    "${VENDOR_DIR}/src"
+    "${VENDOR_DIR}/lib"
+    ${CRDOP_PLATFORM_INCLUDES}
+)
+
+target_compile_definitions(ardopcf_vendor_objs PRIVATE CRDOP_BUILD=1)
+
+if(WIN32)
+    target_compile_definitions(ardopcf_vendor_objs PRIVATE WIN32 _CRT_SECURE_NO_DEPRECATE)
+endif()
+
+if(APPLE)
+    target_compile_definitions(ardopcf_vendor_objs PRIVATE __APPLE__)
+endif()
+
+crdop_set_compile_options(ardopcf_vendor_objs)
+
+add_executable(crdopc
+    "${CRDOP_ROOT}/src/crdop_version.c"
+    $<TARGET_OBJECTS:ardopcf_vendor_objs>
+)
+
+target_include_directories(crdopc PRIVATE
+    "${CRDOP_ROOT}/include"
+    "${VENDOR_DIR}/src"
+    "${VENDOR_DIR}/lib"
+    ${CRDOP_PLATFORM_INCLUDES}
+)
+
+target_compile_definitions(crdopc PRIVATE CRDOP_BUILD=1)
+
+if(WIN32)
+    target_compile_definitions(crdopc PRIVATE WIN32 _CRT_SECURE_NO_DEPRECATE)
+endif()
+
+if(APPLE)
+    target_compile_definitions(crdopc PRIVATE __APPLE__)
+endif()
+
+crdop_set_compile_options(crdopc)
+target_link_libraries(crdopc PRIVATE ${CRDOP_PLATFORM_LIBS})
+
+add_library(ardopcf_vendor STATIC
+    "${CRDOP_ROOT}/src/crdop_version.c"
+    $<TARGET_OBJECTS:ardopcf_vendor_objs>
+)
+target_include_directories(ardopcf_vendor PUBLIC
+    "${CRDOP_ROOT}/include"
+    "${VENDOR_DIR}/src"
+    "${VENDOR_DIR}/lib"
+    ${CRDOP_PLATFORM_INCLUDES}
+)
+target_compile_definitions(ardopcf_vendor PUBLIC CRDOP_BUILD=1)
+target_link_libraries(ardopcf_vendor PUBLIC ${CRDOP_PLATFORM_LIBS})
+
+include("${CRDOP_ROOT}/cmake/CRDOPTests.cmake")
+
+install(TARGETS crdopc RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
diff --git a/stacks/crdop/cmake/toolchains/aarch64-linux-gnu.cmake b/stacks/crdop/cmake/toolchains/aarch64-linux-gnu.cmake
new file mode 100644
index 0000000..59e3a37
--- /dev/null
+++ b/stacks/crdop/cmake/toolchains/aarch64-linux-gnu.cmake
@@ -0,0 +1,4 @@
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR aarch64)
+set(CMAKE_C_COMPILER aarch64-linux-gnu-gcc)
+set(CMAKE_CXX_COMPILER aarch64-linux-gnu-g++)
diff --git a/stacks/crdop/cmake/toolchains/arm-linux-gnueabihf.cmake b/stacks/crdop/cmake/toolchains/arm-linux-gnueabihf.cmake
new file mode 100644
index 0000000..bb70e64
--- /dev/null
+++ b/stacks/crdop/cmake/toolchains/arm-linux-gnueabihf.cmake
@@ -0,0 +1,4 @@
+set(CMAKE_SYSTEM_NAME Linux)
+set(CMAKE_SYSTEM_PROCESSOR armv7l)
+set(CMAKE_C_COMPILER arm-linux-gnueabihf-gcc)
+set(CMAKE_CXX_COMPILER arm-linux-gnueabihf-g++)
diff --git a/stacks/crdop/cmake/toolchains/x86_64-w64-mingw32.cmake b/stacks/crdop/cmake/toolchains/x86_64-w64-mingw32.cmake
new file mode 100644
index 0000000..1b44215
--- /dev/null
+++ b/stacks/crdop/cmake/toolchains/x86_64-w64-mingw32.cmake
@@ -0,0 +1,4 @@
+set(CMAKE_SYSTEM_NAME Windows)
+set(CMAKE_SYSTEM_PROCESSOR x86_64)
+set(CMAKE_C_COMPILER x86_64-w64-mingw32-gcc)
+set(CMAKE_CXX_COMPILER x86_64-w64-mingw32-g++)
diff --git a/stacks/crdop/docs/ACOUSTIC-TEST-PROTOCOL.md b/stacks/crdop/docs/ACOUSTIC-TEST-PROTOCOL.md
new file mode 100644
index 0000000..9656c2a
--- /dev/null
+++ b/stacks/crdop/docs/ACOUSTIC-TEST-PROTOCOL.md
@@ -0,0 +1,84 @@
+# Acoustic bench test protocol — P0 bench acceptance
+
+**Purpose:** Close CRDOP P0 bench without RF. All steps runnable offline in CI or on a dev host.
+
+**Related:** [HOST-PROTOCOL-SPEC.md](HOST-PROTOCOL-SPEC.md) · [DEVELOPER.md](DEVELOPER.md) · [ROADMAP.md](../ROADMAP.md) P0 bench.
+
+---
+
+## Prerequisites
+
+| Item | Requirement |
+|------|-------------|
+| Build | `MAX25_BUILD_CRDOP=ON`, `cmake --install` or source tree |
+| Python | 3.10+ with repo on `PYTHONPATH` |
+| ALSA | Optional for tests 3–4; loopback tests need no hardware |
+| PulseAudio | **Off** or bypassed (`no_pulse=yes` in INI) |
+
+---
+
+## Test matrix
+
+| ID | Name | RF | Pass criteria |
+|----|------|-----|---------------|
+| **T0** | Bell 202 round-trip | No | `test_bell202_line_code.py` green |
+| **T1** | HDLC + CRC | No | `hdlc_codec` round-trip in unit tests |
+| **T2** | Software loopback | No | `max25-signal-sniffer.py --loopback` decodes AX.25 UI |
+| **T3** | `acoustic_engine` self-test | No | `AcousticEngine.loopback_self_test()` returns True |
+| **T4** | `audio-dummyd` + host TCP | No | Connect :8515/:8516, `PROTOCOLMODE KISS` → `OK` |
+| **T5** | `max25d` audio-dummy backend | No | `test_audio_dummy_backend.py` green |
+| **T6** | `max25d` crdop-tcp backend | No | `test_crdop_backend.py` green |
+| **T7** | ALSA loopback cable | No* | Sniffer decodes tone from `aplay`/`arecord` pair |
+| **T8** | WAV fixture | No | Sniffer `--wav` decodes recorded Bell 202 capture |
+
+\*Requires `snd-aloop` or physical loopback interface.
+
+---
+
+## Commands (copy-paste)
+
+```bash
+cd MAX25-Stack
+./scripts/build.sh
+
+# T0–T1
+python3 -m pytest stacks/crdop/test_bell202_line_code.py -q
+python3 -m pytest stacks/daemon/test_crdop_backend.py stacks/daemon/test_audio_dummy_backend.py -q
+
+# T2
+python3 stacks/crdop/tools/max25-signal-sniffer.py --loopback
+
+# T4 (background)
+python3 stacks/crdop/tools/audio-dummyd.py --ctrl-port 8515 --data-port 8516 &
+sleep 1
+python3 -c "
+import socket
+c=socket.create_connection(('127.0.0.1',8515),timeout=2)
+c.sendall(b'PROTOCOLMODE KISS\n')
+print(c.recv(64))
+"
+```
+
+---
+
+## P0 bench exit gate
+
+**100 % P0 bench** when:
+
+- [x] T0, T1, T2, T5, T6 pass in `release-check.sh`
+- [ ] T3 documented green in CI log (or explicit skip reason)
+- [ ] T4 manual or scripted smoke in release-check
+- [ ] Host ports unified: launcher, `audio-dummyd`, `max25d` use [HOST-PROTOCOL-SPEC.md](HOST-PROTOCOL-SPEC.md) defaults
+
+P0 on-air starts only after P0 bench exit — see [docs/HARDWARE-ACCEPTANCE.md](../../docs/HARDWARE-ACCEPTANCE.md).
+
+---
+
+## Failure triage
+
+| Symptom | Check |
+|---------|-------|
+| Wrong tones | Mark 1200 Hz / Space 2200 Hz, sample rate 48000 |
+| CRC fail | `ax25_codec.ax25_crc` vs `hdlc_codec` |
+| TCP refuse | Port 8515 free; `audio-dummyd` running for host tests |
+| ALSA xrun | `period_frames`, cable levels — [SOUNDCARD-QUALIFICATION.md](SOUNDCARD-QUALIFICATION.md) |
diff --git a/stacks/crdop/docs/AUDIO-ARCHITECTURE.md b/stacks/crdop/docs/AUDIO-ARCHITECTURE.md
new file mode 100644
index 0000000..6320253
--- /dev/null
+++ b/stacks/crdop/docs/AUDIO-ARCHITECTURE.md
@@ -0,0 +1,80 @@
+# CRDOP audio architecture — kernel ALSA only
+
+**CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`).
+
+MAX25-SoftModem (CRDOP) talks to the radio **through the sound hardware directly**. There is **no PulseAudio**, **no PipeWire default route**, and **no desktop sound server** in the path.
+
+## Stack layers
+
+```
+┌─────────────┐   M25/1 TCP    ┌──────────────┐   host TCP   ┌─────────────┐
+│  max25d     │ ◄────────────► │ CRDOP modem  │ ◄──────────► │ max25-      │
+│  (stack)    │                │ (DSP/AX.25)  │              │ terminal    │
+└─────────────┘                └──────┬───────┘              └─────────────┘
+                                      │
+                              MAX25 sound-proxy
+                              (buffer, timing, duplex)
+                                      │
+                                      ▼
+                              libasound (userspace)
+                                      │
+                                      ▼
+                              Linux kernel ALSA
+                              (/dev/snd/*, drivers)
+                                      │
+                                      ▼
+                              Sound hardware (USB/PCI codec)
+                                      │
+                                      ▼
+                              Radio interface (line / acoustic)
+```
+
+| Layer | Role | Allowed |
+|-------|------|---------|
+| **max25d** | Device lifecycle, `CrdopTcpBackend`, no audio I/O | — |
+| **CRDOP modem** | AFSK encode/decode, AX.25 framing, duplex policy | — |
+| **MAX25 sound-proxy** | **Only** audio shim between modem and ALSA — period size, xrun recovery, hw params, PTT timing hooks | MAX25-owned |
+| **ALSA userspace** | `snd_pcm_*` on **`hw:` / `plughw:`** devices | Direct libasound |
+| **Kernel ALSA** | Driver, DMA, card registry | Required |
+| **PulseAudio / PipeWire** | — | **Forbidden** in production path |
+
+The sound-proxy is **not** a second network hop — it is the in-process (or co-process) module that owns ALSA opens and keeps modem timing off the desktop audio stack.
+
+## Why no PulseAudio
+
+PulseAudio and PipeWire insert mixing, resampling, and variable latency between applications and the kernel. CRDOP must:
+
+- Reproduce **exact mark/space frequencies** on playback
+- Sample capture with **stable phase** for demodulation
+- Meet **tighter deadlines** as baud rises toward 19200
+
+A userspace mixer breaks those guarantees. Operators must bind **card and device explicitly** (`hw:Card,Device` or tested `plughw:`).
+
+## Operator setup
+
+1. Identify hardware: `arecord -l` and `aplay -l` (kernel cards, not `pulse` pseudo-devices).
+2. Set INI `[audio] capture` and `playback` to **hardware ALSA names**.
+3. Ensure no session steals the device (`pasuspender` / stop PulseAudio on dedicated hosts).
+4. Verify loopback before on-air traffic.
+
+Example INI:
+
+```ini
+[audio]
+backend = alsa-kernel
+no_pulse = yes
+capture = hw:1,0
+playback = hw:1,0
+```
+
+Dedicated packet-radio hosts: prefer **single-purpose Linux** without a desktop sound daemon, or `PULSE_SERVER=` / `PIPEWIRE_RUNTIME_DIR=` unset for the `crdop` service unit.
+
+## Development (Eigenentwicklung)
+
+Native CRDOP will implement the sound-proxy in-tree (`include/crdop/sound_proxy.h`). Legacy optional vendor builds used `ALSASound.c` with the same rule: **open ALSA devices directly**.
+
+## See also
+
+- [SOFTMODEM.md](SOFTMODEM.md) — product scope, baud, duplex
+- [CONFIG.md](CONFIG.md) — INI keys
+- [BUILD.md](BUILD.md) — `libasound2-dev` dependency
diff --git a/stacks/crdop/docs/BUILD.md b/stacks/crdop/docs/BUILD.md
new file mode 100644
index 0000000..e72fac0
--- /dev/null
+++ b/stacks/crdop/docs/BUILD.md
@@ -0,0 +1,99 @@
+# Build
+
+Standalone CRDOP (**MAX25-SoftModem** — MAX25-SoftModem) — embedded `vendor/ardopcf/`, no submodules.
+
+## Requirements
+
+- CMake ≥ 3.16
+- **GCC** or **Clang / LLVM**
+- Platform libraries (see table below)
+- Optional tests: **cmocka** (Linux, *BSD)
+
+## Platform matrix (tested)
+
+| OS | Toolchain | Audio / libs | Status |
+|----|-----------|----------------|--------|
+| **Linux** | GCC, Clang | `libasound2-dev`, `pkg-config` | tested |
+| **FreeBSD** | GCC, Clang | `alsa-lib`, `pkgconf` | tested |
+| **OpenBSD / NetBSD** | GCC, Clang | `alsa-lib` if available | experimental |
+| **Windows** | MinGW-w64, MSVC | WinMM (built-in) | **untested** |
+| **macOS** | Clang (Xcode) | CoreAudio (built-in) | **untested** |
+
+Other operating systems are not tested.
+
+### Debian / Ubuntu
+
+```bash
+sudo apt install build-essential cmake libasound2-dev pkg-config
+sudo apt install libcmocka-dev    # optional unit tests
+```
+
+### FreeBSD
+
+```bash
+pkg install cmake alsa-lib pkgconf cmocka
+```
+
+### macOS
+
+```bash
+xcode-select --install
+# or: brew install cmake
+```
+
+### Windows (MinGW-w64 on Linux host)
+
+```bash
+sudo apt install mingw-w64
+CRDOP_TOOLCHAIN=x86_64-w64-mingw32 ./scripts/build-crdop.sh
+# → build/crdopc.exe
+```
+
+Native Windows: Visual Studio 2022+ with CMake, or MSYS2 MinGW.
+
+## Build
+
+```bash
+./scripts/build-crdop.sh
+CC=clang ./scripts/build-crdop.sh
+./scripts/test-all.sh              # smoke + cmocka (Unix)
+```
+
+Output: `build/crdopc` (Windows: `build/crdopc.exe`)
+
+## Install
+
+```bash
+./scripts/install-crdop.sh                    # → /usr/local
+CRDOP_PREFIX=$HOME/.local ./scripts/install-crdop.sh
+```
+
+Installs:
+
+| Path | Contents |
+|------|----------|
+| `bin/crdopc` | Modem binary |
+| `bin/crdop` | Profile launcher (`scripts/crdopc`) |
+| `share/crdop/` | INI examples, `VERSION` |
+
+Run: `crdop` or `CRDOP_INI=~/.config/crdop/crdop.ini crdop`
+
+## Cross-compile (Linux host)
+
+```bash
+CRDOP_TOOLCHAIN=aarch64-linux-gnu ./scripts/build-crdop.sh
+CRDOP_TOOLCHAIN=arm-linux-gnueabihf ./scripts/build-crdop.sh
+CRDOP_TOOLCHAIN=x86_64-w64-mingw32 ./scripts/build-crdop.sh
+```
+
+## Troubleshooting
+
+| Problem | Fix |
+|---------|-----|
+| `vendor/ardopcf missing` | Full repo checkout |
+| No ALSA (Linux/BSD) | Install dev package / `alsa-lib` port |
+| macOS build fails | Xcode CLI tools; CMake ≥ 3.16 |
+| Tests skipped | Install cmocka dev package |
+| Stale build | `rm -rf build && ./scripts/build-crdop.sh` |
+
+Vendor refresh (maintainers): `./scripts/refresh-vendor-ardopcf.sh`
diff --git a/stacks/crdop/docs/CHANGELOG.md b/stacks/crdop/docs/CHANGELOG.md
new file mode 100644
index 0000000..2bbfbf6
--- /dev/null
+++ b/stacks/crdop/docs/CHANGELOG.md
@@ -0,0 +1,25 @@
+# Changelog
+
+## [CUR999] — dev track (current)
+
+**CUR999** — internal dev track id for MAX25-SoftModem inside MAX25-Stack v1.0.0. Dev track `CUR999`; ships with MAX25-Stack v1.0.0.
+
+- Dev track id `CUR999` in `$SRC/stacks/crdop/VERSION`
+- Native modem DSP in development; optional legacy vendor build (`-DCRDOP_VENDOR_ARDOPCF=ON`); **ARDOP-plugin** documented separately
+- `max25d` `crdop-tcp` backend, INI scaffold, launcher, HyBBX attach examples
+
+## [0.5.0] — planned (not yet released)
+
+Target standalone CRDOP v0.5 after v1.0.0 stack ship.
+
+- Standalone CRDOP modem (`crdopc`) with native DSP
+- Embedded optional `vendor/ardopcf` (MIT) for dev-only legacy builds only
+- CB / dual / amateur profiles; Linux and *BSD tested
+
+## [0.1.0-l2-cb] — 2026-07-03
+
+Experimental CB profile bootstrap.
+
+## [0.0.0-bootstrap]
+
+Repository scaffold.
diff --git a/stacks/crdop/docs/CONFIG.md b/stacks/crdop/docs/CONFIG.md
new file mode 100644
index 0000000..821fd1c
--- /dev/null
+++ b/stacks/crdop/docs/CONFIG.md
@@ -0,0 +1,50 @@
+# Configuration
+
+`scripts/crdopc` reads INI → starts native `audio-dummyd` (M25/KISS host).
+
+## INI search order
+
+1. `$CRDOP_INI`
+2. `~/.config/crdop/crdop.ini`
+3. `share/crdop.ini.example`
+
+Templates: `share/crdop.ini.example` · `share/crdop-dual.ini.example` · `share/crdop-amateur.ini.example`
+
+## Keys
+
+### `[profile]`
+
+| Key | Default | Values |
+|-----|---------|--------|
+| `radio_profile` | `cb` | `cb` · `dual` · `amateur` |
+
+### `[modem]`
+
+| Key | Default | Notes |
+|-----|---------|-------|
+| `arq_bandwidth` | profile | `500MAX` (cb/dual) · `1000MAX` (amateur) |
+| `duplex` | `half` | `half` · `full` (`full` → `EXTRADELAY 0`) |
+| `extra_delay_ms` | _(auto)_ | Override delay; empty = profile default |
+
+### `[host]` · `[mycall]` · `[audio]`
+
+| Section | Key | Default | Notes |
+|---------|-----|---------|-------|
+| host | `port` | `8515` | TCP control |
+| mycall | `call` | `NOCALL-0` | On-air ID |
+| audio | `backend` | `alsa-kernel` | Kernel ALSA only — see [AUDIO-ARCHITECTURE.md](AUDIO-ARCHITECTURE.md) |
+| audio | `no_pulse` | `yes` | Reject PulseAudio/PipeWire pseudo devices |
+| audio | `capture` | _(required)_ | e.g. `hw:1,0` from `arecord -l` |
+| audio | `playback` | _(required)_ | e.g. `hw:1,0` from `aplay -l` |
+| audio | `sample_rate` | modem default | Hz |
+| audio | `period_frames` | auto | Buffer tuning |
+
+**No PulseAudio** in the production path. The **MAX25 sound-proxy** opens ALSA directly; `scripts/crdopc` clears Pulse/PipeWire session env when `no_pulse=yes`.
+
+## Environment
+
+| Variable | Purpose |
+|----------|---------|
+| `CRDOP_INI` | Config file path |
+
+Examples: [EXAMPLES.md](EXAMPLES.md)
diff --git a/stacks/crdop/docs/DEVELOPER.md b/stacks/crdop/docs/DEVELOPER.md
new file mode 100644
index 0000000..af43252
--- /dev/null
+++ b/stacks/crdop/docs/DEVELOPER.md
@@ -0,0 +1,188 @@
+# CRDOP developer guide
+
+**CRDOP** = **MAX25-SoftModem**. In-house GPLv3 sound-card modem (`stacks/crdop/`). Project rule: [docs/CRDOP.md](../../../docs/CRDOP.md).
+
+---
+
+## Source tree
+
+```
+stacks/crdop/
+├── lib/                    # Native DSP (Python — leads validation)
+│   ├── bell202_line_code.py
+│   ├── afsk_modulator.py
+│   ├── afsk_demodulator.py
+│   ├── hdlc_codec.py
+│   ├── sound_proxy.py
+│   ├── m25_host_protocol.py
+│   ├── acoustic_engine.py
+│   └── test_bell202_line_code.py
+├── include/crdop/          # C API scaffold (future native binary)
+│   ├── sound_proxy.h
+│   └── version.h
+├── tools/
+│   ├── audio-dummyd.py     # M25 host TCP daemon
+│   └── max25-signal-sniffer.py
+├── scripts/
+│   ├── crdopc              # Launcher → audio-dummyd by default
+│   ├── build-crdop.sh
+│   └── install-crdop.sh
+├── share/                  # crdop.ini.example (+ dual, amateur)
+├── cmake/                  # Platform, vendor (dev-only), tests
+├── docs/                   # This tree
+├── ROADMAP.md
+└── CMakeLists.txt
+```
+
+**Daemon integration:** `stacks/daemon/device_backends.py` → `CrdopTcpBackend` (`soft-crdop`), `AudioDummyBackend` (`audio-dummy`).
+
+**AX.25 codec:** `stacks/daemon/ax25_codec.py` — shared with on-air framing in `acoustic_engine.py`.
+
+---
+
+## Module map
+
+| Module | Layer | Responsibility |
+|--------|-------|----------------|
+| `bell202_line_code.py` | Line code | Bell 202 frequency-toggle: bit 0 → tone change; mark 1200 Hz / space 2200 Hz |
+| `afsk_modulator.py` | PHY TX | Continuous-phase AFSK PCM @ configurable sample rate (default 48 kHz) |
+| `afsk_demodulator.py` | PHY RX | Per-symbol Goertzel demod (1200 baud class) |
+| `hdlc_codec.py` | Framing | HDLC flags `0x7E`, bit-stuffing, CRC-16-CCITT |
+| `sound_proxy.py` | Audio I/O | ALSA capture/playback via `arecord`/`aplay`; buffer config |
+| `m25_host_protocol.py` | Host | TCP ctrl (:8515) + data (:8516); M25-family + KISS-semantics |
+| `acoustic_engine.py` | Bench | Full path: AX.25 UI → HDLC → AFSK → demod → parse; loopback self-test |
+
+**Host vs on-air:** `m25_host_protocol.py` carries AX.25 UI on the data port **without** HDLC wrapping. `acoustic_engine.encode_ax25_ui()` builds full on-air HDLC + AFSK for RF/audio output.
+
+**Not yet in `lib/`:** G3RUH scrambler/FSK (P1), 300 baud HF AFSK (P2), optional short-block FEC.
+
+---
+
+## Running tests
+
+### MAX25-Stack (recommended)
+
+```bash
+./scripts/build.sh
+cmake --build build --target max25_test          # all offline tests
+cmake --build build --target max25_daemon_smoke  # daemon + CRDOP subset
+```
+
+CRDOP-related tests in `max25_daemon_smoke`:
+
+| Test file | What it checks |
+|-----------|----------------|
+| `stacks/crdop/lib/test_bell202_line_code.py` | Bell 202 encode/decode round-trip |
+| `stacks/daemon/test_crdop_backend.py` | `CrdopTcpBackend` attach, TX (native M25/KISS) |
+| `stacks/daemon/test_audio_dummy_backend.py` | `audio-dummy` loopback backend |
+| `stacks/daemon/test_multi_device.py` | Multi-device registry incl. `soft-crdop` |
+
+### Direct (no CMake)
+
+```bash
+python3 stacks/crdop/lib/test_bell202_line_code.py
+python3 stacks/daemon/test_crdop_backend.py
+python3 stacks/daemon/test_audio_dummy_backend.py
+```
+
+### Sniffer loopback (no audio hardware)
+
+```bash
+python3 stacks/crdop/tools/max25-signal-sniffer.py --loopback
+# or after install:
+max25-signal-sniffer --loopback
+```
+
+Exit 0 when loopback decode produces AX.25 UI lines.
+
+### audio-dummyd bench
+
+```bash
+python3 stacks/crdop/tools/audio-dummyd.py --ctrl-port 8515 --data-port 8516
+# Terminal probe (separate shell):
+max25-terminal -H 127.0.0.1 -P 8515
+```
+
+### Standalone CRDOP vendor tests (dev-only)
+
+When built with `-DCRDOP_VENDOR_ARDOPCF=ON` and cmocka installed:
+
+```bash
+./scripts/build-crdop.sh
+CRDOP_BUILD_TESTS=ON ./scripts/test-all.sh
+```
+
+Vendor tree is **never** installed in MAX25 releases.
+
+---
+
+## Extending the modem
+
+### Add a modulation mode
+
+1. Add PHY module under `lib/` (e.g. `g3ruh_fsk.py`).
+2. Wire into `acoustic_engine.py` — select by `baud` / `modulation` parameter.
+3. Extend `crdop.ini` `[modem]` keys in `share/crdop.ini.example` and [CONFIG.md](CONFIG.md).
+4. Add unit tests beside the module (`test_*.py`).
+5. Update [ROADMAP.md](../ROADMAP.md) implementation status table.
+
+### Extend host protocol
+
+1. Edit `m25_host_protocol.py` — keep ctrl/data port split.
+2. Mirror changes in `stacks/daemon/device_backends.py` (`CrdopTcpBackend`).
+3. Document in [PROTOCOL.md](PROTOCOL.md).
+4. Add cases to `test_crdop_backend.py`.
+
+### C port path
+
+`include/crdop/sound_proxy.h` is the C ABI target. Python `lib/` leads until acoustic bench gates close; then port validated algorithms to native `crdopc` binary.
+
+---
+
+## Build modes
+
+| Mode | CMake flag | Output |
+|------|------------|--------|
+| **MAX25-Stack (default)** | `MAX25_BUILD_CRDOP=ON` | `bin/crdop`, `bin/audio-dummyd`, `bin/max25-signal-sniffer`, `share/crdop/` |
+| **MAX25 without CRDOP** | `-DMAX25_BUILD_CRDOP=OFF` | No CRDOP install artifacts |
+| **Standalone CRDOP** | `stacks/crdop/scripts/build-crdop.sh` | Same scaffold; optional vendor `crdopc` with `-DCRDOP_VENDOR_ARDOPCF=ON` |
+| **Dev vendor ARDOP** | `-DCRDOP_VENDOR_ARDOPCF=ON` | Legacy ardopcf binary — local only, never released |
+
+### Install paths (MAX25 `cmake --install`)
+
+| Artifact | Destination |
+|----------|-------------|
+| `crdop` (launcher) | `${CMAKE_INSTALL_PREFIX}/bin/` |
+| `audio-dummyd`, `max25-signal-sniffer` | `${CMAKE_INSTALL_PREFIX}/bin/` |
+| `crdop.ini.example`, `lib/*.py`, `VERSION` | `${CMAKE_INSTALL_PREFIX}/share/crdop/` |
+
+---
+
+## Dependencies
+
+| Component | Requirement |
+|-----------|-------------|
+| Runtime | Python 3, ALSA utils (`arecord`/`aplay`) on Linux |
+| Build | CMake ≥ 3.16 |
+| Audio | `libasound` — kernel ALSA direct opens only |
+| Tests | None beyond Python 3 (cmocka optional for vendor C tests) |
+
+---
+
+## Conventions
+
+- **English** for all shipped docs and user-facing strings.
+- **No PulseAudio / PipeWire** in production audio path.
+- **ARDOP** is a separate optional plugin — not part of CRDOP — see [plugins/external/ardop/README.md](../../../plugins/external/ardop/README.md).
+- Baud ceiling: **19200** (P1 G3RUH direct FSK). Above that: out of scope.
+
+---
+
+## Related
+
+| Doc | Topic |
+|-----|--------|
+| [MAX25-USAGE.md](MAX25-USAGE.md) | Operator workflow in MAX25-Stack |
+| [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md) | Radio interface spec for builders |
+| [AUDIO-ARCHITECTURE.md](AUDIO-ARCHITECTURE.md) | Sound-proxy design |
+| [ROADMAP.md](../ROADMAP.md) | P0/P1/P2 milestones and module status |
diff --git a/stacks/crdop/docs/EXAMPLES.md b/stacks/crdop/docs/EXAMPLES.md
new file mode 100644
index 0000000..b6d32c5
--- /dev/null
+++ b/stacks/crdop/docs/EXAMPLES.md
@@ -0,0 +1,91 @@
+# Examples
+
+MAX25-Stack integration (plugins, `max25d`, terminal): [MAX25-USAGE.md](MAX25-USAGE.md).
+
+## Build
+
+```bash
+./scripts/build-crdop.sh
+CC=clang ./scripts/build-crdop.sh
+CRDOP_BUILD_TESTS=ON ./scripts/test-all.sh    # needs libcmocka-dev
+```
+
+Cross-build (Linux host): see [BUILD.md](BUILD.md).
+
+## Run — CB (default, native M25 host)
+
+```bash
+./scripts/crdopc
+# or explicit example INI:
+CRDOP_INI=share/crdop.ini.example ./scripts/crdopc
+```
+
+This starts `audio-dummyd` with native M25/KISS host on TCP :8515/:8516.
+
+Copy config for daily use:
+
+```bash
+mkdir -p ~/.config/crdop
+cp share/crdop.ini.example ~/.config/crdop/crdop.ini
+$EDITOR ~/.config/crdop/crdop.ini
+./scripts/crdopc
+```
+
+## Run — dual (CB ↔ amateur)
+
+```bash
+CRDOP_INI=share/crdop-dual.ini.example ./scripts/crdopc
+```
+
+## Run — amateur (secondary)
+
+```bash
+CRDOP_INI=share/crdop-amateur.ini.example ./scripts/crdopc
+```
+
+## Full-duplex CB
+
+`share/crdop.ini.example` with:
+
+```ini
+[modem]
+duplex = full
+arq_bandwidth = 500MAX
+```
+
+## Custom call / ALSA devices
+
+```ini
+[mycall]
+call = CB01-0
+
+[audio]
+capture = plughw:1,0
+playback = plughw:1,0
+```
+
+Pass extra args after port (reserved for future native modem flags):
+
+```bash
+./scripts/crdopc 8515
+```
+
+## Direct audio-dummyd (no launcher)
+
+```bash
+./build/bin/audio-dummyd --ctrl-port 8515 --data-port 8516
+```
+
+## max25d integration
+
+```ini
+[devices]
+soft-crdop = crdop:default
+
+[device.soft-crdop]
+host = 127.0.0.1
+port = 8515
+listen = yes
+```
+
+See [../../docs/PLUGINS-DEVICE-MODEL.md](../../docs/PLUGINS-DEVICE-MODEL.md).
diff --git a/stacks/crdop/docs/FEC-SPEC.md b/stacks/crdop/docs/FEC-SPEC.md
new file mode 100644
index 0000000..53b1f93
--- /dev/null
+++ b/stacks/crdop/docs/FEC-SPEC.md
@@ -0,0 +1,99 @@
+# CRDOP FEC and duplex — implementation spec
+
+**Principle:** *Send more often with shorter frames rather than one long payload.*
+
+**Related:** [ROADMAP.md](../ROADMAP.md) FEC section · [docs/CRDOP.md](../../../docs/CRDOP.md)
+
+**Status:** MAX25-Stack **v1.0.0** / dev track `CUR999` — L1 optional FEC **planned**; operator-layer strategy **active now**.
+
+---
+
+## Layer model
+
+| Layer | Mechanism | v1.0.0 |
+|-------|-----------|--------|
+| **L3 Application** | Short beacons, staggered intervals | HyBBX / `max25d.ini` |
+| **L2 AX.25** | UI = no ARQ; I-frames optional ARQ via host | `ax25_codec.py` |
+| **L1 Modem** | CRC-16-CCITT mandatory; optional repeat/FEC blocks | `hdlc_codec.py` — CRC done |
+| **PHY** | Bell 202 AFSK (P0) | `afsk_*` |
+
+---
+
+## Half-duplex (CB default)
+
+| Parameter | Value | INI / host |
+|-----------|-------|------------|
+| Duplex | half | `[modem] duplex = half` |
+| CSMA persist | 255 | KISS `0x02` / CB profile |
+| Extra TX delay | 150 ms class | `extra_delay_ms` / `EXTRADELAY` |
+| Max UI info | **≤128 bytes** recommended | Application |
+| PTT | explicit | No VOX on CB |
+
+### Retransmission strategy (no L2 ARQ on UI)
+
+1. Prefer **N small identical beacons** over one large burst.
+2. Stagger dual-radio sites (`ax25_auto_interval` + offset).
+3. Optional L1: **2–3 repeats** of same short codeword vs one RS block >256 B.
+
+---
+
+## Full-duplex
+
+| Parameter | Value |
+|-----------|-------|
+| `duplex` | `full` |
+| `EXTRADELAY` | `0` |
+| FEC | Stronger codes allowed when bandwidth permits |
+| Audio | Full-duplex sound card; echo control required |
+
+---
+
+## Reference protocols (not on-air targets)
+
+| Protocol | Lesson for CRDOP |
+|----------|------------------|
+| **FX.25** | RS wrapper around AX.25; bit-stuffing hurts naive FEC |
+| **IL2P** | No bit-stuffing; packet-sync scramble — reference for future L2 |
+| **VARA DSP** | Multi-stage FEC — PHY reference only |
+
+---
+
+## Planned L1 FEC (post P0 on-air)
+
+| Requirement | Target |
+|-------------|--------|
+| Block size | ≤64 B payload + CRC per repeat unit |
+| Latency | <300 ms added on 1200 bd half-duplex |
+| Compatibility | Plain AX.25 receivers must not break (FX.25-style optional path) |
+| Test | AWGN + FM clip simulator before on-air |
+
+### INI keys (future)
+
+```ini
+[fec]
+enabled = no          # default off v1.0.0
+repeat_count = 0      # 0 = no repeat; 2–3 for CB marginal
+profile = half        # half | full
+```
+
+---
+
+## CB 1200 parameters (normative operator)
+
+| Parameter | Value |
+|-----------|-------|
+| Baud | 1200 |
+| Modulation | Bell 202 (1200/2200 Hz) |
+| Frame | AX.25 UI |
+| persist | 255 |
+| Beacon | 300 s + stagger (site INI) |
+
+---
+
+## Implementation checklist
+
+- [x] CRC-16 in `hdlc_codec.py`
+- [x] Duplex INI keys in `crdop.ini.example`
+- [ ] `fec.enabled` INI + launcher
+- [ ] Offline BER vs frame-length simulator
+- [ ] Document measured CB SNR thresholds (field)
diff --git a/stacks/crdop/docs/G3RUH-DESIGN.md b/stacks/crdop/docs/G3RUH-DESIGN.md
new file mode 100644
index 0000000..ae1a164
--- /dev/null
+++ b/stacks/crdop/docs/G3RUH-DESIGN.md
@@ -0,0 +1,72 @@
+# G3RUH FSK — CRDOP P1 design spec
+
+**Scope:** 9600–**19200** baud direct FSK. **Hard maximum 19200** — nothing above.
+
+**Prerequisite:** P0 on-air (1200 AFSK) stable. **Not** CB FM mic path.
+
+See [ROADMAP.md](../ROADMAP.md) P1 milestone (stack scheduling: **DEV-Level 4**).
+
+---
+
+## PHY difference from P0
+
+| | 1200 AFSK (P0) | G3RUH FSK (P1) |
+|---|----------------|----------------|
+| Modulation | Audio tones 1200/2200 Hz | Scrambled baseband FSK |
+| RF path | Mic / speaker / line | **Direct** varactor + discriminator |
+| CB FM voice channel | ✅ | ❌ |
+| VHF backbone | Access only at 1200 | ✅ at 9600–19200 |
+
+---
+
+## Parameters (normative)
+
+| Baud | Peak deviation | RF bandwidth (~-60 dB) |
+|------|----------------|------------------------|
+| 4800 | ±1.5 kHz | ~8 kHz |
+| **9600** | **±3 kHz** | **~20 kHz** |
+| **19200** | **±6 kHz** | **~30 kHz** |
+
+CRDOP implements **up to 19200** only.
+
+---
+
+## Radio interface requirements
+
+| Requirement | Detail |
+|-------------|--------|
+| TX | Direct modulation input (varactor), not acoustic |
+| RX | Discriminator / data output, wide IF |
+| Filter | Flat amplitude 10 Hz–5 kHz, constant group delay |
+| Scrambler | G3RUH compatible — interoperate with standard 9600 peers |
+
+Standard narrow FM voice audio **fails** eye-diagram tests at 9600+.
+
+---
+
+## Software modules (planned)
+
+| Module | Path | Status |
+|--------|------|--------|
+| Scrambler | `stacks/crdop/lib/g3ruh_scrambler.py` | Not started |
+| FSK modulator | `stacks/crdop/lib/g3ruh_modulator.py` | Not started |
+| FSK demodulator | `stacks/crdop/lib/g3ruh_demodulator.py` | Not started |
+| HDLC/framing | Reuse `hdlc_codec.py` | Done |
+
+Host protocol unchanged — same M25/KISS TCP; baud selected via INI `speed_baud` (future).
+
+---
+
+## P1 exit criteria
+
+1. Loopback with recorded baseband fixtures at 9600.
+2. Over-the-air exchange with reference 9600 FSK peer.
+3. 19200 optional stretch after 9600 stable.
+
+---
+
+## Out of scope
+
+- 38400+ satellite/backbone rates
+- Acoustic coupling at 9600+
+- CB 27 MHz deployment
diff --git a/stacks/crdop/docs/HARDWARE-INTERFACE.md b/stacks/crdop/docs/HARDWARE-INTERFACE.md
new file mode 100644
index 0000000..9c36e21
--- /dev/null
+++ b/stacks/crdop/docs/HARDWARE-INTERFACE.md
@@ -0,0 +1,194 @@
+# CRDOP hardware interface specification
+
+Generic specification for builders who manufacture **radio ↔ sound-card interfaces** for CRDOP (MAX25-SoftModem). **No product-specific wiring examples** — apply these rules to your own design.
+
+**CRDOP** = **MAX25-SoftModem**. Project rule: [docs/CRDOP.md](../../../docs/CRDOP.md).
+
+---
+
+## Scope
+
+CRDOP connects a host sound card to a transceiver via one of:
+
+| Path | Typical use | Max practical baud |
+|------|-------------|-------------------|
+| **Audio AFSK** | Mic IN / speaker OUT / line level | **1200** (P0) |
+| **Direct FSK** | Varactor TX + FM discriminator RX | **9600–19200** (P1) |
+| **SSB audio** | USB/LSB suppressed carrier | **300** (P2 optional) |
+| **Acoustic coupling** | Speaker ↔ microphone (test / field) | **1200** |
+
+RF path matrix and delivery milestones: [ROADMAP.md](../ROADMAP.md).
+
+---
+
+## Audio levels
+
+### Line level (preferred)
+
+| Signal | Typical level | Notes |
+|--------|---------------|-------|
+| **Playback → radio mic IN** | −20 to −10 dBV (adjust per rig sensitivity) | Use potentiometer or fixed attenuator; verify with sniffer or oscilloscope |
+| **Radio speaker/line → capture** | 0.1–1.0 V RMS typical | Attenuate hot speaker outputs before codec input |
+| **Full-scale digital** | Avoid clipping on TX and RX | Leave 6–12 dB headroom |
+
+### Mic level
+
+Some transceivers expose mic-level inputs only. Attenuate line output to mic sensitivity (often 5–20 mV). Use coupling capacitor if DC bias is present on the mic jack.
+
+### Isolation
+
+| Method | Purpose |
+|--------|---------|
+| **Audio transformer** (1:1 or step-down) | Galvanic isolation; breaks ground loops |
+| **Opto-isolator** (digital PTT path) | Isolate PTT from radio ground |
+| **Separate ground reference** | Star ground at interface PCB; one tie point to radio chassis if required |
+
+**Ground loops** cause hum, false transitions, and decode failures. Always isolate PC USB ground from radio chassis when using direct cable coupling.
+
+---
+
+## PTT control
+
+CRDOP is **half-duplex by default**. The host must key the transmitter before playback and unkey after tail.
+
+| Method | Interface | Caveats |
+|--------|-----------|---------|
+| **GPIO** | USB-serial RTS/DTR, parallel port, dedicated GPIO | Cleanest; software-controlled timing |
+| **Serial CAT** | Radio command port | Latency depends on radio firmware |
+| **VOX** | Audio-derived keying | **Not recommended** for packet — tail timing unpredictable; false keys from noise |
+| **Manual** | Operator PTT | Acceptable for bench only |
+
+### Timing parameters
+
+Configure in `crdop.ini` / `max25d.ini`:
+
+| Parameter | Typical half-duplex | Full-duplex |
+|-----------|--------------------|-------------|
+| Pre-TX delay (`extra_delay_ms`) | 80–200 ms | 0 |
+| TXTAIL | Match radio requirement | N/A |
+| PTT release | After last space tone + margin | N/A |
+
+**Rule:** explicit GPIO/serial PTT beats VOX for AX.25 UI bursts.
+
+---
+
+## Acoustic coupling
+
+Valid for **bench validation** and some field setups:
+
+```
+[Host speaker] ──air gap──► [Radio mic]
+[Radio speaker] ──air gap──► [Host mic]
+```
+
+| Principle | Detail |
+|-----------|--------|
+| **Distance** | Minimize path loss; foam gasket reduces room noise |
+| **Frequency response** | FM voice channel ≈ 3 kHz — sufficient for 1200/2200 Hz Bell 202 |
+| **Level** | Low volume on playback; avoid speaker distortion |
+| **Duplex** | Half-duplex only — acoustic feedback if TX and RX paths overlap |
+| **Test** | Run `max25-signal-sniffer --loopback` on host before acoustic trial |
+
+Acoustic coupling does **not** scale to G3RUH direct FSK (P1).
+
+---
+
+## Direct FSK path (P1 — G3RUH)
+
+When audio AFSK is insufficient (9600–19200 baud):
+
+| Element | Requirement |
+|---------|-------------|
+| **TX** | Discriminator input bypassed; varactor or dedicated FSK input on data port |
+| **RX** | Flat FM discriminator output (de-emphasis off or compensated) |
+| **Bandwidth** | ~20 kHz IF for 9600; wider for 19200 |
+| **Scrambler** | G3RUH polynomial — implemented in future `lib/` module |
+| **Radio** | Data-port capable; standard FM mic/speaker path **not** sufficient |
+
+CB FM rigs at 27 MHz are generally **not** direct-FSK capable at 9600+ — P1 targets VHF/UHF amateur backbone paths.
+
+---
+
+## Sound card requirements
+
+| Requirement | 1200 baud (P0) | 9600–19200 (P1) |
+|-------------|----------------|-----------------|
+| **Sample rate** | ≥ 48 kHz recommended | ≥ 48 kHz; 96 kHz preferred |
+| **Bit depth** | 16-bit mono | 16-bit mono |
+| **Duplex** | Full-duplex USB codec or half-duplex with PTT | Full-duplex, low jitter |
+| **Clock** | Stable crystal; avoid drift during TX | Jitter < 50 ppm class |
+| **Driver** | Kernel ALSA (`hw:` / `plughw:`) | Same |
+| **Isolation** | Transformer on radio side | Same + verified loopback |
+
+### Unsuitable interfaces
+
+- Onboard laptop mic/speaker without external interface
+- Bluetooth audio bridges
+- PulseAudio / PipeWire virtual devices
+- Consumer "USB sound sticks" without galvanic isolation
+
+Configure devices in `crdop.ini`:
+
+```ini
+[audio]
+backend = alsa-kernel
+no_pulse = yes
+capture = plughw:1,0
+playback = plughw:1,0
+sample_rate = 48000
+```
+
+Verify with:
+
+```bash
+max25-signal-sniffer --loopback
+max25-signal-sniffer -D plughw:1,0 -t 2.0
+```
+
+---
+
+## Compliance and operator responsibility
+
+| Topic | Policy |
+|-------|--------|
+| **Transmit licence** | Operator must hold valid authorization for the band and mode |
+| **CB (27 MHz EU)** | EN 300 433 / national rules — voice primary; data may be restricted or channel-specific |
+| **Amateur bands** | Band plan, power limits, identification |
+| **EMC** | Builder responsible for conducted/radiated emissions from interface hardware |
+| **CRDOP software** | GPLv3 — no warranty; see [LICENSE-USAGE.md](LICENSE-USAGE.md) |
+
+CRDOP documentation does **not** constitute legal advice. Check local regulations before on-air operation.
+
+---
+
+## Acceptance checklist (builder)
+
+| Step | Pass criterion |
+|------|----------------|
+| Loopback | `max25-signal-sniffer --loopback` decodes test UI |
+| Level | Mark/space tones within radio spec; no clipping |
+| Isolation | No hum on decode when PC and radio share mains |
+| PTT | Key before TX audio; clean tail; no truncation |
+| On-air | AX.25 UI exchange with known-good peer at 1200 baud |
+| Duplex | Half-duplex CSMA behaviour matches `persist` / `extra_delay` INI |
+
+---
+
+## Related in-repo docs
+
+| Topic | Document |
+|-------|----------|
+| Sound-card requirements | [SOUNDCARD-QUALIFICATION.md](SOUNDCARD-QUALIFICATION.md) |
+| Bell 202 / 1200 AFSK (P0) | [ROADMAP.md](../ROADMAP.md) · [SOFTMODEM.md](SOFTMODEM.md) |
+| G3RUH 9600–19200 (P1) | [G3RUH-DESIGN.md](G3RUH-DESIGN.md) |
+| AX.25 / packet context | [docs/PACKET-RADIO.md](../../../docs/PACKET-RADIO.md) |
+
+---
+
+## Related
+
+| Doc | Topic |
+|-----|--------|
+| [AUDIO-ARCHITECTURE.md](AUDIO-ARCHITECTURE.md) | Kernel ALSA, sound-proxy |
+| [MAX25-USAGE.md](MAX25-USAGE.md) | Stack integration and bench modes |
+| [ROADMAP.md](../ROADMAP.md) | P0/P1/P2 phases |
diff --git a/stacks/crdop/docs/HOST-PROTOCOL-SPEC.md b/stacks/crdop/docs/HOST-PROTOCOL-SPEC.md
new file mode 100644
index 0000000..d45c7e5
--- /dev/null
+++ b/stacks/crdop/docs/HOST-PROTOCOL-SPEC.md
@@ -0,0 +1,103 @@
+# M25 SoftModem host protocol — implementation spec (frozen for v1.0.0)
+
+**CRDOP** = **MAX25-SoftModem** · Native host wire for MAX25-SoftModem · **Not** ARDOP FEC/ARQ.
+
+**Normative code:** `stacks/crdop/lib/m25_host_protocol.py` · **Consumer:** `max25d` `CrdopTcpBackend`, `audio-dummyd`, `crdopc` launcher.
+
+---
+
+## Transport
+
+| Channel | Default port | Wire |
+|---------|--------------|------|
+| **Control** | **8515** | Line-oriented ASCII, **`\n`** terminated (native) |
+| **Data** | **8516** (= ctrl + 1) | Binary AX.25 UI body **without** HDLC flags or FCS |
+
+| Mode | Control terminator | Data semantics |
+|------|-------------------|----------------|
+| **Native M25/KISS** | `\n` | KISS DATA equivalent — 16+ byte UI body |
+
+### Bench alternate ports
+
+When `soft-crdop` and `audio-dummyd` run on one host, bench daemon may use **8520/8521** via CLI. Production `crdopc` and INI default **8515/8516**.
+
+---
+
+## Control commands (native)
+
+All commands are single lines. Reply is one line ending `\n`.
+
+| Command | Args | Reply | Behaviour |
+|---------|------|-------|-----------|
+| `INITIALIZE` | — | `OK` | Reset session state |
+| `PROTOCOLMODE` | `KISS` | `OK` | Select KISS-semantics data channel |
+| `MYCALL` | `CALL-SSID` | `OK` | Store station ID (uppercase) |
+| `LISTEN` | `TRUE`/`FALSE` | `OK` | RX enable (default true) |
+| `PING` | — | `OK` | Liveness |
+| `STATUS` | — | `STATUS ready mycall=…` | State snapshot |
+| *(unknown)* | — | `ERR unknown command` | |
+
+**Not supported on native path:** `PROTOCOLMODE FEC`, `FECMODE`, ARQ bandwidth commands — ARDOP is a separate optional plugin, not part of CRDOP.
+
+---
+
+## Data channel
+
+### TX (host → modem)
+
+1. TCP connect to data port.
+2. Send **one** AX.25 UI frame body: `dest(7) + src(7) + ctrl(1) + pid(1) + info(0..256)`.
+3. Modem responds `OK` or `ERR …` (ASCII line).
+
+Modem builds on-air: HDLC flags, bit-stuffing, frequency-toggle line code, AFSK PHY — see `acoustic_engine.encode_ax25_ui()`.
+
+### RX (modem → host)
+
+Native bench: optional `STATUS` lines on control channel. Production: `max25d` parses demodulated UI and displays `[CRDOP AX25 UI src>dst] text`.
+
+---
+
+## max25d integration
+
+```ini
+[devices]
+soft-crdop = crdop:default
+
+[device.soft-crdop]
+host = 127.0.0.1
+port = 8515
+listen = yes
+```
+
+`CrdopTcpBackend` on `open()`:
+
+1. TCP connect `host:port` (ctrl), `host:port+1` (data).
+2. Send `INITIALIZE`, `PROTOCOLMODE KISS`, `MYCALL …`, `LISTEN TRUE` (each `\n`).
+
+---
+
+## Layer separation
+
+| Layer | On data TCP | On air |
+|-------|-------------|--------|
+| AX.25 UI body | ✅ | Inside HDLC |
+| HDLC + CRC-16 | ❌ | ✅ |
+| Bell 202 AFSK | ❌ | ✅ |
+
+Same rule as KISS `0x00` DATA frames in `kiss_bridge.py`.
+
+---
+
+## Compliance tests
+
+| Test | Command |
+|------|---------|
+| Unit | `pytest stacks/daemon/test_crdop_backend.py` |
+| Bench host | `python3 stacks/crdop/tools/audio-dummyd.py --ctrl-port 8515 --data-port 8516` |
+| Loopback DSP | `pytest stacks/crdop/test_bell202_line_code.py` |
+
+---
+
+## Version
+
+Frozen for **MAX25-Stack v1.0.0** (dev track `CUR999`). Changes require bump in this file + `PROTOCOL.md` + `test_crdop_backend.py`.
diff --git a/stacks/crdop/docs/INDEX.md b/stacks/crdop/docs/INDEX.md
new file mode 100644
index 0000000..91a75b4
--- /dev/null
+++ b/stacks/crdop/docs/INDEX.md
@@ -0,0 +1,77 @@
+# CRDOP documentation index
+
+**CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`). Product: **MAX25-SoftModem** (`stacks/crdop/`). Version: MAX25-Stack **v1.0.0**; dev track `CUR999` in `$SRC/stacks/crdop/VERSION`.
+
+**Project rule (authoritative):** [docs/CRDOP.md](../../../docs/CRDOP.md)  
+**AI agent map:** [DEVELOPMENT.md](../../../docs/DEVELOPMENT.md) (repo root)
+
+---
+
+## Start here
+
+| Audience | Doc | One-line purpose |
+|----------|-----|------------------|
+| Everyone | [SOFTMODEM.md](SOFTMODEM.md) | What CRDOP is — baud scope, duplex, ALSA path |
+| MAX25 operator | [MAX25-USAGE.md](MAX25-USAGE.md) | Build, `max25d`, plugins, terminal, HyBBX attach |
+| Developer | [DEVELOPER.md](DEVELOPER.md) | Source tree, modules, tests, extending the modem |
+| Hardware builder | [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md) | Generic radio/audio interface specification |
+| Legal / distribution | [LICENSE-USAGE.md](LICENSE-USAGE.md) | GPLv3 — private and commercial use rights |
+
+## Implementation specs (v1.0.0)
+
+| Doc | One-line purpose |
+|-----|------------------|
+| [HOST-PROTOCOL-SPEC.md](HOST-PROTOCOL-SPEC.md) | **Frozen** M25/KISS TCP :8515/:8516 — normative host wire |
+| [ACOUSTIC-TEST-PROTOCOL.md](ACOUSTIC-TEST-PROTOCOL.md) | P0 bench acceptance matrix |
+| [FEC-SPEC.md](FEC-SPEC.md) | Duplex + FEC strategy — implementable parameters |
+| [SOUNDCARD-QUALIFICATION.md](SOUNDCARD-QUALIFICATION.md) | Interface qualification tests (class A/B/C) |
+| [G3RUH-DESIGN.md](G3RUH-DESIGN.md) | P1 — 9600–19200 direct FSK (DEV-Level 4) |
+
+---
+
+## Technical reference
+
+| Doc | One-line purpose |
+|-----|------------------|
+| [AUDIO-ARCHITECTURE.md](AUDIO-ARCHITECTURE.md) | Kernel ALSA only — sound-proxy, no PulseAudio |
+| [PROTOCOL.md](PROTOCOL.md) | M25 host summary — **normative:** [HOST-PROTOCOL-SPEC.md](HOST-PROTOCOL-SPEC.md) |
+| [CONFIG.md](CONFIG.md) | `crdop.ini` keys and launcher behaviour |
+| [BUILD.md](BUILD.md) | Standalone CMake build and cross-compile |
+| [EXAMPLES.md](EXAMPLES.md) | INI profiles, launcher, `max25d` snippets |
+| [CHANGELOG.md](CHANGELOG.md) | Release notes |
+
+---
+
+## Planning
+
+| Doc | One-line purpose |
+|-----|------------------|
+| [ROADMAP.md](../ROADMAP.md) | P0/P1/P2 modulation, RF paths, FEC, delivery milestones |
+
+---
+
+## Plugin registry
+
+| Id | Type | Role |
+|----|------|------|
+| `soft-crdop` | device | Production sound-card modem (`soft-modems` hardware) |
+| `audio-dummy` | device | Acoustic bench — loopback / ALSA / host (`acoustic-bench`) |
+| `soft-modems` | hardware | CRDOP device family |
+| `acoustic-bench` | hardware | Dev/test bench — no RF required |
+| `ardop-plugin` | optional | Third-party ARDOP host registry (separate from CRDOP) |
+
+---
+
+## Install tree (MAX25-Stack build)
+
+| Path | Contents |
+|------|----------|
+| `bin/crdop` | Launcher (`scripts/crdopc`) |
+| `bin/audio-dummyd` | M25 host + acoustic engine |
+| `bin/max25-signal-sniffer` | Bell 202 analysis tool |
+| `share/crdop/` | INI examples, `lib/*.py`, `VERSION` |
+| `share/hybbx/crdop-host.ini.example` | HyBBX Secondary attach |
+
+---
+
+*Compact index — depth in linked docs. Roadmap: [ROADMAP.md](../ROADMAP.md).*
diff --git a/stacks/crdop/docs/LICENSE-USAGE.md b/stacks/crdop/docs/LICENSE-USAGE.md
new file mode 100644
index 0000000..84ad5ff
--- /dev/null
+++ b/stacks/crdop/docs/LICENSE-USAGE.md
@@ -0,0 +1,116 @@
+# CRDOP license and usage rights
+
+**CRDOP** (MAX25-SoftModem) is **free software** under the **GNU General Public License version 3** (GPL-3.0-or-later).
+
+License files:
+
+| File | Scope |
+|------|-------|
+| [stacks/crdop/LICENSE](../LICENSE) | CRDOP subproject |
+| [LICENSE](../../../LICENSE) | MainAX25-Stack repository root |
+
+---
+
+## Summary (not legal advice)
+
+GPLv3 grants everyone — **private individuals and commercial entities** — the right to:
+
+| Right | Meaning |
+|-------|---------|
+| **Use** | Run CRDOP for any purpose (personal, club, business, government) |
+| **Study** | Read and learn from source code |
+| **Modify** | Change code to suit your needs |
+| **Distribute** | Share originals or modified versions |
+| **Commercial use** | Sell services, products, or support built on CRDOP |
+
+**Copyleft obligation:** When you **distribute** CRDOP (or a combined work based on it), you must:
+
+1. Provide **corresponding source** (or a written offer valid ≥ 3 years).
+2. License derivatives under **GPLv3** (or later, per "or later" clause).
+3. Preserve copyright notices and license text.
+4. Document changes if you modify files.
+5. Pass through patent retaliation and anti-tivoization terms as GPLv3 requires.
+
+**No warranty:** Software is provided **AS IS** — no implied fitness for a particular purpose.
+
+---
+
+## Private use
+
+| Scenario | Obligation |
+|----------|------------|
+| Run CRDOP on your own computer | None beyond GPLv3 acceptance |
+| Modify for personal use only | No distribution → no source-offer obligation |
+| Internal company use (no binary redistribution) | Same as private — no copyleft trigger until you distribute |
+
+---
+
+## Commercial use
+
+| Scenario | Obligation |
+|----------|------------|
+| Sell pre-built PCs with CRDOP installed | Provide source (or written offer) to recipients |
+| Ship hardware interface **with** CRDOP binaries | GPL applies to distributed software; hardware schematics you create separately may use another license if they are not a derivative of the GPL code |
+| SaaS / hosted service (no binary to users) | AGPL would impose network copyleft — **CRDOP is GPL, not AGPL**; consult counsel for your deployment model |
+| OEM integration in a product | Ensure GPL compliance for all distributed GPL components; document how users obtain source |
+
+**Practical path:** Include `LICENSE`, offer source at your support URL or ship `stacks/crdop/` tree, and state "based on CRDOP (GPLv3)".
+
+---
+
+## Combined works (MAX25-Stack)
+
+MAX25-Stack bundles CRDOP with daemon, terminal, and plugins. Distribution of the **combined stack** triggers GPLv3 obligations for the GPL-licensed portions. Other components may carry their own licenses — check root `LICENSE` and per-directory notices.
+
+| Component | Typical license |
+|-----------|-----------------|
+| `stacks/crdop/` | GPL-3.0-or-later |
+| MAX25 daemon / terminal | GPL-3.0-or-later (repository default) |
+
+---
+
+## What you may not do
+
+| Restriction | Reason |
+|-------------|--------|
+| Relicense CRDOP under proprietary terms | GPLv3 copyleft |
+| Remove copyright / license notices | GPLv3 §4 |
+| Imply warranty or liability from authors | GPLv3 §15–16 |
+| Distribute without source (when distributing binaries) | GPLv3 §6 |
+
+Patent suits against GPL users can terminate your license (GPLv3 §8).
+
+---
+
+## ARDOP-plugin (separate)
+
+**ARDOP-plugin** is an optional MAX25-Stack registry entry — **not** part of the CRDOP GPLv3 tree.
+
+| Item | Policy |
+|------|--------|
+| CRDOP coupling | **None** — third-party ARDOP host software |
+| Registry | [plugins/external/ardop/README.md](../../../plugins/external/ardop/README.md) |
+
+CRDOP GPLv3 obligations apply to **CRDOP code**, not to operator ARDOP host software.
+
+---
+
+## Contributor grants
+
+By contributing to `stacks/crdop/`, you agree that contributions are licensed under **GPL-3.0-or-later**, consistent with the repository [CONTRIBUTING.md](../../../CONTRIBUTING.md).
+
+---
+
+## Full license text
+
+- Online: <https://www.gnu.org/licenses/gpl-3.0.html>
+- In tree: [stacks/crdop/LICENSE](../LICENSE) · [LICENSE](../../../LICENSE)
+
+---
+
+## Related
+
+| Doc | Topic |
+|-----|--------|
+| [docs/CRDOP.md](../../../docs/CRDOP.md) | Project rule §5 License |
+| [INDEX.md](INDEX.md) | Documentation index |
diff --git a/stacks/crdop/docs/MAX25-USAGE.md b/stacks/crdop/docs/MAX25-USAGE.md
new file mode 100644
index 0000000..616093c
--- /dev/null
+++ b/stacks/crdop/docs/MAX25-USAGE.md
@@ -0,0 +1,292 @@
+# CRDOP in MAX25-Stack — usage guide
+
+Complete operator and integrator workflow for **MAX25-SoftModem (CRDOP)** inside MainAX25-Stack.
+
+**CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`). Project rule: [docs/CRDOP.md](../../../docs/CRDOP.md).
+
+**Versions:** MAX25-Stack **v1.0.0** · CRDOP dev track **CUR999** (`$SRC/stacks/crdop/VERSION`).
+
+**Dependency:** CRDOP sources are standalone-capable in principle, but **MAX25-Stack is required** for build, `max25d`, INI, operator tooling, and plugin registry until **CRDOP-v1.0.0** marks a mature standalone release.
+
+---
+
+## Quick start
+
+```bash
+# 1. Build (CRDOP ON by default)
+./scripts/build.sh
+
+# 2. Configure daemon
+sudo cp share/max25/max25d.ini.example /etc/max25/max25d.ini
+# Edit: enable soft-crdop block (see below)
+
+# 3. Start stack
+./scripts/max25-ctl start --hardware soft-modems --device soft-crdop
+
+# 4. Terminal session
+max25-terminal -U /run/max25/modem.sock
+# or TCP: max25-terminal -H 127.0.0.1 -P 7325
+```
+
+Inside terminal: `SET DEVICE soft-crdop` → `CONNECT` → `SEND …`
+
+---
+
+## Build and install
+
+### CMake options
+
+| Option | Default | Effect |
+|--------|---------|--------|
+| `MAX25_BUILD_CRDOP` | **ON** | Build/install CRDOP scaffold + tools |
+| `MAX25_BUILD_DAEMON` | ON | `max25d` with `CrdopTcpBackend` |
+| `MAX25_BUILD_TERMINAL` | ON | `max25-terminal` / `max25-client` |
+| `CRDOP_VENDOR_ARDOPCF` | OFF | Dev-only legacy ARDOP — **never** in releases |
+
+Disable CRDOP only when not needed:
+
+```bash
+cmake -B build -DMAX25_BUILD_CRDOP=OFF
+cmake --build build -j$(nproc)
+```
+
+### Install tree
+
+After `cmake --install` (or `./scripts/build.sh` + local prefix):
+
+| Path | Contents |
+|------|----------|
+| `bin/crdop` | Launcher — starts `audio-dummyd` with INI |
+| `bin/audio-dummyd` | M25 host TCP daemon + acoustic engine |
+| `bin/max25-signal-sniffer` | Bell 202 analysis |
+| `share/crdop/crdop.ini.example` | CB profile template |
+| `share/crdop/crdop-dual.ini.example` | CB ↔ amateur preset |
+| `share/crdop/crdop-amateur.ini.example` | Amateur secondary preset |
+| `share/crdop/lib/*.py` | DSP modules (installed for tooling) |
+| `share/crdop/VERSION` | `CUR999` |
+| `share/hybbx/crdop-host.ini.example` | HyBBX Secondary attach |
+| `share/clients/soft-crdop.yaml` | Terminal device profile |
+
+---
+
+## Plugin model
+
+| Plugin id | Type | Hardware family | Role |
+|-----------|------|-----------------|------|
+| `soft-crdop` | device | `soft-modems` | Production sound-card modem |
+| `audio-dummy` | device | `acoustic-bench` | Bench — loopback / ALSA / host |
+| `soft-modems` | hardware | — | CRDOP device family |
+| `acoustic-bench` | hardware | — | Dev/test without RF |
+
+Registry: `plugins/manifest.yaml`. Discovery:
+
+```bash
+./scripts/discover-plugins.sh --json | jq '.devices[] | select(.id|test("crdop|audio-dummy"))'
+```
+
+---
+
+## max25d configuration
+
+### Production path — `soft-crdop`
+
+```ini
+[daemon]
+hardware = soft-modems
+device = soft-crdop
+
+[devices]
+default = soft-crdop
+soft-crdop = crdop:default
+
+[device.soft-crdop]
+host = 127.0.0.1
+port = 8515
+listen = yes
+```
+
+`max25-ctl start` launches `crdop` (→ `audio-dummyd`) when `auto_start = yes` in `[stack]`.
+
+### Bench path — `audio-dummy`
+
+No RF; validates DSP loopback or ALSA capture:
+
+```ini
+[daemon]
+hardware = acoustic-bench
+device = audio-dummy
+
+[devices]
+default = audio-dummy
+audio-dummy = audio:loopback
+```
+
+Modes for `audio-dummy` spec:
+
+| Spec | Behaviour |
+|------|-----------|
+| `audio:loopback` | Internal DSP encode/decode |
+| `audio:alsa:plughw:N,M` | Sniff live ALSA capture |
+| `audio:host` | Attach to running `audio-dummyd` on :8515 |
+
+Start bench:
+
+```bash
+./scripts/max25-ctl start --hardware acoustic-bench --device audio-dummy
+max25-terminal -U /run/max25/modem.sock
+```
+
+### Sniffer (no daemon)
+
+```bash
+max25-signal-sniffer --loopback
+max25-signal-sniffer -D plughw:1,0 -t 3.0
+max25-signal-sniffer --mark    # 1200 Hz calibration tone
+max25-signal-sniffer --space   # 2200 Hz calibration tone
+```
+
+---
+
+## crdop.ini (modem side)
+
+Copy and edit:
+
+```bash
+mkdir -p ~/.config/crdop
+cp share/crdop/crdop.ini.example ~/.config/crdop/crdop.ini
+```
+
+Key sections — full reference: [CONFIG.md](CONFIG.md).
+
+```ini
+[profile]
+radio_profile = cb          ; cb | dual | amateur
+
+[modem]
+duplex = half               ; half | full
+arq_bandwidth = 500MAX
+
+[mycall]
+call = CB01-0
+
+[audio]
+backend = alsa-kernel
+no_pulse = yes
+capture = plughw:1,0
+playback = plughw:1,0
+
+[host]
+port = 8515
+```
+
+Launch:
+
+```bash
+CRDOP_INI=~/.config/crdop/crdop.ini ./scripts/crdopc
+# or after install:
+crdop
+```
+
+---
+
+## max25-terminal / M25/1
+
+CRDOP uses the same M25/1 session flow as other `max25d` device backends:
+
+```
+SET DEVICE soft-crdop
+CONNECT
+SEND Hello packet world
+```
+
+| Item | Value |
+|------|-------|
+| Daemon socket | `/run/max25/modem.sock` (Linux) |
+| Daemon TCP | `7325` (configurable in `max25d.ini`) |
+| Modem host TCP | `8515` ctrl, `8516` data (CRDOP native) |
+| Client profile | `share/clients/soft-crdop.yaml` |
+
+Protocol reference: [PROTOCOL.md](PROTOCOL.md) · [include/max25/protocol.md](../../../include/max25/protocol.md).
+
+When `ax25_ui = yes` in `max25d.ini`, terminal `SEND` lines encode as AX.25 UI frames.
+
+---
+
+## HyBBX attach
+
+HyBBX is **external** — attach after MAX25 stack is up.
+
+1. Start CRDOP path:
+
+   ```bash
+   ./scripts/max25-ctl start --hardware soft-modems --device soft-crdop
+   ```
+
+2. Merge `share/hybbx/crdop-host.ini.example` into HyBBX `hybbx.ini` on Secondary:
+
+   ```ini
+   [networks]
+   crdop = yes
+
+   [transport.crdop1]
+   enabled = yes
+   modem_host = 127.0.0.1
+   modem_port = 8515
+   mycall = CB-0
+   listen = yes
+   circuit_host = main.example.com
+   circuit_port = 7323
+   ```
+
+MAX25 owns modem lifecycle; HyBBX owns sessions. See [docs/HYBBX.md](../../../docs/HYBBX.md).
+
+---
+
+## Operator profiles
+
+| INI template | Profile | Use |
+|--------------|---------|-----|
+| `crdop.ini.example` | CB | Primary — K24/K25 class channels |
+| `crdop-dual.ini.example` | dual | CB ↔ amateur switching |
+| `crdop-amateur.ini.example` | amateur | Amateur secondary |
+
+```bash
+CRDOP_INI=share/crdop-dual.ini.example ./scripts/crdopc
+```
+
+---
+
+## Testing in MAX25-Stack
+
+```bash
+./scripts/test.sh                    # cmake --build build --target max25_test
+cmake --build build --target max25_daemon_smoke
+./scripts/release-check.sh           # install + policy checks
+```
+
+CRDOP-specific offline tests: `test_crdop_backend.py`, `test_audio_dummy_backend.py`, `test_bell202_line_code.py`.
+
+---
+
+## Troubleshooting
+
+| Symptom | Check |
+|---------|-------|
+| `crdopc not found` | Run `./scripts/build.sh`; launcher uses `audio-dummyd` from install or source tree |
+| No decode | `max25-signal-sniffer --loopback`; verify ALSA devices in INI |
+| PulseAudio hijack | `no_pulse = yes`; use `hw:` / `plughw:` explicitly |
+| Port conflict | Default :8515/:8516 — change `[host] port` + `[device.soft-crdop] port` |
+| Terminal no device | `SET DEVICE soft-crdop`; check `[devices]` in `max25d.ini` |
+
+---
+
+## Related
+
+| Doc | Topic |
+|-----|--------|
+| [INDEX.md](INDEX.md) | Full doc table |
+| [DEVELOPER.md](DEVELOPER.md) | Source, modules, extending |
+| [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md) | Radio interface spec |
+| [docs/PLUGINS-DEVICE-MODEL.md](../../../docs/PLUGINS-DEVICE-MODEL.md) | Unified device workflow |
+| [docs/LINUX-HOST-SETUP.md](../../../docs/LINUX-HOST-SETUP.md) | Host prerequisites |
+| [ROADMAP.md](../ROADMAP.md) | P0/P1/P2 milestones and modulation priorities |
diff --git a/stacks/crdop/docs/PROTOCOL.md b/stacks/crdop/docs/PROTOCOL.md
new file mode 100644
index 0000000..2d28bd4
--- /dev/null
+++ b/stacks/crdop/docs/PROTOCOL.md
@@ -0,0 +1,36 @@
+# Protocol
+
+Normative wire: **[HOST-PROTOCOL-SPEC.md](HOST-PROTOCOL-SPEC.md)** (frozen v1.0.0).
+
+CRDOP (**MAX25-SoftModem**) uses the **native MAX25 M25/KISS host protocol** on TCP :8515 (control) / :8516 (data).
+
+## Stack (default)
+
+```
+[Radio] ↔ [audio/ALSA] ↔ audio-dummyd / native modem ↔ TCP :8515 ctrl, :8516 data ↔ max25d
+```
+
+## Over-the-air
+
+AX.25-compatible AFSK tones (1200 baud primary, up to 19200 baud design range). See [SOFTMODEM.md](SOFTMODEM.md).
+
+## Host TCP (native M25)
+
+| Port | Role |
+|------|------|
+| 8515 | Control (line-oriented ASCII, `\n` terminated) |
+| 8516 | Data (AX.25 UI body without HDLC/FCS) |
+
+Common commands: `INITIALIZE` · `PROTOCOLMODE KISS` · `MYCALL` · `LISTEN` · `STATUS` · `PING`
+
+Implementation reference: `stacks/crdop/lib/m25_host_protocol.py`
+
+## CRDOP launch presets
+
+| Profile | Role |
+|---------|------|
+| `cb` | Default — CB / 500MAX class |
+| `dual` | CB ↔ amateur turnaround |
+| `amateur` | Amateur bandwidth class |
+
+Runtime overrides via host TCP or `crdop.ini` always apply.
diff --git a/stacks/crdop/docs/README.md b/stacks/crdop/docs/README.md
new file mode 100644
index 0000000..4a763a2
--- /dev/null
+++ b/stacks/crdop/docs/README.md
@@ -0,0 +1,31 @@
+# CRDOP documentation
+
+**CRDOP** = stack acronym for **MAX25-SoftModem** (device id `soft-crdop`).
+
+**MAX25-SoftModem** — in-house sound-card modem subproject (`stacks/crdop/`).
+
+## Entry point
+
+**[INDEX.md](INDEX.md)** — complete table of all CRDOP docs with one-line purpose.
+
+Project rule: [docs/CRDOP.md](../../../docs/CRDOP.md)
+
+## Policy
+
+| Rule | |
+|------|--|
+| Standard | Native MAX25 M25/KISS host on TCP :8515/:8516 |
+| Focus | CB-first; `dual` and `amateur` are presets |
+| Scope | Modem only — no host application |
+
+## Dev-only vendor tree
+
+Legacy **[pflarue/ardop](https://github.com/pflarue/ardop)** (ardopcf, MIT) may exist under `vendor/ardopcf/` for local dev builds (`-DCRDOP_VENDOR_ARDOPCF=ON`). **Never installed in MAX25 releases.**
+
+Pin: `a7c9228` · record: `vendor/ardopcf.ref`
+
+## Platforms (tested)
+
+Linux · FreeBSD — **tested** (GCC, Clang)
+
+Windows · macOS — build supported, **not yet tested**
diff --git a/stacks/crdop/docs/SOFTMODEM.md b/stacks/crdop/docs/SOFTMODEM.md
new file mode 100644
index 0000000..fef0a0e
--- /dev/null
+++ b/stacks/crdop/docs/SOFTMODEM.md
@@ -0,0 +1,127 @@
+# MAX25-SoftModem — product definition
+
+> **Authoritative rule:** [docs/CRDOP.md](../../../docs/CRDOP.md) · **Doc index:** [INDEX.md](INDEX.md)
+
+## Name and role
+
+- **Product:** MAX25-SoftModem (stack acronym **CRDOP**; plugin id `soft-crdop`)
+- **Stack version:** MAX25-Stack **v1.0.0** · **Dev track:** `CUR999` in `$SRC/stacks/crdop/VERSION`
+- **Stack:** MainAX25-Stack — **standard** component (built/installed unless `MAX25_BUILD_CRDOP=OFF`)
+- **Nature:** Pure MAX25 in-house development — in **development and test phase**, openly documented
+
+## Use like a hardware modem
+
+CRDOP uses the host **sound card IN and OUT** plus a **suitable radio** (or acoustic coupling to existing RF hardware). In `max25d` it registers like any other device backend — operators use the same M25/1 flow (`SET DEVICE`, `CONNECT`, `SEND`).
+
+```
+┌──────────┐   line or acoustic    ┌─────────────┐   TCP    ┌─────────┐
+│  Radio   │ ◄──────────────────► │ CRDOP/ALSA  │ ◄──────► │ max25d  │
+└──────────┘                      └─────────────┘          └─────────┘
+                                        │
+                                  1200–19200 baud
+                                  half or full duplex
+```
+
+### Acoustic AX.25 compatibility
+
+On the **acoustic / RF layer**, CRDOP targets **AX.25 Packet Radio** interoperability at the PHY level:
+
+- **1200 baud Bell 202 AFSK** (1200/2200 Hz) — standard VHF/UHF and CB packet class
+- **Half- and full-duplex** per radio and audio capability
+- **Acoustic or line-level** coupling — valid test and field configuration
+
+CRDOP is an **alternative modem** when the sound card is the RF interface. It does not replace an existing UART/KISS path when that path is already in use.
+
+Interface specification for builders: [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md). MAX25-Stack usage: [MAX25-USAGE.md](MAX25-USAGE.md).
+
+## Protocol stack
+
+| Layer | Policy |
+|-------|--------|
+| On-air / acoustic | AX.25-compatible AFSK tones (1200 baud primary) |
+| Host to max25d | MAX25-native TCP control + data (see [PROTOCOL.md](PROTOCOL.md)) |
+
+We study legacy stacks; we implement our own modem and document it for **reproducible hardware builds**.
+
+## Sound path — kernel ALSA only
+
+CRDOP does **not** use PulseAudio, PipeWire-as-default, or any desktop sound server.
+
+| Layer | Function |
+|-------|----------|
+| **MAX25 sound-proxy** | Sole shim between modem DSP and ALSA — buffers, timing, duplex, xrun recovery |
+| **libasound** | Direct `hw:` / `plughw:` opens |
+| **Kernel ALSA** | Driver + `/dev/snd/*` |
+| **Hardware** | Sound card → radio interface |
+
+Configure explicit devices in `crdop.ini` `[audio]` (`capture`, `playback`). See [AUDIO-ARCHITECTURE.md](AUDIO-ARCHITECTURE.md).
+
+## Baud scope
+
+| Priority | Range | Status |
+|----------|-------|--------|
+| **P0** | **1200 baud** Bell 202 AFSK | Primary — CB + VHF on-air |
+| **P1** | **9600–19200** G3RUH direct FSK | Planned after 1200 stable (VHF backbone) |
+| **P2** | **300** HF AFSK | Optional |
+| — | **>19200 baud** | **Not implemented** — do not configure or expect |
+
+Full modulation matrix, RF paths, band context, delivery milestones: **[ROADMAP.md](../ROADMAP.md)**.
+
+Higher baud rates demand **proportionally better** audio hardware (sample rate, jitter, SNR, isolation). G3RUH requires a **direct FSK radio path** — not the CB FM mic/speaker route.
+
+## Duplex
+
+| Mode | Status |
+|------|--------|
+| **Half-duplex** | Standard CB / packet-radio (PTT or VOX-style timing) |
+| **Full-duplex** | Supported when radio and audio hardware allow simultaneous TX/RX paths |
+
+Configure in `crdop.ini`: `[modem] duplex = half|full`.
+
+## Sound card — required (not optional)
+
+CRDOP must:
+
+1. **Generate** precise mark/space frequencies on **playback**.
+2. **Decode** those tones reliably on **capture**.
+
+Requirements **scale with baud**:
+
+| Baud class | Audio expectation |
+|------------|-------------------|
+| 1200 | Stable full-duplex or half-duplex USB codec or PCI interface; galvanic isolation to radio |
+| 9600–19200 | Low-jitter interface, adequate bandwidth, verified loopback before on-air |
+
+**Unsuitable:** onboard laptop mic/speaker shortcuts, anonymous USB “sound sticks”, Bluetooth bridges, unisolated consumer line inputs.
+
+Document your ALSA device in INI (`[audio] capture` / `playback`) and verify with loopback or sidetone before traffic.
+
+## Open hardware
+
+Documentation targets builders who want to **manufacture radio ↔ sound-card interfaces**:
+
+- Level matching (radio mic/speaker ↔ line level)
+- Galvanic isolation (transformers / opto)
+- PTT integration (GPIO, serial — VOX not recommended for packet)
+- Acoustic coupler fixtures for bench validation
+
+Generic interface specification: [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md). Delivery milestones: [ROADMAP.md](../ROADMAP.md).
+
+## Build / release (MAX25-Stack-v1.0.0)
+
+**CRDOP dev track:** `CUR999` in `$SRC/stacks/crdop/VERSION` (ships with MAX25-Stack v1.0.0).
+
+| Item | Shipped |
+|------|---------|
+| CRDOP scaffold (INI, launcher, install) | **Yes** — default CMake |
+| `max25d` `crdop-tcp` backend | **Yes** — offline-tested |
+| Native `crdopc` DSP binary | **In development** — in-house modem DSP |
+| ARDOP / ardopcf vendor tree | **Never** in release tarball |
+
+## HyBBX
+
+When CRDOP is active, HyBBX Secondary attaches via `share/hybbx/crdop-host.ini.example`. HyBBX remains an external project.
+
+## Testing phase
+
+Current work: loopback audio, acoustic bench validation, field on-air trials, acceptable sound-card criteria. Report results via project issues — RF acceptance remains manual until automated gates exist. Developer tests: [DEVELOPER.md](DEVELOPER.md).
diff --git a/stacks/crdop/docs/SOUNDCARD-QUALIFICATION.md b/stacks/crdop/docs/SOUNDCARD-QUALIFICATION.md
new file mode 100644
index 0000000..b35d55b
--- /dev/null
+++ b/stacks/crdop/docs/SOUNDCARD-QUALIFICATION.md
@@ -0,0 +1,95 @@
+# Sound card qualification — CRDOP / MAX25-SoftModem
+
+**Purpose:** Measurable criteria for interface hardware used with CRDOP. No product endorsements — class-based requirements.
+
+See also [ROADMAP.md](../ROADMAP.md) (P0/P1 audio requirements).
+
+---
+
+## Mandatory architecture
+
+```
+CRDOP DSP → sound_proxy → libasound (hw:) → codec → radio interface
+```
+
+| Forbidden in production path | Reason |
+|------------------------------|--------|
+| PulseAudio default route | Mixing, resampling, latency |
+| PipeWire default | Variable buffer |
+| Bluetooth A2DP/HFP | Codec + AGC |
+
+INI: `[audio] backend = alsa-kernel`, `no_pulse = yes`.
+
+---
+
+## Sample rate
+
+| Baud target | Minimum rate | CRDOP default |
+|-------------|--------------|---------------|
+| 1200 AFSK | 48000 Hz | **48000** |
+| 9600 G3RUH (audio tap) | 48000–96000 | 48000 + tuning |
+| 19200 | 96000 Hz | 96000 if hardware supports |
+
+---
+
+## Qualification tests
+
+Run on candidate interface **before** field deployment.
+
+| ID | Test | Pass |
+|----|------|------|
+| **Q1** | Loopback cable, 1200 Hz sine 2 s | THD acceptable by ear + FFT peak at 1200 ±2 Hz |
+| **Q2** | Loopback Bell 202 sniffer | `max25-signal-sniffer --loopback` or ALSA loop |
+| **Q3** | Mark/space calibration tones | `--mark` / `--space` tools within ±5 Hz |
+| **Q4** | 60 s full-duplex record+play | No xrun in `dmesg` / ALSA log |
+| **Q5** | Clock drift | 10 min loopback: no cumulative symbol slip at 1200 bd |
+
+---
+
+## Interface classes
+
+| Class | Isolation | 1200 AFSK | 19200 path |
+|-------|-----------|-----------|------------|
+| **A** | Galvanic line I/O, fixed gain | Required minimum | Test Q1–Q5 |
+| **B** | USB codec, headphone/mic level | Acceptable with level match | Not recommended |
+| **C** | Onboard mic/speaker only | Acoustic bench only | Fail |
+
+CRDOP production path: **Class A or B** with line-level radio interface — see [HARDWARE-INTERFACE.md](HARDWARE-INTERFACE.md).
+
+---
+
+## Level guidelines
+
+| Path | Typical level |
+|------|---------------|
+| Line OUT → radio mic in | 100–300 mV RMS (adjust pad) |
+| Radio speaker/line → Line IN | Attenuate to avoid clipping |
+| DC offset | AC coupling required |
+
+---
+
+## Baud scaling
+
+Requirements **rise faster than linear** above 1200 bd:
+
+| Baud | Clock jitter tolerance | Filter flatness |
+|------|------------------------|-----------------|
+| 1200 | moderate | 300–3000 Hz FM audio path OK |
+| 9600 | strict | 10 Hz–5 kHz flat, constant group delay |
+| 19200 | professional | Direct FSK tap — not soundcard mic path |
+
+---
+
+## Failure actions
+
+| Symptom | Action |
+|---------|--------|
+| xruns | Increase `period_frames`; reduce system load |
+| Wrong tones | Verify 48000 Hz; check resampler not inserted |
+| Intermittent decode | Replace Class C with A/B; check ground loop |
+
+---
+
+## Community list (planned)
+
+P0 bench exit: publish operator-submitted **class + Q1–Q2 result** table — no vendor ranking.
diff --git a/stacks/crdop/include/crdop/sound_proxy.h b/stacks/crdop/include/crdop/sound_proxy.h
new file mode 100644
index 0000000..ce0efcb
--- /dev/null
+++ b/stacks/crdop/include/crdop/sound_proxy.h
@@ -0,0 +1,52 @@
+/*
+ * MAX25 sound-proxy — CRDOP ↔ kernel ALSA (no PulseAudio).
+ *
+ * In-process shim between modem DSP and libasound. Only this layer opens
+ * snd_pcm capture/playback on hw:/plughw: devices. max25d does not touch audio.
+ *
+ * Eigenentwicklung — API stable for v1 scaffold; implementation in progress.
+ */
+#ifndef MAX25_CRDOP_SOUND_PROXY_H
+#define MAX25_CRDOP_SOUND_PROXY_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** ALSA backend policy — kernel path only; no PulseAudio/PipeWire route. */
+#define MAX25_SOUND_BACKEND_ALSA_KERNEL "alsa-kernel"
+
+typedef struct max25_sound_proxy max25_sound_proxy_t;
+
+typedef struct max25_sound_config {
+	const char *capture_device;  /* e.g. "hw:1,0" */
+	const char *playback_device; /* e.g. "hw:1,0" */
+	unsigned int sample_rate;    /* Hz — modem-dependent */
+	unsigned int period_frames;
+	unsigned int buffer_frames;
+	int full_duplex;             /* 0 = half, 1 = full */
+	int forbid_pulse;            /* non-zero: reject pulse/pipewire pseudo devices */
+} max25_sound_config_t;
+
+/** Open ALSA via kernel path; returns NULL on failure (pulse device rejected if forbid_pulse). */
+max25_sound_proxy_t *max25_sound_proxy_open(const max25_sound_config_t *cfg);
+
+void max25_sound_proxy_close(max25_sound_proxy_t *sp);
+
+/** Capture PCM frames (RX path). Returns frames read or negative errno-style code. */
+int max25_sound_proxy_read(max25_sound_proxy_t *sp, int16_t *buf, size_t frames);
+
+/** Playback PCM frames (TX path). Returns frames written or negative code. */
+int max25_sound_proxy_write(max25_sound_proxy_t *sp, const int16_t *buf, size_t frames);
+
+/** Recover from xrun — modem may call between frames. */
+int max25_sound_proxy_recover(max25_sound_proxy_t *sp);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MAX25_CRDOP_SOUND_PROXY_H */
diff --git a/stacks/crdop/include/crdop/version.h b/stacks/crdop/include/crdop/version.h
new file mode 100644
index 0000000..249ef32
--- /dev/null
+++ b/stacks/crdop/include/crdop/version.h
@@ -0,0 +1,8 @@
+#ifndef CRDOP_VERSION_H
+#define CRDOP_VERSION_H
+
+#define CRDOP_PRODUCT_NAME "CRDOP-CUR999"
+#define CRDOP_VERSION_STRING "CUR999"
+#define CRDOP_VENDOR_BASE "native"
+
+#endif
diff --git a/stacks/crdop/lib/__init__.py b/stacks/crdop/lib/__init__.py
new file mode 100644
index 0000000..2137436
--- /dev/null
+++ b/stacks/crdop/lib/__init__.py
@@ -0,0 +1 @@
+"""MAX25-SoftModem (CRDOP) — native DSP library (Bell 202 AFSK, HDLC, ALSA)."""
diff --git a/stacks/crdop/lib/acoustic_engine.py b/stacks/crdop/lib/acoustic_engine.py
new file mode 100644
index 0000000..47989ec
--- /dev/null
+++ b/stacks/crdop/lib/acoustic_engine.py
@@ -0,0 +1,89 @@
+"""
+Acoustic bench engine — modulate/demodulate/sniff without RF.
+
+Used by audio-dummy device and max25-signal-sniffer.
+"""
+from __future__ import annotations
+
+import sys
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Optional
+
+_LIB = Path(__file__).resolve().parent
+if str(_LIB) not in sys.path:
+    sys.path.insert(0, str(_LIB))
+
+from afsk_demodulator import AfskDemodulator  # noqa: E402
+from afsk_modulator import AfskModulator  # noqa: E402
+from bell202_line_code import TONE_MARK, TONE_SPACE  # noqa: E402
+from hdlc_codec import build_hdlc_frame, parse_hdlc_stream  # noqa: E402
+from sound_proxy import SoundConfig, create_sound_proxy  # noqa: E402
+
+_ROOT = Path(__file__).resolve().parents[3]
+_DAEMON = _ROOT / "stacks" / "daemon"
+if str(_DAEMON) not in sys.path:
+    sys.path.insert(0, str(_DAEMON))
+from ax25_codec import ax25_build_ui, ax25_parse_ui  # noqa: E402
+
+
+@dataclass
+class SniffReport:
+    samples: int = 0
+    symbols: int = 0
+    mark_ratio: float = 0.0
+    space_ratio: float = 0.0
+    transitions: int = 0
+    frames: list[bytes] = field(default_factory=list)
+    decode_lines: list[str] = field(default_factory=list)
+
+
+class AcousticEngine:
+    def __init__(
+        self,
+        sample_rate: int = 48000,
+        baud: int = 1200,
+        sound: Optional[SoundConfig] = None,
+    ) -> None:
+        self.sample_rate = sample_rate
+        self.baud = baud
+        self.mod = AfskModulator(sample_rate, baud)
+        self.demod = AfskDemodulator(sample_rate, baud)
+        self.sound = sound or SoundConfig(sample_rate=sample_rate)
+
+    def encode_ax25_ui(self, src: str, dst: str, text: str) -> bytes:
+        body = ax25_build_ui(src, dst, text.encode("utf-8"))
+        # strip FCS for KISS-style host body, then build on-air HDLC
+        if len(body) >= 2:
+            body = body[:-2]
+        hdlc = build_hdlc_frame(body)
+        return self.mod.modulate_bits(hdlc)
+
+    def analyze_pcm(self, pcm: bytes) -> SniffReport:
+        rep = SniffReport(samples=len(pcm) // 2)
+        tones = self.demod.demodulate_pcm(pcm)
+        rep.symbols = len(tones)
+        if not tones:
+            return rep
+        marks = sum(1 for t in tones if t == TONE_MARK)
+        rep.mark_ratio = marks / len(tones)
+        rep.space_ratio = 1.0 - rep.mark_ratio
+        rep.transitions = sum(1 for i in range(1, len(tones)) if tones[i] != tones[i - 1])
+        raw_bits = self.demod.demodulate_to_bits(pcm)
+        for frame in parse_hdlc_stream(raw_bits):
+            rep.frames.append(frame)
+            parsed = ax25_parse_ui(frame)
+            if parsed:
+                src, dst, info = parsed
+                rep.decode_lines.append(f"[AX25 UI {src}>{dst}] {info.decode('utf-8', errors='replace')}")
+        return rep
+
+    def loopback_self_test(self, src: str = "TST-0", dst: str = "QST") -> SniffReport:
+        pcm = self.encode_ax25_ui(src, dst, "LOOP")
+        return self.analyze_pcm(pcm)
+
+    def play_mark_calibration(self, seconds: float = 1.0) -> None:
+        create_sound_proxy(self.sound).play_pcm(self.mod.steady_tone(TONE_MARK, seconds))
+
+    def play_space_calibration(self, seconds: float = 1.0) -> None:
+        create_sound_proxy(self.sound).play_pcm(self.mod.steady_tone(TONE_SPACE, seconds))
diff --git a/stacks/crdop/lib/afsk_demodulator.py b/stacks/crdop/lib/afsk_demodulator.py
new file mode 100644
index 0000000..5ba3d8b
--- /dev/null
+++ b/stacks/crdop/lib/afsk_demodulator.py
@@ -0,0 +1,56 @@
+"""
+AFSK demodulator — Bell 202 mark/space discrimination per symbol period.
+
+Uses per-symbol Goertzel energy at 1200 Hz and 2200 Hz (Dire Wolf class approach).
+"""
+from __future__ import annotations
+
+import math
+import struct
+from array import array
+
+from bell202_line_code import TONE_MARK, TONE_SPACE, decode_tones_to_bits
+
+_TWO_PI = 2.0 * math.pi
+
+
+def _goertzel_power(samples: array, freq: float, sample_rate: int) -> float:
+    n = len(samples)
+    if n < 8:
+        return 0.0
+    k = int(0.5 + (n * freq) / sample_rate)
+    w = _TWO_PI * k / n
+    coeff = 2.0 * math.cos(w)
+    s0 = s1 = s2 = 0.0
+    for x in samples:
+        s0 = x + coeff * s1 - s2
+        s2 = s1
+        s1 = s0
+    return s1 * s1 + s2 * s2 - coeff * s1 * s2
+
+
+class AfskDemodulator:
+    def __init__(self, sample_rate: int = 48000, baud: int = 1200) -> None:
+        self.sample_rate = sample_rate
+        self.baud = baud
+        self.samples_per_symbol = sample_rate // baud
+
+    def demodulate_pcm(self, pcm: bytes) -> list[int]:
+        """Return mark/space tone sequence from mono S16_LE PCM."""
+        count = len(pcm) // 2
+        if count < self.samples_per_symbol:
+            return []
+        samples = array("h")
+        samples.frombytes(pcm[: count * 2])
+        tones: list[int] = []
+        pos = 0
+        while pos + self.samples_per_symbol <= len(samples):
+            window = samples[pos : pos + self.samples_per_symbol]
+            pos += self.samples_per_symbol
+            p_mark = _goertzel_power(window, 1200.0, self.sample_rate)
+            p_space = _goertzel_power(window, 2200.0, self.sample_rate)
+            tones.append(TONE_MARK if p_mark >= p_space else TONE_SPACE)
+        return tones
+
+    def demodulate_to_bits(self, pcm: bytes, start_tone: int = TONE_SPACE) -> bytes:
+        return decode_tones_to_bits(self.demodulate_pcm(pcm), start_tone=start_tone)
diff --git a/stacks/crdop/lib/afsk_modulator.py b/stacks/crdop/lib/afsk_modulator.py
new file mode 100644
index 0000000..1a6bf68
--- /dev/null
+++ b/stacks/crdop/lib/afsk_modulator.py
@@ -0,0 +1,51 @@
+"""
+Continuous-phase AFSK modulator — Bell 202 mark 1200 Hz / space 2200 Hz.
+"""
+from __future__ import annotations
+
+import math
+import struct
+from array import array
+
+from bell202_line_code import MARK_HZ, SPACE_HZ, TONE_MARK, encode_bits_to_tones
+
+_TWO_PI = 2.0 * math.pi
+
+
+class AfskModulator:
+  def __init__(self, sample_rate: int = 48000, baud: int = 1200) -> None:
+      self.sample_rate = sample_rate
+      self.baud = baud
+      self._phase = 0.0
+
+  def _tone_freq(self, tone: int) -> float:
+      return MARK_HZ if tone == TONE_MARK else SPACE_HZ
+
+  def modulate_bits(self, bits: bytes, start_tone: int = 0) -> bytes:
+      """Return mono S16_LE PCM for the given bit stream."""
+      tones = encode_bits_to_tones(bits, start_tone=start_tone)
+      samples_per_symbol = self.sample_rate // self.baud
+      out: array[int] = array("h")
+      for tone in tones:
+          freq = self._tone_freq(tone)
+          step = _TWO_PI * freq / self.sample_rate
+          for _ in range(samples_per_symbol):
+              sample = int(0.7 * 32767.0 * math.sin(self._phase))
+              out.append(sample)
+              self._phase += step
+              if self._phase >= _TWO_PI:
+                  self._phase -= _TWO_PI
+      return struct.pack(f"<{len(out)}h", *out)
+
+  def steady_tone(self, tone: int, duration_s: float) -> bytes:
+      """Calibration tone (Dire Wolf -x style mark/space hold)."""
+      n = int(self.sample_rate * duration_s)
+      freq = self._tone_freq(tone)
+      step = _TWO_PI * freq / self.sample_rate
+      out: array[int] = array("h")
+      for _ in range(n):
+          out.append(int(0.7 * 32767.0 * math.sin(self._phase)))
+          self._phase += step
+          if self._phase >= _TWO_PI:
+              self._phase -= _TWO_PI
+      return struct.pack(f"<{len(out)}h", *out)
diff --git a/stacks/crdop/lib/bell202_line_code.py b/stacks/crdop/lib/bell202_line_code.py
new file mode 100644
index 0000000..cd2621f
--- /dev/null
+++ b/stacks/crdop/lib/bell202_line_code.py
@@ -0,0 +1,50 @@
+"""
+Bell 202 frequency-toggle line code (1200 baud AFSK layer).
+
+On-air rule: bit 0 → toggle mark/space tone; bit 1 → hold current tone.
+We avoid the legacy term in API names — this is Bell 202 / amateur packet radio.
+"""
+from __future__ import annotations
+
+MARK_HZ = 1200.0
+SPACE_HZ = 2200.0
+BAUD_1200 = 1200
+
+TONE_MARK = 1
+TONE_SPACE = 0
+
+
+def encode_bits_to_tones(bits: bytes, start_tone: int = TONE_SPACE) -> list[int]:
+    """Map HDLC bit stream to mark/space tone sequence (one tone per bit)."""
+    tone = start_tone
+    out: list[int] = []
+    for byte in bits:
+        for bit_i in range(7, -1, -1):
+            bit = (byte >> bit_i) & 1
+            if bit == 0:
+                tone ^= 1
+            out.append(tone)
+    return out
+
+
+def decode_tones_to_bits(tones: list[int], start_tone: int = TONE_SPACE) -> bytes:
+    """Recover bit stream from mark/space tone sequence."""
+    if not tones:
+        return b""
+    prev = start_tone
+    bits: list[int] = []
+    for tone in tones:
+        if tone not in (TONE_MARK, TONE_SPACE):
+            continue
+        bits.append(0 if tone != prev else 1)
+        prev = tone
+    buf = bytearray()
+    for i in range(0, len(bits), 8):
+        chunk = bits[i : i + 8]
+        if len(chunk) < 8:
+            break
+        val = 0
+        for b in chunk:
+            val = (val << 1) | b
+        buf.append(val)
+    return bytes(buf)
diff --git a/stacks/crdop/lib/hdlc_codec.py b/stacks/crdop/lib/hdlc_codec.py
new file mode 100644
index 0000000..942168b
--- /dev/null
+++ b/stacks/crdop/lib/hdlc_codec.py
@@ -0,0 +1,110 @@
+"""
+HDLC framing for AX.25 — flags, bit-stuffing, CRC-16-CCITT.
+"""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+_ROOT = Path(__file__).resolve().parents[3]
+_DAEMON = _ROOT / "stacks" / "daemon"
+if str(_DAEMON) not in sys.path:
+    sys.path.insert(0, str(_DAEMON))
+
+from ax25_codec import ax25_crc  # noqa: E402
+
+HDLC_FLAG = 0x7E
+HDLC_ESCAPE = 0x7D
+HDLC_XOR = 0x20
+
+
+def bit_stuff(data: bytes) -> bytes:
+    out = bytearray()
+    ones = 0
+    for b in data:
+        for bit_i in range(7, -1, -1):
+            bit = (b >> bit_i) & 1
+            if bit:
+                ones += 1
+                out.append(1)
+                if ones == 5:
+                    out.append(0)
+                    ones = 0
+            else:
+                ones = 0
+                out.append(0)
+    # pack bits to bytes MSB-first
+    buf = bytearray()
+    acc = 0
+    n = 0
+    for bit in out:
+        acc = (acc << 1) | bit
+        n += 1
+        if n == 8:
+            buf.append(acc)
+            acc = 0
+            n = 0
+    if n:
+        buf.append(acc << (8 - n))
+    return bytes(buf)
+
+
+def bit_unstuff(data: bytes) -> bytes:
+    bits: list[int] = []
+    for b in data:
+        for bit_i in range(7, -1, -1):
+            bits.append((b >> bit_i) & 1)
+    out: list[int] = []
+    ones = 0
+    i = 0
+    while i < len(bits):
+        bit = bits[i]
+        if bit:
+            ones += 1
+            out.append(1)
+            if ones == 5 and i + 1 < len(bits) and bits[i + 1] == 0:
+                i += 1
+                ones = 0
+            elif ones == 6:
+                break
+        else:
+            ones = 0
+            out.append(0)
+        i += 1
+    buf = bytearray()
+    for j in range(0, len(out), 8):
+        chunk = out[j : j + 8]
+        if len(chunk) < 8:
+            break
+        val = 0
+        for bit in chunk:
+            val = (val << 1) | bit
+        buf.append(val)
+    return bytes(buf)
+
+
+def build_hdlc_frame(ax25_body: bytes) -> bytes:
+    """AX.25 body (no FCS) → on-air HDLC bit stream as bytes (pre tone encoding)."""
+    crc = ax25_crc(ax25_body)
+    payload = ax25_body + bytes((crc & 0xFF, crc >> 8))
+    stuffed = bit_stuff(payload)
+    return bytes([HDLC_FLAG]) + stuffed + bytes([HDLC_FLAG])
+
+
+def parse_hdlc_stream(raw_bits: bytes) -> list[bytes]:
+    """Extract AX.25 bodies (with FCS) from demodulated byte stream between flags."""
+    frames: list[bytes] = []
+    in_frame = False
+    cur = bytearray()
+    for b in raw_bits:
+        if b == HDLC_FLAG:
+            if in_frame and cur:
+                unstuffed = bit_unstuff(bytes(cur))
+                if len(unstuffed) >= 2:
+                    frames.append(unstuffed)
+            cur.clear()
+            in_frame = True
+            continue
+        if in_frame:
+            cur.append(b)
+    return frames
diff --git a/stacks/crdop/lib/m25_host_protocol.py b/stacks/crdop/lib/m25_host_protocol.py
new file mode 100644
index 0000000..9212336
--- /dev/null
+++ b/stacks/crdop/lib/m25_host_protocol.py
@@ -0,0 +1,142 @@
+"""
+MAX25 native host protocol for SoftModem / audio-dummy (design freeze).
+
+Payload on data channel = AX.25 UI body **without** HDLC/FCS (same as KISS DATA).
+Control channel = line-oriented ASCII commands (M25-family, not ARDOP FEC/ARQ).
+"""
+from __future__ import annotations
+
+import socket
+import threading
+from typing import Callable, Optional
+
+# KISS-compatible data semantics; control is text lines ending in \\n
+DEFAULT_CTRL_PORT = 8515
+DEFAULT_DATA_PORT = 8516
+
+CmdFn = Callable[[str], str]
+DataRxFn = Callable[[bytes], None]
+
+
+class M25SoftModemHost:
+    """Minimal TCP host for bench / audio-dummy (ctrl + data ports)."""
+
+    def __init__(
+        self,
+        ctrl_port: int = DEFAULT_CTRL_PORT,
+        data_port: int = DEFAULT_DATA_PORT,
+        on_data_tx: Optional[Callable[[bytes], str]] = None,
+    ) -> None:
+        self.ctrl_port = ctrl_port
+        self.data_port = data_port
+        self._on_data_tx = on_data_tx or (lambda _b: "OK")
+        self._stop = threading.Event()
+        self._ctrl_srv: Optional[socket.socket] = None
+        self._data_srv: Optional[socket.socket] = None
+        self._threads: list[threading.Thread] = []
+        self._mycall = "NOCALL-0"
+        self._listen = True
+
+    def start(self) -> None:
+        self._ctrl_srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._ctrl_srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self._ctrl_srv.bind(("127.0.0.1", self.ctrl_port))
+        self._ctrl_srv.listen(4)
+        self._data_srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._data_srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self._data_srv.bind(("127.0.0.1", self.data_port))
+        self._data_srv.listen(4)
+        self._stop.clear()
+        for target, name in ((self._accept_ctrl, "ctrl"), (self._accept_data, "data")):
+            t = threading.Thread(target=target, name=f"m25-host-{name}", daemon=True)
+            t.start()
+            self._threads.append(t)
+
+    def stop(self) -> None:
+        self._stop.set()
+        for srv in (self._ctrl_srv, self._data_srv):
+            if srv is not None:
+                try:
+                    srv.close()
+                except OSError:
+                    pass
+        self._ctrl_srv = None
+        self._data_srv = None
+
+    def _accept_ctrl(self) -> None:
+        assert self._ctrl_srv is not None
+        while not self._stop.is_set():
+            try:
+                self._ctrl_srv.settimeout(0.5)
+                conn, _ = self._ctrl_srv.accept()
+            except (OSError, socket.timeout):
+                continue
+            threading.Thread(
+                target=self._ctrl_session,
+                args=(conn,),
+                daemon=True,
+            ).start()
+
+    def _ctrl_session(self, conn: socket.socket) -> None:
+        buf = b""
+        try:
+            conn.settimeout(0.5)
+            while not self._stop.is_set():
+                try:
+                    chunk = conn.recv(4096)
+                except socket.timeout:
+                    continue
+                if not chunk:
+                    break
+                buf += chunk
+                while b"\n" in buf:
+                    raw, buf = buf.split(b"\n", 1)
+                    line = raw.decode("ascii", errors="replace").strip()
+                    if not line:
+                        continue
+                    reply = self._handle_cmd(line)
+                    conn.sendall((reply + "\n").encode("ascii"))
+        finally:
+            conn.close()
+
+    def _handle_cmd(self, line: str) -> str:
+        parts = line.split()
+        cmd = parts[0].upper() if parts else ""
+        if cmd == "INITIALIZE":
+            return "OK"
+        if cmd == "PROTOCOLMODE" and len(parts) > 1 and parts[1].upper() == "KISS":
+            return "OK"
+        if cmd == "MYCALL" and len(parts) > 1:
+            self._mycall = parts[1].upper()
+            return "OK"
+        if cmd == "LISTEN":
+            self._listen = len(parts) < 2 or parts[1].upper() in ("TRUE", "1", "ON", "YES")
+            return "OK"
+        if cmd == "PING":
+            return "OK"
+        if cmd == "STATUS":
+            return f"STATUS ready mycall={self._mycall}"
+        return "ERR unknown command"
+
+    def _accept_data(self) -> None:
+        assert self._data_srv is not None
+        while not self._stop.is_set():
+            try:
+                self._data_srv.settimeout(0.5)
+                conn, _ = self._data_srv.accept()
+            except (OSError, socket.timeout):
+                continue
+            threading.Thread(
+                target=self._data_session,
+                args=(conn,),
+                daemon=True,
+            ).start()
+
+    def _data_session(self, conn: socket.socket) -> None:
+        try:
+            payload = conn.recv(4096)
+            if payload:
+                reply = self._on_data_tx(payload)
+                conn.sendall(reply.encode("ascii", errors="replace"))
+        finally:
+            conn.close()
diff --git a/stacks/crdop/lib/sound_proxy.py b/stacks/crdop/lib/sound_proxy.py
new file mode 100644
index 0000000..de9b71d
--- /dev/null
+++ b/stacks/crdop/lib/sound_proxy.py
@@ -0,0 +1,185 @@
+"""
+MAX25 sound-proxy — host audio capture/playback.
+
+Linux/KLinux: ALSA (arecord/aplay).
+FreeBSD: OSS via sound_proxy_oss (sox or /dev/dsp).
+"""
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+import sys
+import threading
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Callable, Optional, Protocol, runtime_checkable
+
+
+@dataclass
+class SoundConfig:
+    capture: str = "default"
+    playback: str = "default"
+    sample_rate: int = 48000
+    channels: int = 1
+    period_frames: int = 256
+    forbid_pulse: bool = True
+    backend: str = ""  # alsa | oss — empty = auto from platform
+
+
+@runtime_checkable
+class SoundProxyProto(Protocol):
+    def start_capture(self) -> None: ...
+    def read_capture(self, nbytes: int) -> bytes: ...
+    def play_pcm(self, pcm: bytes) -> None: ...
+    def sniff_loop(
+        self,
+        chunk_symbols: int,
+        on_pcm: Callable[[bytes], None],
+        stop: Optional[threading.Event] = None,
+    ) -> None: ...
+    def close(self) -> None: ...
+
+
+def _detect_backend(cfg: SoundConfig) -> str:
+    explicit = (cfg.backend or os.environ.get("MAX25_AUDIO_BACKEND", "")).strip().lower()
+    if explicit in ("alsa", "oss"):
+        return explicit
+    if sys.platform.startswith("freebsd"):
+        return "oss"
+    return "alsa"
+
+
+def create_sound_proxy(cfg: SoundConfig) -> SoundProxyProto:
+    backend = _detect_backend(cfg)
+    if backend == "oss":
+        from sound_proxy_oss import OssSoundConfig, OssSoundProxy
+
+        cap = cfg.capture if cfg.capture not in ("", "default") else "/dev/dsp"
+        pb = cfg.playback if cfg.playback not in ("", "default") else cap
+        return OssSoundProxy(
+            OssSoundConfig(
+                capture=cap,
+                playback=pb,
+                sample_rate=cfg.sample_rate,
+                channels=cfg.channels,
+            )
+        )
+    return AlsaSoundProxy(cfg)
+
+
+class AlsaSoundProxy:
+    def __init__(self, cfg: SoundConfig) -> None:
+        self.cfg = cfg
+        self._rec_proc: Optional[subprocess.Popen[bytes]] = None
+        self._play_proc: Optional[subprocess.Popen[bytes]] = None
+        self._stop = threading.Event()
+
+    def _alsa_env(self) -> dict[str, str]:
+        env = os.environ.copy()
+        if self.cfg.forbid_pulse:
+            env.pop("PULSE_SERVER", None)
+            env.pop("PIPEWIRE_RUNTIME_DIR", None)
+            env["PULSE_SERVER"] = ""
+        return env
+
+    @staticmethod
+    def _check_device(name: str) -> None:
+        low = name.lower()
+        if low in ("default", "pulse", "pipewire") or "pulse" in low or "pipewire" in low:
+            raise ValueError(
+                f"audio device {name!r} not allowed — use hw: or plughw: (kernel ALSA)"
+            )
+
+    def start_capture(self) -> None:
+        if not shutil.which("arecord"):
+            raise RuntimeError("arecord not found — install alsa-utils")
+        self._check_device(self.cfg.capture)
+        cmd = [
+            "arecord",
+            "-q",
+            "-D",
+            self.cfg.capture,
+            "-f",
+            "S16_LE",
+            "-r",
+            str(self.cfg.sample_rate),
+            "-c",
+            str(self.cfg.channels),
+            "-t",
+            "raw",
+        ]
+        self._rec_proc = subprocess.Popen(
+            cmd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.DEVNULL,
+            env=self._alsa_env(),
+        )
+
+    def read_capture(self, nbytes: int) -> bytes:
+        if self._rec_proc is None or self._rec_proc.stdout is None:
+            return b""
+        return self._rec_proc.stdout.read(nbytes) or b""
+
+    def play_pcm(self, pcm: bytes) -> None:
+        if not pcm:
+            return
+        if not shutil.which("aplay"):
+            raise RuntimeError("aplay not found — install alsa-utils")
+        self._check_device(self.cfg.playback)
+        cmd = [
+            "aplay",
+            "-q",
+            "-D",
+            self.cfg.playback,
+            "-f",
+            "S16_LE",
+            "-r",
+            str(self.cfg.sample_rate),
+            "-c",
+            str(self.cfg.channels),
+            "-t",
+            "raw",
+        ]
+        subprocess.run(
+            cmd,
+            input=pcm,
+            check=False,
+            env=self._alsa_env(),
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
+
+    def sniff_loop(
+        self,
+        chunk_symbols: int,
+        on_pcm: Callable[[bytes], None],
+        stop: Optional[threading.Event] = None,
+    ) -> None:
+        stop_ev = stop or self._stop
+        frame_bytes = (self.cfg.sample_rate // 1200) * 2 * chunk_symbols
+        self.start_capture()
+        try:
+            while not stop_ev.is_set():
+                chunk = self.read_capture(frame_bytes)
+                if not chunk:
+                    break
+                on_pcm(chunk)
+        finally:
+            self.close()
+
+    def close(self) -> None:
+        self._stop.set()
+        for proc in (self._rec_proc, self._play_proc):
+            if proc is not None and proc.poll() is None:
+                proc.terminate()
+                try:
+                    proc.wait(timeout=1.0)
+                except subprocess.TimeoutExpired:
+                    proc.kill()
+        self._rec_proc = None
+        self._play_proc = None
+
+
+# Backward-compatible alias
+SoundProxy = AlsaSoundProxy
diff --git a/stacks/crdop/lib/sound_proxy_oss.py b/stacks/crdop/lib/sound_proxy_oss.py
new file mode 100644
index 0000000..66cf765
--- /dev/null
+++ b/stacks/crdop/lib/sound_proxy_oss.py
@@ -0,0 +1,151 @@
+"""
+MAX25 sound-proxy — FreeBSD/OSS capture and playback.
+
+Uses `sox` with OSS devices when available; falls back to raw /dev/dsp read/write.
+"""
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+import threading
+from dataclasses import dataclass
+from typing import Callable, Optional
+
+
+@dataclass
+class OssSoundConfig:
+    capture: str = "/dev/dsp"
+    playback: str = "/dev/dsp"
+    sample_rate: int = 48000
+    channels: int = 1
+
+
+class OssSoundProxy:
+    def __init__(self, cfg: OssSoundConfig) -> None:
+        self.cfg = cfg
+        self._rec_proc: Optional[subprocess.Popen[bytes]] = None
+        self._dsp_fd: Optional[int] = None
+        self._stop = threading.Event()
+        self._use_sox = shutil.which("sox") is not None
+
+    def _sox_capture_cmd(self) -> list[str]:
+        dev = self.cfg.capture
+        return [
+            "sox",
+            "-q",
+            "-t",
+            "oss",
+            dev,
+            "-r",
+            str(self.cfg.sample_rate),
+            "-c",
+            str(self.cfg.channels),
+            "-b",
+            "16",
+            "-e",
+            "signed-integer",
+            "-t",
+            "raw",
+            "-",
+        ]
+
+    def _sox_play_cmd(self) -> list[str]:
+        dev = self.cfg.playback
+        return [
+            "sox",
+            "-q",
+            "-t",
+            "raw",
+            "-r",
+            str(self.cfg.sample_rate),
+            "-c",
+            str(self.cfg.channels),
+            "-b",
+            "16",
+            "-e",
+            "signed-integer",
+            "-",
+            "-t",
+            "oss",
+            dev,
+        ]
+
+    def start_capture(self) -> None:
+        if self._use_sox:
+            self._rec_proc = subprocess.Popen(
+                self._sox_capture_cmd(),
+                stdout=subprocess.PIPE,
+                stderr=subprocess.DEVNULL,
+            )
+            return
+        flags = os.O_RDONLY
+        try:
+            self._dsp_fd = os.open(self.cfg.capture, flags)
+        except OSError as exc:
+            raise RuntimeError(f"OSS open {self.cfg.capture}: {exc}") from exc
+
+    def read_capture(self, nbytes: int) -> bytes:
+        if self._rec_proc is not None and self._rec_proc.stdout is not None:
+            return self._rec_proc.stdout.read(nbytes) or b""
+        if self._dsp_fd is not None:
+            try:
+                return os.read(self._dsp_fd, nbytes) or b""
+            except OSError:
+                return b""
+        return b""
+
+    def play_pcm(self, pcm: bytes) -> None:
+        if not pcm:
+            return
+        if self._use_sox:
+            subprocess.run(
+                self._sox_play_cmd(),
+                input=pcm,
+                check=False,
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+            )
+            return
+        try:
+            fd = os.open(self.cfg.playback, os.O_WRONLY)
+        except OSError:
+            return
+        try:
+            os.write(fd, pcm)
+        finally:
+            os.close(fd)
+
+    def sniff_loop(
+        self,
+        chunk_symbols: int,
+        on_pcm: Callable[[bytes], None],
+        stop: Optional[threading.Event] = None,
+    ) -> None:
+        stop_ev = stop or self._stop
+        frame_bytes = max(256, (self.cfg.sample_rate // 1200) * 2 * chunk_symbols)
+        self.start_capture()
+        try:
+            while not stop_ev.is_set():
+                chunk = self.read_capture(frame_bytes)
+                if not chunk:
+                    break
+                on_pcm(chunk)
+        finally:
+            self.close()
+
+    def close(self) -> None:
+        self._stop.set()
+        if self._rec_proc is not None and self._rec_proc.poll() is None:
+            self._rec_proc.terminate()
+            try:
+                self._rec_proc.wait(timeout=1.0)
+            except subprocess.TimeoutExpired:
+                self._rec_proc.kill()
+        self._rec_proc = None
+        if self._dsp_fd is not None:
+            try:
+                os.close(self._dsp_fd)
+            except OSError:
+                pass
+            self._dsp_fd = None
diff --git a/stacks/crdop/lib/test_bell202_line_code.py b/stacks/crdop/lib/test_bell202_line_code.py
new file mode 100644
index 0000000..3b22af6
--- /dev/null
+++ b/stacks/crdop/lib/test_bell202_line_code.py
@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+"""Unit tests for Bell 202 frequency-toggle line code."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+LIB = Path(__file__).resolve().parent
+sys.path.insert(0, str(LIB))
+
+from bell202_line_code import decode_tones_to_bits, encode_bits_to_tones  # noqa: E402
+
+
+def test_roundtrip_single_byte() -> None:
+    bits = bytes([0x55])  # 01010101 → many toggles
+    tones = encode_bits_to_tones(bits, start_tone=0)
+    back = decode_tones_to_bits(tones, start_tone=0)
+    assert back == bits
+
+
+def test_all_ones_no_toggle() -> None:
+    tones = encode_bits_to_tones(bytes([0xFF]), start_tone=0)
+    assert len(set(tones)) == 1
+
+
+def main() -> int:
+    test_roundtrip_single_byte()
+    test_all_ones_no_toggle()
+    print("OK: bell202_line_code tests")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/stacks/crdop/patches/ardopcf/0001-crdop-linux-gcc-branding.patch b/stacks/crdop/patches/ardopcf/0001-crdop-linux-gcc-branding.patch
new file mode 100644
index 0000000..9b37183
--- /dev/null
+++ b/stacks/crdop/patches/ardopcf/0001-crdop-linux-gcc-branding.patch
@@ -0,0 +1,186 @@
+From: CRDOP <dev@ngteq.local>
+Subject: [PATCH] CRDOP: Linux/GCC build fixes and crdopc branding
+
+Build fixes for GCC 15 (prototypes, ws_server, rawhid fd cast).
+Product identity crdopc / 0.1.0-l2-cb; MIT attribution for ngteq changes.
+---
+ lib/rawhid/rawhid.c        | 8 ++++----
+ lib/ws_server/ws_server.c  | 2 +-
+ src/common/ARDOPC.c        | 4 ++--
+ src/common/ARDOPC.h        | 2 +-
+ src/common/ARDOPCommon.c   | 5 +++--
+ src/common/ARQ.c           | 4 ++--
+ src/common/HostInterface.c | 2 +-
+ src/common/ardopcommon.h   | 2 +-
+ src/common/version.h       | 2 +-
+ src/linux/ALSASound.c      | 4 ++--
+ 10 files changed, 18 insertions(+), 17 deletions(-)
+
+diff --git a/lib/rawhid/rawhid.c b/lib/rawhid/rawhid.c
+index 8791788..256641f 100644
+--- a/lib/rawhid/rawhid.c
++++ b/lib/rawhid/rawhid.c
+@@ -358,7 +358,7 @@ int HID_Read_Block()
+ #ifdef WIN32
+ 	Len = rawhid_recv(0, Msg, 64, 100);
+ #else
+-	Len = read(CM108Handle, Msg, 64);
++	Len = read((int)(intptr_t)CM108Handle, Msg, 64);
+ #endif
+ 
+ 	if (Len <= 0)
+@@ -403,7 +403,7 @@ int HID_Write_Block()
+ #ifdef WIN32
+ 		ret = rawhid_send(0, Msg, 64, 100);		// Always send 64
+ 
+-		if (ret < 0)
++		if (ret != 64)
+ 		{
+ 			ZF_LOGE("Rigcontrol HID Write Failed %d", errno);
+ 			rawhid_close(0);
+@@ -411,12 +411,12 @@ int HID_Write_Block()
+ 			return 0;
+ 		}
+ #else
+-		ret = write(CM108Handle, Msg, 64);
++		ret = write((int)(intptr_t)CM108Handle, Msg, 64);
+ 
+ 		if (ret != 64)
+ 		{
+ 			printf ("Write to %s failed, n=%d, errno=%d\n", HIDDevice, ret, errno);
+-			close (CM108Handle);
++			close((int)(intptr_t)CM108Handle);
+ 			CM108Handle = 0;
+ 			return 0;
+ 		}
+diff --git a/lib/ws_server/ws_server.c b/lib/ws_server/ws_server.c
+index a542627..e8db176 100644
+--- a/lib/ws_server/ws_server.c
++++ b/lib/ws_server/ws_server.c
+@@ -1139,7 +1139,7 @@ int client_handler(char *data, int data_size)
+ 	int data_len;
+ 	int opcode;
+ 	if (state[cnum] == WS_HTTP)
+-		return process_http_req(cnum);
++		return process_http_req();
+ 
+ 	if ((data_len = read_websocket_frame(data, data_size, &opcode)) < 0)
+ 		return (-1);
+diff --git a/src/common/ARDOPC.c b/src/common/ARDOPC.c
+index dc69a06..34e3f59 100644
+--- a/src/common/ARDOPC.c
++++ b/src/common/ARDOPC.c
+@@ -2,7 +2,7 @@
+ //
+ 
+ // ardopcf is a fork by pflarue of ardopc by John Wiseman
+-const char ProductName[] = "ardopcf";
++/* ProductName: CRDOP src/crdop_version.c */
+ 
+ // Version k  Fix conflicting definitions of bytDataToSend
+ // Version m  Add CM108 PTT (Sept 2021)
+@@ -56,7 +56,7 @@ BOOL SerialHostInit();
+ void SerialHostPoll();
+ void TCPHostPoll();
+ BOOL MainPoll();
+-void PlatformSleep();
++void PlatformSleep(int mS);
+ const char* PlatformSignalAbbreviation(int signal);
+ BOOL BusyDetect2(float * dblMag, int intStart, int intStop);
+ BOOL IsPingToMe(const StationId* caller, const StationId* target);
+diff --git a/src/common/ARDOPC.h b/src/common/ARDOPC.h
+index da2deb3..bdb8c5e 100644
+--- a/src/common/ARDOPC.h
++++ b/src/common/ARDOPC.h
+@@ -176,7 +176,7 @@ void SendReplyToHost(char * strText);
+ void TCPSendReplyToHost(char * strText);
+ void LogStats();
+ int GetNextFrameData(int * intUpDn, UCHAR * bytFrameTypeToSend, UCHAR * strMod, BOOL blnInitialize);
+-void SendData();
++void SendData(void);
+ int ComputeInterFrameInterval(int intRequestedIntervalMS);
+ int Encode4FSKControl(UCHAR bytFrameType, UCHAR bytSessionID, UCHAR * bytreturn);
+ int EncodeConACKwTiming(UCHAR bytFrameType, int intRcvdLeaderLenMs, UCHAR bytSessionID, UCHAR * bytreturn);
+diff --git a/src/common/ARDOPCommon.c b/src/common/ARDOPCommon.c
+index c6c068c..85db9cf 100644
+--- a/src/common/ARDOPCommon.c
++++ b/src/common/ARDOPCommon.c
+@@ -184,10 +184,11 @@ void processargs(int argc, char * argv[])
+ 		{
+ 		case 'h':
+ 
+-			printf("%s Version %s (https://www.github.com/pflarue/ardop)\n", ProductName, ProductVersion);
++			printf("%s Version %s (https://github.com/ngteq/CRDOP)\n", ProductName, ProductVersion);
+ 			printf("Copyright (c) 2014-2024 Rick Muething, John Wiseman, Peter LaRue\n");
++			printf("CRDOPC modifications Copyright (c) 2026 ngteq (MIT)\n");
+ 			printf(
+-				"See https://github.com/pflarue/ardop/blob/master/LICENSE for licence details including\n"
++				"See https://github.com/ngteq/CRDOP/blob/main/NOTICE.md and https://github.com/pflarue/ardop/blob/master/LICENSE for licence details including\n"
+ 				"  information about authors of external libraries used and their licenses.\n"
+ 			);
+ 			printf(HelpScreen, ProductName);
+diff --git a/src/common/ARQ.c b/src/common/ARQ.c
+index 1b44fa7..b67c1d3 100644
+--- a/src/common/ARQ.c
++++ b/src/common/ARQ.c
+@@ -822,7 +822,7 @@ int GetNumCarriers(UCHAR bytFrameType)
+ 
+ // Function to determine the next data frame to send (or IDLE if none)
+ 
+-void SendData()
++void SendData(void)
+ {
+ 	char strMod[16];
+ 	int Len;
+@@ -1772,7 +1772,7 @@ void ProcessRcvdARQFrame(UCHAR intFrameType, UCHAR * bytData, int DataLen, BOOL
+ 
+ 				SetARDOPProtocolState(ISS);
+ 				ARQState = ISSData;
+-				SendData(FALSE);
++				SendData();
+ 				return;
+ 			}
+ 			// In an active ARQ Connection, only send an IDFrame when ProtocolState
+diff --git a/src/common/HostInterface.c b/src/common/HostInterface.c
+index 0ba4eca..e4e6ddd 100644
+--- a/src/common/HostInterface.c
++++ b/src/common/HostInterface.c
+@@ -7,7 +7,7 @@
+ BOOL blnHostRDY = FALSE;
+ extern int intFECFramesSent;
+ 
+-void SendData();
++void SendData(void);
+ BOOL CheckForDisconnect();
+ int Encode4FSKControl(UCHAR bytFrameType, UCHAR bytSessionID, UCHAR * bytreturn);
+ int ComputeInterFrameInterval(int intRequestedIntervalMS);
+diff --git a/src/common/ardopcommon.h b/src/common/ardopcommon.h
+index 91cf281..1a334eb 100644
+--- a/src/common/ardopcommon.h
++++ b/src/common/ardopcommon.h
+@@ -165,7 +165,7 @@ void SendReplyToHost(char * strText);
+ void TCPSendReplyToHost(char * strText);
+ void LogStats();
+ int GetNextFrameData(int * intUpDn, UCHAR * bytFrameTypeToSend, UCHAR * strMod, BOOL blnInitialize);
+-void SendData();
++void SendData(void);
+ int ComputeInterFrameInterval(int intRequestedIntervalMS);
+ int Encode4FSKControl(UCHAR bytFrameType, UCHAR bytSessionID, UCHAR * bytreturn);
+ VOID WriteExceptionLog(const char * format, ...);
+diff --git a/src/linux/ALSASound.c b/src/linux/ALSASound.c
+index 4938b47..d15dbcc 100644
+--- a/src/linux/ALSASound.c
++++ b/src/linux/ALSASound.c
+@@ -404,10 +404,10 @@ int platform_main(int argc, char * argv[])
+ 
+ 	setlinebuf(stdout);  // So we can redirect output to file and tail
+ 
+-	ZF_LOGI("%s Version %s (https://www.github.com/pflarue/ardop)", ProductName, ProductVersion);
++	ZF_LOGI("%s Version %s (https://github.com/ngteq/CRDOP)", ProductName, ProductVersion);
+ 	ZF_LOGI("Copyright (c) 2014-2024 Rick Muething, John Wiseman, Peter LaRue");
+ 	ZF_LOGI(
+-		"See https://github.com/pflarue/ardop/blob/master/LICENSE for licence details including\n"
++		"See https://github.com/ngteq/CRDOP/blob/main/NOTICE.md and https://github.com/pflarue/ardop/blob/master/LICENSE for licence details including\n"
+ 		"  information about authors of external libraries used and their licenses."
+ 	);
+ 	ZF_LOGD("Command line: %s", cmdstr);
diff --git a/stacks/crdop/patches/ardopcf/0002-crdop-version-override.patch b/stacks/crdop/patches/ardopcf/0002-crdop-version-override.patch
new file mode 100644
index 0000000..cda40d2
--- /dev/null
+++ b/stacks/crdop/patches/ardopcf/0002-crdop-version-override.patch
@@ -0,0 +1,18 @@
+From: CRDOP <dev@ngteq.local>
+Subject: [PATCH 2/2] CRDOP: version from CRDOP tree (single source of truth)
+
+ProductName and ProductVersion live in src/crdop_version.c / include/crdop/version.h.
+---
+ src/common/version.h | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/common/version.h b/src/common/version.h
+index faabb3e..c4d0e1f 100644
+--- a/src/common/version.h
++++ b/src/common/version.h
+@@ -4,4 +4,4 @@
+ // ardopcf was a mistake.  This was due to a bug and misunderstanding
+ // of the ardop version numbering scheme.  So ardopcf v1.0.4.1.1 comes
+ // after and replaces v2.0.3.2.1
+-const char ProductVersion[] = "1.0.4.1.3";
++extern const char ProductVersion[];  /* CRDOP src/crdop_version.c */
diff --git a/stacks/crdop/scripts/apply-vendor-patches.sh b/stacks/crdop/scripts/apply-vendor-patches.sh
new file mode 100755
index 0000000..da62bf5
--- /dev/null
+++ b/stacks/crdop/scripts/apply-vendor-patches.sh
@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# Apply CRDOP patch series — only if vendor tree is still pristine upstream.
+# Released CRDOP commits ship vendor/ardopcf with patches already integrated.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+VENDOR="${ROOT}/vendor/ardopcf"
+PATCH_DIR="${ROOT}/patches/ardopcf"
+STAMP="${VENDOR}/.crdop-patches-applied"
+MARKER="${VENDOR}/src/common/ARDOPC.c"
+
+if [[ ! -d "${VENDOR}/src" ]]; then
+    echo "error: ${VENDOR} missing" >&2
+    exit 1
+fi
+
+if grep -q 'CRDOP src/crdop_version.c' "${MARKER}" 2>/dev/null; then
+    date -u +'%Y-%m-%dT%H:%M:%SZ' > "${STAMP}"
+    echo "CRDOP vendor already integrated ($(cat "${STAMP}"))"
+    exit 0
+fi
+
+if [[ ! -d "${PATCH_DIR}" ]] || ! compgen -G "${PATCH_DIR}/*.patch" >/dev/null; then
+    echo "error: no patches in ${PATCH_DIR}" >&2
+    exit 1
+fi
+
+cd "${VENDOR}"
+for p in "${PATCH_DIR}"/*.patch; do
+    echo "applying ${p#${ROOT}/}"
+    git apply --check "${p}" 2>/dev/null || patch -p1 --forward -r - < "${p}"
+    git apply "${p}" 2>/dev/null || patch -p1 --forward < "${p}"
+done
+
+date -u +'%Y-%m-%dT%H:%M:%SZ' > "${STAMP}"
+echo "CRDOP patches applied ($(cat "${STAMP}"))"
diff --git a/stacks/crdop/scripts/build-crdop.sh b/stacks/crdop/scripts/build-crdop.sh
new file mode 100755
index 0000000..2253d5a
--- /dev/null
+++ b/stacks/crdop/scripts/build-crdop.sh
@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# CRDOP unified build — vendor embedded; GCC, Clang, or MSVC via CMake.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+BUILD="${CRDOP_BUILD_DIR:-${ROOT}/build}"
+TYPE="${CRDOP_BUILD_TYPE:-Release}"
+TOOLCHAIN="${CRDOP_TOOLCHAIN:-}"
+BUILD_TESTS="${CRDOP_BUILD_TESTS:-OFF}"
+RUN_TESTS="${CRDOP_RUN_TESTS:-OFF}"
+
+if [[ -f "${BUILD}/CMakeCache.txt" ]]; then
+    cached_home="$(grep -m1 '^CMAKE_HOME_DIRECTORY:INTERNAL=' "${BUILD}/CMakeCache.txt" 2>/dev/null | cut -d= -f2- || true)"
+    if [[ -n "${cached_home}" && "${cached_home}" != "${ROOT}" ]]; then
+        echo "CRDOP: removing stale CMake cache (was ${cached_home}, now ${ROOT})" >&2
+        rm -rf "${BUILD}"
+    fi
+fi
+
+"${ROOT}/scripts/import-ardopcf.sh"
+
+CMAKE_ARGS=(-B "${BUILD}" -DCMAKE_BUILD_TYPE="${TYPE}" -DCRDOP_BUILD_TESTS="${BUILD_TESTS}")
+
+if [[ -n "${TOOLCHAIN}" ]]; then
+    CMAKE_ARGS+=(-DCMAKE_TOOLCHAIN_FILE="${ROOT}/cmake/toolchains/${TOOLCHAIN}.cmake")
+fi
+
+if [[ -n "${CC:-}" ]]; then
+    CMAKE_ARGS+=(-DCMAKE_C_COMPILER="${CC}")
+fi
+if [[ -n "${CXX:-}" ]]; then
+    CMAKE_ARGS+=(-DCMAKE_CXX_COMPILER="${CXX}")
+fi
+
+cmake "${ROOT}" "${CMAKE_ARGS[@]}"
+cmake --build "${BUILD}" -j"$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 4)"
+
+"${ROOT}/scripts/test-smoke.sh"
+
+if [[ "${BUILD_TESTS}" == "ON" || "${BUILD_TESTS}" == "1" || "${RUN_TESTS}" == "ON" || "${RUN_TESTS}" == "1" ]]; then
+    if [[ -f "${BUILD}/CTestTestfile.cmake" ]]; then
+        ctest --test-dir "${BUILD}" --output-on-failure
+    else
+        echo "NOTE: CRDOP_BUILD_TESTS requested but no CTest targets (install libcmocka-dev?)" >&2
+    fi
+fi
+
+echo "CRDOP $(cat "${ROOT}/VERSION") built: ${BUILD}/crdopc"
diff --git a/stacks/crdop/scripts/crdopc b/stacks/crdop/scripts/crdopc
new file mode 100755
index 0000000..2fc82bd
--- /dev/null
+++ b/stacks/crdop/scripts/crdopc
@@ -0,0 +1,171 @@
+#!/usr/bin/env bash
+# CRDOP launcher — native MAX25-SoftModem (audio-dummyd / M25 host).
+# ARDOP is a separate optional MAX25-Stack plugin — not part of CRDOP.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+MAX25_ROOT="$(cd "${SCRIPT_DIR}/../.." && pwd)"
+PREFIX_SHARE="${SCRIPT_DIR}/../share/crdop"
+
+if [[ -n "${CRDOP_INI:-}" ]]; then
+    INI="${CRDOP_INI}"
+elif [[ -f "${HOME}/.config/crdop/crdop.ini" ]]; then
+    INI="${HOME}/.config/crdop/crdop.ini"
+elif [[ -f "${PREFIX_SHARE}/crdop.ini.example" ]]; then
+    INI="${PREFIX_SHARE}/crdop.ini.example"
+else
+    INI="${ROOT}/share/crdop.ini.example"
+fi
+
+ini_get() {
+    local section="$1" key="$2" default="$3" file="$4"
+    [[ -f "${file}" ]] || { echo "${default}"; return; }
+    awk -F= -v sec="[${section}]" -v k="${key}" -v d="${default}" '
+        $0 ~ /^[[:space:]]*[#;]/ { next }
+        $1 ~ /^\[/ { cur=$0; gsub(/[][]/, "", cur); next }
+        cur == substr(sec, 2, length(sec)-2) {
+            gsub(/^[[:space:]]+|[[:space:]]+$/, "", $1)
+            if ($1 == k) {
+                v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/, "", v); gsub(/^"|"$/, "", v)
+                print v; found=1; exit
+            }
+        }
+        END { if (!found) print d }
+    ' "${file}"
+}
+
+resolve_ini() {
+    if [[ ! -f "${INI}" && -f "${ROOT}/share/crdop.ini.example" ]]; then
+        INI="${ROOT}/share/crdop.ini.example"
+    fi
+}
+
+normalize_profile() {
+    case "${1,,}" in
+        cb|dual|amateur) echo "${1,,}" ;;
+        *)
+            echo "warn: unknown radio_profile '${1}', using cb" >&2
+            echo "cb"
+            ;;
+    esac
+}
+
+normalize_duplex() {
+    case "${1,,}" in
+        full|half) echo "${1,,}" ;;
+        *)
+            echo "warn: unknown duplex '${1}', using half" >&2
+            echo "half"
+            ;;
+    esac
+}
+
+enforce_host_audio() {
+    local backend
+    backend="$(ini_get audio backend "" "${INI}")"
+    if [[ -z "${backend}" ]]; then
+        case "$(uname -s)" in
+            FreeBSD) backend="oss" ;;
+            *) backend="alsa" ;;
+        esac
+    fi
+    if [[ "${backend}" == "alsa" ]]; then
+        local no_pulse
+        no_pulse="$(ini_get audio no_pulse yes "${INI}")"
+        case "${no_pulse,,}" in
+            1|yes|true|on)
+                unset PULSE_SERVER PULSE_COOKIE PIPEWIRE_RUNTIME_DIR 2>/dev/null || true
+                export PULSE_SERVER=
+                export ALSA_CARD="${ALSA_CARD:-}"
+                ;;
+        esac
+    fi
+}
+
+audio_cli_args() {
+    local cap pb backend
+    backend="$(ini_get audio backend "" "${INI}")"
+    if [[ -z "${backend}" ]]; then
+        case "$(uname -s)" in
+            FreeBSD) backend="oss" ;;
+            *) backend="alsa" ;;
+        esac
+    fi
+    cap="$(ini_get audio capture "" "${INI}")"
+    pb="$(ini_get audio playback "" "${INI}")"
+    local args=()
+    [[ -n "${cap}" ]] && args+=("${cap}")
+    [[ -n "${pb}" ]] && args+=("${pb}")
+    if [[ ${#args[@]} -gt 0 ]]; then
+        if [[ "${backend}" == "alsa" ]]; then
+            for a in "${args[@]}"; do
+                if [[ "${a}" == *pulse* || "${a}" == *pipewire* || "${a}" == default ]]; then
+                    echo "error: audio device '${a}' — use hw:/plughw: kernel ALSA" >&2
+                    exit 1
+                fi
+            done
+        fi
+        printf '%s\n' "${args[@]}"
+    elif [[ "${backend}" == "oss" ]]; then
+        echo "/dev/dsp"
+        echo "/dev/dsp"
+    fi
+}
+
+find_audio_dummyd() {
+  for candidate in \
+    "${MAX25_ROOT}/build/bin/audio-dummyd" \
+    "${MAX25_ROOT}/stacks/crdop/tools/audio-dummyd" \
+    "$(command -v audio-dummyd 2>/dev/null || true)"; do
+    [[ -n "${candidate}" && -x "${candidate}" ]] || continue
+    echo "${candidate}"
+    return
+  done
+  return 1
+}
+
+resolve_ini
+
+if [[ -f "${PREFIX_SHARE}/VERSION" ]]; then
+    CRDOP_VERSION="$(tr -d '[:space:]' < "${PREFIX_SHARE}/VERSION")"
+elif [[ -f "${ROOT}/VERSION" ]]; then
+    CRDOP_VERSION="$(tr -d '[:space:]' < "${ROOT}/VERSION")"
+else
+    CRDOP_VERSION="CUR999"
+fi
+
+PROFILE="$(normalize_profile "$(ini_get profile radio_profile cb "${INI}")")"
+DUPLEX="$(normalize_duplex "$(ini_get modem duplex half "${INI}")")"
+MYCALL="$(ini_get mycall call NOCALL-0 "${INI}")"
+HOST_PORT="$(ini_get host port 8515 "${INI}")"
+DATA_PORT=$((HOST_PORT + 1))
+SAMPLE_RATE="$(ini_get audio sample_rate 48000 "${INI}")"
+
+if [[ $# -ge 1 && "${1}" =~ ^[0-9]+$ ]]; then
+    HOST_PORT="$1"
+    DATA_PORT=$((HOST_PORT + 1))
+    shift
+fi
+
+mapfile -t AUDIO_ARGS < <(audio_cli_args || true)
+enforce_host_audio
+
+DUMMY="$(find_audio_dummyd || true)"
+if [[ -z "${DUMMY}" ]]; then
+    echo "error: audio-dummyd not found — build MAX25 or set path" >&2
+    exit 1
+fi
+
+DUMMY_ARGS=(--ctrl-port "${HOST_PORT}" --data-port "${DATA_PORT}" -r "${SAMPLE_RATE}")
+if [[ ${#AUDIO_ARGS[@]} -ge 1 ]]; then
+    DUMMY_ARGS+=(-D "${AUDIO_ARGS[0]}")
+fi
+if [[ ${#AUDIO_ARGS[@]} -ge 2 ]]; then
+    DUMMY_ARGS+=(-P "${AUDIO_ARGS[1]}")
+fi
+
+AUDIO_BACKEND="$(ini_get audio backend "" "${INI}")"
+[[ -z "${AUDIO_BACKEND}" ]] && case "$(uname -s)" in FreeBSD) AUDIO_BACKEND="oss" ;; *) AUDIO_BACKEND="alsa" ;; esac
+echo "CRDOP ${CRDOP_VERSION} profile=${PROFILE} duplex=${DUPLEX} ctrl=:${HOST_PORT} data=:${DATA_PORT} call=${MYCALL} audio=${AUDIO_BACKEND} (native M25)"
+exec "${DUMMY}" "${DUMMY_ARGS[@]}" "$@"
diff --git a/stacks/crdop/scripts/import-ardopcf.sh b/stacks/crdop/scripts/import-ardopcf.sh
new file mode 100755
index 0000000..26ac003
--- /dev/null
+++ b/stacks/crdop/scripts/import-ardopcf.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Verify vendor/ardopcf is present (embedded in repo — no submodule/download).
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+VENDOR="${ROOT}/vendor/ardopcf"
+
+if [[ ! -f "${VENDOR}/LICENSE" || ! -f "${VENDOR}/src/common/ARDOPC.c" ]]; then
+    echo "error: vendor/ardopcf missing — clone CRDOP with full tree or run scripts/refresh-vendor-ardopcf.sh" >&2
+    exit 1
+fi
+
+if ! grep -q 'CRDOP src/crdop_version.c' "${VENDOR}/src/common/ARDOPC.c" 2>/dev/null; then
+    echo "warn: vendor/ardopcf may need CRDOP patches — run scripts/apply-vendor-patches.sh" >&2
+fi
+
+echo "vendor/ardopcf OK (embedded, commit $(grep '^commit=' "${ROOT}/vendor/ardopcf.ref" 2>/dev/null | cut -d= -f2 || echo unknown))"
diff --git a/stacks/crdop/scripts/install-crdop.sh b/stacks/crdop/scripts/install-crdop.sh
new file mode 100755
index 0000000..23f631c
--- /dev/null
+++ b/stacks/crdop/scripts/install-crdop.sh
@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Build and install CRDOP to PREFIX (default /usr/local).
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+PREFIX="${CRDOP_PREFIX:-/usr/local}"
+BUILD="${CRDOP_BUILD_DIR:-${ROOT}/build}"
+
+"${ROOT}/scripts/build-crdop.sh"
+
+cmake --install "${BUILD}" --prefix "${PREFIX}"
+
+echo "Installed:"
+echo "  ${PREFIX}/bin/crdopc      — modem binary"
+echo "  ${PREFIX}/bin/crdop       — profile launcher"
+echo "  ${PREFIX}/share/crdop/    — INI examples, VERSION"
diff --git a/stacks/crdop/scripts/refresh-vendor-ardopcf.sh b/stacks/crdop/scripts/refresh-vendor-ardopcf.sh
new file mode 100755
index 0000000..b9d2f93
--- /dev/null
+++ b/stacks/crdop/scripts/refresh-vendor-ardopcf.sh
@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# Maintainer tool: re-download upstream ardopcf and re-apply CRDOP patches.
+# Normal builds use the committed vendor/ardopcf tree — no network required.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+VENDOR="${ROOT}/vendor/ardopcf"
+REF_FILE="${ROOT}/vendor/ardopcf.ref"
+URL="${CRDOP_UPSTREAM_URL:-https://github.com/pflarue/ardop.git}"
+PIN="$(grep '^commit_full=' "${REF_FILE}" 2>/dev/null | cut -d= -f2- | head -1)"
+PIN="${PIN:-$(grep '^commit=' "${REF_FILE}" 2>/dev/null | cut -d= -f2- | head -1)}"
+
+echo "This replaces vendor/ardopcf from upstream. Press Ctrl+C to abort."
+sleep 2
+
+rm -rf "${VENDOR}"
+git clone --depth 1 --branch master "${URL}" "${VENDOR}"
+if [[ -n "${PIN}" ]]; then
+    git -C "${VENDOR}" fetch --depth 1 origin "${PIN}"
+    git -C "${VENDOR}" checkout "${PIN}"
+fi
+rm -rf "${VENDOR}/.git"
+rm -f "${VENDOR}/.crdop-patches-applied"
+
+"${ROOT}/scripts/apply-vendor-patches.sh"
+echo "Done. Review diff, update vendor/ardopcf.ref if needed, commit vendor/ardopcf/"
diff --git a/stacks/crdop/scripts/sync-upstream.sh b/stacks/crdop/scripts/sync-upstream.sh
new file mode 100755
index 0000000..a1353ad
--- /dev/null
+++ b/stacks/crdop/scripts/sync-upstream.sh
@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Test whether CRDOP patches still apply to fresh upstream (maintainers).
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+TMP="$(mktemp -d)"
+trap 'rm -rf "${TMP}"' EXIT
+
+REF="${ROOT}/vendor/ardopcf.ref"
+PIN="$(grep '^commit_full=' "${REF}" | cut -d= -f2-)"
+URL="https://github.com/pflarue/ardop.git"
+
+git clone --depth 1 "${URL}" "${TMP}/ardopcf"
+git -C "${TMP}/ardopcf" fetch --depth 1 origin "${PIN}"
+git -C "${TMP}/ardopcf" checkout "${PIN}"
+
+for p in "${ROOT}"/patches/ardopcf/*.patch; do
+    git -C "${TMP}/ardopcf" apply --check "${p}"
+done
+
+echo "OK: patches apply to upstream ${PIN}"
diff --git a/stacks/crdop/scripts/test-all.sh b/stacks/crdop/scripts/test-all.sh
new file mode 100755
index 0000000..f12181e
--- /dev/null
+++ b/stacks/crdop/scripts/test-all.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Smoke test + optional upstream cmocka unit tests (CTest).
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+BUILD="${CRDOP_BUILD_DIR:-${ROOT}/build}"
+
+export CRDOP_BUILD_TESTS="${CRDOP_BUILD_TESTS:-ON}"
+export CRDOP_RUN_TESTS="${CRDOP_RUN_TESTS:-ON}"
+
+"${ROOT}/scripts/build-crdop.sh"
+
+if [[ ! -f "${BUILD}/CTestTestfile.cmake" ]]; then
+    echo "NOTE: unit tests not built (libcmocka missing or unsupported platform)" >&2
+fi
+
+echo "OK: CRDOP test-all finished"
diff --git a/stacks/crdop/scripts/test-smoke.sh b/stacks/crdop/scripts/test-smoke.sh
new file mode 100755
index 0000000..6ee6eff
--- /dev/null
+++ b/stacks/crdop/scripts/test-smoke.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+REPO="$(cd "${ROOT}/../.." && pwd)"
+BIN="${CRDOP_BIN:-${ROOT}/build/crdopc}"
+
+if [[ ! -x "${BIN}" ]]; then
+    for alt in "${REPO}/build/bin/crdopc" "${REPO}/build/crdop/crdopc"; do
+        if [[ -x "${alt}" ]]; then
+            BIN="${alt}"
+            break
+        fi
+    done
+fi
+VER="$(tr -d '[:space:]' < "${ROOT}/VERSION")"
+
+[[ -x "${BIN}" ]] || { echo "FAIL: ${BIN} missing" >&2; exit 1; }
+
+OUT="$("${BIN}" -h 2>&1 || true)"
+echo "${OUT}" | grep -qi crdopc || { echo "FAIL: crdopc branding"; exit 1; }
+echo "${OUT}" | grep -q "${VER}" || { echo "FAIL: expected version ${VER}"; exit 1; }
+
+echo "OK: CRDOP ${VER} smoke test passed"
diff --git a/stacks/crdop/scripts/test-with-host.sh b/stacks/crdop/scripts/test-with-host.sh
new file mode 100755
index 0000000..f14baac
--- /dev/null
+++ b/stacks/crdop/scripts/test-with-host.sh
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# P1 — loopback host integration (placeholder).
+set -euo pipefail
+
+echo "Host loopback test not automated yet."
+echo "  1. ./scripts/crdopc"
+echo "  2. Connect M25/KISS host client to 127.0.0.1:8515"
+echo "  3. INITIALIZE / PROTOCOLMODE KISS / LISTEN — verify STATUS ready"
+exit 0
diff --git a/stacks/crdop/share/crdop-amateur.ini.example b/stacks/crdop/share/crdop-amateur.ini.example
new file mode 100644
index 0000000..dd76f68
--- /dev/null
+++ b/stacks/crdop/share/crdop-amateur.ini.example
@@ -0,0 +1,15 @@
+; CRDOP — amateur profile (secondary)
+; Docs: docs/EXAMPLES.md
+
+[profile]
+radio_profile = amateur
+
+[modem]
+arq_bandwidth = 1000MAX
+duplex = half
+
+[host]
+port = 8515
+
+[mycall]
+call = CALL-1
diff --git a/stacks/crdop/share/crdop-dual.ini.example b/stacks/crdop/share/crdop-dual.ini.example
new file mode 100644
index 0000000..4601d5c
--- /dev/null
+++ b/stacks/crdop/share/crdop-dual.ini.example
@@ -0,0 +1,15 @@
+; CRDOP — dual profile (CB ↔ amateur turnaround)
+; Docs: docs/EXAMPLES.md
+
+[profile]
+radio_profile = dual
+
+[modem]
+arq_bandwidth = 500MAX
+duplex = half
+
+[host]
+port = 8515
+
+[mycall]
+call = CB01-0
diff --git a/stacks/crdop/share/crdop.freebsd.ini.example b/stacks/crdop/share/crdop.freebsd.ini.example
new file mode 100644
index 0000000..3d0f347
--- /dev/null
+++ b/stacks/crdop/share/crdop.freebsd.ini.example
@@ -0,0 +1,25 @@
+; MAX25-SoftModem (CRDOP) — FreeBSD / OSS
+; Copy: cp share/crdop/crdop.freebsd.ini.example ~/.config/crdop/crdop.ini
+; pkg install sox  (recommended for OSS capture/playback)
+
+[profile]
+radio_profile = cb
+
+[modem]
+speed_baud = 1200
+duplex = half
+max_speed_baud = 19200
+
+[host]
+port = 8515
+
+[mycall]
+call = NOCALL-0
+
+[audio]
+backend = oss
+no_pulse = yes
+; pcm0 from sysctl dev.pcm — typical OSS path:
+capture = /dev/dsp
+playback = /dev/dsp
+sample_rate = 48000
diff --git a/stacks/crdop/share/crdop.ini.example b/stacks/crdop/share/crdop.ini.example
new file mode 100644
index 0000000..52dc3a1
--- /dev/null
+++ b/stacks/crdop/share/crdop.ini.example
@@ -0,0 +1,37 @@
+; MAX25-SoftModem (CRDOP) — CB profile (default)
+; Copy: cp share/crdop.ini.example ~/.config/crdop/crdop.ini
+; Docs: docs/SOFTMODEM.md · docs/AUDIO-ARCHITECTURE.md · docs/CONFIG.md
+;
+; Development/test phase — in-house MAX25-Stack standard.
+; Audio: kernel ALSA ONLY via MAX25 sound-proxy — NO PulseAudio / PipeWire route.
+; Good sound card REQUIRED (accurate tones; stricter at higher baud).
+; 1200 baud primary, max 19200 baud. Duplex: half | full
+
+[profile]
+radio_profile = cb
+
+[modem]
+speed_baud = 1200
+duplex = half
+max_speed_baud = 19200
+
+[host]
+port = 8515
+
+[mycall]
+call = NOCALL-0
+
+[audio]
+; MAX25 sound-proxy → libasound → kernel ALSA → hardware (direct)
+backend = alsa-kernel
+; Reject pulse/pipewire pseudo devices — production path is kernel-only
+no_pulse = yes
+; REQUIRED: explicit hw: or plughw: from arecord -l / aplay -l
+; capture = hw:1,0
+; playback = hw:1,0
+; sample_rate = 48000
+; period_frames = 256
+
+[coupling]
+; line | acoustic — radio or TNC/BayCom reference path
+mode = line
diff --git a/stacks/crdop/src/crdop_version.c b/stacks/crdop/src/crdop_version.c
new file mode 100644
index 0000000..7136d4a
--- /dev/null
+++ b/stacks/crdop/src/crdop_version.c
@@ -0,0 +1,5 @@
+#include "crdop/version.h"
+
+/* CRDOP product identity — overrides vendor version.h when linked first. */
+const char ProductName[] = CRDOP_PRODUCT_NAME;
+const char ProductVersion[] = CRDOP_VERSION_STRING;
diff --git a/stacks/crdop/tools/audio-dummyd b/stacks/crdop/tools/audio-dummyd
new file mode 100755
index 0000000..e64bda5
--- /dev/null
+++ b/stacks/crdop/tools/audio-dummyd
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -euo pipefail
+ROOT="$(CDPATH= cd -- "$(dirname -- "$0")/../.." && pwd)"
+exec python3 "${ROOT}/stacks/crdop/tools/audio-dummyd.py" "$@"
diff --git a/stacks/crdop/tools/audio-dummyd.py b/stacks/crdop/tools/audio-dummyd.py
new file mode 100644
index 0000000..a4bb922
--- /dev/null
+++ b/stacks/crdop/tools/audio-dummyd.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""Audio dummy daemon — M25 host TCP + acoustic DSP bench for max25d."""
+from __future__ import annotations
+
+import argparse
+import sys
+import threading
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[3]
+LIB = ROOT / "stacks" / "crdop" / "lib"
+sys.path.insert(0, str(LIB))
+
+from acoustic_engine import AcousticEngine  # noqa: E402
+from m25_host_protocol import DEFAULT_CTRL_PORT, DEFAULT_DATA_PORT, M25SoftModemHost  # noqa: E402
+from sound_proxy import SoundConfig  # noqa: E402
+
+_DAEMON = ROOT / "stacks" / "daemon"
+sys.path.insert(0, str(_DAEMON))
+from ax25_codec import ax25_build_ui  # noqa: E402
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description="MAX25 audio-dummy device daemon")
+    ap.add_argument("--ctrl-port", type=int, default=DEFAULT_CTRL_PORT)
+    ap.add_argument("--data-port", type=int, default=DEFAULT_DATA_PORT)
+    ap.add_argument("-D", "--capture", default="")
+    ap.add_argument("-P", "--playback", default="")
+    ap.add_argument("-r", "--rate", type=int, default=48000)
+    args = ap.parse_args()
+
+    sound = SoundConfig(
+        capture=args.capture or "default",
+        playback=args.playback or args.capture or "default",
+        sample_rate=args.rate,
+    )
+    eng = AcousticEngine(sample_rate=args.rate, sound=sound)
+    rx_lock = threading.Lock()
+    last_rx: list[str] = []
+
+    def on_tx(payload: bytes) -> str:
+        if len(payload) < 16:
+            return "ERR short payload"
+        pcm = eng.mod.modulate_bits(payload)
+        eng.sound.playback = sound.playback
+        from sound_proxy import create_sound_proxy
+
+        create_sound_proxy(sound).play_pcm(pcm)
+        return "OK"
+
+    host = M25SoftModemHost(args.ctrl_port, args.data_port, on_data_tx=on_tx)
+    host.start()
+    print(
+        f"audio-dummyd ctrl=:{args.ctrl_port} data=:{args.data_port} rate={args.rate}",
+        flush=True,
+    )
+    try:
+        while True:
+            threading.Event().wait(3600.0)
+    except KeyboardInterrupt:
+        host.stop()
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/stacks/crdop/tools/max25-signal-sniffer b/stacks/crdop/tools/max25-signal-sniffer
new file mode 100755
index 0000000..e412997
--- /dev/null
+++ b/stacks/crdop/tools/max25-signal-sniffer
@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# MAX25 signal sniffer launcher
+set -euo pipefail
+ROOT="$(CDPATH= cd -- "$(dirname -- "$0")/../.." && pwd)"
+exec python3 "${ROOT}/stacks/crdop/tools/max25-signal-sniffer.py" "$@"
diff --git a/stacks/crdop/tools/max25-signal-sniffer.py b/stacks/crdop/tools/max25-signal-sniffer.py
new file mode 100644
index 0000000..fed95f7
--- /dev/null
+++ b/stacks/crdop/tools/max25-signal-sniffer.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""MAX25 signal sniffer — analyze Bell 202 AFSK on ALSA capture or PCM file."""
+from __future__ import annotations
+
+import argparse
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[3]
+LIB = ROOT / "stacks" / "crdop" / "lib"
+sys.path.insert(0, str(LIB))
+
+from acoustic_engine import AcousticEngine  # noqa: E402
+from sound_proxy import SoundConfig, SoundProxy  # noqa: E402
+
+
+def read_wav_pcm(path: Path) -> bytes:
+    import wave
+
+    with wave.open(str(path), "rb") as wf:
+        if wf.getsampwidth() != 2 or wf.getnchannels() != 1:
+            raise SystemExit("WAV must be mono S16_LE")
+        return wf.readframes(wf.getnframes())
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description="MAX25 acoustic signal sniffer (Bell 202 1200 bd)")
+    ap.add_argument("-D", "--device", default="", help="ALSA capture device (hw: or plughw:)")
+    ap.add_argument("-r", "--rate", type=int, default=48000)
+    ap.add_argument("-f", "--file", type=Path, help="Read mono S16 WAV instead of ALSA")
+    ap.add_argument("-t", "--seconds", type=float, default=2.0, help="ALSA capture duration")
+    ap.add_argument("--loopback", action="store_true", help="Internal DSP loopback (no audio hw)")
+    ap.add_argument("--mark", action="store_true", help="Play mark calibration tone (1200 Hz)")
+    ap.add_argument("--space", action="store_true", help="Play space calibration tone (2200 Hz)")
+    args = ap.parse_args()
+
+    cfg = SoundConfig(capture=args.device or "default", sample_rate=args.rate)
+    eng = AcousticEngine(sample_rate=args.rate, sound=cfg)
+
+    if args.loopback:
+        rep = eng.loopback_self_test()
+        print(f"loopback samples={rep.samples} symbols={rep.symbols} transitions={rep.transitions}")
+        print(f"mark={rep.mark_ratio:.2%} space={rep.space_ratio:.2%}")
+        for line in rep.decode_lines:
+            print(line)
+        return 0 if rep.decode_lines else 1
+
+    if args.mark:
+        eng.play_mark_calibration(args.seconds)
+        print(f"played mark tone {args.seconds}s")
+        return 0
+    if args.space:
+        eng.play_space_calibration(args.seconds)
+        print(f"played space tone {args.seconds}s")
+        return 0
+
+    if args.file:
+        pcm = read_wav_pcm(args.file)
+    else:
+        if not args.device:
+            print("error: -D hw:... or --file or --loopback required", file=sys.stderr)
+            return 2
+        proxy = SoundProxy(cfg)
+        proxy.start_capture()
+        nbytes = int(args.rate * args.seconds) * 2
+        pcm = proxy.read_capture(nbytes)
+        proxy.close()
+
+    rep = eng.analyze_pcm(pcm)
+    print(f"sniff samples={rep.samples} symbols={rep.symbols} transitions={rep.transitions}")
+    print(f"mark={rep.mark_ratio:.2%} space={rep.space_ratio:.2%} frames={len(rep.frames)}")
+    for line in rep.decode_lines:
+        print(line)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/stacks/crdop/vendor/README.md b/stacks/crdop/vendor/README.md
new file mode 100644
index 0000000..d5f9c02
--- /dev/null
+++ b/stacks/crdop/vendor/README.md
@@ -0,0 +1,5 @@
+# Vendor tree (dev-only)
+
+Legacy **ardopcf** may exist under `vendor/ardopcf/` for local developer builds (`-DCRDOP_VENDOR_ARDOPCF=ON`). **Not** part of MAX25 release install.
+
+Operator ARDOP (third-party host): [plugins/external/ardop/README.md](../../plugins/external/ardop/README.md) — separate from CRDOP.
diff --git a/stacks/crdop/vendor/ardopcf.ref b/stacks/crdop/vendor/ardopcf.ref
new file mode 100644
index 0000000..54a0ab6
--- /dev/null
+++ b/stacks/crdop/vendor/ardopcf.ref
@@ -0,0 +1,9 @@
+# Pinned upstream for CRDOP vendor submodule (vendor/ardopcf)
+# Update with: scripts/sync-upstream.sh
+
+url=https://github.com/pflarue/ardop.git
+branch=master
+commit=a7c9228
+commit_full=a7c92289b569afbe4259dc556d749405ebc008f5
+describe=ardopcf baseline (Update CONTRIBUTING.md fix typo)
+imported=2026-07-04
diff --git a/stacks/daemon/README.md b/stacks/daemon/README.md
new file mode 100644
index 0000000..bfba87e
--- /dev/null
+++ b/stacks/daemon/README.md
@@ -0,0 +1,72 @@
+# max25d — Linux daemon
+
+**max25d** supervises TNC/modem hardware, runs per-device RX/TX backends, and exposes M25/1 to `max25-terminal`.
+
+Linux only. Config: `share/max25/max25d.ini.example`.
+
+## Components
+
+| File | Role |
+|------|------|
+| `max25d` | Python 3 daemon — M25/1 server, stack lifecycle |
+| `device_backends.py` | Backend abstraction (TNC, BayCom, CRDOP) |
+| `kiss_bridge.py` | Serial KISS for command-mode TNCs (TNC2C/PK-TNC2) |
+| `banlist.py` | AX.25 source ban list (silent RX drop) |
+| `test_multi_device.py` | Multi-device routing smoke |
+
+## Backends
+
+| Device id | Backend | Notes |
+|-----------|---------|-------|
+| `tnc2c`, `pktnc2` | `KissSerialBackend` | CI-tested |
+| `max25e0` (`max25-bcpr:bc0`) | bcpr / KISS PTY | BayCom/based SER12 userspace — [docs/BAYCOM.md](../../docs/BAYCOM.md) |
+| `baycom-kiss` | `KissRawSerialBackend` | USB/async KISS (not SER12 product face) |
+| `soft-crdop` | `CrdopTcpBackend` | MAX25-SoftModem (CRDOP) — standard; KISS default; sound IN/OUT + radio like hardware modem |
+
+Untested backends log a startup warning; SEND/RX return `ERR link not ready` when the stack path is unavailable.
+
+## Quick start
+
+```bash
+# Protocol only (no hardware):
+./max25d --no-stack -c ../../share/max25/max25d.ini.example
+
+# With stack auto-start:
+sudo ./max25d -c /etc/max25/max25d.ini
+```
+
+## One RF device per Linux host
+
+**Target:** one `[devices]` id per `max25d`. See [ARCHITECTURE.md](../../docs/ARCHITECTURE.md#linux-host-policy--one-rf-device).
+
+```ini
+[devices]
+default = tnc2c
+tnc2c = /dev/ttyS4
+```
+
+**Legacy multi-id** (deprecated for new sites): `share/max25/max25d.full-station.ini.example`, `max25d.dual-baycom.ini.example`.
+
+M25/1: `devices=` in `STATUS`, `SET DEVICE <id>`, `GET DEVICES`, `RX device=<id> …`.
+
+## Source ban list
+
+Block unwanted AX.25 callers (source address on incoming UI frames). Banned traffic is dropped silently — no terminal display, no daemon log line.
+
+```ini
+[modem]
+bans_file = /etc/max25/bans.txt
+```
+
+File format: one callsign per line (`#` comments allowed). Ban without SSID blocks all SSIDs of that call (`DG1ABC` blocks `DG1ABC-7`). Ban with SSID (`DK0WC-7`) matches only that SSID.
+
+M25/1: `BAN <callsign>`, `UNBAN <callsign>`, `BANS`. Changes persist to `bans_file` immediately.
+
+## Install
+
+```bash
+./scripts/install-max25.sh --deps
+# Installs: /usr/local/bin/max25d, kiss_bridge.py, device_backends.py, max25-terminal
+```
+
+Host setup guide: [docs/LINUX-HOST-SETUP.md](../../docs/LINUX-HOST-SETUP.md). Protocol: [include/max25/protocol.md](../../include/max25/protocol.md). Client: [docs/MAX25-CLIENT.md](../../docs/MAX25-CLIENT.md).
diff --git a/stacks/daemon/ax25_codec.py b/stacks/daemon/ax25_codec.py
new file mode 100644
index 0000000..03ee671
--- /dev/null
+++ b/stacks/daemon/ax25_codec.py
@@ -0,0 +1,176 @@
+"""
+AX.25 UI frame codec for max25d — address fields, CRC-CCITT FCS, UI parse/build.
+
+Derived from libax25 axutils.c (address encoding) and ax25ipd/crc.c (RFC 1171 FCS).
+KISS DATA carries the AX.25 body without FCS; over-the-air and some paths include FCS.
+"""
+from __future__ import annotations
+
+import re
+from typing import Optional
+
+# HDLC CRC-CCITT (polynomial 0x1021), RFC 1171 / ax25ipd table
+_FCS_TABLE: tuple[int, ...] = (
+    0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
+    0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
+    0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E,
+    0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
+    0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD,
+    0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
+    0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C,
+    0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
+    0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB,
+    0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
+    0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A,
+    0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
+    0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9,
+    0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
+    0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738,
+    0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
+    0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7,
+    0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
+    0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036,
+    0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
+    0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5,
+    0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
+    0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134,
+    0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
+    0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3,
+    0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
+    0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232,
+    0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
+    0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1,
+    0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
+    0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330,
+    0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,
+)
+
+_FCS_GOOD = 0xF0B8  # ax25ipd PPPGOODFCS — residual after valid frame + FCS
+
+AX25_UI_CONTROL = 0x03
+AX25_UI_PID = 0xF0
+MIN_UI_FRAME = 16  # dest(7) + src(7) + ctrl + pid
+
+_CALLSIGN_RE = re.compile(r"^([A-Z0-9]{1,6})(?:-([0-9]{1,2}))?$")
+
+
+def parse_callsign(text: str) -> tuple[str, int]:
+    """Parse operator callsign text; invalid SSID clamps to 0 (legacy helper)."""
+    text = text.strip().upper()
+    if "-" in text:
+        call, ssid_s = text.split("-", 1)
+        try:
+            ssid = int(ssid_s)
+        except ValueError:
+            ssid = 0
+        if ssid < 0 or ssid > 15:
+            ssid = 0
+        return call[:6], ssid
+    return text[:6], 0
+
+
+def validate_callsign(text: str) -> tuple[str, int]:
+    """Strict callsign parse (libax25 ax25_aton_entry rules)."""
+    text = text.strip().upper()
+    match = _CALLSIGN_RE.match(text)
+    if not match:
+        raise ValueError(f"invalid AX.25 callsign: {text!r}")
+    call = match.group(1)
+    ssid = int(match.group(2)) if match.group(2) is not None else 0
+    if ssid < 0 or ssid > 15:
+        raise ValueError(f"invalid AX.25 SSID in {text!r}")
+    return call, ssid
+
+
+def format_callsign(call: str, ssid: int) -> str:
+    """Textual callsign; omit -0 suffix (libax25 ax25_ntoa convention)."""
+    call = call.strip().upper()
+    if ssid <= 0:
+        return call
+    if ssid >= 10:
+        return f"{call}-{ssid}"
+    return f"{call}-{ssid}"
+
+
+def ax25_crc(data: bytes) -> int:
+    """Compute AX.25 FCS over body (addresses + control + PID + info)."""
+    fcs = 0xFFFF
+    for b in data:
+        fcs = (fcs >> 8) ^ _FCS_TABLE[(fcs ^ b) & 0xFF]
+    return fcs ^ 0xFFFF
+
+
+def ax25_crc_valid(frame: bytes) -> bool:
+    """True when frame includes a valid little-endian FCS trailer."""
+    fcs = 0xFFFF
+    for b in frame:
+        fcs = (fcs >> 8) ^ _FCS_TABLE[(fcs ^ b) & 0xFF]
+    return fcs == _FCS_GOOD
+
+
+def ax25_encode_address(call: str, ssid: int, last: bool) -> bytes:
+    """Seven-byte AX.25 address field (libax25 ax25_aton_entry layout)."""
+    padded = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in padded)
+    ssid_b = ((ssid & 0x0F) << 1) | (0x01 if last else 0x00)
+    return raw + bytes([ssid_b])
+
+
+def ax25_decode_address(raw: bytes) -> tuple[str, int, bool]:
+    call = "".join(chr((b >> 1) & 0x7F) for b in raw[:6]).strip()
+    ssid = (raw[6] >> 1) & 0x0F
+    last = bool(raw[6] & 0x01)
+    return call, ssid, last
+
+
+def ax25_build_ui(src: str, dst: str, info: bytes) -> bytes:
+    src_call, src_ssid = validate_callsign(src)
+    dst_call, dst_ssid = validate_callsign(dst)
+    body = (
+        ax25_encode_address(dst_call, dst_ssid, last=False)
+        + ax25_encode_address(src_call, src_ssid, last=True)
+        + bytes([AX25_UI_CONTROL, AX25_UI_PID])
+        + info
+    )
+    crc = ax25_crc(body)
+    return body + bytes((crc & 0xFF, crc >> 8))
+
+
+def ax25_parse_ui(frame: bytes) -> Optional[tuple[str, str, bytes]]:
+    """
+    Parse a UI frame. Strips FCS only when the trailer validates (ax25ipd ok_crc).
+    KISS payloads are usually FCS-free; over-the-air captures may include FCS.
+    """
+    if len(frame) < MIN_UI_FRAME:
+        return None
+
+    body = frame
+    if len(frame) >= MIN_UI_FRAME + 2 and ax25_crc_valid(frame):
+        body = frame[:-2]
+
+    pos = 0
+    addresses: list[tuple[str, int, bool]] = []
+    while pos + 7 <= len(body):
+        call, ssid, last = ax25_decode_address(body[pos : pos + 7])
+        addresses.append((call, ssid, last))
+        pos += 7
+        if last:
+            break
+    else:
+        return None
+
+    if len(addresses) < 2:
+        return None
+    if pos + 2 > len(body):
+        return None
+    if body[pos] != AX25_UI_CONTROL or body[pos + 1] != AX25_UI_PID:
+        return None
+
+    payload = body[pos + 2 :]
+    dst_call, dst_ssid, _ = addresses[0]
+    src_call, src_ssid, _ = addresses[-1]
+    return (
+        format_callsign(src_call, src_ssid),
+        format_callsign(dst_call, dst_ssid),
+        payload,
+    )
diff --git a/stacks/daemon/banlist.py b/stacks/daemon/banlist.py
new file mode 100644
index 0000000..061ed1f
--- /dev/null
+++ b/stacks/daemon/banlist.py
@@ -0,0 +1,89 @@
+"""Simple AX.25 source ban list for max25d — silent RX drop."""
+from __future__ import annotations
+
+import re
+import sys
+import threading
+from pathlib import Path
+from typing import Optional
+
+DEFAULT_BANS_FILE = Path("/etc/max25/bans.txt")
+
+_AX25_UI_SRC_RE = re.compile(r"\[AX25 UI ([^>]+)>")
+
+
+def extract_ax25_source(line: str) -> Optional[str]:
+    """Return source callsign from a formatted AX.25 UI RX line, or None."""
+    match = _AX25_UI_SRC_RE.search(line)
+    if not match:
+        return None
+    return match.group(1).strip().upper()
+
+
+def callsign_banned(ban_entry: str, source: str) -> bool:
+    """Match ban entry against an incoming source callsign."""
+    ban = ban_entry.strip().upper()
+    src = source.strip().upper()
+    if not ban or not src:
+        return False
+    if "-" in ban:
+        return ban == src
+    return ban == src.split("-", 1)[0]
+
+
+class BanList:
+    """Persistent set of banned AX.25 source addresses."""
+
+    def __init__(self, path: Path | str = DEFAULT_BANS_FILE) -> None:
+        self.path = Path(path)
+        self._lock = threading.Lock()
+        self._entries: set[str] = set()
+        self.load()
+
+    def load(self) -> None:
+        entries: set[str] = set()
+        try:
+            if self.path.is_file():
+                text = self.path.read_text(encoding="utf-8")
+                for raw in text.splitlines():
+                    line = raw.split("#", 1)[0].strip().upper()
+                    if line:
+                        entries.add(line)
+        except OSError as exc:
+            print(f"max25d: banlist load failed ({self.path}): {exc}", file=sys.stderr)
+        with self._lock:
+            self._entries = entries
+
+    def save(self) -> None:
+        lines = sorted(self._entries)
+        content = "\n".join(lines)
+        if content:
+            content += "\n"
+        self.path.parent.mkdir(parents=True, exist_ok=True)
+        self.path.write_text(content, encoding="utf-8")
+
+    def list(self) -> list[str]:
+        with self._lock:
+            return sorted(self._entries)
+
+    def add(self, callsign: str) -> None:
+        call = callsign.strip().upper()
+        with self._lock:
+            self._entries.add(call)
+            self.save()
+
+    def remove(self, callsign: str) -> bool:
+        call = callsign.strip().upper()
+        with self._lock:
+            if call not in self._entries:
+                return False
+            self._entries.remove(call)
+            self.save()
+            return True
+
+    def is_banned(self, source: str) -> bool:
+        src = source.strip().upper()
+        if not src:
+            return False
+        with self._lock:
+            return any(callsign_banned(entry, src) for entry in self._entries)
diff --git a/stacks/daemon/daemon_log.py b/stacks/daemon/daemon_log.py
new file mode 100644
index 0000000..f1696df
--- /dev/null
+++ b/stacks/daemon/daemon_log.py
@@ -0,0 +1,237 @@
+"""
+Structured stderr logging for max25d — human- and machine-readable lines.
+
+Format:
+  max25d [LEVEL] [area] message
+  max25d [LEVEL] [area] [device] message
+
+Levels: INFO, OK, WARN, ERROR, EVENT, RECOVERY
+"""
+from __future__ import annotations
+
+import sys
+from dataclasses import dataclass
+from typing import Callable, Optional
+
+PREFIX = "max25d"
+DEVICE_TOKENS = ("tnc2c", "pktnc2", "tmodem", "max25e0", "max25e0:bc0", "max25e0:bc1", "baycom-kiss", "soft-crdop")
+
+
+@dataclass(frozen=True)
+class DeviceSummary:
+    device_id: str
+    backend: str
+    hardware: str
+    serial: str
+    enabled: bool
+    tested: bool
+
+
+class DaemonLogger:
+    """Thread-safe enough for max25d (GIL); all lines go to stderr."""
+
+    def __init__(self, emit: Optional[Callable[[str], None]] = None) -> None:
+        self._emit = emit or self._default_emit
+
+    @staticmethod
+    def _default_emit(line: str) -> None:
+        print(line, file=sys.stderr, flush=True)
+
+    def _line(
+        self,
+        level: str,
+        msg: str,
+        *,
+        area: str = "",
+        device: str = "",
+    ) -> None:
+        parts = [PREFIX, f"[{level}]"]
+        if area:
+            parts.append(f"[{area}]")
+        if device:
+            parts.append(f"[{device}]")
+        parts.append(msg)
+        self._emit(" ".join(parts))
+
+    def info(self, msg: str, *, area: str = "", device: str = "") -> None:
+        self._line("INFO", msg, area=area, device=device)
+
+    def ok(self, msg: str, *, area: str = "", device: str = "") -> None:
+        self._line("OK", msg, area=area, device=device)
+
+    def warn(self, msg: str, *, area: str = "", device: str = "") -> None:
+        self._line("WARN", msg, area=area, device=device)
+
+    def error(self, msg: str, *, area: str = "", device: str = "") -> None:
+        self._line("ERROR", msg, area=area, device=device)
+
+    def event(self, msg: str, *, area: str = "", device: str = "") -> None:
+        self._line("EVENT", msg, area=area, device=device)
+
+    def recovery(self, msg: str, *, device: str = "") -> None:
+        self._line("RECOVERY", msg, area="serial", device=device)
+
+    def _parse_device_prefix(self, text: str) -> tuple[str, str]:
+        head, sep, tail = text.partition(":")
+        if sep and head in DEVICE_TOKENS:
+            return head, tail.strip()
+        device = ""
+        for token in DEVICE_TOKENS:
+            if f"({token})" in text or f" {token})" in text:
+                device = token
+                break
+        return device, text
+
+    def emit_unstructured(self, msg: str) -> None:
+        """Map legacy free-form strings to structured levels."""
+        device, text = self._parse_device_prefix(msg.strip())
+        lower = text.lower()
+        if lower.startswith("warning:"):
+            self.warn(text[8:].strip(), device=device)
+        elif lower.startswith("recovery:"):
+            self.recovery(text[9:].strip(), device=device)
+        elif " prep ok" in lower or lower.startswith("ok:"):
+            self.ok(text, device=device)
+        elif any(x in lower for x in ("failed", "error", "fail:")):
+            self.error(text, device=device)
+        elif lower.startswith("serial watch:"):
+            self.info(text, area="watch", device=device)
+        elif lower.startswith("serial "):
+            self.info(text, area="serial", device=device)
+        elif lower.startswith("stack "):
+            self.info(text, area="stack", device=device)
+        elif lower.startswith("rx ") or lower.startswith("tx "):
+            self.event(text, device=device)
+        else:
+            self.info(text, device=device)
+
+    def banner(self, title: str) -> None:
+        self._emit(f"{PREFIX} === {title} ===")
+
+    def section(self, name: str) -> None:
+        self._emit(f"{PREFIX} [{name}]")
+
+    def kv(self, key: str, value: str, *, indent: int = 0) -> None:
+        pad = "  " * indent
+        self._emit(f"{PREFIX} {pad}{key}={value}")
+
+
+LOGGER = DaemonLogger()
+
+
+def device_serial_label(dev) -> str:
+    """Human-readable serial/KISS path for startup summary."""
+    spec = (dev.device_spec or dev.serial_device or "").strip()
+    if dev.backend_type == "kiss-serial":
+        baud = dev.serial_baud or "?"
+        line = (dev.serial_line or "?").upper()
+        dtr = dev.serial_dtr_rts or "default"
+        kiss = dev.serial_kiss_entry or "default"
+        path = spec or dev.serial_device or "?"
+        return f"{path} {baud} {line} dtr={dtr} kiss_entry={kiss}"
+    if dev.backend_type == "baycom-kiss":
+        return f"baycom:{dev.baycom_modem or 'a'} kiss={dev.kiss_link or '?'}"
+    if dev.backend_type == "crdop-tcp":
+        host = dev.crdop_host or "127.0.0.1"
+        port = dev.crdop_port or "?"
+        return f"crdop-tcp {host}:{port}"
+    if spec:
+        return spec
+    return dev.backend_type or "auto"
+
+
+def emit_startup_banner(
+    *,
+    config_path: Optional[str],
+    cfg,
+    devices: list,
+    tested_fn: Callable[[str], bool],
+) -> None:
+    LOGGER.banner("MAX25d starting")
+    LOGGER.section("config")
+    if config_path:
+        LOGGER.kv("ini", config_path, indent=1)
+    else:
+        LOGGER.kv("ini", "(built-in defaults)", indent=1)
+    LOGGER.kv("mode", cfg.mode, indent=1)
+    LOGGER.kv("default_device", cfg.default_device or cfg.device, indent=1)
+    LOGGER.kv("devices", str(len(devices)), indent=1)
+
+    LOGGER.section("network")
+    LOGGER.kv("tcp", f"{cfg.tcp_host}:{cfg.tcp_port}", indent=1)
+    LOGGER.kv("unix", cfg.unix_socket or "(disabled)", indent=1)
+    if cfg.tcp_password:
+        LOGGER.kv("tcp_auth", "enabled", indent=1)
+    else:
+        LOGGER.warn("TCP has no password — set tcp_password before exposing LAN", area="security")
+
+    LOGGER.section("modem")
+    LOGGER.kv("callerid", cfg.callerid, indent=1)
+    LOGGER.kv("callid", cfg.callid, indent=1)
+    LOGGER.kv("ax25_ui", "yes" if cfg.ax25_ui else "no", indent=1)
+    if cfg.bans_file:
+        LOGGER.kv("bans_file", cfg.bans_file, indent=1)
+
+    LOGGER.section("stack")
+    LOGGER.kv("auto_start", "yes" if cfg.auto_start else "no", indent=1)
+    LOGGER.kv("serial_enabled", "yes" if cfg.serial_enabled else "no", indent=1)
+    LOGGER.kv("stack_recover_only", "yes" if cfg.stack_recover_only else "no", indent=1)
+    LOGGER.kv("serial_watch", "yes" if cfg.serial_watch else "no", indent=1)
+    if cfg.serial_watch:
+        LOGGER.kv("serial_watch_interval", f"{cfg.serial_watch_interval}s", indent=1)
+        LOGGER.kv("serial_watch_startup_grace", f"{cfg.serial_watch_startup_grace}s", indent=1)
+    LOGGER.kv("serial_bootwait_escalate", "yes" if cfg.serial_bootwait_escalate else "no", indent=1)
+
+    LOGGER.section("session")
+    LOGGER.kv(
+        "detach",
+        "max25d --session tmux  |  max25d-session start/attach/stop",
+        indent=1,
+    )
+
+    LOGGER.section("devices")
+    for dev in devices:
+        if not dev.enabled:
+            LOGGER.kv(
+                dev.device_id,
+                f"disabled backend={dev.backend_type or 'auto'}",
+                indent=1,
+            )
+            continue
+        serial = device_serial_label(dev)
+        hw = dev.hardware or cfg.hardware
+        tested = tested_fn(dev.device_id)
+        note = "" if tested else " — not hardware-validated in CI"
+        LOGGER.kv(
+            dev.device_id,
+            f"{hw} {serial}{note}",
+            indent=1,
+        )
+        if not tested and dev.backend_type == "kiss-serial":
+            LOGGER.warn(
+                "RF path not CI-validated — verify on hardware before production",
+                area="devices",
+                device=dev.device_id,
+            )
+
+
+def emit_startup_complete(
+    *,
+    device_lines: list[tuple[str, str, str]],
+    tcp_host: str,
+    tcp_port: int,
+    unix_socket: str,
+) -> None:
+    LOGGER.banner("MAX25d ready")
+    LOGGER.section("listen")
+    LOGGER.kv("tcp", f"{tcp_host}:{tcp_port}", indent=1)
+    LOGGER.kv("unix", unix_socket or "(disabled)", indent=1)
+    if device_lines:
+        LOGGER.section("device_status")
+        for dev_id, stack_st, link_st in device_lines:
+            LOGGER.kv(dev_id, f"stack={stack_st} link={link_st}", indent=1)
+    LOGGER.info(
+        "attach: max25-terminal -U /run/max25/modem.sock  |  "
+        "detach session: max25d-session attach",
+        area="operator",
+    )
diff --git a/stacks/daemon/device_backends.py b/stacks/daemon/device_backends.py
new file mode 100644
index 0000000..b4c6c29
--- /dev/null
+++ b/stacks/daemon/device_backends.py
@@ -0,0 +1,1076 @@
+"""
+Device backends for max25d — heterogeneous RF paths (TNC, BayCom, CRDOP).
+
+Each enabled [devices] id gets one backend instance. Backends without hardware
+validation log a startup warning but still wire real stack paths (not silent no-ops).
+"""
+from __future__ import annotations
+
+import os
+import select
+import socket
+import struct
+import termios
+import threading
+import time
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Callable, Optional
+
+from kiss_bridge import (
+    MAX_PAYLOAD,
+    KissDecoder,
+    SerialProfile,
+    ax25_build_ui,
+    ax25_parse_ui,
+    format_rx_line,
+    kiss_data_frame,
+    serial_profile_for_device,
+)
+from kiss_bridge import KissBridge  # noqa: E402 — re-exported wrapper target
+from paths import normalize_max25_bcpr_path
+
+LogFn = Callable[[str], None]
+RxFn = Callable[[str], None]
+InvalidFn = Callable[[], None]
+
+
+def _spec_int(raw: str, default: int) -> int:
+    try:
+        return int(str(raw).strip())
+    except (TypeError, ValueError):
+        return default
+
+# max25e0 host address defaults (overridable in max25d.ini [device.max25e0])
+MAX25E0_DEFAULT_IPV4 = "127.0.0.25/8"
+MAX25E0_DEFAULT_IPV6 = "::25/128"
+
+# manifest.yaml device ids → default hardware + backend kind
+DEVICE_REGISTRY: dict[str, dict[str, str | bool]] = {
+    "tnc2c": {"hardware": "tncs", "backend": "kiss-serial", "tested": True},
+    "pktnc2": {"hardware": "tncs", "backend": "kiss-serial", "tested": False},
+    "tmodem": {"hardware": "tncs", "backend": "kiss-raw-serial", "tested": False},
+    # Kernel baycom-ser12/par96 removed 2026-07-18 — use max25-bcpr → device max25e0
+    "baycom-kiss": {"hardware": "modems", "backend": "kiss-raw-serial", "tested": False},
+    "pccom-kiss": {"hardware": "modems", "backend": "kiss-raw-serial", "tested": False},
+    "max25e0": {"hardware": "modems", "backend": "max25-bcpr-kiss", "tested": True},
+    "max25e0:bc0": {"hardware": "modems", "backend": "max25-bcpr-kiss", "tested": True},
+    "max25e0:bc1": {"hardware": "modems", "backend": "max25-bcpr-kiss", "tested": True},
+    "soft-crdop": {"hardware": "soft-modems", "backend": "crdop-tcp", "tested": True},
+    "audio-dummy": {"hardware": "acoustic-bench", "backend": "audio-dummy", "tested": True},
+}
+
+
+def registry_hardware(device_id: str, fallback: str = "tncs") -> str:
+    entry = DEVICE_REGISTRY.get(device_id, {})
+    return str(entry.get("hardware", fallback))
+
+
+def registry_backend(device_id: str) -> str:
+    entry = DEVICE_REGISTRY.get(device_id, {})
+    return str(entry.get("backend", "kiss-serial"))
+
+
+def registry_tested(device_id: str) -> bool:
+    entry = DEVICE_REGISTRY.get(device_id, {})
+    return bool(entry.get("tested", False))
+
+
+def baycom_ctl_device_id(dev_cfg: DeviceBackendConfig) -> str:
+    """Legacy helper: kernel BayCom ctl device id (stack removed — prefer max25-bcpr)."""
+    entry = DEVICE_REGISTRY.get(dev_cfg.device_id, {})
+    if entry.get("backend") == "baycom-kiss":
+        return dev_cfg.device_id
+    return "max25e0"
+
+
+@dataclass
+class DeviceBackendConfig:
+    device_id: str
+    hardware: str = ""
+    backend_type: str = ""
+    device_spec: str = ""
+    enabled: bool = True
+    # Serial (TNC / baycom-kiss USB)
+    serial_device: str = ""
+    serial_baud: int = 0
+    serial_line: str = ""
+    serial_dtr_rts: str = ""
+    serial_kiss_entry: str = ""
+    # BayCom kernel KISS PTY
+    kiss_link: str = ""
+    baycom_modem: str = "a"
+    baycom_ini: str = ""
+    # max25-bcpr userspace SER12 — max25e0 (+ forks max25e0:bcN)
+    max25_bcpr_ini: str = ""
+    max25_bcpr_device: str = ""  # bc0 | bc1
+    # Host addresses (max25e0 family only; forks inherit from max25e0)
+    ipv4: str = ""
+    ipv6: str = ""
+    # Legacy field aliases (read-only mirrors filled by parser)
+    bcpr_ini: str = ""
+    bcpr_device: str = ""
+    # CRDOP TCP
+    crdop_host: str = "127.0.0.1"
+    crdop_port: int = 8515
+    crdop_profile: str = "default"
+    crdop_listen: bool = True
+    # Acoustic bench / audio-dummy
+    audio_mode: str = "loopback"  # loopback | alsa | host
+    audio_capture: str = ""
+    audio_playback: str = ""
+    audio_sample_rate: int = 48000
+    audio_host_port: int = 8520
+
+
+class DeviceBackend(ABC):
+    """Common RX/TX/PTT surface for max25d."""
+
+    device_id: str
+    status: str = "closed"
+    backend_type: str = ""
+
+    @abstractmethod
+    def open(self) -> bool:
+        ...
+
+    @abstractmethod
+    def close(self) -> None:
+        ...
+
+    @abstractmethod
+    def attach_session(self, mycall: str) -> bool:
+        ...
+
+    @abstractmethod
+    def detach_session(self) -> None:
+        ...
+
+    @abstractmethod
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        ...
+
+
+class KissSerialBackend(DeviceBackend):
+    """TNC2C / PK-TNC2 — command-mode serial entry into KISS."""
+
+    backend_type = "kiss-serial"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        root: str,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+        prefix: Optional[str] = None,
+        on_invalid: Optional[InvalidFn] = None,
+    ) -> None:
+        self.device_id = cfg.device_id
+        self._cfg = cfg
+        self._root = root
+        self._prefix = prefix
+        self._on_rx = on_rx
+        self._on_invalid = on_invalid
+        self._log = log or (lambda _m: None)
+        self._bridge: Optional[KissBridge] = None
+        self.status = "closed"
+
+    def _bridge_log(self, msg: str) -> None:
+        self._log(f"{self.device_id}: {msg}")
+
+    def _ini_overrides(self) -> dict[str, str]:
+        out: dict[str, str] = {}
+        if self._cfg.serial_device:
+            out["device"] = self._cfg.serial_device
+        if self._cfg.serial_baud:
+            out["baud"] = str(self._cfg.serial_baud)
+        if self._cfg.serial_line:
+            out["line"] = self._cfg.serial_line
+        if self._cfg.serial_dtr_rts:
+            out["dtr_rts"] = self._cfg.serial_dtr_rts
+        if self._cfg.serial_kiss_entry:
+            out["kiss_entry"] = self._cfg.serial_kiss_entry
+        return out
+
+    def open(self) -> bool:
+        profile = serial_profile_for_device(
+            self.device_id,
+            self._root,
+            self._ini_overrides(),
+            prefix=self._prefix,
+        )
+        bridge = KissBridge(
+            profile,
+            self._on_rx,
+            self._bridge_log,
+            tree_root=self._root,
+            install_prefix=self._prefix,
+            on_invalid=self._on_invalid,
+        )
+        if not bridge.open():
+            self._bridge = bridge
+            self.status = bridge.status
+            return False
+        self._bridge = bridge
+        self.status = bridge.status
+        return True
+
+    def close(self) -> None:
+        if self._bridge is not None:
+            self._bridge.close()
+            self.status = self._bridge.status
+            self._bridge = None
+        else:
+            self.status = "closed"
+
+    def stabilize_session(self, mycall: str, *, force: bool = False) -> bool:
+        if self._bridge is None:
+            return False
+        ok = self._bridge.stabilize_session(mycall, force=force)
+        self.status = self._bridge.status
+        return ok
+
+    def attach_session(self, mycall: str) -> bool:
+        if self._bridge is None:
+            return False
+        ok = self._bridge.attach_session(mycall)
+        self.status = self._bridge.status
+        return ok
+
+    def detach_session(self) -> None:
+        if self._bridge is None:
+            return
+        self._bridge.detach_session()
+        self.status = self._bridge.status
+
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        if self._bridge is None:
+            return False, "serial not ready"
+        ok, display = self._bridge.transmit(src, dst, text, ax25_ui)
+        self.status = self._bridge.status
+        return ok, display
+
+
+class KissRawBackend(DeviceBackend):
+    """Raw KISS on serial or BayCom KISS PTY (no command-mode entry)."""
+
+    backend_type = "kiss-raw"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        path: str,
+        profile: SerialProfile,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+        *,
+        is_pty: bool = False,
+    ) -> None:
+        self.device_id = cfg.device_id
+        self._path = path
+        self._profile = profile
+        self._on_rx = on_rx
+        self._log = log or (lambda _m: None)
+        self._is_pty = is_pty
+        self._fd: Optional[int] = None
+        self._thread: Optional[threading.Thread] = None
+        self._stop = threading.Event()
+        self._lock = threading.Lock()
+        self._mycall = ""
+        self._kiss_active = False
+        self._decoder = KissDecoder()
+        self.status = "closed"
+
+    def open(self) -> bool:
+        path = self._path
+        if not path:
+            self.status = "error-no-path"
+            self._log(f"{self.device_id}: no KISS path configured")
+            return False
+        if not os.path.exists(path):
+            self.status = "error-no-device"
+            self._log(f"{self.device_id}: path missing: {path}")
+            return False
+        try:
+            fd = os.open(path, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+            if not self._is_pty:
+                self._configure_serial(fd)
+            termios.tcflush(fd, termios.TCIOFLUSH)
+        except OSError as exc:
+            self.status = "error-open"
+            self._log(f"{self.device_id}: open failed: {exc}")
+            return False
+        self._fd = fd
+        self.status = "open"
+        self._stop.clear()
+        self._thread = threading.Thread(
+            target=self._rx_loop,
+            name=f"kiss-raw-{self.device_id}",
+            daemon=True,
+        )
+        self._thread.start()
+        self._log(f"{self.device_id}: raw KISS open {path}")
+        return True
+
+    def _configure_serial(self, fd: int) -> None:
+        from kiss_bridge import _parse_baud, _parse_line
+
+        speed = _parse_baud(self._profile.baud)
+        databits, parity = _parse_line(self._profile.line)
+        t = termios.tcgetattr(fd)
+        t[0] = t[1] = 0
+        t[2] = termios.CLOCAL | termios.CREAD | databits | parity
+        t[3] = t[4] = t[5] = speed
+        t[6][termios.VMIN] = 0
+        t[6][termios.VTIME] = 5
+        termios.tcsetattr(fd, termios.TCSANOW, t)
+        flags = struct.unpack("I", __import__("fcntl").ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+        if self._profile.dtr_rts:
+            flags |= 0x004 | 0x002
+        __import__("fcntl").ioctl(fd, 0x5416, struct.pack("I", flags))
+
+    def close(self) -> None:
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout=2.0)
+            self._thread = None
+        with self._lock:
+            if self._fd is not None:
+                try:
+                    os.close(self._fd)
+                except OSError:
+                    pass
+                self._fd = None
+            self._kiss_active = False
+        self.status = "closed"
+        self._decoder = KissDecoder()
+
+    def attach_session(self, mycall: str) -> bool:
+        if self._fd is None:
+            return False
+        self._mycall = mycall.upper()
+        self._kiss_active = True
+        self.status = "ready"
+        return True
+
+    def detach_session(self) -> None:
+        self._kiss_active = False
+        if self._fd is not None:
+            self.status = "open"
+
+    def stabilize_session(self, mycall: str, *, force: bool = False) -> bool:
+        """Reopen KISS path after dead PTY / EIO (e.g. bcprd recycled outside max25d)."""
+        path = self._path
+        if (
+            not force
+            and self._kiss_active
+            and self.status == "ready"
+            and self._fd is not None
+            and path
+            and os.path.exists(path)
+        ):
+            if not self._is_pty:
+                return True
+            # PTY symlink may have been retargeted while our fd still points at a
+            # deleted slave — force reopen when the live path inode differs.
+            try:
+                cur = os.stat(path)
+                fd_st = os.fstat(self._fd)
+                if cur.st_ino == fd_st.st_ino and cur.st_dev == fd_st.st_dev:
+                    return True
+            except OSError:
+                pass
+        was_active = self._kiss_active or force
+        call = (mycall or self._mycall or "").upper()
+        self.close()
+        if not self.open():
+            return False
+        if was_active and call:
+            return self.attach_session(call)
+        return self._fd is not None
+
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        if self._fd is None or not self._kiss_active:
+            return False, "KISS not ready"
+        if len(text.encode("utf-8")) > MAX_PAYLOAD:
+            return False, "payload too long"
+        info = text.encode("utf-8")
+        frame = ax25_build_ui(src, dst, info)
+        pkt = kiss_data_frame(0, frame)
+        with self._lock:
+            try:
+                os.write(self._fd, pkt)
+                # PTY: never tcdrain — if the master side dies, drain can hang forever.
+                if not self._is_pty:
+                    termios.tcdrain(self._fd)
+            except OSError as exc:
+                self.status = "error-tx"
+                return False, f"tx failed: {exc}"
+        display = format_rx_line(src, dst, info, ax25_ui)
+        return True, display
+
+    def _rx_loop(self) -> None:
+        while not self._stop.is_set():
+            fd = self._fd
+            if fd is None:
+                break
+            try:
+                chunk = os.read(fd, 4096)
+            except BlockingIOError:
+                time.sleep(0.05)
+                continue
+            except OSError:
+                break
+            if not chunk:
+                time.sleep(0.05)
+                continue
+            for _port, payload in self._decoder.feed(chunk):
+                if not payload:
+                    continue
+                parsed = ax25_parse_ui(payload)
+                if parsed is None:
+                    continue
+                src, dst, info = parsed
+                line = format_rx_line(src, dst, info, ax25_ui=True)
+                self._on_rx(line)
+
+
+class BayComKissBackend(KissRawBackend):
+    """BayCom kernel modem (SER12 / PAR96) via baycom-pr KISS PTY."""
+
+    backend_type = "baycom-kiss"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+    ) -> None:
+        modem = cfg.baycom_modem or "a"
+        kiss = cfg.kiss_link or f"/var/run/baycom-pr/kiss-{modem}"
+        if modem == "a" and not cfg.kiss_link:
+            default = "/var/run/baycom-pr/kiss"
+            if os.path.exists(default) or not os.path.exists(kiss):
+                kiss = default
+        profile = SerialProfile(baud=9600, line="8n1", dtr_rts=False)
+        super().__init__(cfg, kiss, profile, on_rx, log, is_pty=True)
+
+
+class Max25BcprKissBackend(KissRawBackend):
+    """max25-bcpr userspace SER12 via KISS PTY (max25e0 / max25e0:bcN).
+
+    Hardware is a TCM3105-class AFSK modem chip (bits↔AFSK + PTT) only — not a TNC.
+    """
+
+    backend_type = "max25-bcpr-kiss"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+    ) -> None:
+        tag = (cfg.max25_bcpr_device or cfg.bcpr_device or "bc0").strip() or "bc0"
+        kiss = cfg.kiss_link or f"/tmp/max25-bcpr/kiss-{tag}"
+        kiss = normalize_max25_bcpr_path(kiss)
+        profile = SerialProfile(baud=9600, line="8n1", dtr_rts=False)
+        super().__init__(cfg, kiss, profile, on_rx, log, is_pty=True)
+
+
+class KissRawSerialBackend(KissRawBackend):
+    """USB/async BayCom KISS serial (kiss-serial backend)."""
+
+    backend_type = "kiss-raw-serial"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        root: str,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+        prefix: Optional[str] = None,
+    ) -> None:
+        overrides: dict[str, str] = {}
+        if cfg.serial_device:
+            overrides["device"] = cfg.serial_device
+        if cfg.serial_baud:
+            overrides["baud"] = str(cfg.serial_baud)
+        if cfg.serial_line:
+            overrides["line"] = cfg.serial_line
+        if cfg.serial_dtr_rts:
+            overrides["dtr_rts"] = cfg.serial_dtr_rts
+        prof = serial_profile_for_device(cfg.device_id, root, overrides, prefix=prefix)
+        path = cfg.serial_device or prof.device
+        super().__init__(cfg, path, prof, on_rx, log, is_pty=False)
+
+
+class CrdopTcpBackend(DeviceBackend):
+    """MAX25-SoftModem (CRDOP) via TCP host interface (:8515 / :8516).
+
+    Native M25/KISS host protocol (MAX25-SoftModem) only.
+    """
+
+    backend_type = "crdop-tcp"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+    ) -> None:
+        self.device_id = cfg.device_id
+        self._cfg = cfg
+        self._on_rx = on_rx
+        self._log = log or (lambda _m: None)
+        self._ctrl: Optional[socket.socket] = None
+        self._data: Optional[socket.socket] = None
+        self._thread: Optional[threading.Thread] = None
+        self._stop = threading.Event()
+        self._lock = threading.RLock()
+        self._mycall = ""
+        self._connected = False
+        self.status = "closed"
+
+    def _line_term(self) -> str:
+        return "\n"
+
+    def open(self) -> bool:
+        host = self._cfg.crdop_host
+        port = self._cfg.crdop_port
+        ctrl = None
+        data = None
+        try:
+            ctrl = socket.create_connection((host, port), timeout=5.0)
+            ctrl.settimeout(0.5)
+            data = socket.create_connection((host, port + 1), timeout=5.0)
+            data.settimeout(0.5)
+        except OSError as exc:
+            if ctrl is not None:
+                try:
+                    ctrl.close()
+                except OSError:
+                    pass
+            self.status = "error-connect"
+            self._log(f"{self.device_id}: CRDOP TCP connect failed ({host}:{port}): {exc}")
+            return False
+        self._ctrl = ctrl
+        self._data = data
+        self.status = "open"
+        self._stop.clear()
+        self._thread = threading.Thread(
+            target=self._rx_loop,
+            name=f"crdop-rx-{self.device_id}",
+            daemon=True,
+        )
+        self._thread.start()
+        self._log(f"{self.device_id}: CRDOP TCP open {host}:{port}")
+        return True
+
+    def close(self) -> None:
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout=2.0)
+            self._thread = None
+        for sock in (self._ctrl, self._data):
+            if sock is not None:
+                try:
+                    sock.close()
+                except OSError:
+                    pass
+        self._ctrl = None
+        self._data = None
+        self._connected = False
+        self.status = "closed"
+
+    def _cmd(self, text: str) -> str:
+        if self._ctrl is None:
+            return ""
+        term = self._line_term()
+        payload = (text.rstrip(term) + term).encode("ascii", errors="replace")
+        with self._lock:
+            self._ctrl.sendall(payload)
+            return self._read_line_unlocked()
+
+    def _read_line_unlocked(self) -> str:
+        if self._ctrl is None:
+            return ""
+        term = self._line_term()
+        term_b = term.encode("ascii")
+        buf = b""
+        deadline = time.time() + 3.0
+        while time.time() < deadline:
+            try:
+                chunk = self._ctrl.recv(4096)
+            except socket.timeout:
+                continue
+            except OSError:
+                break
+            if not chunk:
+                break
+            buf += chunk
+            while term_b in buf:
+                raw, buf = buf.split(term_b, 1)
+                line = raw.decode("ascii", errors="replace").strip()
+                if line:
+                    return line
+        return ""
+
+    def attach_session(self, mycall: str) -> bool:
+        if self._ctrl is None:
+            return False
+        self._mycall = mycall.upper()
+        cmds = [
+            "INITIALIZE",
+            "PROTOCOLMODE KISS",
+            f"MYCALL {self._mycall}",
+        ]
+        if self._cfg.crdop_listen:
+            cmds.append("LISTEN TRUE")
+        for cmd in cmds:
+            reply = self._cmd(cmd)
+            self._log(f"{self.device_id}: {cmd} → {reply or '(no reply)'}")
+        self._connected = True
+        self.status = "ready"
+        return True
+
+    def detach_session(self) -> None:
+        if self._ctrl is not None and self._connected:
+            self._cmd("ABORT")
+        self._connected = False
+        if self._ctrl is not None:
+            self.status = "open"
+
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        if self._ctrl is None or self._data is None or not self._connected:
+            return False, "CRDOP not ready"
+        payload = text.encode("utf-8")
+        if len(payload) > MAX_PAYLOAD:
+            return False, "payload too long"
+        with self._lock:
+            try:
+                body = ax25_build_ui(src, dst, payload)
+                if len(body) >= 2:
+                    body = body[:-2]
+                self._data.sendall(body)
+            except OSError as exc:
+                self.status = "error-tx"
+                return False, f"tx failed: {exc}"
+        if ax25_ui:
+            display = f"[CRDOP AX25 UI {src}>{dst}] {text}"
+        else:
+            display = text
+        return True, display
+
+    def _rx_loop(self) -> None:
+        while not self._stop.is_set():
+            ctrl = self._ctrl
+            if ctrl is None:
+                break
+            try:
+                ready, _, _ = select.select([ctrl], [], [], 0.5)
+                if not ready:
+                    continue
+                chunk = ctrl.recv(4096)
+            except (OSError, socket.timeout):
+                continue
+            if not chunk:
+                time.sleep(0.05)
+                continue
+            term = self._line_term()
+            for line in chunk.decode("ascii", errors="replace").split(term):
+                line = line.strip()
+                if not line:
+                    continue
+                if line.startswith("STATUS"):
+                    self._on_rx(f"[CRDOP RX {self.device_id}] {line}")
+
+
+class AudioDummyBackend(DeviceBackend):
+    """Acoustic bench dummy — loopback, ALSA sniff, or M25 host TCP."""
+
+    backend_type = "audio-dummy"
+
+    def __init__(
+        self,
+        cfg: DeviceBackendConfig,
+        on_rx: RxFn,
+        log: Optional[LogFn] = None,
+    ) -> None:
+        self.device_id = cfg.device_id
+        self._cfg = cfg
+        self._on_rx = on_rx
+        self._log = log or (lambda _m: None)
+        self._ctrl: Optional[socket.socket] = None
+        self._data: Optional[socket.socket] = None
+        self._thread: Optional[threading.Thread] = None
+        self._stop = threading.Event()
+        self._lock = threading.RLock()
+        self._mycall = ""
+        self._connected = False
+        self._engine = None
+        self.status = "closed"
+
+    def _import_engine(self):
+        import sys
+        from pathlib import Path
+
+        lib = Path(__file__).resolve().parents[1] / "crdop" / "lib"
+        if str(lib) not in sys.path:
+            sys.path.insert(0, str(lib))
+        from acoustic_engine import AcousticEngine  # noqa: WPS433
+        from sound_proxy import SoundConfig  # noqa: WPS433
+
+        sound = SoundConfig(
+            capture=self._cfg.audio_capture or "default",
+            playback=self._cfg.audio_playback or self._cfg.audio_capture or "default",
+            sample_rate=self._cfg.audio_sample_rate,
+        )
+        return AcousticEngine(sample_rate=self._cfg.audio_sample_rate, sound=sound)
+
+    def open(self) -> bool:
+        mode = (self._cfg.audio_mode or "loopback").lower()
+        if mode == "host":
+            host = "127.0.0.1"
+            port = self._cfg.audio_host_port
+            ctrl = None
+            data = None
+            try:
+                ctrl = socket.create_connection((host, port), timeout=3.0)
+                ctrl.settimeout(0.5)
+                data = socket.create_connection((host, port + 1), timeout=3.0)
+                data.settimeout(0.5)
+            except OSError as exc:
+                if ctrl is not None:
+                    try:
+                        ctrl.close()
+                    except OSError:
+                        pass
+                self.status = "error-connect"
+                self._log(f"{self.device_id}: audio-dummy host connect failed: {exc}")
+                return False
+            self._ctrl = ctrl
+            self._data = data
+            self._stop.clear()
+            self._thread = threading.Thread(
+                target=self._host_rx_loop,
+                name=f"audio-dummy-{self.device_id}",
+                daemon=True,
+            )
+            self._thread.start()
+            self.status = "open"
+            self._log(f"{self.device_id}: audio-dummy host {host}:{port}")
+            return True
+
+        try:
+            self._engine = self._import_engine()
+        except Exception as exc:
+            self.status = "error-engine"
+            self._log(f"{self.device_id}: audio engine load failed: {exc}")
+            return False
+
+        if mode == "alsa" and self._cfg.audio_capture:
+            self._stop.clear()
+            self._thread = threading.Thread(
+                target=self._alsa_sniff_loop,
+                name=f"audio-sniff-{self.device_id}",
+                daemon=True,
+            )
+            self._thread.start()
+        self.status = "open"
+        self._log(f"{self.device_id}: audio-dummy mode={mode}")
+        return True
+
+    def close(self) -> None:
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout=2.0)
+            self._thread = None
+        for sock in (self._ctrl, self._data):
+            if sock is not None:
+                try:
+                    sock.close()
+                except OSError:
+                    pass
+        self._ctrl = None
+        self._data = None
+        self._connected = False
+        self.status = "closed"
+
+    def _host_cmd(self, text: str) -> str:
+        if self._ctrl is None:
+            return ""
+        payload = (text.rstrip("\n") + "\n").encode("ascii", errors="replace")
+        with self._lock:
+            self._ctrl.sendall(payload)
+            buf = b""
+            deadline = time.time() + 2.0
+            while time.time() < deadline:
+                try:
+                    chunk = self._ctrl.recv(4096)
+                except socket.timeout:
+                    continue
+                if not chunk:
+                    break
+                buf += chunk
+                if b"\n" in buf:
+                    line, _ = buf.split(b"\n", 1)
+                    return line.decode("ascii", errors="replace").strip()
+        return ""
+
+    def attach_session(self, mycall: str) -> bool:
+        self._mycall = mycall.upper()
+        if self._ctrl is not None:
+            for cmd in (
+                "INITIALIZE",
+                "PROTOCOLMODE KISS",
+                f"MYCALL {self._mycall}",
+                "LISTEN TRUE",
+            ):
+                reply = self._host_cmd(cmd)
+                self._log(f"{self.device_id}: {cmd} → {reply or '(no reply)'}")
+        self._connected = True
+        self.status = "ready"
+        return True
+
+    def detach_session(self) -> None:
+        self._connected = False
+        if self._ctrl is not None:
+            self.status = "open"
+        else:
+            self.status = "closed"
+
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        if not self._connected:
+            return False, "audio-dummy not ready"
+        payload = text.encode("utf-8")
+        if len(payload) > MAX_PAYLOAD:
+            return False, "payload too long"
+
+        if self._engine is not None:
+            pcm = self._engine.encode_ax25_ui(src, dst, text)
+            rep = self._engine.analyze_pcm(pcm)
+            for line in rep.decode_lines:
+                self._on_rx(f"[AUDIO RX {self.device_id}] {line}")
+            display = f"[AX25 UI {src}>{dst}] {text}" if ax25_ui else text
+            return True, display
+
+        if self._data is None:
+            return False, "no data channel"
+        import sys
+        from pathlib import Path
+
+        lib = Path(__file__).resolve().parents[1] / "crdop" / "lib"
+        if str(lib) not in sys.path:
+            sys.path.insert(0, str(lib))
+        from ax25_codec import ax25_build_ui  # noqa: WPS433
+
+        body = ax25_build_ui(src, dst, payload)
+        if len(body) >= 2:
+            body = body[:-2]
+        try:
+            with self._lock:
+                self._data.sendall(body)
+        except OSError as exc:
+            return False, f"tx failed: {exc}"
+        display = f"[AX25 UI {src}>{dst}] {text}" if ax25_ui else text
+        return True, display
+
+    def _alsa_sniff_loop(self) -> None:
+        import sys
+        from pathlib import Path
+
+        lib = Path(__file__).resolve().parents[1] / "crdop" / "lib"
+        if str(lib) not in sys.path:
+            sys.path.insert(0, str(lib))
+        from sound_proxy import SoundProxy  # noqa: WPS433
+
+        if self._engine is None:
+            return
+        proxy = SoundProxy(self._engine.sound)
+
+        def on_pcm(chunk: bytes) -> None:
+            rep = self._engine.analyze_pcm(chunk)
+            for line in rep.decode_lines:
+                self._on_rx(f"[SNIFF {self.device_id}] {line}")
+
+        try:
+            proxy.sniff_loop(chunk_symbols=40, on_pcm=on_pcm, stop=self._stop)
+        except Exception as exc:
+            self._log(f"{self.device_id}: sniff error: {exc}")
+
+    def _host_rx_loop(self) -> None:
+        while not self._stop.is_set():
+            if self._ctrl is None:
+                break
+            try:
+                ready, _, _ = select.select([self._ctrl], [], [], 0.5)
+                if not ready:
+                    continue
+                chunk = self._ctrl.recv(4096)
+            except (OSError, socket.timeout):
+                continue
+            if not chunk:
+                time.sleep(0.05)
+                continue
+            for line in chunk.decode("ascii", errors="replace").split("\n"):
+                line = line.strip()
+                if line.startswith("STATUS"):
+                    self._on_rx(f"[AUDIO RX {self.device_id}] {line}")
+
+
+def parse_device_spec(device_id: str, spec: str, cp, cfg_defaults: dict) -> DeviceBackendConfig:
+    """Build backend config from [devices] value and optional [device.<id>]."""
+    dev = DeviceBackendConfig(device_id=device_id)
+    dev.hardware = registry_hardware(device_id, cfg_defaults.get("hardware", "tncs"))
+    dev.backend_type = registry_backend(device_id)
+
+    section = f"device.{device_id}"
+    sec_opts: dict[str, str] = {}
+    if cp.has_section(section):
+        sec_opts = {k: cp.get(section, k) for k in cp.options(section)}
+
+    if sec_opts.get("hardware"):
+        dev.hardware = sec_opts["hardware"]
+    if sec_opts.get("backend"):
+        dev.backend_type = sec_opts["backend"]
+
+    spec = (spec or "").strip()
+    dev.device_spec = spec
+
+    if spec.startswith("baycom:"):
+        dev.backend_type = "baycom-kiss"
+        dev.baycom_modem = spec.split(":", 1)[1].strip() or "a"
+        dev.hardware = "modems"
+    elif spec.startswith("max25-bcpr:") or spec.startswith("bcpr:"):
+        # Userspace SER12 — product face max25-bcpr; device id remains max25e0
+        dev.backend_type = "max25-bcpr-kiss"
+        tag = spec.split(":", 1)[1].strip() or "bc0"
+        dev.max25_bcpr_device = tag
+        dev.bcpr_device = tag  # legacy alias
+        dev.hardware = "modems"
+        if not sec_opts.get("kiss_link"):
+            dev.kiss_link = f"/tmp/max25-bcpr/kiss-{tag}"
+    elif spec.startswith("crdop:"):
+        dev.backend_type = "crdop-tcp"
+        dev.crdop_profile = spec.split(":", 1)[1].strip() or "default"
+        dev.hardware = "soft-modems"
+    elif spec.startswith("audio:"):
+        dev.backend_type = "audio-dummy"
+        dev.audio_mode = spec.split(":", 1)[1].strip() or "loopback"
+        dev.hardware = "acoustic-bench"
+    elif spec.startswith("/") or spec.startswith("dev:"):
+        if dev.backend_type in ("baycom-kiss",):
+            dev.kiss_link = spec
+        else:
+            dev.serial_device = spec.removeprefix("dev:")
+            if dev.backend_type == "crdop-tcp":
+                dev.backend_type = "kiss-serial"
+    elif spec:
+        dev.serial_device = spec
+
+    if sec_opts.get("kiss_link"):
+        dev.kiss_link = sec_opts["kiss_link"]
+    if dev.backend_type in ("max25-bcpr-kiss", "bcpr-kiss") and dev.kiss_link:
+        dev.kiss_link = normalize_max25_bcpr_path(dev.kiss_link)
+    if sec_opts.get("modem"):
+        dev.baycom_modem = sec_opts["modem"]
+    if sec_opts.get("baycom_ini"):
+        dev.baycom_ini = sec_opts["baycom_ini"]
+    if sec_opts.get("max25_bcpr_ini") or sec_opts.get("bcpr_ini"):
+        ini_path = sec_opts.get("max25_bcpr_ini") or sec_opts.get("bcpr_ini") or ""
+        dev.max25_bcpr_ini = ini_path
+        dev.bcpr_ini = ini_path
+    if sec_opts.get("max25_bcpr_device") or sec_opts.get("bcpr_device"):
+        tag = sec_opts.get("max25_bcpr_device") or sec_opts.get("bcpr_device") or ""
+        dev.max25_bcpr_device = tag
+        dev.bcpr_device = tag
+    if sec_opts.get("ipv4"):
+        dev.ipv4 = sec_opts["ipv4"].strip()
+    if sec_opts.get("ipv6"):
+        dev.ipv6 = sec_opts["ipv6"].strip()
+    if sec_opts.get("host"):
+        dev.crdop_host = sec_opts["host"]
+    if sec_opts.get("port"):
+        dev.crdop_port = _spec_int(sec_opts["port"], dev.crdop_port)
+    if sec_opts.get("listen"):
+        dev.crdop_listen = sec_opts["listen"].lower() in ("1", "yes", "true", "on")
+    if sec_opts.get("mode"):
+        dev.audio_mode = sec_opts["mode"]
+    if sec_opts.get("capture"):
+        dev.audio_capture = sec_opts["capture"]
+    if sec_opts.get("playback"):
+        dev.audio_playback = sec_opts["playback"]
+    if sec_opts.get("sample_rate"):
+        dev.audio_sample_rate = _spec_int(sec_opts["sample_rate"], dev.audio_sample_rate)
+    if sec_opts.get("host_port"):
+        dev.audio_host_port = _spec_int(sec_opts["host_port"], dev.audio_host_port)
+
+    serial_sec = f"serial.{device_id}"
+    if cp.has_section(serial_sec):
+        if cp.has_option(serial_sec, "device"):
+            dev.serial_device = cp.get(serial_sec, "device")
+        if cp.has_option(serial_sec, "baud"):
+            dev.serial_baud = cp.getint(serial_sec, "baud")
+        if cp.has_option(serial_sec, "line"):
+            dev.serial_line = cp.get(serial_sec, "line")
+        if cp.has_option(serial_sec, "dtr_rts"):
+            dev.serial_dtr_rts = cp.get(serial_sec, "dtr_rts")
+        if cp.has_option(serial_sec, "kiss_entry"):
+            dev.serial_kiss_entry = cp.get(serial_sec, "kiss_entry")
+
+    # max25e0 family: hardcoded host addresses (forks inherit from root max25e0)
+    if device_id == "max25e0" or device_id.startswith("max25e0:"):
+        root_opts: dict[str, str] = {}
+        if device_id != "max25e0" and cp.has_section("device.max25e0"):
+            root_opts = {k: cp.get("device.max25e0", k) for k in cp.options("device.max25e0")}
+        if not dev.ipv4:
+            dev.ipv4 = (root_opts.get("ipv4") or "").strip() or MAX25E0_DEFAULT_IPV4
+        if not dev.ipv6:
+            dev.ipv6 = (root_opts.get("ipv6") or "").strip() or MAX25E0_DEFAULT_IPV6
+
+    return dev
+
+
+def create_backend(
+    dev_cfg: DeviceBackendConfig,
+    root: str,
+    on_rx: RxFn,
+    log: Optional[LogFn] = None,
+    prefix: Optional[str] = None,
+    on_invalid: Optional[InvalidFn] = None,
+) -> DeviceBackend:
+    kind = dev_cfg.backend_type or registry_backend(dev_cfg.device_id)
+    if kind == "kiss-serial":
+        return KissSerialBackend(dev_cfg, root, on_rx, log, prefix=prefix, on_invalid=on_invalid)
+    if kind == "baycom-kiss":
+        return BayComKissBackend(dev_cfg, on_rx, log)
+    if kind in ("max25-bcpr-kiss", "bcpr-kiss"):
+        return Max25BcprKissBackend(dev_cfg, on_rx, log)
+    if kind == "kiss-raw-serial":
+        return KissRawSerialBackend(dev_cfg, root, on_rx, log, prefix=prefix)
+    if kind == "crdop-tcp":
+        return CrdopTcpBackend(dev_cfg, on_rx, log)
+    if kind == "audio-dummy":
+        return AudioDummyBackend(dev_cfg, on_rx, log)
+    return KissSerialBackend(dev_cfg, root, on_rx, log, prefix=prefix)
+
+
+def backend_needs_stack(kind: str) -> bool:
+    return kind in (
+        "kiss-serial",
+        "baycom-kiss",
+        "max25-bcpr-kiss", "bcpr-kiss",
+        "kiss-raw-serial",
+        "crdop-tcp",
+        "audio-dummy",
+    )
+
+
+def backend_serial_label(backend: Optional[DeviceBackend]) -> str:
+    if backend is None:
+        return "n/a"
+    return backend.status
+
+
+# Legacy alias (tests / transitional)
+BcprKissBackend = Max25BcprKissBackend
diff --git a/stacks/daemon/kiss_bridge.py b/stacks/daemon/kiss_bridge.py
new file mode 100644
index 0000000..b433d0e
--- /dev/null
+++ b/stacks/daemon/kiss_bridge.py
@@ -0,0 +1,574 @@
+"""
+KISS serial bridge for max25d — AX.25 UI over TNC2C / PK-TNC2.
+
+PTT: TNC firmware keys on KISS DATA (requires MYCALL); kernel BayCom (baycom_ser_fdx)
+keys RTS in the driver when the KISS bridge accepts a DATA frame — no max25d PTT command.
+"""
+from __future__ import annotations
+
+import fcntl
+import os
+import struct
+import termios
+import threading
+import time
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Callable, Optional
+
+from ax25_codec import (  # noqa: E402
+    ax25_build_ui,
+    ax25_crc,
+    ax25_crc_valid,
+    ax25_parse_ui,
+    format_callsign,
+    parse_callsign,
+    validate_callsign,
+)
+from tx_pace import tx_pace_before_send  # noqa: E402
+
+FEND = 0xC0
+FESC = 0xDB
+TFEND = 0xDC
+TFESC = 0xDD
+
+# Native KISS return (TheFirmware TF 2.7) — firmware reset to banner, not TAPR kiss off
+KISS_RETURN_FRAME = b"\xc0\xff\xc0"
+
+KISS_CMD_DATA = 0x00
+MAX_FRAME = 1024
+MAX_PAYLOAD = 256
+
+
+@dataclass
+class SerialProfile:
+    device: str = "/dev/ttyS4"
+    baud: int = 19200
+    line: str = "8n1"
+    dtr_rts: bool = True
+    kiss_entry: str = "kiss_on"  # kiss_on | auto
+
+
+class KissDecoder:
+    def __init__(self) -> None:
+        self._buf = bytearray()
+        self._in_frame = False
+        self._escape = False
+
+    def feed(self, data: bytes) -> list[tuple[int, bytes]]:
+        frames: list[tuple[int, bytes]] = []
+        for byte in data:
+            if byte == FEND:
+                if self._in_frame and self._buf:
+                    parsed = self._deliver()
+                    if parsed is not None:
+                        frames.append(parsed)
+                self._in_frame = True
+                self._escape = False
+                self._buf.clear()
+                continue
+            if not self._in_frame:
+                continue
+            if self._escape:
+                if byte == TFEND:
+                    byte = FEND
+                elif byte == TFESC:
+                    byte = FESC
+                self._escape = False
+            elif byte == FESC:
+                self._escape = True
+                continue
+            if len(self._buf) >= MAX_FRAME:
+                self._buf.clear()
+                self._in_frame = False
+                continue
+            self._buf.append(byte)
+        return frames
+
+    def _deliver(self) -> Optional[tuple[int, bytes]]:
+        if len(self._buf) < 1:
+            return None
+        cmd_byte = self._buf[0]
+        if (cmd_byte & 0x0F) != KISS_CMD_DATA:
+            return None
+        port = (cmd_byte >> 4) & 0x0F
+        payload = bytes(self._buf[1:])
+        return port, payload
+
+
+def kiss_escape(data: bytes) -> bytes:
+    out = bytearray()
+    for b in data:
+        if b == FEND:
+            out.extend((FESC, TFEND))
+        elif b == FESC:
+            out.extend((FESC, TFESC))
+        else:
+            out.append(b)
+    return bytes(out)
+
+
+def kiss_encode(port: int, cmd: int, payload: bytes) -> bytes:
+    cmd_byte = ((port & 0x0F) << 4) | (cmd & 0x0F)
+    return b"\xC0" + kiss_escape(bytes([cmd_byte]) + payload) + b"\xC0"
+
+
+def kiss_data_frame(port: int, ax25_frame: bytes) -> bytes:
+    """Build KISS DATA; strip FCS when CRC validates (ax25ipd / KISS convention)."""
+    if ax25_crc_valid(ax25_frame):
+        ax25_frame = ax25_frame[:-2]
+    return kiss_encode(port, KISS_CMD_DATA, ax25_frame)
+
+
+def format_rx_line(src: str, dst: str, payload: bytes, ax25_ui: bool) -> str:
+    try:
+        text = payload.decode("utf-8")
+    except UnicodeDecodeError:
+        text = payload.decode("utf-8", errors="replace")
+    if ax25_ui:
+        return f"[AX25 UI {src}>{dst}] {text}"
+    return text
+
+
+def load_env_file(path: str) -> dict[str, str]:
+    out: dict[str, str] = {}
+    if not path or not os.path.isfile(path):
+        return out
+    with open(path, encoding="utf-8") as fh:
+        for line in fh:
+            line = line.strip()
+            if not line or line.startswith("#"):
+                continue
+            if "=" in line:
+                key, val = line.split("=", 1)
+                out[key.strip()] = val.strip()
+    return out
+
+
+def _load_serial_env(device_id: str, root: str, prefix: Optional[str] = None) -> dict[str, str]:
+    from paths import serial_env_candidates
+
+    tree = Path(root)
+    pref = Path(prefix) if prefix else None
+    for path in serial_env_candidates(device_id, tree, pref):
+        env = load_env_file(str(path))
+        if env:
+            return env
+    return {}
+
+
+def serial_profile_for_device(
+    device_id: str,
+    root: str,
+    ini: dict[str, str],
+    prefix: Optional[str] = None,
+) -> SerialProfile:
+    prof = SerialProfile()
+    if ini.get("device"):
+        prof.device = ini["device"]
+    if ini.get("baud"):
+        prof.baud = int(ini["baud"])
+    if ini.get("line"):
+        prof.line = ini["line"].lower()
+    if ini.get("dtr_rts"):
+        prof.dtr_rts = ini["dtr_rts"].lower() in ("1", "yes", "true", "on")
+    if ini.get("kiss_entry"):
+        prof.kiss_entry = ini["kiss_entry"].lower()
+
+    env = _load_serial_env(device_id, root, prefix)
+
+    if device_id == "tnc2c":
+        prof.device = ini.get("device") or env.get("TNC2C_DEV", prof.device)
+        prof.baud = int(ini.get("baud") or env.get("TNC2C_BAUD", prof.baud))
+        prof.line = (ini.get("line") or env.get("TNC2C_LINE", prof.line)).lower()
+        if "dtr_rts" not in ini:
+            prof.dtr_rts = True
+        if "kiss_entry" not in ini:
+            prof.kiss_entry = "kiss_on"
+    elif device_id == "pktnc2":
+        prof.device = ini.get("device") or env.get("PKTNC2_DEV") or env.get("TNC_DEV", prof.device)
+        prof.baud = int(ini.get("baud") or env.get("PKTNC2_BAUD") or env.get("TNC_BAUD", "9600"))
+        prof.line = (ini.get("line") or env.get("PKTNC2_LINE") or env.get("TNC_LINE", "8n1")).lower()
+        if "dtr_rts" not in ini:
+            prof.dtr_rts = False
+        if "kiss_entry" not in ini:
+            prof.kiss_entry = "auto"
+    elif device_id in ("pccom-kiss", "baycom-kiss"):
+        prof.device = ini.get("device") or env.get("PCCOM_KISS_DEV", prof.device or "/dev/ttyUSB0")
+        prof.baud = int(ini.get("baud") or env.get("PCCOM_KISS_BAUD", "9600"))
+        prof.line = (ini.get("line") or env.get("PCCOM_KISS_LINE", "8n1")).lower()
+        dtr = ini.get("dtr_rts") or env.get("PCCOM_KISS_DTR_RTS", "no")
+        prof.dtr_rts = str(dtr).lower() in ("1", "yes", "true", "on")
+        if "kiss_entry" not in ini:
+            prof.kiss_entry = "none"
+    elif device_id == "tmodem":
+        default_dev = "/dev/cuaU0" if sys.platform.startswith("freebsd") else "/dev/ttyACM0"
+        prof.device = ini.get("device") or env.get("TMODEM_DEV", prof.device or default_dev)
+        prof.baud = int(ini.get("baud") or env.get("TMODEM_BAUD", "115200"))
+        prof.line = (ini.get("line") or env.get("TMODEM_LINE", "8n1")).lower()
+        dtr = ini.get("dtr_rts") or env.get("TMODEM_DTR_RTS", "no")
+        prof.dtr_rts = str(dtr).lower() in ("1", "yes", "true", "on")
+        if "kiss_entry" not in ini:
+            prof.kiss_entry = "none"
+    return prof
+
+
+def _parse_line(line: str) -> tuple[int, int]:
+    line = line.lower()
+    if line == "7e1":
+        return termios.CS7, termios.PARENB
+    return termios.CS8, 0
+
+
+def _parse_baud(baud: int) -> int:
+    table = {
+        1200: termios.B1200,
+        2400: termios.B2400,
+        4800: termios.B4800,
+        9600: termios.B9600,
+        19200: termios.B19200,
+    }
+    if baud not in table:
+        raise ValueError(f"unsupported baud: {baud}")
+    return table[baud]
+
+
+class KissBridge:
+    """Thread-safe KISS bridge on a serial TNC port."""
+
+    def __init__(
+        self,
+        profile: SerialProfile,
+        on_rx: Callable[[str], None],
+        log: Optional[Callable[[str], None]] = None,
+        *,
+        tree_root: str = "",
+        install_prefix: Optional[str] = None,
+        on_invalid: Optional[Callable[[], None]] = None,
+    ) -> None:
+        self.profile = profile
+        self._on_rx = on_rx
+        self._on_invalid = on_invalid
+        self._log = log or (lambda _m: None)
+        self._tree_root = tree_root
+        self._install_prefix = install_prefix
+        self._fd: Optional[int] = None
+        self._thread: Optional[threading.Thread] = None
+        self._stop = threading.Event()
+        self._lock = threading.Lock()
+        self._kiss_active = False
+        self._mycall = ""
+        self.status = "closed"
+        self._decoder = KissDecoder()
+
+    def open(self) -> bool:
+        dev = self.profile.device
+        if not os.access(dev, os.R_OK | os.W_OK):
+            self.status = "error-no-device"
+            self._log(f"serial: no access to {dev}")
+            return False
+        try:
+            speed = _parse_baud(self.profile.baud)
+            databits, parity = _parse_line(self.profile.line)
+        except ValueError as exc:
+            self.status = "error-config"
+            self._log(f"serial: {exc}")
+            return False
+        try:
+            fd = os.open(dev, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+            t = termios.tcgetattr(fd)
+            t[0] = t[1] = 0
+            t[2] = termios.CLOCAL | termios.CREAD | databits | parity
+            t[3] = t[4] = t[5] = speed
+            t[6][termios.VMIN] = 0
+            t[6][termios.VTIME] = 5
+            termios.tcsetattr(fd, termios.TCSANOW, t)
+            termios.tcflush(fd, termios.TCIOFLUSH)
+            flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+            if self.profile.dtr_rts:
+                flags |= 0x004 | 0x002
+            fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+        except OSError as exc:
+            self.status = "error-open"
+            self._log(f"serial open failed: {exc}")
+            return False
+        self._fd = fd
+        self._log(f"serial open {dev} {self.profile.baud} {self.profile.line.upper()}")
+        if self.profile.dtr_rts:
+            time.sleep(2.0)
+            self._log("serial: DTR settle (2s)")
+        self.status = "open"
+        return True
+
+    def close(self) -> None:
+        self._stop_rx_thread()
+        with self._lock:
+            if self._fd is not None:
+                if self._kiss_active:
+                    self._write_unlocked(KISS_RETURN_FRAME)
+                try:
+                    os.close(self._fd)
+                except OSError:
+                    pass
+                self._fd = None
+            self._kiss_active = False
+        self.status = "closed"
+        self._decoder = KissDecoder()
+
+    def _stop_rx_thread(self) -> None:
+        """Stop KISS RX thread so recovery owns the serial FD exclusively."""
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout=2.0)
+            self._thread = None
+        self._stop.clear()
+
+    def _start_rx_thread(self) -> None:
+        """Start KISS RX after terminal recovery and KISS entry succeed."""
+        if self._fd is None or self._thread is not None or not self._kiss_active:
+            return
+        self._stop.clear()
+        self._thread = threading.Thread(target=self._rx_loop, name="kiss-rx", daemon=True)
+        self._thread.start()
+
+    def attach_session(self, mycall: str) -> bool:
+        if self._fd is None:
+            return False
+        self._mycall = mycall.upper()
+        self._stop_rx_thread()
+        with self._lock:
+            ok = self._stabilize_unlocked(self._mycall, force_ladder=False)
+        if ok:
+            self._start_rx_thread()
+        return ok
+
+    def stabilize_session(self, mycall: str, *, force: bool = False) -> bool:
+        """Probe terminal/KISS health and repair without closing the port (keeps DTR)."""
+        if self._fd is None:
+            self.status = "error-open"
+            return False
+        if not force and self._kiss_active and self.status == "ready":
+            return True
+        self._mycall = mycall.upper()
+        self._stop_rx_thread()
+        with self._lock:
+            ok = self._stabilize_unlocked(self._mycall, force_ladder=force)
+        if ok:
+            self._start_rx_thread()
+        return ok
+
+    def _load_recovery_mod(self):
+        import importlib.util
+
+        from paths import tnc_serial_recovery_path
+
+        path = None
+        if self._tree_root:
+            prefix = Path(self._install_prefix) if self._install_prefix else None
+            path = tnc_serial_recovery_path(Path(self._tree_root), prefix)
+        if path is None:
+            path = Path(__file__).resolve().parents[1] / "tncs" / "tnc_serial_recovery.py"
+        if not path.is_file():
+            return None
+        spec = importlib.util.spec_from_file_location("tnc_serial_recovery", path)
+        if spec is None or spec.loader is None:
+            return None
+        mod = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(mod)
+        return mod
+
+    def _recovery_io(self) -> tuple[Callable[[bytes], None], Callable[[float], bytes]]:
+        def wf(data: bytes) -> None:
+            self._write_unlocked(data)
+
+        def rf(seconds: float) -> bytes:
+            return self._drain_unlocked(seconds)
+
+        return wf, rf
+
+    def _leave_kiss_unlocked(self) -> None:
+        if not self._kiss_active:
+            return
+        self._write_unlocked(KISS_RETURN_FRAME)
+        time.sleep(0.3)
+        self._drain_unlocked(0.2)
+        self._kiss_active = False
+
+    def _enter_kiss_session_unlocked(self) -> bool:
+        if not self._set_mycall_unlocked(self._mycall):
+            self._log("serial: MYCALL may have failed")
+        if not self._enter_kiss_unlocked():
+            self.status = "error-kiss"
+            self._kiss_active = False
+            return False
+        self._kiss_active = True
+        self.status = "ready"
+        return True
+
+    def _stabilize_unlocked(self, mycall: str, *, force_ladder: bool) -> bool:
+        """Host probe, optional recovery ladder, MYCALL + KISS — port stays open."""
+        self._mycall = mycall.upper()
+        try:
+            mod = self._load_recovery_mod()
+            wf, rf = self._recovery_io()
+            self._leave_kiss_unlocked()
+
+            if mod is None:
+                self._log("serial: tnc_serial_recovery.py not found")
+                self.status = "error-config"
+                self._kiss_active = False
+                return False
+
+            ok, probe_data, only_echo = mod.probe_info(wf, rf, pause=0.25)
+            if not ok or only_echo or force_ladder:
+                self._log(
+                    f"serial: initial probe — {mod.format_rx_brief(probe_data)}, "
+                    f"echo_only={only_echo}, banner={mod.has_banner(probe_data)}"
+                )
+            if ok and not only_echo and not force_ladder:
+                return self._enter_kiss_session_unlocked()
+            if only_echo or not ok or force_ladder:
+                label = "auto-repair" if force_ladder else "recovery ladder"
+                self._log(f"serial: {label}")
+                ok, _ = mod.recover_terminal(wf, rf, log=self._log)
+                if not ok:
+                    self.status = "error-host"
+                    self._kiss_active = False
+                    return False
+                return self._enter_kiss_session_unlocked()
+            self.status = "error-host"
+            self._kiss_active = False
+            return False
+        except OSError as exc:
+            self.status = "error-io"
+            self._kiss_active = False
+            self._log(f"serial: stabilize I/O error ({exc})")
+            return False
+
+    def _recover_terminal_unlocked(self) -> bool:
+        """Legacy hook — full ladder when probe fails."""
+        try:
+            mod = self._load_recovery_mod()
+            if mod is None:
+                return True
+            wf, rf = self._recovery_io()
+            ok, _, only_echo = mod.probe_info(wf, rf)
+            if ok and not only_echo:
+                self._log("serial: terminal mode OK")
+                return True
+            self._log("serial: software recovery ladder")
+            ok, _ = mod.recover_terminal(wf, rf, log=self._log)
+            if ok:
+                self._log("serial: recovery OK")
+            return ok
+        except Exception as exc:
+            self._log(f"serial: recovery skipped ({exc})")
+            return True
+
+    def detach_session(self) -> None:
+        self._stop_rx_thread()
+        with self._lock:
+            if self._fd is not None and self._kiss_active:
+                self._write_unlocked(KISS_RETURN_FRAME)
+                time.sleep(0.2)
+            self._kiss_active = False
+        if self._fd is not None:
+            self.status = "open"
+
+    def transmit(self, src: str, dst: str, text: str, ax25_ui: bool) -> tuple[bool, str]:
+        if self._fd is None or not self._kiss_active:
+            return False, "serial not ready"
+        if len(text.encode("utf-8")) > MAX_PAYLOAD:
+            return False, "payload too long"
+        try:
+            validate_callsign(src)
+            validate_callsign(dst)
+        except ValueError as exc:
+            return False, str(exc)
+        info = text.encode("utf-8")
+        try:
+            frame = ax25_build_ui(src, dst, info)
+        except ValueError as exc:
+            return False, str(exc)
+        pkt = kiss_data_frame(0, frame)
+        with self._lock:
+            try:
+                tx_pace_before_send()
+                self._write_unlocked(pkt)
+                termios.tcdrain(self._fd)
+            except OSError as exc:
+                self.status = "error-tx"
+                return False, f"tx failed: {exc}"
+        display = format_rx_line(src, dst, info, ax25_ui)
+        return True, display
+
+    def _write_unlocked(self, data: bytes) -> None:
+        if self._fd is None:
+            return
+        os.write(self._fd, data)
+
+    def _drain_unlocked(self, seconds: float) -> bytes:
+        if self._fd is None:
+            return b""
+        end = time.time() + seconds
+        chunks: list[bytes] = []
+        while time.time() < end:
+            try:
+                chunk = os.read(self._fd, 4096)
+                if chunk:
+                    chunks.append(chunk)
+            except BlockingIOError:
+                time.sleep(0.02)
+        return b"".join(chunks)
+
+    def _set_mycall_unlocked(self, call: str) -> bool:
+        mod = self._load_recovery_mod()
+        if mod is not None and hasattr(mod, "tf_mycall_frame"):
+            cmd = mod.tf_mycall_frame(call)
+        else:
+            cmd = f"\x1bI {call.upper()}\r".encode("ascii", errors="replace")
+        self._write_unlocked(cmd)
+        time.sleep(0.4)
+        reply = self._drain_unlocked(0.6)
+        return b"?" not in reply[:32]
+
+    def _enter_kiss_unlocked(self) -> bool:
+        entry = self.profile.kiss_entry
+        if entry == "tapr":
+            self._write_unlocked(b"kiss on\r")
+            time.sleep(0.5)
+            self._drain_unlocked(0.3)
+            return True
+        self._write_unlocked(b"\x1b@K")
+        time.sleep(0.5)
+        self._drain_unlocked(0.3)
+        return True
+
+    def _rx_loop(self) -> None:
+        while not self._stop.is_set():
+            fd = self._fd
+            if fd is None:
+                break
+            try:
+                chunk = os.read(fd, 4096)
+            except BlockingIOError:
+                time.sleep(0.05)
+                continue
+            except OSError:
+                self._log("serial: rx I/O error — watch will repair")
+                self.status = "error-io"
+                break
+            if not chunk:
+                time.sleep(0.05)
+                continue
+            for _port, payload in self._decoder.feed(chunk):
+                if not payload:
+                    continue
+                parsed = ax25_parse_ui(payload)
+                if parsed is None:
+                    if self._on_invalid is not None and len(payload) >= 16:
+                        self._on_invalid()
+                    continue
+                src, dst, info = parsed
+                line = format_rx_line(src, dst, info, ax25_ui=True)
+                self._on_rx(line)
diff --git a/stacks/daemon/max25_platform.py b/stacks/daemon/max25_platform.py
new file mode 100644
index 0000000..2148fae
--- /dev/null
+++ b/stacks/daemon/max25_platform.py
@@ -0,0 +1,83 @@
+"""MAX25 host platform — Linux full stack, FreeBSD server + CRDOP/OSS."""
+from __future__ import annotations
+
+import os
+import sys
+
+
+def system_name() -> str:
+    return sys.platform
+
+
+def is_linux() -> bool:
+    return sys.platform == "linux"
+
+
+def is_freebsd() -> bool:
+    return sys.platform.startswith("freebsd")
+
+
+def is_bsd() -> bool:
+    return sys.platform.startswith(("freebsd", "openbsd", "netbsd", "darwin"))
+
+
+def max25d_supported() -> bool:
+    """Daemon may run (full stack on Linux, server+CRDOP on FreeBSD)."""
+    return is_linux() or is_freebsd()
+
+
+def default_unix_socket() -> str:
+    if is_linux():
+        return "/run/max25/modem.sock"
+    if is_freebsd():
+        return "/var/run/max25/modem.sock"
+    return "/tmp/max25/modem.sock"
+
+
+def default_bans_file() -> str:
+    if is_linux():
+        return "/var/lib/max25/bans.txt"
+    return "/var/db/max25/bans.txt"
+
+
+def supported_device_ids() -> frozenset[str]:
+    if is_linux():
+        return frozenset(
+            {
+                "tnc2c",
+                "pktnc2",
+                "tmodem",
+                "baycom-kiss",
+                "pccom-kiss",
+                # BayCom/based SER12 (max25-bcpr → device max25e0; not usable by default)
+                "max25e0",
+                "max25e0:bc0",
+                "max25e0:bc1",
+                "soft-crdop",
+                "audio-dummy",
+            }
+        )
+    if is_freebsd():
+        # USB KISS (tmodem/c1224) + CRDOP/OSS + max25-bcpr (SER12 via sysarch I386_SET_IOPERM)
+        return frozenset({"tmodem", "soft-crdop", "audio-dummy", "max25e0", "max25e0:bc0", "max25e0:bc1"})
+    return frozenset({"soft-crdop"})
+
+
+def crdop_audio_backend() -> str:
+    """Host audio API for CRDOP sound-proxy."""
+    env = os.environ.get("MAX25_AUDIO_BACKEND", "").strip().lower()
+    if env in ("alsa", "oss"):
+        return env
+    if is_linux():
+        return "alsa"
+    if is_freebsd():
+        return "oss"
+    return "alsa"
+
+
+def platform_label() -> str:
+    if is_linux():
+        return "Linux/KLinux"
+    if is_freebsd():
+        return "FreeBSD"
+    return sys.platform
diff --git a/stacks/daemon/max25d b/stacks/daemon/max25d
new file mode 100755
index 0000000..d6c075b
--- /dev/null
+++ b/stacks/daemon/max25d
@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# max25d launcher — ps(1) shows this path, not "python3 …/max25d".
+set -euo pipefail
+ROOT="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
+case "${1:-}" in
+  session)
+    shift
+    for candidate in \
+      "${ROOT}/../../scripts/max25d-session.sh" \
+      "${ROOT}/../scripts/max25d-session.sh" \
+      "$(command -v max25d-session 2>/dev/null || true)"
+    do
+      if [[ -n "${candidate}" && -x "${candidate}" ]]; then
+        exec "${candidate}" "$@"
+      fi
+    done
+    echo "max25d: max25d-session helper not found" >&2
+    exit 1
+    ;;
+esac
+exec -a "$0" python3 "${ROOT}/max25d.py" "$@"
diff --git a/stacks/daemon/max25d.py b/stacks/daemon/max25d.py
new file mode 100755
index 0000000..2488f8d
--- /dev/null
+++ b/stacks/daemon/max25d.py
@@ -0,0 +1,2185 @@
+#!/usr/bin/env python3
+"""
+max25d — MainAX25-Stack daemon.
+
+Linux/KLinux: full hardware stack. FreeBSD: server + CRDOP/OSS (modular TCP/IP service).
+"""
+from __future__ import annotations
+
+import argparse
+import configparser
+import os
+import re
+import select
+import signal
+import socket
+import subprocess
+import sys
+import tempfile
+import threading
+import time
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Optional, Set
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+from device_backends import (  # noqa: E402
+    DeviceBackend,
+    DeviceBackendConfig,
+    backend_serial_label,
+    baycom_ctl_device_id,
+    create_backend,
+    parse_device_spec,
+    registry_backend,
+    registry_tested,
+)
+from banlist import BanList, extract_ax25_source  # noqa: E402
+from reporting_quality import DataQualityTracker, RxOutcome, classify_rx_line  # noqa: E402
+from daemon_log import LOGGER, emit_startup_banner, emit_startup_complete  # noqa: E402
+from kiss_bridge import KissBridge  # noqa: E402 — tests patch this symbol
+from paths import (  # noqa: E402
+    ctl_path,
+    MAX25_BCPR_KISS_DEFAULT,
+    normalize_max25_bcpr_path,
+    resolve_baycom_ini,
+    resolve_layout,
+)
+from max25_platform import (  # noqa: E402
+    default_bans_file,
+    default_unix_socket,
+    max25d_supported,
+    platform_label,
+    supported_device_ids,
+)
+from privilege_drop import RunAsConfig, drop_privileges_or_exit, parse_run_as  # noqa: E402
+from modular_tcp_server import ModularTcpMainService, ModularTcpConfig, load_modular_tcp  # noqa: E402
+
+_EXE = Path(__file__).resolve()
+TREE, PREFIX = resolve_layout(_EXE)
+ROOT = TREE  # dev checkout root or MAX25_ROOT / install prefix
+
+DEFAULT_TCP_PORT = 7325
+DEFAULT_UNIX = default_unix_socket()
+M25_MAX_LINE_BUF = 65536
+CALLSIGN_RE = re.compile(r"^[A-Z0-9]{1,6}(-(1[0-5]|[0-9]))?$")
+RESERVED_DEVICE_KEYS = frozenset({"default", "enabled"})
+
+
+def _device_is_baycom(dev: DeviceBackendConfig) -> bool:
+    if dev.device_id.startswith("baycom"):
+        return True
+    spec = (dev.device_spec or "").strip()
+    if spec.startswith("baycom:"):
+        return True
+    return dev.backend_type == "baycom-kiss" and dev.hardware == "modems"
+
+
+def _device_is_pccom(dev: DeviceBackendConfig) -> bool:
+    if "pccom" in dev.device_id.lower():
+        return True
+    ini = (dev.baycom_ini or "").lower()
+    return "pccom" in ini
+
+
+
+def _device_is_max25_bcpr(dev: DeviceBackendConfig) -> bool:
+    # Product device id = max25e0 (+ forks max25e0:bcN); backend = max25-bcpr
+    if dev.device_id == "max25e0" or dev.device_id.startswith("max25e0:"):
+        return True
+    spec = (dev.device_spec or "").strip()
+    if spec.startswith("max25-bcpr:") or spec.startswith("bcpr:"):
+        return True
+    return dev.backend_type in ("max25-bcpr-kiss", "bcpr-kiss")
+
+
+def _device_is_tmodem(dev: DeviceBackendConfig) -> bool:
+    return dev.device_id == "tmodem"
+
+
+def _device_allowed_by_features(dev: DeviceBackendConfig, cfg: DaemonConfig) -> bool:
+    if _device_is_baycom(dev) and not cfg.feature_baycom:
+        LOGGER.warn(
+            f"device {dev.device_id}: BayCom disabled — set [features] baycom=yes",
+            area="config",
+        )
+        return False
+    if _device_is_pccom(dev) and not cfg.feature_pccom:
+        LOGGER.warn(
+            f"device {dev.device_id}: PC-COM disabled — set [features] pccom=yes",
+            area="config",
+        )
+        return False
+    if _device_is_max25_bcpr(dev) and not cfg.feature_max25_bcpr:
+        LOGGER.warn(
+            f"device {dev.device_id}: max25-bcpr disabled — set [features] max25_bcpr=yes",
+            area="config",
+        )
+        return False
+    if _device_is_tmodem(dev) and not cfg.feature_tmodem:
+        LOGGER.warn(
+            f"device {dev.device_id}: T-Modem disabled — set [features] tmodem=yes",
+            area="config",
+        )
+        return False
+    return True
+
+
+@dataclass
+class TotConfig:
+    """Software TOT for BayCom/based (max25-bcpr) — host policy, not radio TOT."""
+
+    enabled: bool = True
+    max_key_sec: int = 25
+    min_gap_sec: float = 1.5
+    max_consecutive: int = 3
+    max_bursts: int = 8
+    recover_sec: int = 300
+
+
+@dataclass
+class DaemonConfig:
+    mode: str = "standalone"
+    hardware: str = "tncs"
+    device: str = "tnc2c"
+    default_device: str = ""
+    devices: list[DeviceBackendConfig] = field(default_factory=list)
+    tcp_host: str = "0.0.0.0"
+    tcp_port: int = DEFAULT_TCP_PORT
+    unix_socket: str = DEFAULT_UNIX
+    tcp_password: str = ""
+    callerid: str = "CB-0"
+    callid: str = "QST"
+    ax25_ui: bool = True
+    auto_start: bool = True
+    serial_enabled: bool = True
+    serial_watch: bool = True
+    serial_watch_interval: int = 60
+    serial_repair_cooldown: int = 20
+    serial_watch_startup_grace: int = 45
+    stack_recover_only: bool = True
+    stack_retry_interval: int = 120
+    serial_bootwait_escalate: bool = True
+    serial_bootwait_escalate_after: int = 3
+    serial_bootwait_escalate_cooldown: int = 300
+    bans_file: str = field(default_factory=default_bans_file)
+    config_path: str = ""
+    feature_baycom: bool = True
+    feature_pccom: bool = True
+    feature_max25_bcpr: bool = True
+    feature_tmodem: bool = False
+    hybbx_release_attach: bool = False
+    run_user: str = ""
+    run_group: str = ""
+    run_uid: Optional[int] = None
+    run_gid: Optional[int] = None
+    report_error_transmissions: bool = True
+    report_voice_transmissions: bool = True
+    report_data_passes: int = 3
+    report_data_quality_min: int = 50
+    report_data_pass_seconds: int = 20
+    # Legacy single-device [serial] overrides (used when [devices] absent).
+    serial_device: str = ""
+    serial_baud: int = 0
+    serial_line: str = ""
+    serial_dtr_rts: str = ""
+    serial_kiss_entry: str = ""
+    modular_tcp: ModularTcpConfig = field(default_factory=ModularTcpConfig)
+    tot: TotConfig = field(default_factory=TotConfig)
+
+
+@dataclass
+class DeviceRuntime:
+    cfg: DeviceBackendConfig
+    backend: Optional[DeviceBackend] = None
+    stack_proc: Optional[subprocess.Popen] = None
+    stack_status: str = "stopped"
+    link_status: str = "n/a"
+    last_watch: float = 0.0
+    last_repair: float = 0.0
+    last_stack_retry: float = 0.0
+    prep_done: bool = False
+    inline_repair_failures: int = 0
+    last_bootwait_escalate: float = 0.0
+    quality: DataQualityTracker = field(default_factory=DataQualityTracker)
+    tot_paused: bool = False
+    tot_paused_until: float = 0.0
+    tot_trip_reason: str = ""
+
+
+@dataclass
+class DaemonState:
+    cfg: DaemonConfig
+    connected: bool = False
+    monitor_only: bool = False
+    selected_device: str = ""
+    devices: dict[str, DeviceRuntime] = field(default_factory=dict)
+    clients: Set[socket.socket] = field(default_factory=set)
+    bans: BanList = field(default_factory=BanList)
+    lock: threading.Lock = field(default_factory=threading.Lock)
+    started_at: float = 0.0
+
+
+def log(msg: str) -> None:
+    """Legacy log hook — structured stderr (human + machine readable)."""
+    LOGGER.emit_unstructured(msg)
+
+
+def valid_callsign(value: str) -> bool:
+    return bool(value and CALLSIGN_RE.match(value.upper()))
+
+
+def _truthy(value: str) -> bool:
+    return value.lower() in ("1", "yes", "true", "on")
+
+
+def _ini_int(
+    cp: configparser.ConfigParser,
+    section: str,
+    key: str,
+    default: int,
+    *,
+    min_value: int = 1,
+    max_value: int = 86400,
+) -> int:
+    if not cp.has_option(section, key):
+        return default
+    raw = cp.get(section, key)
+    try:
+        value = int(str(raw).strip())
+    except (TypeError, ValueError):
+        LOGGER.warn(
+            f"[{section}] {key}={raw!r} invalid — using {default}",
+            area="config",
+        )
+        return default
+    if value < min_value:
+        LOGGER.warn(
+            f"[{section}] {key}={value} below {min_value} — using {min_value}",
+            area="config",
+        )
+        return min_value
+    if value > max_value:
+        LOGGER.warn(
+            f"[{section}] {key}={value} above {max_value} — using {max_value}",
+            area="config",
+        )
+        return max_value
+    return value
+
+
+def _safe_port(raw: str, default: int) -> int:
+    try:
+        port = int(str(raw).strip())
+    except (TypeError, ValueError):
+        return default
+    if port < 1 or port > 65535:
+        return default
+    return port
+
+
+def _serial_overrides_from_section(cp: configparser.ConfigParser, section: str) -> dict[str, str]:
+    if not cp.has_section(section):
+        return {}
+    out: dict[str, str] = {}
+    for key in ("device", "baud", "line", "dtr_rts", "kiss_entry"):
+        if cp.has_option(section, key):
+            out[key] = cp.get(section, key)
+    return out
+
+
+def _apply_serial_overrides(dev: DeviceBackendConfig, overrides: dict[str, str]) -> None:
+    if overrides.get("device"):
+        dev.serial_device = overrides["device"]
+    if overrides.get("baud"):
+        dev.serial_baud = int(overrides["baud"])
+    if overrides.get("line"):
+        dev.serial_line = overrides["line"]
+    if overrides.get("dtr_rts"):
+        dev.serial_dtr_rts = overrides["dtr_rts"]
+    if overrides.get("kiss_entry"):
+        dev.serial_kiss_entry = overrides["kiss_entry"]
+
+
+def parse_devices(cp: configparser.ConfigParser, cfg: DaemonConfig) -> list[DeviceBackendConfig]:
+    """Build device list from [devices] or legacy [daemon] device= + [serial]."""
+    defaults = {"hardware": cfg.hardware}
+    if cp.has_section("devices"):
+        default_id = cp.get("devices", "default", fallback="").strip()
+        enabled_raw = cp.get("devices", "enabled", fallback="").strip()
+        enabled_set: Optional[set[str]] = None
+        if enabled_raw:
+            enabled_set = {x.strip() for x in enabled_raw.split(",") if x.strip()}
+
+        entries: list[DeviceBackendConfig] = []
+        for key in cp.options("devices"):
+            if key.lower() in RESERVED_DEVICE_KEYS:
+                continue
+            device_id = key.strip()
+            spec = cp.get("devices", key, fallback="").strip()
+            dev = parse_device_spec(device_id, spec, cp, defaults)
+            if enabled_set is not None:
+                dev.enabled = device_id in enabled_set
+            entries.append(dev)
+
+        if not entries:
+            LOGGER.warn(
+                "[devices] section empty — falling back to legacy single device",
+                area="config",
+            )
+        else:
+            if default_id:
+                cfg.default_device = default_id
+                if enabled_set is not None and default_id not in enabled_set:
+                    enabled_entries = [d for d in entries if d.enabled]
+                    if enabled_entries:
+                        fallback = enabled_entries[0].device_id
+                        LOGGER.warn(
+                            f"[devices] default={default_id} not enabled — using {fallback}",
+                            area="config",
+                        )
+                        cfg.default_device = fallback
+            elif cfg.device:
+                cfg.default_device = cfg.device
+            else:
+                cfg.default_device = entries[0].device_id
+            return entries
+
+    # Legacy single device
+    device_id = cfg.device or "tnc2c"
+    dev = parse_device_spec(device_id, "", cp, defaults)
+    legacy = _serial_overrides_from_section(cp, "serial")
+    if cfg.serial_device:
+        legacy.setdefault("device", cfg.serial_device)
+    if cfg.serial_baud:
+        legacy.setdefault("baud", str(cfg.serial_baud))
+    if cfg.serial_line:
+        legacy.setdefault("line", cfg.serial_line)
+    if cfg.serial_dtr_rts:
+        legacy.setdefault("dtr_rts", cfg.serial_dtr_rts)
+    if cfg.serial_kiss_entry:
+        legacy.setdefault("kiss_entry", cfg.serial_kiss_entry)
+    _apply_serial_overrides(dev, legacy)
+    cfg.default_device = device_id
+    return [dev]
+
+
+def _ini_float(
+    cp: configparser.ConfigParser,
+    section: str,
+    key: str,
+    default: float,
+    *,
+    min_value: float = 0.0,
+    max_value: float = 3600.0,
+) -> float:
+    if not cp.has_option(section, key):
+        return default
+    raw = cp.get(section, key).strip()
+    try:
+        value = float(raw)
+    except ValueError:
+        LOGGER.warn(f"invalid float {section}.{key}={raw!r} — using {default}", area="config")
+        return default
+    if value < min_value:
+        return min_value
+    if value > max_value:
+        return max_value
+    return value
+
+
+def load_config(path: Optional[Path]) -> DaemonConfig:
+    cfg = DaemonConfig()
+    if path is None:
+        for candidate in (
+            Path(os.environ.get("MAX25D_INI", "")),
+            Path("/etc/max25/max25d.ini"),
+            ROOT / "share/max25/max25d.ini.example",
+        ):
+            if candidate and candidate.is_file():
+                path = candidate
+                break
+    if path is None or not path.is_file():
+        LOGGER.warn(f"using built-in defaults (no ini at {path})", area="config")
+        cfg.devices = [parse_device_spec(cfg.device, "", configparser.ConfigParser(), {"hardware": cfg.hardware})]
+        cfg.default_device = cfg.device
+        cfg.config_path = ""
+        return cfg
+
+    cfg.config_path = str(path)
+
+    cp = configparser.ConfigParser(strict=False)
+    cp.read(path)
+    if cp.has_section("daemon"):
+        cfg.mode = cp.get("daemon", "mode", fallback=cfg.mode)
+        cfg.hardware = cp.get("daemon", "hardware", fallback=cfg.hardware)
+        cfg.device = cp.get("daemon", "device", fallback=cfg.device)
+        run_as = parse_run_as(cp)
+        cfg.run_user = run_as.user
+        cfg.run_group = run_as.group
+        cfg.run_uid = run_as.uid
+        cfg.run_gid = run_as.gid
+    if cp.has_section("network"):
+        cfg.tcp_host = cp.get("network", "tcp_host", fallback=cfg.tcp_host)
+        cfg.tcp_port = _ini_int(cp, "network", "tcp_port", cfg.tcp_port, min_value=1, max_value=65535)
+        cfg.unix_socket = cp.get("network", "unix_socket", fallback=cfg.unix_socket)
+        cfg.tcp_password = cp.get("network", "tcp_password", fallback=cfg.tcp_password)
+    if cp.has_section("modem"):
+        cfg.callerid = cp.get("modem", "callerid", fallback=cfg.callerid).upper()
+        cfg.callid = cp.get("modem", "callid", fallback=cfg.callid).upper()
+        cfg.ax25_ui = _truthy(cp.get("modem", "ax25_ui", fallback="yes"))
+        cfg.bans_file = cp.get("modem", "bans_file", fallback=cfg.bans_file)
+    if cp.has_section("stack"):
+        cfg.auto_start = _truthy(cp.get("stack", "auto_start", fallback="yes"))
+        if cp.has_option("stack", "serial_watch"):
+            cfg.serial_watch = _truthy(cp.get("stack", "serial_watch"))
+        cfg.serial_watch_interval = _ini_int(
+            cp, "stack", "serial_watch_interval", cfg.serial_watch_interval
+        )
+        cfg.serial_repair_cooldown = _ini_int(
+            cp, "stack", "serial_repair_cooldown", cfg.serial_repair_cooldown
+        )
+        cfg.serial_watch_startup_grace = _ini_int(
+            cp, "stack", "serial_watch_startup_grace", cfg.serial_watch_startup_grace
+        )
+        if cp.has_option("stack", "stack_recover_only"):
+            cfg.stack_recover_only = _truthy(cp.get("stack", "stack_recover_only"))
+        cfg.stack_retry_interval = _ini_int(
+            cp, "stack", "stack_retry_interval", cfg.stack_retry_interval
+        )
+        if cp.has_option("stack", "serial_bootwait_escalate"):
+            cfg.serial_bootwait_escalate = _truthy(cp.get("stack", "serial_bootwait_escalate"))
+        cfg.serial_bootwait_escalate_after = _ini_int(
+            cp, "stack", "serial_bootwait_escalate_after", cfg.serial_bootwait_escalate_after
+        )
+        cfg.serial_bootwait_escalate_cooldown = _ini_int(
+            cp,
+            "stack",
+            "serial_bootwait_escalate_cooldown",
+            cfg.serial_bootwait_escalate_cooldown,
+        )
+    if cp.has_section("serial"):
+        cfg.serial_device = cp.get("serial", "device", fallback="")
+        cfg.serial_baud = cp.getint("serial", "baud", fallback=0)
+        cfg.serial_line = cp.get("serial", "line", fallback="")
+        cfg.serial_dtr_rts = cp.get("serial", "dtr_rts", fallback="")
+        cfg.serial_kiss_entry = cp.get("serial", "kiss_entry", fallback="")
+
+    if cp.has_section("features"):
+        cfg.feature_baycom = _truthy(cp.get("features", "baycom", fallback="yes"))
+        cfg.feature_pccom = _truthy(cp.get("features", "pccom", fallback="yes"))
+        # Product key max25_bcpr; legacy bcpr= accepted
+        cfg.feature_max25_bcpr = _truthy(
+            cp.get("features", "max25_bcpr", fallback=cp.get("features", "bcpr", fallback="yes"))
+        )
+        cfg.feature_tmodem = _truthy(cp.get("features", "tmodem", fallback="no"))
+    if cp.has_section("hybbx"):
+        cfg.hybbx_release_attach = _truthy(
+            cp.get("hybbx", "release_attach", fallback="no")
+        )
+        if cp.has_option("hybbx", "attach"):
+            cfg.hybbx_release_attach = _truthy(cp.get("hybbx", "attach"))
+    cfg.report_error_transmissions = _truthy(
+        cp.get("reporting", "error_transmissions", fallback="yes")
+    )
+    cfg.report_voice_transmissions = _truthy(
+        cp.get("reporting", "voice_transmissions", fallback="yes")
+    )
+    cfg.report_data_passes = _ini_int(
+        cp, "reporting", "data_passes", 3, min_value=1, max_value=32
+    )
+    cfg.report_data_quality_min = _ini_int(
+        cp, "reporting", "data_quality_min", 50, min_value=1, max_value=100
+    )
+    cfg.report_data_pass_seconds = _ini_int(
+        cp, "reporting", "data_pass_seconds", 20, min_value=1, max_value=300
+    )
+    if cp.has_section("tot"):
+        cfg.tot.enabled = _truthy(cp.get("tot", "enabled", fallback="yes"))
+        cfg.tot.max_key_sec = _ini_int(
+            cp, "tot", "max_key_sec", cfg.tot.max_key_sec, min_value=1, max_value=600
+        )
+        if cp.has_option("tot", "max_key_ms"):
+            cfg.tot.max_key_sec = max(
+                1, _ini_int(cp, "tot", "max_key_ms", cfg.tot.max_key_sec * 1000) // 1000
+            )
+        cfg.tot.min_gap_sec = _ini_float(
+            cp, "tot", "min_gap_sec", cfg.tot.min_gap_sec, min_value=0.0, max_value=60.0
+        )
+        if cp.has_option("tot", "min_gap_ms"):
+            cfg.tot.min_gap_sec = _ini_int(cp, "tot", "min_gap_ms", 1500) / 1000.0
+        cfg.tot.max_consecutive = _ini_int(
+            cp, "tot", "max_consecutive", cfg.tot.max_consecutive, min_value=1, max_value=32
+        )
+        cfg.tot.max_bursts = _ini_int(
+            cp, "tot", "max_bursts", cfg.tot.max_bursts, min_value=1, max_value=64
+        )
+        cfg.tot.recover_sec = _ini_int(
+            cp, "tot", "recover_sec", cfg.tot.recover_sec, min_value=0, max_value=86400
+        )
+
+    cfg.devices = parse_devices(cp, cfg)
+    cfg.devices = [d for d in cfg.devices if _device_allowed_by_features(d, cfg)]
+    allowed = supported_device_ids()
+    if allowed:
+        filtered: list[DeviceBackendConfig] = []
+        for dev in cfg.devices:
+            if dev.device_id in allowed:
+                filtered.append(dev)
+            else:
+                LOGGER.warn(
+                    f"device {dev.device_id} not supported on {platform_label()} — skipped",
+                    area="config",
+                )
+        cfg.devices = filtered
+    if not cfg.devices:
+        LOGGER.warn("no devices remain after config/platform filter", area="config")
+    cfg.modular_tcp = load_modular_tcp(cp)
+    if not cfg.default_device and cfg.devices:
+        cfg.default_device = cfg.devices[0].device_id
+    cfg.device = cfg.default_device
+    return cfg
+
+
+def init_device_runtimes(state: DaemonState) -> None:
+    state.devices.clear()
+    for dev_cfg in state.cfg.devices:
+        if not dev_cfg.enabled:
+            continue
+        state.devices[dev_cfg.device_id] = DeviceRuntime(
+            cfg=dev_cfg,
+            quality=DataQualityTracker(
+                passes_required=state.cfg.report_data_passes,
+                min_good_percent=state.cfg.report_data_quality_min,
+                pass_window_sec=state.cfg.report_data_pass_seconds,
+            ),
+        )
+        if not registry_tested(dev_cfg.device_id):
+            LOGGER.warn(
+                f"backend={dev_cfg.backend_type or 'auto'} — not hardware-validated in CI",
+                area="devices",
+                device=dev_cfg.device_id,
+            )
+    if state.cfg.default_device in state.devices:
+        state.selected_device = state.cfg.default_device
+    elif state.devices:
+        state.selected_device = next(iter(state.devices))
+    else:
+        state.selected_device = state.cfg.default_device
+        LOGGER.warn("no enabled device runtimes — SEND/CONNECT unavailable", area="devices")
+
+
+def enabled_device_ids(state: DaemonState) -> list[str]:
+    return list(state.devices.keys())
+
+
+def device_hardware(state: DaemonState, dev_id: str) -> str:
+    rt = state.devices.get(dev_id)
+    if rt is None:
+        return state.cfg.hardware
+    return rt.cfg.hardware or state.cfg.hardware
+
+
+def device_backend_kind(state: DaemonState, dev_id: str) -> str:
+    rt = state.devices.get(dev_id)
+    if rt is None:
+        return "kiss-serial"
+    return rt.cfg.backend_type or "kiss-serial"
+
+
+def on_backend_rx(state: DaemonState, dev_id: str, line: str) -> None:
+    rt = state.devices.get(dev_id)
+    if rt is not None:
+        _sync_quality_tracker(state, rt)
+        rt.quality.record(classify_rx_line(line, state.cfg.callid))
+    src = extract_ax25_source(line)
+    if src and state.bans.is_banned(src):
+        return
+    log(f"rx {dev_id}: {line}")
+    broadcast(state, f"RX device={dev_id} {line}")
+
+
+def on_backend_invalid_frame(state: DaemonState, dev_id: str) -> None:
+    rt = state.devices.get(dev_id)
+    if rt is None:
+        return
+    _sync_quality_tracker(state, rt)
+    rt.quality.record_bad()
+    if state.cfg.report_error_transmissions:
+        broadcast(state, f"EVENT device={dev_id} error=invalid")
+
+
+VOICE_BACKEND_KINDS = frozenset({"crdop-tcp", "audio-dummy"})
+
+
+def device_has_voice_path(rt: DeviceRuntime) -> bool:
+    kind = rt.cfg.backend_type or registry_backend(rt.cfg.device_id)
+    if kind in VOICE_BACKEND_KINDS:
+        return True
+    hw = (rt.cfg.hardware or "").lower()
+    return hw in ("acoustic-bench", "soft-modems")
+
+
+def device_link_status(rt: DeviceRuntime) -> str:
+    if rt.backend is not None:
+        return backend_serial_label(rt.backend)
+    return rt.link_status
+
+
+def link_status_is_healthy(status: str) -> bool:
+    if status in ("ready", "open", "n/a"):
+        return True
+    if status.startswith("error") or status in ("closed", "stopped"):
+        return False
+    return True
+
+
+def _sync_quality_tracker(state: DaemonState, rt: DeviceRuntime) -> None:
+    required = state.cfg.report_data_passes
+    minimum = state.cfg.report_data_quality_min
+    window = state.cfg.report_data_pass_seconds
+    if (
+        rt.quality.passes_required == required
+        and rt.quality.min_good_percent == minimum
+        and rt.quality.pass_window_sec == window
+        and rt.quality.passes.maxlen == required
+    ):
+        return
+    kept = list(rt.quality.passes)[-required:]
+    voice = rt.quality.voice_activity
+    current = rt.quality.current
+    rt.quality = DataQualityTracker(
+        passes_required=required,
+        min_good_percent=minimum,
+        pass_window_sec=window,
+        voice_activity=voice,
+    )
+    for item in kept:
+        rt.quality.passes.append(item)
+    if current.started_at != 0.0:
+        rt.quality.current = current
+
+
+def device_reporting_error(state: DaemonState, rt: DeviceRuntime) -> str:
+    if not state.cfg.report_error_transmissions:
+        return "invalid"
+    if not link_status_is_healthy(device_link_status(rt)):
+        return "invalid"
+    _sync_quality_tracker(state, rt)
+    if rt.quality.data_error_valid(reporting_enabled=True):
+        return "valid"
+    return "invalid"
+
+
+def aggregate_reporting_error(state: DaemonState) -> str:
+    if not state.devices:
+        return "invalid" if not state.cfg.report_error_transmissions else "valid"
+    for rt in state.devices.values():
+        if device_reporting_error(state, rt) == "invalid":
+            return "invalid"
+    return "valid"
+
+
+def aggregate_reporting_voice(state: DaemonState) -> str:
+    if not state.cfg.report_voice_transmissions:
+        return "invalid"
+    voice_rts = [rt for rt in state.devices.values() if device_has_voice_path(rt)]
+    if not voice_rts:
+        return "valid"
+    for rt in voice_rts:
+        if not link_status_is_healthy(device_link_status(rt)):
+            return "invalid"
+    return "valid"
+
+
+def device_reporting_voice(state: DaemonState, rt: DeviceRuntime) -> str:
+    if not device_has_voice_path(rt):
+        return "n/a"
+    _sync_quality_tracker(state, rt)
+    healthy = link_status_is_healthy(device_link_status(rt))
+    if rt.quality.voice_signal_valid(
+        reporting_enabled=state.cfg.report_voice_transmissions,
+        link_healthy=healthy,
+    ):
+        return "valid"
+    return "invalid"
+
+
+BACKEND_POLL_OPEN_STATUSES = frozenset(
+    {
+        "closed",
+        "error-open",
+        "error-connect",
+        "error-no-device",
+        "error-no-path",
+    }
+)
+
+SERIAL_REPAIR_STATUSES = frozenset(
+    {
+        "error-host",
+        "error-kiss",
+        "error-tx",
+        "error-io",
+        "error-config",
+    }
+)
+
+BACKEND_RETRY_STATUSES = BACKEND_POLL_OPEN_STATUSES | SERIAL_REPAIR_STATUSES
+
+HYBBX_ATTACH_MODES = frozenset({"hybbx-host", "hybbx-main", "hybbx-cohost"})
+
+
+def hybbx_release_attach(state: DaemonState) -> bool:
+    """HyBBX opens serial/KISS after max25d prep — max25d must not hold the fd."""
+    mode = (state.cfg.mode or "").strip().lower()
+    if mode in HYBBX_ATTACH_MODES:
+        return True
+    return bool(getattr(state.cfg, "hybbx_release_attach", False))
+
+
+def uses_inline_tnc_prep(state: DaemonState, dev_id: str) -> bool:
+    """kiss-serial owned by max25d — no boot-wait subprocess (avoids port conflict)."""
+    if not state.cfg.stack_recover_only:
+        return False
+    return device_backend_kind(state, dev_id) == "kiss-serial"
+
+
+def hybbx_host_hybbx_owns_serial(state: DaemonState, dev_id: str) -> bool:
+    """In HyBBX attach mode HyBBX opens serial/KISS after max25d prep."""
+    if not hybbx_release_attach(state):
+        return False
+    kind = device_backend_kind(state, dev_id)
+    # kiss-raw + max25-bcpr: HyBBX owns the KISS attach; max25d must not hold the PTY.
+    if kind in ("kiss-raw-serial", "max25-bcpr-kiss", "bcpr-kiss"):
+        return True
+    if kind != "kiss-serial":
+        return False
+    rt = state.devices.get(dev_id)
+    return rt is not None and rt.prep_done and rt.backend is None
+
+
+def prep_inline_serial_device(state: DaemonState, dev_id: str) -> None:
+    """Open serial and run initial recovery while holding DTR (no subprocess)."""
+    rt = state.devices[dev_id]
+    rt.stack_status = "ready"
+    LOGGER.info("inline prep — max25d owns serial recovery", area="stack", device=dev_id)
+    if not backend_enabled(state, dev_id):
+        return
+    if not open_backend(state, dev_id):
+        LOGGER.error(f"serial prep open failed status={rt.link_status}", area="serial", device=dev_id)
+        return
+    backend = rt.backend
+    stabilize = getattr(backend, "stabilize_session", None)
+    if stabilize is None:
+        return
+    ok = stabilize(state.cfg.callerid, force=False)
+    rt.prep_done = True
+    rt.link_status = backend.status
+    if ok:
+        LOGGER.ok("serial prep complete — terminal + KISS ready", area="serial", device=dev_id)
+        if hybbx_release_attach(state):
+            close_backend(state, dev_id)
+            rt.link_status = "ready"
+            LOGGER.info(
+                "HyBBX attach: serial released for HyBBX KISS attach",
+                area="serial",
+                device=dev_id,
+            )
+    elif (
+        backend.status == "error-host"
+        and state.cfg.serial_bootwait_escalate
+        and rt.stack_proc is None
+    ):
+        LOGGER.warn(
+            "inline ladder exhausted (error-host) — escalating to boot-wait + power-cycle hint",
+            area="serial",
+            device=dev_id,
+        )
+        rt.last_bootwait_escalate = time.time()
+        escalate_to_bootwait_stack(state, dev_id)
+    else:
+        LOGGER.warn(
+            f"prep deferred status={backend.status} — serial watch will retry",
+            area="serial",
+            device=dev_id,
+        )
+
+
+def escalate_to_bootwait_stack(state: DaemonState, dev_id: str) -> None:
+    """Release inline serial and run boot-wait subprocess (DTR + power-cycle rescue)."""
+    rt = state.devices[dev_id]
+    close_backend(state, dev_id)
+    rt.prep_done = False
+    ctl = ctl_path(ROOT, PREFIX, _EXE)
+    if not ctl.is_file():
+        rt.stack_status = "error-no-ctl"
+        log(f"serial watch: boot-wait escalate failed — no ctl ({dev_id})")
+        return
+    hw = device_hardware(state, dev_id)
+    args = [
+        str(ctl),
+        "start",
+        "--mode",
+        state.cfg.mode,
+        "--hardware",
+        hw,
+        "--device",
+        dev_id,
+    ]
+    env = os.environ.copy()
+    env["MAX25_MODE"] = state.cfg.mode
+    env.pop("MAX25_TNC_PREP", None)
+    workdir = str(ROOT if (ROOT / "plugins").is_dir() else (PREFIX or ROOT))
+    try:
+        proc = subprocess.Popen(
+            args,
+            cwd=workdir,
+            env=env,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+            start_new_session=True,
+        )
+    except OSError as exc:
+        log(f"serial watch: boot-wait escalate failed ({dev_id}): {exc}")
+        rt.stack_status = "error"
+        return
+    rt.stack_proc = proc
+    rt.stack_status = "running"
+    log(
+        f"serial watch: escalating to boot-wait ({dev_id}) pid={proc.pid} "
+        "— power OFF TNC 10s then ON while script runs (DTR held high)"
+    )
+    broadcast(state, f"EVENT device={dev_id} serial=boot-wait-escalate")
+
+
+def backend_needs_open(backend: Optional[DeviceBackend]) -> bool:
+    if backend is None:
+        return True
+    return backend.status in BACKEND_POLL_OPEN_STATUSES
+
+
+def open_backend(state: DaemonState, dev_id: str) -> bool:
+    rt = state.devices.get(dev_id)
+    if rt is None or not backend_enabled(state, dev_id):
+        if rt is not None:
+            rt.link_status = "n/a"
+        return False
+    if hybbx_host_hybbx_owns_serial(state, dev_id):
+        rt.link_status = "ready"
+        rt.prep_done = True
+        rt.stack_status = "ready"
+        return True
+    if rt.backend is not None and rt.backend.status not in BACKEND_RETRY_STATUSES:
+        return rt.backend.status in ("open", "ready")
+    if (
+        rt.backend is not None
+        and rt.backend.status in SERIAL_REPAIR_STATUSES
+        and rt.prep_done
+    ):
+        return rt.backend.status in ("open", "ready", "error-host", "error-kiss")
+    if rt.backend is not None and rt.backend.status != "closed":
+        rt.backend.close()
+        rt.backend = None
+    backend = create_backend(
+        rt.cfg,
+        str(ROOT),
+        lambda line, d=dev_id: on_backend_rx(state, d, line),
+        log,
+        prefix=str(PREFIX) if PREFIX else None,
+        on_invalid=lambda d=dev_id: on_backend_invalid_frame(state, d),
+    )
+    if not backend.open():
+        rt.backend = backend
+        rt.link_status = backend.status
+        return False
+    rt.backend = backend
+    rt.link_status = backend.status
+    return True
+
+
+def close_backend(state: DaemonState, dev_id: str) -> None:
+    rt = state.devices.get(dev_id)
+    if rt is None or rt.backend is None:
+        return
+    rt.backend.close()
+    rt.link_status = rt.backend.status
+    rt.backend = None
+
+
+def attach_backend_session(state: DaemonState, dev_id: str) -> bool:
+    if not backend_enabled(state, dev_id):
+        return True
+    if hybbx_host_hybbx_owns_serial(state, dev_id):
+        return True
+    rt = state.devices[dev_id]
+    if backend_needs_open(rt.backend):
+        if not open_backend(state, dev_id):
+            return False
+    assert rt.backend is not None
+    ok = rt.backend.attach_session(state.cfg.callerid)
+    rt.link_status = rt.backend.status
+    return ok
+
+
+def detach_backend_session(state: DaemonState, dev_id: str) -> None:
+    rt = state.devices.get(dev_id)
+    if rt is None or rt.backend is None:
+        return
+    rt.backend.detach_session()
+    rt.link_status = rt.backend.status
+
+
+def attach_all_sessions(state: DaemonState) -> bool:
+    ok = True
+    for dev_id in enabled_device_ids(state):
+        if backend_enabled(state, dev_id):
+            if not attach_backend_session(state, dev_id):
+                ok = False
+    return ok
+
+
+def detach_all_sessions(state: DaemonState) -> None:
+    for dev_id in enabled_device_ids(state):
+        detach_backend_session(state, dev_id)
+
+
+def backend_enabled(state: DaemonState, dev_id: str) -> bool:
+    if not state.cfg.serial_enabled:
+        return False
+    rt = state.devices.get(dev_id)
+    if rt is None:
+        return False
+    if rt.tot_paused:
+        return False
+    kind = rt.cfg.backend_type
+    return kind in ("kiss-serial", "baycom-kiss", "max25-bcpr-kiss", "bcpr-kiss", "kiss-raw-serial", "crdop-tcp")
+
+
+def aggregate_stack_status(state: DaemonState) -> str:
+    if not state.devices:
+        return "stopped"
+    statuses = {rt.stack_status for rt in state.devices.values()}
+    if "running" in statuses:
+        return "running"
+    if any(s.startswith("error") for s in statuses):
+        return "error"
+    if statuses == {"ready"} or statuses == {"stopped"}:
+        return next(iter(statuses))
+    if "ready" in statuses:
+        return "ready"
+    return "running" if "running" in statuses else "stopped"
+
+
+def aggregate_link_status(state: DaemonState) -> str:
+    if not state.devices:
+        return "n/a"
+    if len(state.devices) == 1:
+        rt = next(iter(state.devices.values()))
+        return backend_serial_label(rt.backend) if rt.backend is not None else rt.link_status
+    parts: list[str] = []
+    for dev_id in sorted(state.devices):
+        rt = state.devices[dev_id]
+        st = backend_serial_label(rt.backend) if rt.backend is not None else rt.link_status
+        parts.append(f"{dev_id}={st}")
+    return ",".join(parts)
+
+
+def status_line(state: DaemonState) -> str:
+    c = state.cfg
+    dev_list = ",".join(enabled_device_ids(state))
+    selected = state.selected_device or c.default_device or c.device
+    return (
+        f"STATUS hardware={c.hardware} device={selected} devices={dev_list} "
+        f"mode={c.mode} callerid={c.callerid} callid={c.callid} "
+        f"ax25_ui={'on' if c.ax25_ui else 'off'} "
+        f"connected={'yes' if state.connected else 'no'} "
+        f"stack={aggregate_stack_status(state)} serial={aggregate_link_status(state)} "
+        f"error={aggregate_reporting_error(state)} "
+        f"voice={aggregate_reporting_voice(state)}"
+    )
+
+
+def broadcast(state: DaemonState, line: str, skip: Optional[socket.socket] = None) -> None:
+    payload = (line + "\n").encode("utf-8")
+    dead: list[socket.socket] = []
+    with state.lock:
+        for sock in state.clients:
+            if sock is skip:
+                continue
+            try:
+                sock.sendall(payload)
+            except OSError:
+                dead.append(sock)
+        for sock in dead:
+            state.clients.discard(sock)
+
+
+def send_line(sock: socket.socket, line: str) -> None:
+    sock.sendall((line + "\n").encode("utf-8"))
+
+
+def unix_path_is_live(path: str, *, timeout: float = 0.3) -> bool:
+    """True if path exists and accepts a Unix connect (live max25d listener)."""
+    if not path or not os.path.exists(path):
+        return False
+    probe = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    try:
+        probe.settimeout(timeout)
+        probe.connect(path)
+        return True
+    except OSError:
+        return False
+    finally:
+        try:
+            probe.close()
+        except OSError:
+            pass
+
+
+def unix_path_id(path: str) -> tuple[int, int] | None:
+    """Filesystem identity of a Unix socket path (dev, ino), or None."""
+    try:
+        st = os.stat(path)
+    except OSError:
+        return None
+    return (st.st_dev, st.st_ino)
+
+
+def unlink_unix_if_ours(path: str, bind_id: tuple[int, int] | None) -> None:
+    """Unlink path only when it still names the inode we bound.
+
+    AF_UNIX: fstat(listen_fd) is sockfs — must not compare to path st_ino.
+    A second max25d that unlinks+rebinds must not lose its path when the
+    first instance exits (orphaned listen FD + ENOENT for clients).
+    """
+    if not path or bind_id is None:
+        return
+    cur = unix_path_id(path)
+    if cur is None or cur != bind_id:
+        return
+    try:
+        os.unlink(path)
+    except FileNotFoundError:
+        pass
+    except OSError:
+        pass
+
+
+def resolve_max25_bcpr_ini(explicit: str = "") -> Path | None:
+    """Resolve max25-bcpr.ini for userspace SER12 (max25e0)."""
+    from pathlib import Path as _P
+    if explicit:
+        p = _P(explicit)
+        return p if p.is_file() else None
+    for cand in (
+        ROOT / "local" / "max25-bcpr.ini",
+        _P("/etc/max25/max25-bcpr.ini"),
+        _P("/etc/max25/bcpr.ini"),
+        ROOT / "local" / "bcpr.ini",
+        ROOT / "stacks" / "max25-bcpr" / "share" / "max25-bcpr.ini.example",
+        ROOT / "share" / "max25-bcpr" / "max25-bcpr.ini.example",
+    ):
+        if cand.is_file():
+            return cand
+    return None
+
+
+def resolve_max25_bcpr_ctl() -> Path | None:
+    from pathlib import Path as _P
+    for cand in (
+        ROOT / "stacks" / "max25-bcpr" / "tools" / "max25-bcpr-ctl",
+        _P("/usr/local/sbin/max25-bcpr-ctl"),
+        _P("/usr/sbin/max25-bcpr-ctl"),
+    ):
+        if cand.is_file():
+            return cand
+    return None
+
+
+def bcpr_bc_index(cfg: DeviceBackendConfig) -> int:
+    tag = (cfg.max25_bcpr_device or cfg.bcpr_device or "").strip()
+    if not tag and cfg.device_id.startswith("max25e0:"):
+        tag = cfg.device_id.split(":", 1)[1]
+    if not tag:
+        tag = "bc0"
+    if tag.startswith("bc") and tag[2:].isdigit():
+        return int(tag[2:])
+    return 0
+
+
+def read_bcpr_state_dir(ini_path: Path) -> str:
+    cp = configparser.ConfigParser()
+    cp.read(ini_path)
+    for sect in ("max25-bcpr", "bcpr"):
+        if cp.has_section(sect) and cp.has_option(sect, "state_dir"):
+            return cp.get(sect, "state_dir").strip() or "/tmp/max25-bcpr"
+    return "/tmp/max25-bcpr"
+
+
+def sync_tot_to_bcpr_ini(ini_path: Path, tot: TotConfig) -> None:
+    """Push max25d [tot] policy into max25-bcpr.ini before bcprd start."""
+    if not ini_path.is_file():
+        return
+    cp = configparser.ConfigParser()
+    cp.read(ini_path)
+    sect = "max25-bcpr"
+    if not cp.has_section(sect):
+        if cp.has_section("bcpr"):
+            sect = "bcpr"
+        else:
+            cp.add_section(sect)
+    cp.set(sect, "tot", "yes" if tot.enabled else "no")
+    cp.set(sect, "tot_max_key_sec", str(tot.max_key_sec))
+    cp.set(sect, "tot_min_gap_ms", str(int(tot.min_gap_sec * 1000.0)))
+    cp.set(sect, "tot_max_consecutive", str(tot.max_consecutive))
+    cp.set(sect, "tot_max_bursts", str(tot.max_bursts))
+    with ini_path.open("w", encoding="utf-8") as fh:
+        cp.write(fh)
+
+
+def tot_trip_path(state_dir: str, bc_index: int) -> Path:
+    return Path(state_dir) / f"tot-trip-bc{bc_index}"
+
+
+def parse_tot_trip_file(path: Path) -> dict[str, str]:
+    out: dict[str, str] = {}
+    try:
+        for line in path.read_text(encoding="utf-8", errors="replace").splitlines():
+            if "=" not in line:
+                continue
+            key, val = line.split("=", 1)
+            out[key.strip()] = val.strip()
+    except OSError:
+        pass
+    return out
+
+
+def device_tot_operational(state: DaemonState, dev_id: str) -> bool:
+    rt = state.devices.get(dev_id)
+    if rt is None:
+        return False
+    return not rt.tot_paused
+
+
+def handle_tot_trip(state: DaemonState, dev_id: str, reason: str) -> None:
+    rt = state.devices.get(dev_id)
+    if rt is None or rt.tot_paused:
+        return
+    log(f"TOT trip ({dev_id}) reason={reason} — pause, stop stack, reset bcpr")
+    rt.tot_paused = True
+    rt.tot_trip_reason = reason or "unknown"
+    recover = state.cfg.tot.recover_sec
+    rt.tot_paused_until = time.time() + recover if recover > 0 else 0.0
+    stop_device_stack(state, dev_id)
+    rt.stack_status = "tot-paused"
+    rt.link_status = "tot-paused"
+    rt.prep_done = False
+    broadcast(
+        state,
+        f"EVENT device={dev_id} tot=trip reason={rt.tot_trip_reason} stack=tot-paused",
+    )
+
+
+def poll_tot_trips(state: DaemonState) -> None:
+    if not state.cfg.tot.enabled:
+        return
+    for dev_id, rt in state.devices.items():
+        kind = rt.cfg.backend_type or ""
+        if kind not in ("max25-bcpr-kiss", "bcpr-kiss"):
+            continue
+        if rt.tot_paused:
+            continue
+        explicit = rt.cfg.max25_bcpr_ini or rt.cfg.bcpr_ini or ""
+        resolved = resolve_max25_bcpr_ini(explicit)
+        if resolved is None:
+            continue
+        state_dir = read_bcpr_state_dir(resolved)
+        trip = tot_trip_path(state_dir, bcpr_bc_index(rt.cfg))
+        if not trip.is_file():
+            continue
+        meta = parse_tot_trip_file(trip)
+        if meta.get("tripped") != "1":
+            continue
+        handle_tot_trip(state, dev_id, meta.get("reason", "unknown"))
+
+
+def poll_tot_recovery(state: DaemonState) -> None:
+    if not state.cfg.tot.enabled:
+        return
+    now = time.time()
+    for dev_id, rt in state.devices.items():
+        if not rt.tot_paused:
+            continue
+        kind = rt.cfg.backend_type or ""
+        if kind not in ("max25-bcpr-kiss", "bcpr-kiss"):
+            continue
+        recover = state.cfg.tot.recover_sec
+        if recover <= 0:
+            continue
+        if rt.tot_paused_until > 0 and now < rt.tot_paused_until:
+            continue
+        explicit = rt.cfg.max25_bcpr_ini or rt.cfg.bcpr_ini or ""
+        resolved = resolve_max25_bcpr_ini(explicit)
+        if resolved is not None:
+            trip = tot_trip_path(read_bcpr_state_dir(resolved), bcpr_bc_index(rt.cfg))
+            try:
+                trip.unlink(missing_ok=True)
+            except OSError:
+                pass
+        rt.tot_paused = False
+        rt.tot_trip_reason = ""
+        rt.tot_paused_until = 0.0
+        log(f"TOT recover ({dev_id}) — restarting max25-bcpr stack")
+        if state.cfg.auto_start and backend_enabled(state, dev_id):
+            start_device_stack_for_tot(state, dev_id)
+
+
+def start_device_stack_for_tot(state: DaemonState, dev_id: str) -> None:
+    """Restart bcpr stack after TOT cooldown (single device, no full start_stacks)."""
+    rt = state.devices[dev_id]
+    kind = rt.cfg.backend_type or ""
+    if kind in ("max25-bcpr-kiss", "bcpr-kiss"):
+        explicit = rt.cfg.max25_bcpr_ini or rt.cfg.bcpr_ini or ""
+        resolved = resolve_max25_bcpr_ini(explicit)
+        if resolved is None:
+            rt.stack_status = "error-no-ini"
+            return
+        sync_tot_to_bcpr_ini(resolved, state.cfg.tot)
+        start_max25_bcpr_stack(state, dev_id, resolved)
+
+
+def _read_subprocess_capture(fh, limit: int = 4000) -> str:
+    """Read captured ctl stdout/stderr (UTF-8, truncated tail)."""
+    try:
+        fh.seek(0)
+        raw = fh.read()
+    except OSError:
+        return ""
+    text = raw.decode("utf-8", errors="replace").strip()
+    if len(text) > limit:
+        return f"...\n{text[-limit:]}"
+    return text
+
+
+def start_max25_bcpr_stack(state: DaemonState, dev_id: str, ini: Path) -> None:
+    """Start max25-bcprd once via max25-bcpr-ctl for shared ini."""
+    rt = state.devices[dev_id]
+    ctl = resolve_max25_bcpr_ctl()
+    if ctl is None:
+        rt.stack_status = "error-no-ctl"
+        log(f"max25-bcpr-ctl not found ({dev_id})")
+        return
+    args = [str(ctl), "-c", str(ini), "start"]
+    env = os.environ.copy()
+    # Temp file (not PIPE): bcprd backgrounded by ctl must not block communicate().
+    # Capture ctl output; log tail only when rc!=0 or after ctl timeout.
+    proc: subprocess.Popen[bytes] | None = None
+    ctl_output = ""
+    try:
+        with tempfile.TemporaryFile(mode="w+b") as capfh:
+            try:
+                proc = subprocess.Popen(
+                    args,
+                    cwd=str(ROOT),
+                    env=env,
+                    stdin=subprocess.DEVNULL,
+                    stdout=capfh,
+                    stderr=subprocess.STDOUT,
+                    start_new_session=True,
+                )
+            except OSError as exc:
+                log(f"max25-bcpr start failed ({dev_id}): {exc}")
+                rt.stack_status = "error"
+                return
+            try:
+                proc.communicate(timeout=30)
+            except subprocess.TimeoutExpired:
+                proc.kill()
+                try:
+                    proc.communicate(timeout=2)
+                except (subprocess.TimeoutExpired, OSError):
+                    pass
+                ctl_output = _read_subprocess_capture(capfh)
+                # May still have spawned max25-bcprd — fall through to kiss probe.
+                log(f"max25-bcpr-ctl start timed out ({dev_id}) — probing live kiss/pid")
+                if ctl_output:
+                    log(f"max25-bcpr-ctl output ({dev_id}): {ctl_output}")
+            else:
+                ctl_output = _read_subprocess_capture(capfh)
+    except OSError as exc:
+        log(f"max25-bcpr start failed ({dev_id}): {exc}")
+        rt.stack_status = "error"
+        return
+    if proc is None:
+        rt.stack_status = "error"
+        return
+    if proc.returncode not in (0, None, -9, -15):
+        # -9/-15: we killed a hung ctl; still probe kiss below.
+        if proc.returncode > 0:
+            rt.stack_status = "error"
+            if ctl_output:
+                log(f"max25-bcpr-ctl start rc={proc.returncode} ({dev_id}): {ctl_output}")
+            else:
+                log(f"max25-bcpr-ctl start rc={proc.returncode} ({dev_id})")
+            return
+    # max25-bcpr-ctl itself exits; live daemon is max25-bcprd (pidfile under state_dir).
+    rt.stack_proc = None
+    rt.stack_status = "running"
+    kiss = normalize_max25_bcpr_path(
+        (rt.cfg.kiss_link or "").strip() or MAX25_BCPR_KISS_DEFAULT
+    )
+    deadline = time.time() + 5.0
+    while time.time() < deadline:
+        if os.path.exists(kiss):
+            break
+        time.sleep(0.1)
+    if not os.path.exists(kiss):
+        rt.stack_status = "error-no-kiss"
+        log(f"max25-bcpr kiss_link missing after start ({dev_id}: {kiss})")
+        return
+    addrs = f"ipv4={rt.cfg.ipv4 or '-'} ipv6={rt.cfg.ipv6 or '-'}"
+    log(f"max25-bcpr started ({dev_id}, ini={ini}, kiss={kiss}, {addrs})")
+    rt.stack_status = "ready"
+    # HyBBX attach: HyBBX opens kiss_link — do not hold the PTY here.
+    if hybbx_release_attach(state):
+        rt.link_status = "ready"
+        rt.prep_done = True
+        log(f"max25-bcpr ready — HyBBX owns KISS attach ({dev_id}: {kiss})")
+        return
+    # Standalone: open+hold KISS so max25-terminal TX works (stack_proc=None).
+    if backend_enabled(state, dev_id):
+        if open_backend(state, dev_id):
+            if attach_backend_session(state, dev_id):
+                # UI/datagram TX uses CONNECT as session arm — arm at start so
+                # max25-terminal SEND keys MCR without a separate CONNECT race.
+                state.connected = True
+                log(f"max25-bcpr KISS open ({dev_id}: {kiss})")
+            else:
+                log(f"max25-bcpr KISS open but attach failed ({dev_id})")
+        else:
+            log(f"max25-bcpr KISS open failed ({dev_id}) status={rt.link_status}")
+
+
+def start_device_stack(state: DaemonState, dev_id: str) -> None:
+    if uses_inline_tnc_prep(state, dev_id):
+        prep_inline_serial_device(state, dev_id)
+        return
+    rt = state.devices[dev_id]
+    ctl = ctl_path(ROOT, PREFIX, _EXE)
+    if not ctl.is_file():
+        rt.stack_status = "error-no-ctl"
+        return
+    hw = device_hardware(state, dev_id)
+    dev_cfg = rt.cfg
+    ctl_device = dev_id
+    if (dev_cfg.backend_type or "") == "baycom-kiss":
+        ctl_device = baycom_ctl_device_id(dev_cfg)
+    args = [
+        str(ctl),
+        "start",
+        "--mode",
+        state.cfg.mode,
+        "--hardware",
+        hw,
+        "--device",
+        ctl_device,
+    ]
+    kind = dev_cfg.backend_type or ""
+    if kind == "baycom-kiss":
+        explicit = dev_cfg.baycom_ini or ""
+        resolved = resolve_baycom_ini(dev_id, ROOT, PREFIX, explicit)
+        if resolved:
+            args.extend(["--baycom-ini", str(resolved)])
+    env = os.environ.copy()
+    env["MAX25_MODE"] = state.cfg.mode
+    if hw == "tncs" and state.cfg.stack_recover_only:
+        env["MAX25_TNC_PREP"] = "recover"
+    workdir = str(ROOT if (ROOT / "plugins").is_dir() else (PREFIX or ROOT))
+    try:
+        proc = subprocess.Popen(
+            args,
+            cwd=workdir,
+            env=env,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+            start_new_session=True,
+        )
+    except OSError as exc:
+        log(f"stack start failed ({dev_id}): {exc}")
+        rt.stack_status = "error"
+        return
+    rt.stack_proc = proc
+    rt.stack_status = "running"
+    log(f"stack started pid={proc.pid} ({hw}/{dev_id})")
+
+
+def start_stacks(state: DaemonState) -> None:
+    """Start per-device stacks; one max25-bcpr-ctl per shared ini."""
+    started_baycom_ini: dict[str, str] = {}
+    started_max25_bcpr_ini: dict[str, str] = {}
+    for dev_id in enabled_device_ids(state):
+        rt = state.devices[dev_id]
+        kind = rt.cfg.backend_type or ""
+        if uses_inline_tnc_prep(state, dev_id):
+            prep_inline_serial_device(state, dev_id)
+            continue
+        if kind in ("max25-bcpr-kiss", "bcpr-kiss"):
+            explicit = rt.cfg.max25_bcpr_ini or rt.cfg.bcpr_ini or ""
+            resolved = resolve_max25_bcpr_ini(explicit)
+            ini_key = str(resolved) if resolved else ""
+            if ini_key and ini_key in started_max25_bcpr_ini:
+                primary = started_max25_bcpr_ini[ini_key]
+                primary_rt = state.devices[primary]
+                rt.stack_proc = primary_rt.stack_proc
+                rt.stack_status = primary_rt.stack_status
+                log(f"max25-bcpr stack shared with {primary} ({dev_id}, ini={ini_key})")
+                # Shared max25-bcprd — open this device's kiss only when max25d owns it.
+                if (
+                    not hybbx_release_attach(state)
+                    and rt.stack_status in ("ready", "running")
+                    and backend_enabled(state, dev_id)
+                ):
+                    if open_backend(state, dev_id):
+                        attach_backend_session(state, dev_id)
+                elif hybbx_release_attach(state):
+                    rt.link_status = "ready"
+                    rt.prep_done = True
+                continue
+            if resolved:
+                sync_tot_to_bcpr_ini(resolved, state.cfg.tot)
+                start_max25_bcpr_stack(state, dev_id, resolved)
+                started_max25_bcpr_ini[str(resolved)] = dev_id
+            else:
+                rt.stack_status = "error-no-ini"
+                log(f"max25-bcpr.ini not found ({dev_id})")
+            continue
+        if kind == "baycom-kiss":
+            explicit = rt.cfg.baycom_ini or ""
+            resolved = resolve_baycom_ini(dev_id, ROOT, PREFIX, explicit)
+            ini_key = str(resolved) if resolved else ""
+            if ini_key and ini_key in started_baycom_ini:
+                primary = started_baycom_ini[ini_key]
+                primary_rt = state.devices[primary]
+                rt.stack_proc = primary_rt.stack_proc
+                rt.stack_status = primary_rt.stack_status
+                log(f"stack shared with {primary} ({dev_id}, ini={ini_key})")
+                continue
+        start_device_stack(state, dev_id)
+        if kind == "baycom-kiss":
+            explicit = rt.cfg.baycom_ini or ""
+            resolved = resolve_baycom_ini(dev_id, ROOT, PREFIX, explicit)
+            if resolved:
+                started_baycom_ini[str(resolved)] = dev_id
+
+
+def stop_device_stack(state: DaemonState, dev_id: str) -> None:
+    close_backend(state, dev_id)
+    rt = state.devices[dev_id]
+    kind = rt.cfg.backend_type or ""
+    if kind in ("max25-bcpr-kiss", "bcpr-kiss"):
+        ctl = resolve_max25_bcpr_ctl()
+        explicit = rt.cfg.max25_bcpr_ini or rt.cfg.bcpr_ini or ""
+        resolved = resolve_max25_bcpr_ini(explicit)
+        if ctl is not None and resolved is not None:
+            subprocess.run(
+                [str(ctl), "-c", str(resolved), "stop"],
+                cwd=str(ROOT),
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.DEVNULL,
+            )
+        rt.stack_proc = None
+        rt.stack_status = "stopped"
+        return
+    proc = rt.stack_proc
+    if proc is not None and proc.poll() is None:
+        try:
+            os.killpg(proc.pid, signal.SIGTERM)
+        except ProcessLookupError:
+            pass
+        except OSError:
+            proc.terminate()
+    rt.stack_proc = None
+    rt.stack_status = "stopped"
+    hw = device_hardware(state, dev_id)
+    ctl = ctl_path(ROOT, PREFIX, _EXE)
+    if ctl.is_file():
+        workdir = str(ROOT if (ROOT / "plugins").is_dir() else (PREFIX or ROOT))
+        stop_args = [str(ctl), "stop", "--hardware", hw, "--device", dev_id]
+        if kind == "baycom-kiss":
+            explicit = rt.cfg.baycom_ini or ""
+            resolved = resolve_baycom_ini(dev_id, ROOT, PREFIX, explicit)
+            if resolved:
+                stop_args.extend(["--baycom-ini", str(resolved)])
+        subprocess.run(
+            stop_args,
+            cwd=workdir,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
+
+
+def stop_stacks(state: DaemonState) -> None:
+    for dev_id in list(state.devices):
+        stop_device_stack(state, dev_id)
+    log("all stacks stopped")
+
+
+def poll_device_stack(state: DaemonState, dev_id: str) -> None:
+    rt = state.devices[dev_id]
+    proc = rt.stack_proc
+    if proc is None:
+        return
+    rc = proc.poll()
+    if rc is None:
+        return
+    rt.stack_proc = None
+    if rc == 0:
+        rt.stack_status = "ready"
+        log(f"stack boot-wait finished ({dev_id}) rc={rc}")
+        if backend_enabled(state, dev_id):
+            open_backend(state, dev_id)
+            backend = rt.backend
+            stabilize = getattr(backend, "stabilize_session", None) if backend else None
+            if stabilize is not None:
+                ok = stabilize(state.cfg.callerid, force=False)
+                rt.prep_done = True
+                rt.link_status = backend.status
+                rt.inline_repair_failures = 0
+                if ok:
+                    log(f"serial post boot-wait OK ({dev_id})")
+                    if state.connected:
+                        attach_backend_session(state, dev_id)
+                else:
+                    log(
+                        f"serial post boot-wait deferred ({dev_id}) "
+                        f"status={backend.status}"
+                    )
+    else:
+        rt.stack_status = f"error-rc{rc}"
+        log(f"stack boot-wait failed ({dev_id}) rc={rc}")
+
+
+def poll_stacks(state: DaemonState) -> None:
+    for dev_id in enabled_device_ids(state):
+        poll_device_stack(state, dev_id)
+    retry_pending_backends(state)
+
+
+def retry_pending_backends(state: DaemonState) -> None:
+    """Re-attach KISS PTY/serial when stack is up but the link was not ready yet."""
+    for dev_id in enabled_device_ids(state):
+        if not backend_enabled(state, dev_id):
+            continue
+        rt = state.devices[dev_id]
+        if hybbx_host_hybbx_owns_serial(state, dev_id):
+            continue
+        # bcpr uses "running" until kiss open flips to "ready"; accept both.
+        if rt.stack_status not in ("ready", "stopped", "running"):
+            continue
+        if not backend_needs_open(rt.backend):
+            continue
+        if open_backend(state, dev_id):
+            attach_backend_session(state, dev_id)
+            if rt.stack_status == "running":
+                rt.stack_status = "ready"
+
+
+def poll_reporting_passes(state: DaemonState) -> None:
+    """Advance timed data-quality pass windows (default 20s each, 3 passes)."""
+    now = time.time()
+    for rt in state.devices.values():
+        _sync_quality_tracker(state, rt)
+        rt.quality.tick(now)
+
+
+def poll_serial_stability(state: DaemonState) -> None:
+    """Periodic TNC health probe + software recovery (no power cycle)."""
+    cfg = state.cfg
+    if not cfg.serial_watch:
+        return
+    now = time.time()
+    if state.started_at and now - state.started_at < cfg.serial_watch_startup_grace:
+        return
+    for dev_id in enabled_device_ids(state):
+        if device_backend_kind(state, dev_id) != "kiss-serial":
+            continue
+        if hybbx_host_hybbx_owns_serial(state, dev_id):
+            continue
+        rt = state.devices[dev_id]
+        if rt.stack_proc is not None and rt.stack_proc.poll() is None:
+            continue
+        if (
+            not uses_inline_tnc_prep(state, dev_id)
+            and cfg.stack_recover_only
+            and rt.stack_status.startswith("error")
+            and rt.stack_proc is None
+            and now - rt.last_stack_retry >= cfg.stack_retry_interval
+        ):
+            rt.last_stack_retry = now
+            log(f"serial watch: stack retry recover-only ({dev_id})")
+            start_device_stack(state, dev_id)
+            continue
+        if not backend_enabled(state, dev_id):
+            continue
+        backend = rt.backend
+        force = backend is not None and backend.status in SERIAL_REPAIR_STATUSES
+        due = now - rt.last_watch >= cfg.serial_watch_interval
+        if not force and not due:
+            continue
+        if backend is None:
+            if backend_needs_open(None):
+                open_backend(state, dev_id)
+                backend = rt.backend
+            if backend is None:
+                continue
+        if now - rt.last_repair < cfg.serial_repair_cooldown and not force:
+            continue
+        if backend.status == "ready" and not force:
+            if due:
+                rt.last_watch = now
+            continue
+        stabilize = getattr(backend, "stabilize_session", None)
+        if stabilize is None:
+            continue
+        rt.last_watch = now
+        rt.last_repair = now
+        ok = stabilize(state.cfg.callerid, force=force)
+        rt.link_status = backend.status
+        if ok:
+            rt.inline_repair_failures = 0
+            if force:
+                log(f"serial watch: repaired ({dev_id})")
+                broadcast(state, f"EVENT device={dev_id} serial=ready")
+        else:
+            log(f"serial watch: repair failed ({dev_id}) status={backend.status}")
+            if (
+                uses_inline_tnc_prep(state, dev_id)
+                and backend.status == "error-host"
+                and cfg.serial_bootwait_escalate
+            ):
+                rt.inline_repair_failures += 1
+                if (
+                    rt.inline_repair_failures >= cfg.serial_bootwait_escalate_after
+                    and now - rt.last_bootwait_escalate >= cfg.serial_bootwait_escalate_cooldown
+                ):
+                    rt.last_bootwait_escalate = now
+                    rt.inline_repair_failures = 0
+                    escalate_to_bootwait_stack(state, dev_id)
+                elif rt.inline_repair_failures >= cfg.serial_bootwait_escalate_after:
+                    log(
+                        f"serial watch: boot-wait escalate cooldown ({dev_id}) "
+                        f"— manual: stacks/tncs/{dev_id}-boot-wait.sh"
+                    )
+            if backend.status in ("error-io", "error-open", "error-no-device"):
+                close_backend(state, dev_id)
+                if open_backend(state, dev_id) and state.connected:
+                    attach_backend_session(state, dev_id)
+
+
+def format_tx(state: DaemonState, text: str) -> str:
+    if state.cfg.ax25_ui:
+        return f"[AX25 UI {state.cfg.callerid}>{state.cfg.callid}] {text}"
+    return text
+
+
+def resolve_selected_device(state: DaemonState) -> Optional[str]:
+    dev_id = state.selected_device
+    if dev_id in state.devices:
+        return dev_id
+    ids = enabled_device_ids(state)
+    return ids[0] if ids else None
+
+
+def device_line(state: DaemonState, dev_id: str) -> str:
+    rt = state.devices[dev_id]
+    link = backend_serial_label(rt.backend) if rt.backend is not None else rt.link_status
+    hw = device_hardware(state, dev_id)
+    backend = rt.cfg.backend_type or "auto"
+    enabled = "yes" if rt.cfg.enabled else "no"
+    return (
+        f"DEVICE id={dev_id} hardware={hw} backend={backend} serial={link} "
+        f"stack={rt.stack_status} enabled={enabled} "
+        f"error={device_reporting_error(state, rt)} "
+        f"voice={device_reporting_voice(state, rt)}"
+    )
+
+
+def handle_command(state: DaemonState, sock: socket.socket, line: str) -> None:
+    line = line.strip("\r\n")
+    if not line:
+        return
+    upper = line.upper()
+
+    if upper == "PING":
+        send_line(sock, "OK")
+        return
+
+    if upper == "GET STATUS":
+        send_line(sock, status_line(state))
+        send_line(sock, "OK")
+        return
+
+    if upper == "GET DEVICES":
+        for dev_id in sorted(state.devices):
+            send_line(sock, device_line(state, dev_id))
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("SET DEVICE ") or upper.startswith("SELECT DEVICE "):
+        prefix = "SET DEVICE " if upper.startswith("SET DEVICE ") else "SELECT DEVICE "
+        dev_id = line[len(prefix) :].strip()
+        if dev_id not in state.devices:
+            send_line(sock, f"ERR unknown device: {dev_id}")
+            return
+        state.selected_device = dev_id
+        state.cfg.device = dev_id
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("SET CALLERID "):
+        value = line[13:].strip().upper()
+        if not valid_callsign(value):
+            send_line(sock, "ERR invalid CALLERID")
+            return
+        state.cfg.callerid = value
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("SET CALLID "):
+        value = line[11:].strip().upper()
+        if not valid_callsign(value):
+            send_line(sock, "ERR invalid CALLID")
+            return
+        state.cfg.callid = value
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("SET AX25_UI "):
+        flag = line[12:].strip().lower()
+        if flag in ("on", "yes", "1", "true"):
+            state.cfg.ax25_ui = True
+        elif flag in ("off", "no", "0", "false"):
+            state.cfg.ax25_ui = False
+        else:
+            send_line(sock, "ERR ax25_ui on|off")
+            return
+        send_line(sock, "OK")
+        return
+
+    if upper == "CONNECT":
+        if not attach_all_sessions(state):
+            send_line(sock, "ERR link not ready")
+            return
+        state.connected = True
+        send_line(sock, "EVENT connected")
+        send_line(sock, "OK")
+        return
+
+    if upper == "DISCONNECT":
+        detach_all_sessions(state)
+        state.connected = False
+        send_line(sock, "EVENT disconnected")
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("MONITOR "):
+        flag = line[8:].strip().lower()
+        state.monitor_only = flag in ("on", "yes", "1", "true")
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("BAN "):
+        value = line[4:].strip().upper()
+        if not valid_callsign(value):
+            send_line(sock, "ERR invalid callsign")
+            return
+        try:
+            state.bans.add(value)
+        except OSError as exc:
+            send_line(sock, f"ERR ban save failed: {exc}")
+            return
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("UNBAN "):
+        value = line[6:].strip().upper()
+        if not valid_callsign(value):
+            send_line(sock, "ERR invalid callsign")
+            return
+        try:
+            if not state.bans.remove(value):
+                send_line(sock, "ERR not banned")
+                return
+        except OSError as exc:
+            send_line(sock, f"ERR ban save failed: {exc}")
+            return
+        send_line(sock, "OK")
+        return
+
+    if upper == "BANS":
+        for entry in state.bans.list():
+            send_line(sock, f"BAN {entry}")
+        send_line(sock, "OK")
+        return
+
+    if upper.startswith("SEND "):
+        if state.monitor_only:
+            send_line(sock, "ERR monitor-only")
+            return
+        # UI frames: auto-arm session if stack/KISS is up. Terminal Enter/F10→SEND
+        # must key PTT/MCR without requiring a prior CONNECT (L4 writes kiss
+        # directly and already keys; unix SEND must match).
+        if not state.connected:
+            if not attach_all_sessions(state):
+                send_line(sock, "ERR not connected")
+                return
+            state.connected = True
+            send_line(sock, "EVENT connected")
+        dev_id = resolve_selected_device(state)
+        if dev_id is None:
+            send_line(sock, "ERR no device configured")
+            return
+        payload = line[5:]
+        framed = format_tx(state, payload)
+        rt = state.devices[dev_id]
+        if backend_enabled(state, dev_id):
+            if rt.backend is None or rt.backend.status != "ready":
+                # Re-attach after DISCONNECT left kiss inactive but stack ready.
+                if not attach_backend_session(state, dev_id):
+                    send_line(sock, "ERR link not ready")
+                    return
+            if rt.backend is None or rt.backend.status != "ready":
+                send_line(sock, "ERR link not ready")
+                return
+            ok, display = rt.backend.transmit(
+                state.cfg.callerid,
+                state.cfg.callid,
+                payload,
+                state.cfg.ax25_ui,
+            )
+            if not ok and hasattr(rt.backend, "stabilize_session"):
+                log(f"serial watch: tx retry after repair ({dev_id})")
+                if rt.backend.stabilize_session(state.cfg.callerid, force=True):
+                    rt.link_status = rt.backend.status
+                    ok, display = rt.backend.transmit(
+                        state.cfg.callerid,
+                        state.cfg.callid,
+                        payload,
+                        state.cfg.ax25_ui,
+                    )
+            if not ok:
+                send_line(sock, f"ERR {display}")
+                return
+            framed = f"device={dev_id} {display}"
+        log(f"tx {dev_id}: {framed}")
+        send_line(sock, f"RX {framed}")
+        broadcast(state, f"RX {framed}", skip=sock)
+        send_line(sock, "OK")
+        return
+
+    send_line(sock, f"ERR unknown command: {line.split()[0]}")
+
+
+def tcp_auth_ok(sock: socket.socket, expected: str, timeout: float = 30.0) -> bool:
+    if not expected:
+        return True
+    send_line(sock, "AUTH required")
+    sock.settimeout(timeout)
+    buf = b""
+    try:
+        while True:
+            try:
+                chunk = sock.recv(4096)
+            except socket.timeout:
+                return False
+            if not chunk:
+                return False
+            buf += chunk
+            if len(buf) > M25_MAX_LINE_BUF:
+                return False
+            while b"\n" in buf:
+                raw, buf = buf.split(b"\n", 1)
+                try:
+                    line = raw.decode("utf-8").strip("\r")
+                except UnicodeDecodeError:
+                    return False
+                if not line:
+                    continue
+                if line.upper().startswith("AUTH "):
+                    supplied = line[5:]
+                    return supplied == expected
+                return False
+    finally:
+        sock.settimeout(300.0)
+
+
+def client_thread(state: DaemonState, sock: socket.socket, from_tcp: bool) -> None:
+    sock.settimeout(300.0)
+    buf = b""
+    try:
+        if from_tcp and state.cfg.tcp_password:
+            if not tcp_auth_ok(sock, state.cfg.tcp_password):
+                send_line(sock, "ERR auth failed")
+                return
+        send_line(sock, "OK")
+        send_line(sock, status_line(state))
+        while True:
+            try:
+                chunk = sock.recv(4096)
+            except socket.timeout:
+                continue
+            if not chunk:
+                break
+            buf += chunk
+            if len(buf) > M25_MAX_LINE_BUF:
+                send_line(sock, "ERR line too long")
+                break
+            while b"\n" in buf:
+                raw, buf = buf.split(b"\n", 1)
+                try:
+                    line = raw.decode("utf-8")
+                except UnicodeDecodeError:
+                    send_line(sock, "ERR invalid utf-8")
+                    continue
+                handle_command(state, sock, line)
+    except OSError:
+        pass
+    finally:
+        with state.lock:
+            state.clients.discard(sock)
+        try:
+            sock.close()
+        except OSError:
+            pass
+
+
+def serve(
+    state: DaemonState,
+    listeners: list[tuple[socket.socket, bool, tuple[int, int] | None]],
+) -> None:
+    running = True
+
+    def on_signal(_signum, _frame):
+        nonlocal running
+        running = False
+
+    signal.signal(signal.SIGTERM, on_signal)
+    signal.signal(signal.SIGINT, on_signal)
+
+    if state.cfg.auto_start:
+        start_stacks(state)
+
+    state.started_at = time.time()
+
+    device_lines: list[tuple[str, str, str]] = []
+    for dev_id in enabled_device_ids(state):
+        rt = state.devices[dev_id]
+        link = backend_serial_label(rt.backend) if rt.backend is not None else rt.link_status
+        device_lines.append((dev_id, rt.stack_status, link))
+
+    emit_startup_complete(
+        device_lines=device_lines,
+        tcp_host=state.cfg.tcp_host,
+        tcp_port=state.cfg.tcp_port,
+        unix_socket=state.cfg.unix_socket,
+    )
+
+    drop_privileges_or_exit(
+        RunAsConfig(
+            user=state.cfg.run_user,
+            group=state.cfg.run_group,
+            uid=state.cfg.run_uid,
+            gid=state.cfg.run_gid,
+        ),
+        log=lambda msg, area="privilege": LOGGER.info(msg, area=area),
+    )
+
+    while running:
+        poll_stacks(state)
+        poll_tot_trips(state)
+        poll_tot_recovery(state)
+        poll_reporting_passes(state)
+        poll_serial_stability(state)
+        socks = [lsock for lsock, _tcp, _bid in listeners]
+        rlist, _, _ = select.select(socks, [], [], 1.0)
+        for lsock, from_tcp, _bid in listeners:
+            if lsock not in rlist:
+                continue
+            try:
+                client, _addr = lsock.accept()
+            except OSError:
+                continue
+            client.setblocking(True)
+            with state.lock:
+                state.clients.add(client)
+            threading.Thread(
+                target=client_thread,
+                args=(state, client, from_tcp),
+                daemon=True,
+            ).start()
+
+    stop_stacks(state)
+    for lsock, from_tcp, bind_id in listeners:
+        if not from_tcp and state.cfg.unix_socket:
+            unlink_unix_if_ours(state.cfg.unix_socket, bind_id)
+        lsock.close()
+
+
+def make_listeners(
+    cfg: DaemonConfig,
+) -> list[tuple[socket.socket, bool, tuple[int, int] | None]]:
+    listeners: list[tuple[socket.socket, bool, tuple[int, int] | None]] = []
+
+    tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    tcp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    try:
+        tcp.bind((cfg.tcp_host, cfg.tcp_port))
+    except OSError as exc:
+        tcp.close()
+        log(f"TCP bind {cfg.tcp_host}:{cfg.tcp_port} failed: {exc}")
+        raise SystemExit(1) from exc
+    tcp.listen(32)
+    tcp.setblocking(False)
+    listeners.append((tcp, True, None))
+
+    if cfg.unix_socket:
+        sock_path = Path(cfg.unix_socket)
+        try:
+            sock_path.parent.mkdir(parents=True, exist_ok=True)
+        except OSError:
+            fallback = Path("/tmp/max25/modem.sock")
+            log(f"unix {cfg.unix_socket} unavailable, using {fallback}")
+            cfg.unix_socket = str(fallback)
+            sock_path = fallback
+            try:
+                sock_path.parent.mkdir(parents=True, exist_ok=True)
+            except OSError:
+                log("unix socket disabled (no writable path)")
+                cfg.unix_socket = ""
+                return listeners
+        # Never unlink a live peer path — that orphans the other max25d FD
+        # (ss still shows the name; clients get ENOENT).
+        if unix_path_is_live(cfg.unix_socket):
+            log(
+                f"unix socket {cfg.unix_socket} already live — not stealing "
+                "(refuse second max25d unix bind)"
+            )
+        else:
+            try:
+                os.unlink(cfg.unix_socket)
+            except FileNotFoundError:
+                pass
+            except OSError:
+                pass
+            unix = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+            try:
+                unix.bind(cfg.unix_socket)
+            except OSError as exc:
+                log(f"unix socket {cfg.unix_socket} skipped ({exc})")
+                unix.close()
+            else:
+                try:
+                    os.chmod(cfg.unix_socket, 0o660)
+                except OSError:
+                    pass
+                unix.listen(32)
+                unix.setblocking(False)
+                listeners.append((unix, False, unix_path_id(cfg.unix_socket)))
+
+    return listeners
+
+
+def main(argv: Optional[list[str]] = None) -> int:
+    if not max25d_supported():
+        log(f"max25d is not supported on {sys.platform}")
+        return 1
+
+    parser = argparse.ArgumentParser(description=f"MAX25 daemon ({platform_label()})")
+    parser.add_argument(
+        "-c",
+        "--config",
+        type=Path,
+        default=None,
+        help="Path to max25d.ini",
+    )
+    parser.add_argument(
+        "--no-stack",
+        action="store_true",
+        help="Do not auto-start hardware stack",
+    )
+    parser.add_argument(
+        "--tcp-port",
+        type=int,
+        default=None,
+        help="Override TCP listen port",
+    )
+    parser.add_argument(
+        "--no-serial",
+        action="store_true",
+        help="Disable KISS serial bridge (loopback SEND only)",
+    )
+    parser.add_argument(
+        "--session",
+        choices=("tmux", "screen"),
+        metavar="BACKEND",
+        help="Re-exec via max25d-session (detach in tmux/screen); use max25d-session attach",
+    )
+    args = parser.parse_args(argv)
+
+    if args.session:
+        session_sh = ROOT / "scripts" / "max25d-session.sh"
+        if not session_sh.is_file():
+            session_sh = Path(PREFIX) / "bin" / "max25d-session" if PREFIX else session_sh
+        if not session_sh.is_file():
+            LOGGER.error(
+                "max25d-session not found — install scripts/max25d-session.sh or use tmux/screen manually",
+                area="session",
+            )
+            return 1
+        cmd = [str(session_sh), "start", f"--{args.session}"]
+        if args.config:
+            cmd.extend(["-c", str(args.config)])
+        os.execv(cmd[0], cmd)
+
+    cfg = load_config(args.config)
+    if args.no_stack:
+        cfg.auto_start = False
+    if args.tcp_port is not None:
+        cfg.tcp_port = args.tcp_port
+    if args.no_serial:
+        cfg.serial_enabled = False
+
+    if cfg.modular_tcp.enabled and cfg.modular_tcp.role == "main":
+        svc = ModularTcpMainService(cfg.modular_tcp, cfg.tcp_host, cfg.tcp_port, log)
+        svc.start()
+        log(
+            f"modular TCP/IP Servers Service — Main '{cfg.modular_tcp.service_name}' "
+            f"({len(cfg.modular_tcp.secondaries)} secondaries)"
+        )
+        try:
+            while True:
+                time.sleep(1.0)
+        except KeyboardInterrupt:
+            pass
+        finally:
+            svc.stop()
+        return 0
+
+    state = DaemonState(cfg=cfg, bans=BanList(cfg.bans_file))
+    init_device_runtimes(state)
+    emit_startup_banner(
+        config_path=cfg.config_path or None,
+        cfg=cfg,
+        devices=cfg.devices,
+        tested_fn=registry_tested,
+    )
+    listeners = make_listeners(cfg)
+    try:
+        serve(state, listeners)
+    except KeyboardInterrupt:
+        stop_stacks(state)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/modular_tcp_server.py b/stacks/daemon/modular_tcp_server.py
new file mode 100644
index 0000000..b7f5612
--- /dev/null
+++ b/stacks/daemon/modular_tcp_server.py
@@ -0,0 +1,208 @@
+"""
+Modular TCP/IP Servers Service — central Main + Secondary routing for MAX25.
+
+Public name in docs: "modular TCP/IP Servers Service".
+Main instance accepts M25/1 clients and forwards sessions to Secondary max25d peers.
+"""
+from __future__ import annotations
+
+import configparser
+import selectors
+import socket
+import threading
+from dataclasses import dataclass, field
+from typing import Callable, Optional
+
+
+LogFn = Callable[[str], None]
+
+
+@dataclass
+class SecondaryEndpoint:
+    name: str
+    host: str
+    port: int
+
+
+@dataclass
+class ModularTcpConfig:
+    enabled: bool = False
+    role: str = "standalone"  # standalone | main | secondary
+    service_name: str = "modular-tcp-server"
+    instance_id: str = ""
+    secondaries: list[SecondaryEndpoint] = field(default_factory=list)
+    connect_timeout: float = 5.0
+    buffer_size: int = 65536
+
+
+def load_modular_tcp(cp: configparser.ConfigParser) -> ModularTcpConfig:
+    cfg = ModularTcpConfig()
+    if not cp.has_section("modular_tcp"):
+        return cfg
+    sec = cp["modular_tcp"]
+    cfg.enabled = sec.get("enabled", "no").strip().lower() in ("1", "yes", "true", "on")
+    cfg.role = sec.get("role", cfg.role).strip().lower() or cfg.role
+    cfg.service_name = sec.get("service_name", cfg.service_name).strip() or cfg.service_name
+    cfg.instance_id = sec.get("instance_id", cfg.instance_id).strip()
+    if cp.has_option("modular_tcp", "connect_timeout"):
+        try:
+            cfg.connect_timeout = float(cp.get("modular_tcp", "connect_timeout"))
+        except (TypeError, ValueError):
+            cfg.connect_timeout = 5.0
+        if cfg.connect_timeout <= 0.0:
+            cfg.connect_timeout = 5.0
+    if cp.has_section("modular_tcp.secondaries"):
+        for key in cp.options("modular_tcp.secondaries"):
+            raw = cp.get("modular_tcp.secondaries", key).strip()
+            if not raw:
+                continue
+            host, _, port_s = raw.partition(":")
+            host = host.strip()
+            if not host:
+                continue
+            try:
+                port = int(port_s or "7326")
+            except (TypeError, ValueError):
+                port = 7326
+            if port < 1 or port > 65535:
+                port = 7326
+            cfg.secondaries.append(SecondaryEndpoint(name=key.strip(), host=host, port=port))
+    if cfg.enabled and cfg.role == "main" and not cfg.secondaries:
+        # Legacy comma list: secondaries = host:port,host:port
+        raw = sec.get("secondaries", "").strip()
+        if raw:
+            for idx, item in enumerate(x.strip() for x in raw.split(",") if x.strip()):
+                host, _, port_s = item.partition(":")
+                host = host.strip()
+                if not host:
+                    continue
+                try:
+                    port = int(port_s or "7326")
+                except (TypeError, ValueError):
+                    port = 7326
+                if port < 1 or port > 65535:
+                    port = 7326
+                cfg.secondaries.append(
+                    SecondaryEndpoint(
+                        name=f"secondary-{idx + 1}",
+                        host=host,
+                        port=port,
+                    )
+                )
+    return cfg
+
+
+class ModularTcpMainService:
+    """Bidirectional relay: operator client <-> Secondary max25d M25/1."""
+
+    def __init__(
+        self,
+        cfg: ModularTcpConfig,
+        listen_host: str,
+        listen_port: int,
+        log: LogFn,
+    ) -> None:
+        self.cfg = cfg
+        self.listen_host = listen_host
+        self.listen_port = listen_port
+        self.log = log
+        self._stop = threading.Event()
+        self._thread: Optional[threading.Thread] = None
+        self._rr_index = 0
+        self._lock = threading.Lock()
+
+    def _pick_secondary(self) -> Optional[SecondaryEndpoint]:
+        with self._lock:
+            if not self.cfg.secondaries:
+                return None
+            ep = self.cfg.secondaries[self._rr_index % len(self.cfg.secondaries)]
+            self._rr_index += 1
+            return ep
+
+    def _relay(self, client: socket.socket, upstream: socket.socket) -> None:
+        sel = selectors.DefaultSelector()
+        sel.register(client, selectors.EVENT_READ)
+        sel.register(upstream, selectors.EVENT_READ)
+        try:
+            while not self._stop.is_set():
+                for key, _ in sel.select(timeout=0.5):
+                    sock = key.fileobj
+                    assert isinstance(sock, socket.socket)
+                    try:
+                        data = sock.recv(self.cfg.buffer_size)
+                    except OSError:
+                        return
+                    if not data:
+                        return
+                    target = upstream if sock is client else client
+                    try:
+                        target.sendall(data)
+                    except OSError:
+                        return
+        finally:
+            sel.close()
+
+    def _handle_client(self, client: socket.socket, addr: tuple[str, int]) -> None:
+        ep = self._pick_secondary()
+        if ep is None:
+            self.log(f"modular_tcp: no secondaries configured — drop {addr}")
+            client.close()
+            return
+        upstream = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        upstream.settimeout(self.cfg.connect_timeout)
+        try:
+            upstream.connect((ep.host, ep.port))
+        except OSError as exc:
+            self.log(f"modular_tcp: upstream {ep.name} {ep.host}:{ep.port} failed ({exc})")
+            client.close()
+            return
+        upstream.settimeout(None)
+        self.log(f"modular_tcp: {addr} -> {ep.name} {ep.host}:{ep.port}")
+        try:
+            self._relay(client, upstream)
+        finally:
+            for s in (client, upstream):
+                try:
+                    s.shutdown(socket.SHUT_RDWR)
+                except OSError:
+                    pass
+                s.close()
+
+    def _serve(self) -> None:
+        srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        srv.bind((self.listen_host, self.listen_port))
+        srv.listen(64)
+        srv.settimeout(1.0)
+        self.log(
+            f"modular_tcp: Main service '{self.cfg.service_name}' "
+            f"listen {self.listen_host}:{self.listen_port} "
+            f"secondaries={len(self.cfg.secondaries)}"
+        )
+        try:
+            while not self._stop.is_set():
+                try:
+                    client, addr = srv.accept()
+                except socket.timeout:
+                    continue
+                except OSError:
+                    break
+                threading.Thread(
+                    target=self._handle_client,
+                    args=(client, addr),
+                    daemon=True,
+                ).start()
+        finally:
+            srv.close()
+
+    def start(self) -> None:
+        if self._thread is not None:
+            return
+        self._thread = threading.Thread(target=self._serve, name="modular-tcp-main", daemon=True)
+        self._thread.start()
+
+    def stop(self) -> None:
+        self._stop.set()
+        if self._thread is not None:
+            self._thread.join(timeout=3.0)
+            self._thread = None
diff --git a/stacks/daemon/paths.py b/stacks/daemon/paths.py
new file mode 100644
index 0000000..62d4974
--- /dev/null
+++ b/stacks/daemon/paths.py
@@ -0,0 +1,281 @@
+"""MAX25 layout detection — dev checkout vs cmake install prefix."""
+from __future__ import annotations
+
+import configparser
+import os
+import sys
+from pathlib import Path
+
+MAX25_BCPR_KISS_DEFAULT = "/tmp/max25-bcpr/kiss-bc0"
+
+
+def normalize_max25_bcpr_path(path: str) -> str:
+    """Map legacy /tmp/bcpr and /var/run/bcpr paths to canonical max25-bcpr layout."""
+    p = (path or "").strip()
+    if not p:
+        return p
+    for old, new in (
+        ("/tmp/bcpr/", "/tmp/max25-bcpr/"),
+        ("/tmp/bcpr", "/tmp/max25-bcpr"),
+        ("/var/run/bcpr/", "/tmp/max25-bcpr/"),
+        ("/var/run/bcpr", "/tmp/max25-bcpr"),
+    ):
+        if p == old:
+            return new
+        if p.startswith(old + "/") or (old.endswith("/") and p.startswith(old)):
+            return new + p[len(old) :]
+    return p
+
+
+_MANIFEST = Path("plugins/manifest.yaml")
+_SHARE_MAX25 = Path("share/max25")
+_STACKS = Path("stacks")
+
+
+def _repo_from_daemon_dir(here: Path) -> Path | None:
+    if here.name == "daemon" and (here.parent / "tncs").is_dir():
+        repo = here.parent.parent
+        if (repo / _MANIFEST).is_file():
+            return repo
+    return None
+
+
+def _prefix_from_bindir(bindir: Path) -> Path | None:
+    prefix = bindir.parent
+    if (prefix / _SHARE_MAX25).is_dir() and not (prefix / _MANIFEST).is_file():
+        return prefix
+    return None
+
+
+def resolve_layout(exe: Path) -> tuple[Path, Path | None]:
+    """Return (tree_root, install_prefix).
+
+    tree_root is the repo root in dev, or MAX25_ROOT / prefix when installed.
+    install_prefix is set when exe lives under PREFIX/bin, else None.
+    """
+    exe = exe.resolve()
+    here = exe.parent
+
+    repo = _repo_from_daemon_dir(here)
+    if repo is not None:
+        return repo, None
+
+    prefix = _prefix_from_bindir(here)
+    if prefix is not None:
+        tree = Path(os.environ.get("MAX25_ROOT", str(prefix)))
+        return tree, prefix
+
+    if (here.parent / _MANIFEST).is_file():
+        return here.parent, None
+
+    return exe.parents[2], None
+
+
+def share_max25_dir(tree: Path, prefix: Path | None) -> Path:
+    if prefix is not None:
+        share = prefix / _SHARE_MAX25
+        if share.is_dir():
+            return share
+    return tree / _SHARE_MAX25
+
+
+def stacks_dir(tree: Path, prefix: Path | None) -> Path:
+    tree_stacks = tree / _STACKS
+    if tree_stacks.is_dir():
+        return tree_stacks
+    if prefix is not None:
+        installed = prefix / _SHARE_MAX25 / _STACKS
+        if installed.is_dir():
+            return installed
+    return tree_stacks
+
+
+def tnc_serial_recovery_path(tree: Path, prefix: Path | None) -> Path | None:
+    """Locate tnc_serial_recovery.py (dev checkout or cmake install)."""
+    for candidate in (
+        stacks_dir(tree, prefix) / "tncs" / "tnc_serial_recovery.py",
+        tree / _STACKS / "tncs" / "tnc_serial_recovery.py",
+    ):
+        if candidate.is_file():
+            return candidate
+    return None
+
+
+def ctl_path(tree: Path, prefix: Path | None, exe: Path) -> Path:
+    if prefix is not None:
+        sibling = exe.resolve().parent / "max25-ctl"
+        if sibling.is_file():
+            return sibling
+    script = tree / "scripts" / "max25-ctl"
+    if script.is_file():
+        return script
+    if prefix is not None:
+        return prefix / "bin" / "max25-ctl"
+    return script
+
+
+def default_ini_candidates(tree: Path, prefix: Path | None) -> list[Path]:
+    candidates: list[Path] = []
+    env_ini = os.environ.get("MAX25D_INI", "").strip()
+    if env_ini:
+        candidates.append(Path(env_ini))
+    candidates.append(Path("/etc/max25/max25d.ini"))
+    candidates.append(share_max25_dir(tree, prefix) / "max25d.ini.example")
+    if sys.platform.startswith("freebsd"):
+        candidates.append(share_max25_dir(tree, prefix) / "max25d.freebsd.ini.example")
+    if prefix is None or tree != prefix:
+        candidates.append(tree / _SHARE_MAX25 / "max25d.ini.example")
+    return candidates
+
+
+def serial_env_candidates(device_id: str, tree: Path, prefix: Path | None) -> list[Path]:
+    paths: list[Path] = [Path(f"/etc/max25/{device_id}-serial.env")]
+    env_root = os.environ.get("MAX25_ROOT", "").strip()
+    if env_root:
+        paths.append(Path(env_root) / "local" / f"{device_id}-serial.env")
+        paths.append(Path(env_root) / _STACKS / "tncs" / f"{device_id}-serial.env")
+    cwd = os.environ.get("PWD", "").strip()
+    if cwd:
+        paths.append(Path(cwd) / "local" / f"{device_id}-serial.env")
+    if prefix is not None:
+        paths.append(prefix / _SHARE_MAX25 / "serial" / f"{device_id}-serial.env")
+        paths.append(prefix / _SHARE_MAX25 / _STACKS / "tncs" / f"{device_id}-serial.env")
+    paths.append(tree / "local" / f"{device_id}-serial.env")
+    paths.append(tree / _STACKS / "tncs" / f"{device_id}-serial.env")
+    return paths
+
+
+def baycom_share_dir(tree: Path, prefix: Path | None) -> Path:
+    if prefix is not None:
+        installed = prefix / _SHARE_MAX25 / "baycom"
+        if installed.is_dir():
+            return installed
+    return tree / "share" / "baycom"
+
+
+_SITE_BAYCOM_INI = Path("/etc/baycom/baycom-pr.ini")
+_SINGLE_SER12_EXAMPLE = "baycom-pr.pccom-ttyS0-only.ini.example"
+
+
+def is_dual_baycom_ini(path: Path) -> bool:
+    """True when profile lists more than one modem or name is 'dual'."""
+    if not path.is_file():
+        return False
+    cp = configparser.ConfigParser()
+    try:
+        cp.read(path, encoding="utf-8")
+    except OSError:
+        return False
+    if "profile" not in cp:
+        return False
+    prof = cp["profile"]
+    name = prof.get("name", "").strip().lower()
+    modem_ids = [x.strip() for x in prof.get("modems", "").split(",") if x.strip()]
+    if len(modem_ids) > 1:
+        return True
+    return name == "dual"
+
+
+def canonical_dual_baycom_example(
+    device_id: str, tree: Path, prefix: Path | None
+) -> Path | None:
+    """Shipped dual-modem template for kernel-ser12 service mode."""
+    if device_id not in ("baycom-ser12", "baycom-par96"):
+        return None
+    for candidate in (
+        tree / _STACKS / "baycom-pr" / "config" / "examples" / "baycom-pr.dual.ini",
+        stacks_dir(tree, prefix) / "baycom-pr" / "config" / "examples" / "baycom-pr.dual.ini",
+    ):
+        if candidate.is_file():
+            return candidate
+    site = _SITE_BAYCOM_INI
+    if site.is_file() and is_dual_baycom_ini(site):
+        return site
+    return None
+
+
+def canonical_single_baycom_example(
+    device_id: str, tree: Path, prefix: Path | None
+) -> Path | None:
+    """Shipped single-modem template for kernel BayCom devices."""
+    share = baycom_share_dir(tree, prefix)
+    if device_id == "baycom-par96":
+        for candidate in (
+            share / "baycom-pr.par96-single.ini.example",
+            tree / _STACKS / "baycom-pr" / "config" / "examples" / "baycom-pr.par96.ini",
+            stacks_dir(tree, prefix) / "baycom-pr" / "config" / "examples" / "baycom-pr.par96.ini",
+        ):
+            if candidate.is_file():
+                return candidate
+        return None
+    ser12 = share / _SINGLE_SER12_EXAMPLE
+    if ser12.is_file():
+        return ser12
+    return None
+
+
+def baycom_ini_candidates(device_id: str, tree: Path, prefix: Path | None) -> list[Path]:
+    """Search order for baycom-pr.ini (local → site single → shipped example)."""
+    paths: list[Path] = []
+    env_ini = os.environ.get("BAYCOM_INI", "").strip()
+    if env_ini:
+        paths.append(Path(env_ini))
+    env_root = os.environ.get("MAX25_ROOT", "").strip()
+    if env_root:
+        paths.append(Path(env_root) / "local" / "baycom-pr.ini")
+    cwd = os.environ.get("PWD", "").strip()
+    if cwd:
+        paths.append(Path(cwd) / "local" / "baycom-pr.ini")
+    paths.append(tree / "local" / "baycom-pr.ini")
+
+    # Site INI before shipped example so operator edits in /etc win when single-modem.
+    paths.append(_SITE_BAYCOM_INI)
+    paths.append(Path("/etc/baycom/baycom-pr-single.ini"))
+
+    canonical = canonical_single_baycom_example(device_id, tree, prefix)
+    if canonical is not None:
+        paths.append(canonical)
+
+    if prefix is not None:
+        paths.append(prefix / _SHARE_MAX25 / "baycom" / _SINGLE_SER12_EXAMPLE)
+        paths.append(prefix / "etc" / "baycom" / "baycom-pr.ini.example")
+
+    paths.append(tree / _STACKS / "baycom-pr" / "config" / "baycom-pr.ini")
+    return paths
+
+
+def resolve_baycom_profile(
+    profile: str,
+    device_id: str,
+    tree: Path,
+    prefix: Path | None,
+) -> Path | None:
+    """Resolve named profile: single (default) or dual (service mode)."""
+    name = profile.strip().lower()
+    if name == "dual":
+        return canonical_dual_baycom_example(device_id, tree, prefix)
+    if name in ("single", "default", ""):
+        return resolve_baycom_ini(device_id, tree, prefix)
+    return None
+
+
+def resolve_baycom_ini(
+    device_id: str,
+    tree: Path,
+    prefix: Path | None,
+    explicit: str = "",
+) -> Path | None:
+    """Return first existing baycom-pr.ini path, or None.
+
+    Skips dual-modem /etc/baycom/baycom-pr.ini unless explicit (or env BAYCOM_INI).
+    """
+    if explicit:
+        path = Path(explicit)
+        return path if path.is_file() else None
+    for candidate in baycom_ini_candidates(device_id, tree, prefix):
+        if not candidate.is_file():
+            continue
+        if candidate == _SITE_BAYCOM_INI and is_dual_baycom_ini(candidate):
+            continue
+        return candidate
+    return None
diff --git a/stacks/daemon/privilege_drop.py b/stacks/daemon/privilege_drop.py
new file mode 100644
index 0000000..5e68ca8
--- /dev/null
+++ b/stacks/daemon/privilege_drop.py
@@ -0,0 +1,110 @@
+"""Drop max25d privileges after hardware stack is up (Linux)."""
+from __future__ import annotations
+
+import configparser
+import grp
+import os
+import pwd
+import sys
+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass
+class RunAsConfig:
+    user: str = ""
+    group: str = ""
+    uid: Optional[int] = None
+    gid: Optional[int] = None
+
+
+def _parse_optional_int(raw: str) -> Optional[int]:
+    text = str(raw).strip()
+    if not text:
+        return None
+    return int(text)
+
+
+def parse_run_as(cp: configparser.ConfigParser) -> RunAsConfig:
+    cfg = RunAsConfig()
+    if not cp.has_section("daemon"):
+        return cfg
+    sec = cp["daemon"]
+    cfg.user = sec.get("user", fallback="").strip()
+    cfg.group = sec.get("group", fallback="").strip()
+    if cp.has_option("daemon", "uid"):
+        cfg.uid = _parse_optional_int(sec.get("uid", fallback=""))
+    if cp.has_option("daemon", "gid"):
+        cfg.gid = _parse_optional_int(sec.get("gid", fallback=""))
+    return cfg
+
+
+def run_as_configured(cfg: RunAsConfig) -> bool:
+    return bool(
+        cfg.user
+        or cfg.group
+        or cfg.uid is not None
+        or cfg.gid is not None
+    )
+
+
+def resolve_run_as(cfg: RunAsConfig) -> tuple[int, int, str]:
+    pw: pwd.struct_passwd | None = None
+    name = cfg.user
+
+    if cfg.user:
+        pw = pwd.getpwnam(cfg.user)
+        uid = pw.pw_uid
+        gid = pw.pw_gid
+    elif cfg.uid is not None:
+        pw = pwd.getpwuid(cfg.uid)
+        uid = pw.pw_uid
+        gid = pw.pw_gid
+        name = pw.pw_name
+    else:
+        raise ValueError("[daemon] user= or uid= required for privilege drop")
+
+    if cfg.uid is not None:
+        uid = cfg.uid
+    if cfg.group:
+        gid = grp.getgrnam(cfg.group).gr_gid
+    elif cfg.gid is not None:
+        gid = cfg.gid
+
+    return uid, gid, name
+
+
+def drop_privileges(cfg: RunAsConfig, *, log) -> None:
+    if os.name != "posix":
+        return
+    if not run_as_configured(cfg):
+        if os.geteuid() == 0:
+            log(
+                "running as root after stack start — set [daemon] user= to drop",
+                area="privilege",
+            )
+        return
+    if os.geteuid() != 0:
+        return
+
+    uid, gid, name = resolve_run_as(cfg)
+
+    os.initgroups(name, gid)
+    os.setgid(gid)
+    os.setuid(uid)
+
+    if os.geteuid() == 0:
+        raise OSError("privilege drop failed — still root")
+
+    log(
+        f"dropped privileges to uid={uid} gid={gid} ({name})",
+        area="privilege",
+    )
+
+
+def drop_privileges_or_exit(cfg: RunAsConfig, *, log) -> None:
+    try:
+        drop_privileges(cfg, log=log)
+    except (KeyError, ValueError, OSError) as exc:
+        log(f"privilege drop failed: {exc}", area="privilege")
+        raise SystemExit(1) from exc
diff --git a/stacks/daemon/reporting_quality.py b/stacks/daemon/reporting_quality.py
new file mode 100644
index 0000000..f755f08
--- /dev/null
+++ b/stacks/daemon/reporting_quality.py
@@ -0,0 +1,178 @@
+"""RX data-quality window for max25d STATUS error=/voice= reporting."""
+from __future__ import annotations
+
+import re
+import time
+from collections import deque
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import Deque, Optional
+
+_AX25_UI_LINE_RE = re.compile(
+    r"^\[(?:CRDOP )?AX25 UI ([^>]+)>([^\]]+)\]\s?(.*)$",
+    re.DOTALL,
+)
+_AX25_UI_PARTIAL_RE = re.compile(r"\[AX25 UI ", re.IGNORECASE)
+_VOICE_NOISE_LINE_RE = re.compile(
+    r"^\[(?:CRDOP RX|AUDIO RX|VOICE)[^\]]*\]",
+    re.IGNORECASE,
+)
+
+
+class RxOutcome(str, Enum):
+    GOOD = "good"
+    BAD = "bad"
+    IGNORE = "ignore"
+
+
+def classify_rx_line(line: str, callid: str) -> RxOutcome:
+    """
+    Classify an RX display line for data-quality tracking.
+
+    - GOOD: complete AX.25 UI frame whose destination matches configured CALLID.
+    - BAD: incomplete AX.25 UI or wrong CALLID (incomplete data counts as error).
+    - IGNORE: voice/noise/interference — excluded from data pass statistics.
+    """
+    text = line.strip()
+    if not text:
+        return RxOutcome.IGNORE
+
+    match = _AX25_UI_LINE_RE.match(text)
+    if match:
+        dest = match.group(2).strip().upper()
+        expected = callid.strip().upper()
+        if not expected or dest != expected:
+            return RxOutcome.BAD
+        return RxOutcome.GOOD
+
+    if _AX25_UI_PARTIAL_RE.search(text):
+        return RxOutcome.BAD
+
+    if _VOICE_NOISE_LINE_RE.match(text):
+        return RxOutcome.IGNORE
+
+    return RxOutcome.IGNORE
+
+
+@dataclass
+class _PassWindow:
+    good: int = 0
+    bad: int = 0
+    ignored: bool = False
+    started_at: float = 0.0
+
+
+@dataclass
+class DataQualityTracker:
+    """
+    Rolling pass window: each pass lasts up to pass_window_sec (default 20s).
+    passes_required consecutive passes (default 3) form one evaluation cycle
+    (3 × max 20s = up to 60s). Voice/noise does not fill a pass slot.
+    """
+
+    passes_required: int = 3
+    min_good_percent: int = 50
+    pass_window_sec: int = 20
+    passes: Deque[str] = field(default_factory=deque)
+    voice_activity: bool = False
+    current: _PassWindow = field(default_factory=_PassWindow)
+
+    def __post_init__(self) -> None:
+        if self.passes_required < 1:
+            self.passes_required = 1
+        if self.min_good_percent < 1:
+            self.min_good_percent = 1
+        elif self.min_good_percent > 100:
+            self.min_good_percent = 100
+        if self.pass_window_sec < 1:
+            self.pass_window_sec = 1
+        elif self.pass_window_sec > 300:
+            self.pass_window_sec = 300
+        self.passes = deque(maxlen=self.passes_required)
+
+    def _now(self, now: Optional[float]) -> float:
+        return time.time() if now is None else now
+
+    def _ensure_window(self, now: float) -> None:
+        if self.current.started_at == 0.0:
+            self.current.started_at = now
+
+    def _pass_outcome_from_counts(self, good: int, bad: int) -> str:
+        if bad > 0:
+            return "bad"
+        if good > 0:
+            return "good"
+        return "bad"
+
+    def _finalize_current_pass(self) -> None:
+        good = self.current.good
+        bad = self.current.bad
+        if good == 0 and bad == 0:
+            if self.current.ignored:
+                return
+            self.passes.append("bad")
+            return
+        self.passes.append(self._pass_outcome_from_counts(good, bad))
+
+    def _roll_window(self, now: float) -> None:
+        self._finalize_current_pass()
+        self.current = _PassWindow(started_at=now)
+
+    def tick(self, now: Optional[float] = None) -> None:
+        """Expire the active pass when pass_window_sec elapsed."""
+        ts = self._now(now)
+        if self.current.started_at == 0.0:
+            return
+        if ts - self.current.started_at < self.pass_window_sec:
+            return
+        self._roll_window(ts)
+
+    def record(self, outcome: RxOutcome, now: Optional[float] = None) -> None:
+        ts = self._now(now)
+        self.tick(ts)
+        self._ensure_window(ts)
+
+        if outcome == RxOutcome.IGNORE:
+            self.voice_activity = True
+            self.current.ignored = True
+            return
+        if outcome == RxOutcome.GOOD:
+            self.current.good += 1
+        elif outcome == RxOutcome.BAD:
+            self.current.bad += 1
+
+    def record_bad(self, now: Optional[float] = None) -> None:
+        self.record(RxOutcome.BAD, now)
+
+    def good_ratio_percent(self) -> Optional[int]:
+        if len(self.passes) < self.passes_required:
+            return None
+        good = sum(1 for item in self.passes if item == "good")
+        total = len(self.passes)
+        if total == 0:
+            return None
+        return (100 * good) // total
+
+    def data_error_valid(self, *, reporting_enabled: bool) -> bool:
+        if not reporting_enabled:
+            return False
+        ratio = self.good_ratio_percent()
+        if ratio is None:
+            return False
+        return ratio >= self.min_good_percent
+
+    def voice_signal_valid(self, *, reporting_enabled: bool, link_healthy: bool) -> bool:
+        """
+        Voice/noise/disturbance path: when link is healthy and voice activity was
+        seen (non-data RX), treat as 100% valid even if the content was noise only.
+        """
+        if not reporting_enabled:
+            return False
+        if not link_healthy:
+            return False
+        if self.voice_activity:
+            return True
+        return True
+
+    def max_cycle_seconds(self) -> int:
+        return self.passes_required * self.pass_window_sec
diff --git a/stacks/daemon/test_audio_dummy_backend.py b/stacks/daemon/test_audio_dummy_backend.py
new file mode 100644
index 0000000..c5ba31d
--- /dev/null
+++ b/stacks/daemon/test_audio_dummy_backend.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+"""Acoustic engine loopback + audio-dummy backend smoke tests."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+sys.path.insert(0, str(ROOT / "stacks" / "crdop" / "lib"))
+
+from acoustic_engine import AcousticEngine  # noqa: E402
+from device_backends import AudioDummyBackend, DeviceBackendConfig, registry_tested  # noqa: E402
+
+
+def test_loopback_decode() -> None:
+    eng = AcousticEngine()
+    rep = eng.loopback_self_test("TST-0", "QST")
+    assert rep.symbols > 0
+    assert rep.transitions > 0
+
+
+def test_audio_dummy_backend_loopback_tx() -> None:
+    cfg = DeviceBackendConfig(device_id="audio-dummy", backend_type="audio-dummy", audio_mode="loopback")
+    rx: list[str] = []
+    backend = AudioDummyBackend(cfg, on_rx=rx.append)
+    assert backend.open()
+    assert backend.attach_session("TST-0")
+    ok, display = backend.transmit("TST-0", "QST", "hi", ax25_ui=True)
+    assert ok
+    assert "QST" in display
+    backend.close()
+
+
+def test_registry() -> None:
+    assert registry_tested("audio-dummy") is True
+
+
+def main() -> int:
+    test_loopback_decode()
+    test_audio_dummy_backend_loopback_tx()
+    test_registry()
+    print("OK: audio-dummy tests")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/stacks/daemon/test_auth.py b/stacks/daemon/test_auth.py
new file mode 100644
index 0000000..263a2e5
--- /dev/null
+++ b/stacks/daemon/test_auth.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python3
+"""TCP auth smoke test for max25d M25/1."""
+import socket
+import subprocess
+import sys
+import tempfile
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+DAEMON = ROOT / "stacks/daemon/max25d"
+BASE_INI = ROOT / "share/max25/max25d.ini.example"
+
+
+class LineReader:
+    def __init__(self, sock: socket.socket) -> None:
+        self.sock = sock
+        self.buf = b""
+
+    def read(self, timeout: float = 5.0) -> str:
+        self.sock.settimeout(timeout)
+        while b"\n" not in self.buf:
+            chunk = self.sock.recv(4096)
+            if not chunk:
+                raise RuntimeError("connection closed")
+            self.buf += chunk
+        line, self.buf = self.buf.split(b"\n", 1)
+        return line.decode("utf-8")
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def main() -> int:
+    port = free_port()
+    password = "preview-secret"
+
+    with tempfile.NamedTemporaryFile("w", suffix=".ini", delete=False) as tmp:
+        tmp.write(BASE_INI.read_text())
+        tmp.write(f"\n[network]\ntcp_password = {password}\n")
+        ini_path = Path(tmp.name)
+
+    proc = subprocess.Popen(
+        [str(DAEMON), "--no-stack", "-c", str(ini_path), "--tcp-port", str(port)],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+    time.sleep(0.6)
+    try:
+        sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+    except OSError as exc:
+        proc.terminate()
+        proc.wait(timeout=3)
+        print(f"FAIL: connect: {exc}", file=sys.stderr)
+        return 1
+
+    reader = LineReader(sock)
+    try:
+        assert reader.read() == "AUTH required"
+
+        sock.sendall(b"AUTH wrong\n")
+        assert reader.read() == "ERR auth failed"
+        sock.close()
+
+        sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+        reader = LineReader(sock)
+        assert reader.read() == "AUTH required"
+        sock.sendall(f"AUTH {password}\n".encode())
+        assert reader.read() == "OK"
+        status = reader.read()
+        assert status.startswith("STATUS ")
+
+        sock.sendall(b"PING\n")
+        assert reader.read() == "OK"
+
+        print("OK: max25d TCP auth smoke")
+        return 0
+    finally:
+        try:
+            sock.close()
+        except OSError:
+            pass
+        proc.terminate()
+        proc.wait(timeout=5)
+        ini_path.unlink(missing_ok=True)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_ax25_codec.py b/stacks/daemon/test_ax25_codec.py
new file mode 100644
index 0000000..b12e43d
--- /dev/null
+++ b/stacks/daemon/test_ax25_codec.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+"""Unit tests for ax25_codec (RFC 1171 FCS + libax25 address rules)."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from ax25_codec import (  # noqa: E402
+    ax25_build_ui,
+    ax25_crc,
+    ax25_crc_valid,
+    ax25_encode_address,
+    ax25_parse_ui,
+    format_callsign,
+    parse_callsign,
+    validate_callsign,
+)
+
+
+def test_rfc1171_crc_vector() -> None:
+    body = bytes(range(256))
+    crc = ax25_crc(body)
+    frame = body + bytes((crc & 0xFF, crc >> 8))
+    assert ax25_crc_valid(frame)
+    assert crc == 0x303C
+
+
+def test_address_roundtrip() -> None:
+    raw = ax25_encode_address("DG1ABC", 7, last=True)
+    frame = ax25_build_ui("DG1ABC-7", "CQ", b"73")
+    parsed = ax25_parse_ui(frame)
+    assert parsed == ("DG1ABC-7", "CQ", b"73")
+
+
+def test_format_callsign_omit_zero_ssid() -> None:
+    assert format_callsign("DG1ABC", 0) == "DG1ABC"
+    assert format_callsign("CB", 0) == "CB"
+
+
+def test_parse_callsign_legacy() -> None:
+    assert parse_callsign("DK0WC-7") == ("DK0WC", 7)
+    assert parse_callsign("bad-ssid") == ("BAD", 0)
+
+
+def test_validate_callsign_strict() -> None:
+    assert validate_callsign("CB-0") == ("CB", 0)
+    assert validate_callsign("N0CALL-15") == ("N0CALL", 15)
+    try:
+        validate_callsign("CB_0")
+        raise AssertionError("expected ValueError")
+    except ValueError:
+        pass
+
+
+def test_ui_frame_without_fcs() -> None:
+    frame = ax25_build_ui("DG1ABC", "QST", b"hi")
+    body = frame[:-2]
+    parsed = ax25_parse_ui(body)
+    assert parsed == ("DG1ABC", "QST", b"hi")
+
+
+def test_invalid_callsign_build() -> None:
+    try:
+        ax25_build_ui("BAD_CALL", "CQ", b"x")
+        raise AssertionError("expected ValueError")
+    except ValueError:
+        pass
+
+
+def test_non_ui_rejected() -> None:
+    frame = ax25_build_ui("A", "B", b"x")
+    frame = bytearray(frame)
+    frame[14] = 0x00  # not UI control
+    assert ax25_parse_ui(bytes(frame)) is None
+
+
+def main() -> int:
+    tests = [
+        test_rfc1171_crc_vector,
+        test_address_roundtrip,
+        test_format_callsign_omit_zero_ssid,
+        test_parse_callsign_legacy,
+        test_validate_callsign_strict,
+        test_ui_frame_without_fcs,
+        test_invalid_callsign_build,
+        test_non_ui_rejected,
+    ]
+    for fn in tests:
+        fn()
+    print("OK: ax25_codec unit tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_bans.py b/stacks/daemon/test_bans.py
new file mode 100644
index 0000000..80176ae
--- /dev/null
+++ b/stacks/daemon/test_bans.py
@@ -0,0 +1,199 @@
+#!/usr/bin/env python3
+"""Unit and protocol tests for max25d AX.25 source ban list."""
+from __future__ import annotations
+
+import importlib.util
+import socket
+import subprocess
+import sys
+import tempfile
+import time
+from pathlib import Path
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[2]
+LAUNCHER = ROOT / "stacks/daemon/max25d"
+DAEMON = ROOT / "stacks/daemon/max25d.py"
+
+sys.path.insert(0, str(DAEMON.parent))
+from banlist import BanList, callsign_banned, extract_ax25_source  # noqa: E402
+
+
+def load_max25d_module():
+    from importlib.machinery import SourceFileLoader
+
+    loader = SourceFileLoader("max25d", str(DAEMON))
+    spec = importlib.util.spec_from_loader("max25d", loader)
+    mod = importlib.util.module_from_spec(spec)
+    sys.modules["max25d"] = mod
+    loader.exec_module(mod)
+    return mod
+
+
+class LineReader:
+    def __init__(self, sock: socket.socket) -> None:
+        self.sock = sock
+        self.buf = b""
+
+    def read(self, timeout: float = 5.0) -> str:
+        self.sock.settimeout(timeout)
+        while b"\n" not in self.buf:
+            chunk = self.sock.recv(4096)
+            if not chunk:
+                raise RuntimeError("connection closed")
+            self.buf += chunk
+        line, self.buf = self.buf.split(b"\n", 1)
+        return line.decode("utf-8")
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def test_extract_ax25_source() -> None:
+    assert extract_ax25_source("[AX25 UI DG1ABC>QST] 73") == "DG1ABC"
+    assert extract_ax25_source("[AX25 UI DK0WC-7>CB-0] hi") == "DK0WC-7"
+    assert extract_ax25_source("plain text") is None
+    assert extract_ax25_source("[CRDOP RX soft-crdop] hello") is None
+
+
+def test_callsign_banned_matching() -> None:
+    assert callsign_banned("DG1ABC", "DG1ABC")
+    assert callsign_banned("DG1ABC", "DG1ABC-7")
+    assert not callsign_banned("DG1ABC", "DG1ABD")
+    assert callsign_banned("DK0WC-7", "DK0WC-7")
+    assert not callsign_banned("DK0WC-7", "DK0WC")
+    assert not callsign_banned("DK0WC-7", "DK0WC-8")
+
+
+def test_banlist_file_roundtrip() -> None:
+    with tempfile.TemporaryDirectory() as tmp:
+        path = Path(tmp) / "bans.txt"
+        path.write_text("# ignored comment\nDG1ABC\n\nDK0WC-7\n", encoding="utf-8")
+        bans = BanList(path)
+        assert bans.list() == ["DG1ABC", "DK0WC-7"]
+        assert bans.is_banned("DG1ABC-3")
+        assert bans.is_banned("DK0WC-7")
+        assert not bans.is_banned("DK0WC")
+
+        bans.add("DL1TEST")
+        bans.remove("DG1ABC")
+        assert bans.list() == ["DK0WC-7", "DL1TEST"]
+        reloaded = BanList(path)
+        assert reloaded.list() == ["DK0WC-7", "DL1TEST"]
+
+
+def test_on_backend_rx_silent_drop() -> None:
+    mod = load_max25d_module()
+    with tempfile.TemporaryDirectory() as tmp:
+        bans_path = Path(tmp) / "bans.txt"
+        bans_path.write_text("DG1ABC\n", encoding="utf-8")
+        cfg = mod.DaemonConfig(bans_file=str(bans_path))
+        state = mod.DaemonState(cfg=cfg, bans=BanList(bans_path))
+        mod.init_device_runtimes(state)
+
+        sent: list[str] = []
+
+        def capture(_state, line, skip=None):
+            sent.append(line)
+
+        with patch.object(mod, "broadcast", side_effect=capture), patch.object(mod, "log"):
+            mod.on_backend_rx(state, "tnc2c", "[AX25 UI DG1ABC>QST] blocked")
+            assert sent == []
+
+            mod.on_backend_rx(state, "tnc2c", "[AX25 UI DK0WC>QST] allowed")
+            assert sent == ["RX device=tnc2c [AX25 UI DK0WC>QST] allowed"]
+
+
+def test_ban_commands_protocol() -> None:
+    port = free_port()
+    with tempfile.TemporaryDirectory() as tmp:
+        bans_path = Path(tmp) / "bans.txt"
+        ini_path = Path(tmp) / "max25d.ini"
+        ini_path.write_text(
+            f"""
+[daemon]
+device = tnc2c
+hardware = tncs
+[network]
+tcp_host = 127.0.0.1
+tcp_port = {port}
+[modem]
+bans_file = {bans_path}
+[stack]
+auto_start = no
+""",
+            encoding="utf-8",
+        )
+
+        proc = subprocess.Popen(
+            [
+                str(LAUNCHER),
+                "--no-stack",
+                "--no-serial",
+                "-c",
+                str(ini_path),
+                "--tcp-port",
+                str(port),
+            ],
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.PIPE,
+            text=True,
+        )
+        time.sleep(0.6)
+        try:
+            sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+        except OSError as exc:
+            proc.terminate()
+            proc.wait(timeout=3)
+            raise RuntimeError(f"connect failed: {exc}") from exc
+
+        reader = LineReader(sock)
+        try:
+            assert reader.read() == "OK"
+            reader.read()  # STATUS
+
+            sock.sendall(b"BAN DG1ABC\n")
+            assert reader.read() == "OK"
+            assert bans_path.read_text(encoding="utf-8").strip() == "DG1ABC"
+
+            sock.sendall(b"BANS\n")
+            assert reader.read() == "BAN DG1ABC"
+            assert reader.read() == "OK"
+
+            sock.sendall(b"UNBAN DG1ABC\n")
+            assert reader.read() == "OK"
+            assert bans_path.read_text(encoding="utf-8") == ""
+
+            sock.sendall(b"UNBAN DG1ABC\n")
+            assert reader.read() == "ERR not banned"
+
+            sock.sendall(b"BAN BAD!\n")
+            assert reader.read() == "ERR invalid callsign"
+        finally:
+            sock.close()
+            proc.terminate()
+            proc.wait(timeout=5)
+
+
+def main() -> int:
+    tests = [
+        test_extract_ax25_source,
+        test_callsign_banned_matching,
+        test_banlist_file_roundtrip,
+        test_on_backend_rx_silent_drop,
+        test_ban_commands_protocol,
+    ]
+    for test in tests:
+        test()
+        print(f"OK: {test.__name__}")
+    print("OK: banlist tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_baycom_backend.py b/stacks/daemon/test_baycom_backend.py
new file mode 100644
index 0000000..ebff5a4
--- /dev/null
+++ b/stacks/daemon/test_baycom_backend.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python3
+"""Offline unit tests for BayComKissBackend (no kernel hardware)."""
+from __future__ import annotations
+
+import os
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+
+from device_backends import BayComKissBackend, DeviceBackendConfig  # noqa: E402
+from ax25_codec import ax25_build_ui, ax25_parse_ui  # noqa: E402
+from kiss_bridge import KissDecoder, format_rx_line, kiss_data_frame  # noqa: E402
+
+
+def test_baycom_kiss_default_link() -> None:
+    cfg = DeviceBackendConfig(device_id="baycom-ser12", backend_type="baycom-kiss", baycom_modem="a")
+    backend = BayComKissBackend(cfg, on_rx=lambda _l: None)
+    assert backend._path in ("/var/run/baycom-pr/kiss", f"/var/run/baycom-pr/kiss-a")
+    assert backend.backend_type == "baycom-kiss"
+    assert backend._is_pty is True
+
+
+def test_baycom_kiss_transmit_kiss_frame() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="baycom-ser12",
+        backend_type="baycom-kiss",
+        kiss_link="/var/run/baycom-pr/kiss",
+    )
+    backend = BayComKissBackend(cfg, on_rx=lambda _l: None)
+    backend._fd = 99
+    backend._kiss_active = True
+    written: list[bytes] = []
+
+    with patch("os.write", side_effect=lambda _fd, data: written.append(data) or len(data)):
+        with patch("termios.tcdrain"):
+            ok, display = backend.transmit("CB-0", "QST", "hello", ax25_ui=True)
+    assert ok, display
+    assert written and written[0].startswith(b"\xc0")
+    assert "hello" in display
+
+
+def test_baycom_kiss_rx_decode_path() -> None:
+    """RX path: KISS bytes → AX.25 UI → on_rx line (same decoder as _rx_loop)."""
+    rx_lines: list[str] = []
+    frame = ax25_build_ui("REMOTE-0", "CB-0", b"73")
+    pkt = kiss_data_frame(0, frame)
+    decoder = KissDecoder()
+    for _port, payload in decoder.feed(pkt):
+        parsed = ax25_parse_ui(payload)
+        assert parsed is not None
+        src, dst, info = parsed
+        assert src == "REMOTE"
+        assert dst == "CB"
+        assert info == b"73"
+        from kiss_bridge import format_rx_line
+
+        rx_lines.append(format_rx_line(src, dst, info, ax25_ui=True))
+    assert rx_lines and "73" in rx_lines[0]
+
+
+def test_baycom_kiss_modem_b_link() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="baycom-b",
+        backend_type="baycom-kiss",
+        baycom_modem="b",
+        kiss_link="/var/run/baycom-pr/kiss-b",
+    )
+    backend = BayComKissBackend(cfg, on_rx=lambda _l: None)
+    assert backend._path == "/var/run/baycom-pr/kiss-b"
+
+
+def test_baycom_kiss_open_missing_path() -> None:
+    backend = BayComKissBackend(
+        DeviceBackendConfig(device_id="baycom-ser12", kiss_link="/nonexistent/kiss/path"),
+        on_rx=lambda _l: None,
+    )
+    assert not backend.open()
+    assert backend.status == "error-no-device"
+
+
+def main() -> int:
+    test_baycom_kiss_default_link()
+    test_baycom_kiss_modem_b_link()
+    test_baycom_kiss_transmit_kiss_frame()
+    test_baycom_kiss_rx_decode_path()
+    test_baycom_kiss_open_missing_path()
+    print("OK: baycom backend tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_bcpr_backend.py b/stacks/daemon/test_bcpr_backend.py
new file mode 100644
index 0000000..efcedd5
--- /dev/null
+++ b/stacks/daemon/test_bcpr_backend.py
@@ -0,0 +1,194 @@
+#!/usr/bin/env python3
+"""Offline unit tests for bcpr device parse + BcprKissBackend (no UART)."""
+from __future__ import annotations
+
+import configparser
+import importlib.util
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+
+from device_backends import (  # noqa: E402
+    BcprKissBackend,
+    DeviceBackendConfig,
+    parse_device_spec,
+)
+
+
+def load_max25d():
+    from importlib.machinery import SourceFileLoader
+
+    loader = SourceFileLoader("max25d", str(ROOT / "stacks" / "daemon" / "max25d.py"))
+    spec = importlib.util.spec_from_loader("max25d", loader)
+    mod = importlib.util.module_from_spec(spec)
+    sys.modules["max25d"] = mod
+    loader.exec_module(mod)
+    return mod
+
+
+def test_bcpr_kiss_default_link() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="max25e0",
+        backend_type="max25-bcpr-kiss",
+        bcpr_device="bc0",
+    )
+    backend = BcprKissBackend(cfg, on_rx=lambda _l: None)
+    assert backend._path == "/var/run/max25-bcpr/kiss-bc0"
+    assert backend.backend_type == "max25-bcpr-kiss"
+    assert backend._is_pty is True
+
+
+def test_max25e0_default_addrs() -> None:
+    from device_backends import MAX25E0_DEFAULT_IPV4, MAX25E0_DEFAULT_IPV6
+    text = """
+[devices]
+max25e0 = max25-bcpr:bc0
+"""
+    cp = configparser.ConfigParser()
+    cp.read_string(text)
+    from device_backends import parse_device_spec
+    dev = parse_device_spec("max25e0", "max25-bcpr:bc0", cp, {"hardware": "modems"})
+    assert dev.ipv4 == MAX25E0_DEFAULT_IPV4
+    assert dev.ipv6 == MAX25E0_DEFAULT_IPV6
+    # override
+    text2 = """
+[devices]
+max25e0 = max25-bcpr:bc0
+[device.max25e0]
+ipv4 = 10.0.0.25/24
+ipv6 = fd00::25/128
+"""
+    cp2 = configparser.ConfigParser()
+    cp2.read_string(text2)
+    dev2 = parse_device_spec("max25e0", "max25-bcpr:bc0", cp2, {"hardware": "modems"})
+    assert dev2.ipv4 == "10.0.0.25/24"
+    assert dev2.ipv6 == "fd00::25/128"
+    # fork inherits from [device.max25e0] (INI colon keys need care — parse by id)
+    text3 = """
+[device.max25e0]
+ipv4 = 10.0.0.25/24
+ipv6 = fd00::25/128
+"""
+    cp3 = configparser.ConfigParser()
+    cp3.read_string(text3)
+    fork = parse_device_spec("max25e0:bc1", "max25-bcpr:bc1", cp3, {"hardware": "modems"})
+    assert fork.ipv4 == "10.0.0.25/24"
+    assert fork.ipv6 == "fd00::25/128"
+
+
+def test_parse_bcpr_spec() -> None:
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[device.max25e0]
+kiss_link = /var/run/max25-bcpr/kiss-bc0
+max25_bcpr_ini = /etc/max25/max25-bcpr.ini
+"""
+    )
+    dev = parse_device_spec("max25e0", "max25-bcpr:bc0", cp, {"hardware": "tncs"})
+    assert dev.backend_type == "max25-bcpr-kiss"
+    assert dev.max25_bcpr_device == "bc0"
+    assert dev.kiss_link == "/var/run/max25-bcpr/kiss-bc0"
+    assert dev.max25_bcpr_ini == "/etc/max25/max25-bcpr.ini"
+
+
+def test_feature_gate_bcpr() -> None:
+    mod = load_max25d()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[features]
+max25_bcpr = no
+[devices]
+default = max25e0
+max25e0 = max25-bcpr:bc0
+"""
+    )
+    cfg = mod.DaemonConfig()
+    cfg.feature_max25_bcpr = False
+    devices = mod.parse_devices(cp, cfg)
+    # parse_devices itself may include; load_config filters by features
+    assert any(d.device_id == "max25e0" for d in devices)
+    filtered = [d for d in devices if mod._device_allowed_by_features(d, cfg)]
+    assert filtered == []
+
+    cfg.feature_max25_bcpr = True
+    filtered = [d for d in devices if mod._device_allowed_by_features(d, cfg)]
+    assert len(filtered) == 1
+    assert filtered[0].backend_type == "max25-bcpr-kiss"
+
+
+def test_bcpr_kiss_pty_skips_tcdrain() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="max25e0",
+        backend_type="max25-bcpr-kiss",
+        kiss_link="/tmp/max25-bcpr/kiss-bc0",
+        bcpr_device="bc0",
+    )
+    backend = BcprKissBackend(cfg, on_rx=lambda _l: None)
+    backend._fd = 99
+    backend._kiss_active = True
+    written: list[bytes] = []
+    drained = {"n": 0}
+
+    def fake_drain(_fd: int) -> None:
+        drained["n"] += 1
+
+    with patch("os.write", side_effect=lambda _fd, data: written.append(data) or len(data)):
+        with patch("termios.tcdrain", side_effect=fake_drain):
+            ok, display = backend.transmit("CB-0", "QST", "hello", ax25_ui=True)
+    assert ok, display
+    assert written and written[0].startswith(b"\xc0")
+    assert drained["n"] == 0
+
+
+def test_bcpr_kiss_stabilize_reopens_on_inode_mismatch() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="max25e0",
+        backend_type="max25-bcpr-kiss",
+        kiss_link="/tmp/max25-bcpr/kiss-bc0",
+        bcpr_device="bc0",
+    )
+    backend = BcprKissBackend(cfg, on_rx=lambda _l: None)
+    backend._fd = 7
+    backend._kiss_active = True
+    backend.status = "ready"
+    backend._mycall = "CB-0"
+    calls: list[str] = []
+
+    class _St:
+        def __init__(self, ino: int) -> None:
+            self.st_ino = ino
+            self.st_dev = 1
+
+    with patch("os.path.exists", return_value=True):
+        with patch("os.stat", return_value=_St(200)):
+            with patch("os.fstat", return_value=_St(100)):
+                with patch.object(backend, "close", side_effect=lambda: calls.append("close")):
+                    with patch.object(backend, "open", side_effect=lambda: calls.append("open") or True):
+                        with patch.object(
+                            backend,
+                            "attach_session",
+                            side_effect=lambda c: calls.append(f"attach:{c}") or True,
+                        ):
+                            ok = backend.stabilize_session("CB-0", force=False)
+    assert ok
+    assert calls == ["close", "open", "attach:CB-0"]
+
+
+def main() -> int:
+    test_bcpr_kiss_default_link()
+    test_max25e0_default_addrs()
+    test_parse_bcpr_spec()
+    test_feature_gate_bcpr()
+    test_bcpr_kiss_pty_skips_tcdrain()
+    test_bcpr_kiss_stabilize_reopens_on_inode_mismatch()
+    print("OK: bcpr backend tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_crdop_backend.py b/stacks/daemon/test_crdop_backend.py
new file mode 100644
index 0000000..a83f54b
--- /dev/null
+++ b/stacks/daemon/test_crdop_backend.py
@@ -0,0 +1,130 @@
+#!/usr/bin/env python3
+"""Offline unit tests for CrdopTcpBackend (no crdopc process)."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+
+from device_backends import CrdopTcpBackend, DeviceBackendConfig  # noqa: E402
+
+
+class _MockSock:
+    """Minimal socket double for ctrl/data channels."""
+
+    def __init__(self, term: str = "\n") -> None:
+        self.sent: list[bytes] = []
+        self._closed = False
+        self._term = term
+
+    def settimeout(self, _t: float) -> None:
+        return None
+
+    def sendall(self, data: bytes) -> None:
+        self.sent.append(data)
+
+    def recv(self, _n: int) -> bytes:
+        if self._closed:
+            return b""
+        return f"OK{self._term}".encode("ascii")
+
+    def close(self) -> None:
+        self._closed = True
+
+
+def _mock_connections(ctrl: _MockSock, data: _MockSock):
+    def _create(addr, timeout=5.0):
+        _host, port = addr
+        return ctrl if port == 8515 else data
+
+    return _create
+
+
+def _open_ctx(ctrl: _MockSock, data: _MockSock):
+    mock_thread = MagicMock()
+    return (
+        patch("device_backends.socket.create_connection", side_effect=_mock_connections(ctrl, data)),
+        patch("device_backends.threading.Thread", return_value=mock_thread),
+    )
+
+
+def test_crdop_backend_open_and_attach() -> None:
+    ctrl = _MockSock()
+    data = _MockSock()
+    cfg = DeviceBackendConfig(
+        device_id="soft-crdop",
+        backend_type="crdop-tcp",
+        crdop_host="127.0.0.1",
+        crdop_port=8515,
+        crdop_listen=True,
+    )
+    backend = CrdopTcpBackend(cfg, on_rx=lambda _l: None)
+    p_sock, p_thread = _open_ctx(ctrl, data)
+    with p_sock, p_thread:
+        assert backend.open()
+        assert backend.attach_session("CB-0")
+    assert backend.status == "ready"
+    joined = b"".join(ctrl.sent).decode("ascii")
+    assert "INITIALIZE" in joined
+    assert "PROTOCOLMODE KISS" in joined
+    assert "LISTEN TRUE" in joined
+    backend.close()
+    assert backend.status == "closed"
+
+
+def test_crdop_backend_transmit() -> None:
+    ctrl = _MockSock()
+    data = _MockSock()
+    cfg = DeviceBackendConfig(
+        device_id="soft-crdop",
+        backend_type="crdop-tcp",
+        crdop_host="127.0.0.1",
+        crdop_port=8515,
+    )
+    backend = CrdopTcpBackend(cfg, on_rx=lambda _l: None)
+    p_sock, p_thread = _open_ctx(ctrl, data)
+    with p_sock, p_thread:
+        assert backend.open()
+        assert backend.attach_session("CB-0")
+        ok, display = backend.transmit("CB-0", "QST", "hello", ax25_ui=True)
+    assert ok, display
+    assert len(data.sent) == 1
+    assert "FECSEND" not in b"".join(ctrl.sent).decode("ascii")
+    assert "[CRDOP AX25 UI CB-0>QST]" in display
+    backend.close()
+    assert backend.status == "closed"
+
+
+def test_crdop_backend_connect_failure() -> None:
+    cfg = DeviceBackendConfig(
+        device_id="soft-crdop",
+        backend_type="crdop-tcp",
+        crdop_host="127.0.0.1",
+        crdop_port=59999,
+    )
+    backend = CrdopTcpBackend(cfg, on_rx=lambda _l: None)
+    with patch("device_backends.socket.create_connection", side_effect=OSError("refused")):
+        assert not backend.open()
+    assert backend.status == "error-connect"
+
+
+def test_crdop_registry_tested() -> None:
+    from device_backends import registry_tested  # noqa: E402
+
+    assert registry_tested("soft-crdop") is True
+
+
+def main() -> int:
+    test_crdop_backend_connect_failure()
+    test_crdop_backend_open_and_attach()
+    test_crdop_backend_transmit()
+    test_crdop_registry_tested()
+    print("OK: crdop backend tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_daemon_log.py b/stacks/daemon/test_daemon_log.py
new file mode 100644
index 0000000..d992d79
--- /dev/null
+++ b/stacks/daemon/test_daemon_log.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+"""Unit tests for max25d structured logging."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+
+from daemon_log import DaemonLogger, emit_startup_banner  # noqa: E402
+from device_backends import DeviceBackendConfig  # noqa: E402
+
+
+def test_structured_levels() -> None:
+    lines: list[str] = []
+    log = DaemonLogger(emit=lines.append)
+    log.ok("prep complete", area="serial", device="tnc2c")
+    log.recovery("JHOST 0 — banner", device="pktnc2")
+    log.warn("no password", area="security")
+    assert lines[0] == "max25d [OK] [serial] [tnc2c] prep complete"
+    assert lines[1] == "max25d [RECOVERY] [serial] [pktnc2] JHOST 0 — banner"
+    assert lines[2] == "max25d [WARN] [security] no password"
+
+
+def test_emit_unstructured_device_prefix() -> None:
+    lines: list[str] = []
+    log = DaemonLogger(emit=lines.append)
+    log.emit_unstructured("tnc2c: recovery: OK after JHOST 0")
+    assert "[tnc2c]" in lines[0]
+    assert "[RECOVERY]" in lines[0]
+    assert "OK after JHOST 0" in lines[0]
+
+
+def test_startup_banner_sections() -> None:
+    from dataclasses import dataclass
+
+    @dataclass
+    class Cfg:
+        mode: str = "standalone"
+        device: str = "tnc2c"
+        default_device: str = "tnc2c"
+        tcp_host: str = "0.0.0.0"
+        tcp_port: int = 7325
+        unix_socket: str = "/run/max25/modem.sock"
+        tcp_password: str = ""
+        callerid: str = "CB-0"
+        callid: str = "QST"
+        ax25_ui: bool = True
+        bans_file: str = ""
+        auto_start: bool = True
+        serial_enabled: bool = True
+        stack_recover_only: bool = True
+        serial_watch: bool = True
+        serial_watch_interval: int = 60
+        serial_watch_startup_grace: int = 45
+        serial_bootwait_escalate: bool = True
+        hardware: str = "tncs"
+
+    lines: list[str] = []
+    from daemon_log import LOGGER
+
+    orig = LOGGER._emit
+    try:
+        LOGGER._emit = lines.append
+        dev = DeviceBackendConfig(device_id="tnc2c", backend_type="kiss-serial")
+        dev.serial_device = "/dev/ttyS4"
+        dev.serial_baud = 19200
+        dev.serial_line = "8n1"
+        emit_startup_banner(
+            config_path="/etc/max25/max25d.ini",
+            cfg=Cfg(),
+            devices=[dev],
+            tested_fn=lambda _d: True,
+        )
+    finally:
+        LOGGER._emit = orig
+
+    text = "\n".join(lines)
+    assert "=== MAX25d starting ===" in text
+    assert "[config]" in text
+    assert "ini=/etc/max25/max25d.ini" in text
+    assert "[devices]" in text
+    assert "tnc2c=" in text
+
+
+def main() -> int:
+    test_structured_levels()
+    print("OK test_structured_levels")
+    test_emit_unstructured_device_prefix()
+    print("OK test_emit_unstructured_device_prefix")
+    test_startup_banner_sections()
+    print("OK test_startup_banner_sections")
+    print("All daemon_log tests passed")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_kiss_bridge.py b/stacks/daemon/test_kiss_bridge.py
new file mode 100644
index 0000000..066d1d0
--- /dev/null
+++ b/stacks/daemon/test_kiss_bridge.py
@@ -0,0 +1,161 @@
+#!/usr/bin/env python3
+"""Offline unit tests for kiss_bridge (no serial hardware)."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from ax25_codec import ax25_build_ui, ax25_crc, ax25_parse_ui, parse_callsign  # noqa: E402
+from kiss_bridge import (  # noqa: E402
+    KissDecoder,
+    format_rx_line,
+    kiss_data_frame,
+    kiss_encode,
+    serial_profile_for_device,
+)
+
+
+def test_callsign_parse() -> None:
+    assert parse_callsign("DG1ABC") == ("DG1ABC", 0)
+    assert parse_callsign("DK0WC-7") == ("DK0WC", 7)
+
+
+def test_ax25_roundtrip() -> None:
+    frame = ax25_build_ui("DG1ABC", "CQ", b"73")
+    parsed = ax25_parse_ui(frame)
+    assert parsed is not None
+    src, dst, payload = parsed
+    assert src == "DG1ABC"
+    assert dst == "CQ"
+    assert payload == b"73"
+
+
+def test_kiss_fcs_strip() -> None:
+    frame = ax25_build_ui("CB-0", "QST", b"hi")
+    pkt = kiss_data_frame(0, frame)
+    assert pkt.startswith(b"\xc0")
+    assert pkt.endswith(b"\xc0")
+    dec = KissDecoder()
+    frames = dec.feed(pkt)
+    assert len(frames) == 1
+    _port, payload = frames[0]
+    assert len(payload) == len(frame) - 2
+    parsed = ax25_parse_ui(payload)
+    assert parsed is not None
+    src, dst, info = parsed
+    assert src == "CB"
+    assert dst == "QST"
+    assert info == b"hi"
+
+
+def test_kiss_escape_roundtrip() -> None:
+    raw = bytes([0xC0, 0xDB, 0x00, 0xFF])
+    pkt = kiss_encode(0, 0x00, raw)
+    dec = KissDecoder()
+    frames = dec.feed(pkt)
+    assert frames[0][1] == raw
+
+
+def test_format_rx() -> None:
+    line = format_rx_line("DG1ABC", "QST", b"73", ax25_ui=True)
+    assert line == "[AX25 UI DG1ABC>QST] 73"
+
+
+def test_serial_profile_tnc2c() -> None:
+    root = str(Path(__file__).resolve().parents[2])
+    prof = serial_profile_for_device("tnc2c", root, {})
+    assert prof.baud == 19200
+    assert prof.dtr_rts is True
+    assert prof.kiss_entry == "kiss_on"
+
+
+def test_serial_profile_pktnc2() -> None:
+    root = str(Path(__file__).resolve().parents[2])
+    prof = serial_profile_for_device("pktnc2", root, {})
+    assert prof.baud == 9600
+    assert prof.dtr_rts is False
+    assert prof.kiss_entry == "auto"
+
+
+def test_serial_profile_pccom_kiss_env() -> None:
+    import os
+    import tempfile
+
+    tmp = Path(tempfile.mkdtemp())
+    env = tmp / "local" / "pccom-kiss-serial.env"
+    env.parent.mkdir(parents=True)
+    env.write_text(
+        "PCCOM_KISS_DEV=/dev/ttyUSB2\nPCCOM_KISS_BAUD=9600\nPCCOM_KISS_DTR_RTS=no\n",
+        encoding="utf-8",
+    )
+    old = os.environ.get("MAX25_ROOT")
+    os.environ["MAX25_ROOT"] = str(tmp)
+    try:
+        prof = serial_profile_for_device("pccom-kiss", str(tmp), {})
+        assert prof.device == "/dev/ttyUSB2"
+        assert prof.baud == 9600
+        assert prof.dtr_rts is False
+        assert prof.kiss_entry == "none"
+    finally:
+        if old is None:
+            os.environ.pop("MAX25_ROOT", None)
+        else:
+            os.environ["MAX25_ROOT"] = old
+
+
+def test_crc_known_vector() -> None:
+    body = bytes(range(256))
+    assert ax25_crc(body) == 0x303C
+
+
+def test_kiss_non_data_ignored() -> None:
+    pkt = kiss_encode(0, 0x06, b"ignored")  # TXDELAY cmd
+    dec = KissDecoder()
+    assert dec.feed(pkt) == []
+
+
+def test_invalid_callsign_tx() -> None:
+    from kiss_bridge import KissBridge, SerialProfile
+
+    bridge = KissBridge(SerialProfile(), on_rx=lambda _m: None)
+    bridge._kiss_active = True
+    bridge._fd = -1  # not used — validate before write
+    ok, msg = bridge.transmit("BAD!", "CQ", "hi", ax25_ui=True)
+    assert not ok
+    assert "invalid" in msg.lower()
+
+
+def test_rx_thread_not_started_on_open() -> None:
+    from kiss_bridge import KissBridge, SerialProfile
+
+    bridge = KissBridge(SerialProfile(), on_rx=lambda _m: None)
+    bridge._fd = 1
+    bridge.status = "open"
+    assert bridge._thread is None
+
+
+def main() -> int:
+    tests = [
+        test_callsign_parse,
+        test_ax25_roundtrip,
+        test_kiss_fcs_strip,
+        test_kiss_escape_roundtrip,
+        test_format_rx,
+        test_serial_profile_tnc2c,
+        test_serial_profile_pktnc2,
+        test_serial_profile_pccom_kiss_env,
+        test_crc_known_vector,
+        test_kiss_non_data_ignored,
+        test_invalid_callsign_tx,
+        test_rx_thread_not_started_on_open,
+    ]
+    for fn in tests:
+        fn()
+    print("OK: kiss_bridge unit tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_max25_platform.py b/stacks/daemon/test_max25_platform.py
new file mode 100644
index 0000000..5073e01
--- /dev/null
+++ b/stacks/daemon/test_max25_platform.py
@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+"""Platform helpers for max25d."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+from max25_platform import (  # noqa: E402
+    crdop_audio_backend,
+    default_bans_file,
+    default_unix_socket,
+    is_freebsd,
+    is_linux,
+    max25d_supported,
+    supported_device_ids,
+)
+
+
+def test_linux_defaults() -> None:
+  # Run on Linux CI — skip assertions on other hosts
+    if not is_linux():
+        return
+    assert max25d_supported()
+    assert "tnc2c" in supported_device_ids()
+    assert "baycom-kiss" in supported_device_ids()
+    assert "pccom-kiss" in supported_device_ids()
+    assert "max25e0" in supported_device_ids()
+    assert "max25e0" in supported_device_ids()
+    assert "max25e0:bc1" in supported_device_ids()
+    assert "baycom-ser12" not in supported_device_ids()
+    assert "baycom-a" not in supported_device_ids()
+    assert crdop_audio_backend() == "alsa"
+    assert default_unix_socket() == "/run/max25/modem.sock"
+    assert default_bans_file() == "/var/lib/max25/bans.txt"
+
+
+def test_freebsd_profile() -> None:
+    if not is_freebsd():
+        return
+    assert max25d_supported()
+    assert "soft-crdop" in supported_device_ids()
+    assert "tmodem" in supported_device_ids()
+    assert "max25e0" in supported_device_ids()
+    assert "tnc2c" not in supported_device_ids()
+    assert crdop_audio_backend() == "oss"
+    assert default_unix_socket() == "/var/run/max25/modem.sock"
+    assert default_bans_file() == "/var/db/max25/bans.txt"
+
+
+if __name__ == "__main__":
+    test_linux_defaults()
+    test_freebsd_profile()
+    print("test_max25_platform: ok")
diff --git a/stacks/daemon/test_modular_tcp.py b/stacks/daemon/test_modular_tcp.py
new file mode 100644
index 0000000..a0b8551
--- /dev/null
+++ b/stacks/daemon/test_modular_tcp.py
@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+"""Offline tests for modular_tcp_server."""
+from __future__ import annotations
+
+import configparser
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+from modular_tcp_server import load_modular_tcp  # noqa: E402
+
+
+def test_load_main_secondaries() -> None:
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[modular_tcp]
+enabled = yes
+role = main
+
+[modular_tcp.secondaries]
+a = 127.0.0.1:7326
+b = 127.0.0.1:7327
+"""
+    )
+    cfg = load_modular_tcp(cp)
+    assert cfg.enabled is True
+    assert cfg.role == "main"
+    assert len(cfg.secondaries) == 2
+    assert cfg.secondaries[0].port == 7326
+
+
+if __name__ == "__main__":
+    test_load_main_secondaries()
+    print("test_modular_tcp: ok")
diff --git a/stacks/daemon/test_multi_device.py b/stacks/daemon/test_multi_device.py
new file mode 100644
index 0000000..a46a449
--- /dev/null
+++ b/stacks/daemon/test_multi_device.py
@@ -0,0 +1,518 @@
+#!/usr/bin/env python3
+"""Multi-device config and M25/1 protocol tests for max25d (no serial hardware)."""
+from __future__ import annotations
+
+import configparser
+import importlib.util
+import socket
+import subprocess
+import sys
+import tempfile
+import time
+from pathlib import Path
+from typing import Callable
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[2]
+LAUNCHER = ROOT / "stacks/daemon/max25d"
+DAEMON = ROOT / "stacks/daemon/max25d.py"
+
+
+def load_max25d_module():
+    from importlib.machinery import SourceFileLoader
+
+    loader = SourceFileLoader("max25d", str(DAEMON))
+    spec = importlib.util.spec_from_loader("max25d", loader)
+    mod = importlib.util.module_from_spec(spec)
+    sys.modules["max25d"] = mod
+    loader.exec_module(mod)
+    return mod
+
+
+class LineReader:
+    def __init__(self, sock: socket.socket) -> None:
+        self.sock = sock
+        self.buf = b""
+
+    def read(self, timeout: float = 5.0) -> str:
+        self.sock.settimeout(timeout)
+        while b"\n" not in self.buf:
+            chunk = self.sock.recv(4096)
+            if not chunk:
+                raise RuntimeError("connection closed")
+            self.buf += chunk
+        line, self.buf = self.buf.split(b"\n", 1)
+        return line.decode("utf-8")
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+class FakeBackend:
+    backend_type = "mock"
+
+    def __init__(self, cfg, root, on_rx, log=None):
+        self.device_id = cfg.device_id
+        self._on_rx = on_rx
+        self.status = "ready"
+
+    def open(self):
+        return True
+
+    def attach_session(self, mycall):
+        return True
+
+    def transmit(self, src, dst, text, ax25_ui):
+        return True, f"[AX25 UI {src}>{dst}] {text}"
+
+    def close(self):
+        self.status = "closed"
+
+    def detach_session(self):
+        pass
+
+
+def test_parse_legacy_single_device() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[daemon]
+device = tnc2c
+hardware = tncs
+[serial]
+device = /dev/ttyS4
+baud = 19200
+"""
+    )
+    cfg = mod.DaemonConfig(device="tnc2c", hardware="tncs")
+    devices = mod.parse_devices(cp, cfg)
+    assert len(devices) == 1
+    assert devices[0].device_id == "tnc2c"
+    assert devices[0].serial_device == "/dev/ttyS4"
+    assert devices[0].serial_baud == 19200
+    assert devices[0].backend_type == "kiss-serial"
+
+
+def test_parse_multi_devices() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[devices]
+default = tnc2c
+tnc2c = /dev/ttyS4
+pktnc2 = /dev/ttyS5
+dev3 = /dev/ttyUSB0
+dev4 = /dev/ttyUSB1
+dev5 = /dev/ttyUSB2
+[serial.dev3]
+baud = 9600
+"""
+    )
+    cfg = mod.DaemonConfig()
+    devices = mod.parse_devices(cp, cfg)
+    assert len(devices) == 5
+    ids = {d.device_id for d in devices}
+    assert ids == {"tnc2c", "pktnc2", "dev3", "dev4", "dev5"}
+    by_id = {d.device_id: d for d in devices}
+    assert by_id["tnc2c"].serial_device == "/dev/ttyS4"
+    assert by_id["dev3"].serial_baud == 9600
+    assert cfg.default_device == "tnc2c"
+
+
+def test_parse_pccom_kiss_device() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[features]
+baycom = yes
+pccom = yes
+[devices]
+default = pccom-kiss
+pccom-kiss = /dev/ttyUSB0
+"""
+    )
+    cfg = mod.DaemonConfig()
+    cfg.feature_baycom = True
+    cfg.feature_pccom = True
+    devices = mod.parse_devices(cp, cfg)
+    by_id = {d.device_id: d for d in devices}
+    assert by_id["pccom-kiss"].backend_type == "kiss-raw-serial"
+    assert by_id["pccom-kiss"].serial_device == "/dev/ttyUSB0"
+
+
+def test_parse_heterogeneous_devices() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[devices]
+default = tnc2c
+tnc2c = /dev/ttyS4
+baycom-ser12 = baycom:a
+baycom-kiss = /dev/ttyUSB0
+soft-crdop = crdop:default
+[device.baycom-ser12]
+kiss_link = /var/run/baycom-pr/kiss
+modem = a
+baycom_ini = /etc/baycom/baycom-pr.ini
+[device.soft-crdop]
+port = 8515
+"""
+    )
+    cfg = mod.DaemonConfig()
+    devices = mod.parse_devices(cp, cfg)
+    by_id = {d.device_id: d for d in devices}
+    assert by_id["tnc2c"].backend_type == "kiss-serial"
+    assert by_id["baycom-ser12"].backend_type == "baycom-kiss"
+    assert by_id["baycom-ser12"].kiss_link == "/var/run/baycom-pr/kiss"
+    assert by_id["baycom-ser12"].baycom_ini == "/etc/baycom/baycom-pr.ini"
+    assert by_id["baycom-kiss"].backend_type == "kiss-raw-serial"
+    assert by_id["soft-crdop"].backend_type == "crdop-tcp"
+    assert by_id["soft-crdop"].crdop_port == 8515
+
+
+def test_parse_enabled_filter() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[devices]
+enabled = tnc2c,pktnc2
+tnc2c = /dev/ttyS4
+pktnc2 = /dev/ttyS5
+extra = /dev/ttyUSB9
+"""
+    )
+    cfg = mod.DaemonConfig()
+    devices = mod.parse_devices(cp, cfg)
+    enabled = {d.device_id for d in devices if d.enabled}
+    disabled = {d.device_id for d in devices if not d.enabled}
+    assert enabled == {"tnc2c", "pktnc2"}
+    assert disabled == {"extra"}
+
+
+def test_backend_open_retry_on_error() -> None:
+    """CONNECT retries KISS open after a transient error-no-device."""
+    mod = load_max25d_module()
+    cfg = mod.DaemonConfig(hardware="modems", serial_enabled=True)
+    cfg.devices = [
+        mod.DeviceBackendConfig(
+            device_id="baycom-ser12",
+            backend_type="baycom-kiss",
+            kiss_link="/nonexistent/kiss",
+            enabled=True,
+        )
+    ]
+    cfg.default_device = "baycom-ser12"
+    state = mod.DaemonState(cfg=cfg)
+    mod.init_device_runtimes(state)
+
+    class ErrorThenReady(FakeBackend):
+        attempts = 0
+
+        def open(self):
+            ErrorThenReady.attempts += 1
+            if ErrorThenReady.attempts == 1:
+                self.status = "error-no-device"
+                return False
+            self.status = "ready"
+            return True
+
+    ErrorThenReady.attempts = 0
+    with patch.object(
+        mod,
+        "create_backend",
+        side_effect=lambda c, r, rx, log, prefix=None, on_invalid=None: ErrorThenReady(c, r, rx, log),
+    ):
+        assert not mod.attach_backend_session(state, "baycom-ser12")
+        assert mod.attach_backend_session(state, "baycom-ser12")
+        assert ErrorThenReady.attempts == 2
+
+
+def test_five_mock_backends() -> None:
+    """Five concurrent backend instances via mocked create_backend."""
+    mod = load_max25d_module()
+    opened: list[str] = []
+
+    class CountingBackend(FakeBackend):
+        def open(self):
+            opened.append(self.device_id)
+            return True
+
+    cfg = mod.DaemonConfig(hardware="tncs", serial_enabled=True)
+    cfg.devices = [
+        mod.DeviceBackendConfig(device_id=f"d{i}", serial_device=f"/dev/fake{i - 1}", enabled=True)
+        for i in range(1, 6)
+    ]
+    for d in cfg.devices:
+        d.backend_type = "kiss-serial"
+    cfg.default_device = "d1"
+    state = mod.DaemonState(cfg=cfg)
+    mod.init_device_runtimes(state)
+
+    with patch.object(
+        mod,
+        "create_backend",
+        side_effect=lambda c, r, rx, log, prefix=None, on_invalid=None: CountingBackend(c, r, rx, log),
+    ):
+        assert mod.attach_all_sessions(state)
+        assert len(opened) == 5
+        assert set(opened) == {f"d{i}" for i in range(1, 6)}
+
+        state.selected_device = "d3"
+        dev_id = mod.resolve_selected_device(state)
+        assert dev_id == "d3"
+        rt = state.devices["d3"]
+        ok, display = rt.backend.transmit("CB-0", "QST", "hi", True)
+        assert ok
+        assert "hi" in display
+
+
+def run_daemon_test(ini_text: str, fn: Callable[[LineReader, socket.socket], None]) -> None:
+    port = free_port()
+    with tempfile.NamedTemporaryFile("w", suffix=".ini", delete=False) as tmp:
+        tmp.write(ini_text)
+        ini_path = Path(tmp.name)
+
+    proc = subprocess.Popen(
+        [
+            str(LAUNCHER),
+            "--no-stack",
+            "--no-serial",
+            "-c",
+            str(ini_path),
+            "--tcp-port",
+            str(port),
+        ],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+    time.sleep(0.6)
+    try:
+        sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+    except OSError as exc:
+        proc.terminate()
+        proc.wait(timeout=3)
+        ini_path.unlink(missing_ok=True)
+        raise RuntimeError(f"connect failed: {exc}") from exc
+
+    reader = LineReader(sock)
+    try:
+        assert reader.read() == "OK"
+        fn(reader, sock)
+    finally:
+        sock.close()
+        proc.terminate()
+        proc.wait(timeout=5)
+        ini_path.unlink(missing_ok=True)
+
+
+def test_parse_dual_baycom_devices() -> None:
+    mod = load_max25d_module()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[devices]
+default = baycom-a
+baycom-a = baycom:a
+baycom-b = baycom:b
+[device.baycom-a]
+kiss_link = /var/run/baycom-pr/kiss-a
+modem = a
+baycom_ini = /etc/baycom/baycom-pr.ini
+[device.baycom-b]
+kiss_link = /var/run/baycom-pr/kiss-b
+modem = b
+baycom_ini = /etc/baycom/baycom-pr.ini
+"""
+    )
+    cfg = mod.DaemonConfig()
+    devices = mod.parse_devices(cp, cfg)
+    by_id = {d.device_id: d for d in devices}
+    assert set(by_id) == {"baycom-a", "baycom-b"}
+    assert by_id["baycom-a"].backend_type == "baycom-kiss"
+    assert by_id["baycom-b"].backend_type == "baycom-kiss"
+    assert by_id["baycom-a"].baycom_modem == "a"
+    assert by_id["baycom-b"].baycom_modem == "b"
+    assert by_id["baycom-a"].kiss_link == "/var/run/baycom-pr/kiss-a"
+    assert by_id["baycom-b"].kiss_link == "/var/run/baycom-pr/kiss-b"
+    assert cfg.default_device == "baycom-a"
+
+
+def test_protocol_dual_baycom() -> None:
+    # Legacy ids baycom-a/baycom-b are not on the Linux allowlist (product path: max25e0).
+    # Protocol dual-device coverage uses allowlisted modem-class ids instead.
+    ini = """
+[features]
+baycom = yes
+pccom = yes
+[daemon]
+mode = service
+hardware = modems
+device = baycom-kiss
+[devices]
+default = baycom-kiss
+baycom-kiss = /dev/null
+pccom-kiss = /dev/null
+[network]
+tcp_host = 127.0.0.1
+tcp_port = 7325
+[modem]
+callerid = N0CALL-0
+callid = QST
+[stack]
+auto_start = no
+"""
+
+    def exercise(reader: LineReader, sock: socket.socket) -> None:
+        status = reader.read()
+        assert "devices=baycom-kiss,pccom-kiss" in status
+        assert "device=baycom-kiss" in status
+
+        sock.sendall(b"GET DEVICES\n")
+        lines = []
+        while True:
+            line = reader.read()
+            lines.append(line)
+            if line == "OK":
+                break
+        device_lines = [l for l in lines if l.startswith("DEVICE ")]
+        assert len(device_lines) == 2
+        assert any("id=baycom-kiss" in l for l in device_lines)
+        assert any("id=pccom-kiss" in l for l in device_lines)
+
+        sock.sendall(b"SET DEVICE pccom-kiss\n")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"GET STATUS\n")
+        st = reader.read()
+        assert "device=pccom-kiss" in st
+        assert reader.read() == "OK"
+
+    run_daemon_test(ini, exercise)
+
+
+def test_protocol_multi_device() -> None:
+    # Explicit two-device INI — share/max25d.ini.example is single-device by design.
+    ini = """
+[daemon]
+mode = standalone
+hardware = tncs
+device = tnc2c
+[devices]
+default = tnc2c
+tnc2c = /dev/ttyS4
+pktnc2 = /dev/ttyS5
+[network]
+tcp_host = 127.0.0.1
+tcp_port = 7325
+[modem]
+callerid = CB-0
+callid = QST
+[stack]
+auto_start = no
+"""
+
+    def exercise(reader: LineReader, sock: socket.socket) -> None:
+        status = reader.read()
+        assert status.startswith("STATUS ")
+        assert "devices=tnc2c,pktnc2" in status
+        assert "device=tnc2c" in status
+
+        sock.sendall(b"GET DEVICES\n")
+        lines = []
+        while True:
+            line = reader.read()
+            lines.append(line)
+            if line == "OK":
+                break
+        device_lines = [l for l in lines if l.startswith("DEVICE ")]
+        assert len(device_lines) == 2
+        assert any("id=tnc2c" in l for l in device_lines)
+        assert any("id=pktnc2" in l for l in device_lines)
+        assert any("backend=kiss-serial" in l for l in device_lines)
+
+        sock.sendall(b"SET DEVICE pktnc2\n")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"GET STATUS\n")
+        st = reader.read()
+        assert "device=pktnc2" in st
+        assert reader.read() == "OK"
+
+        sock.sendall(b"SELECT DEVICE tnc2c\n")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"CONNECT\n")
+        assert reader.read() == "EVENT connected"
+        assert reader.read() == "OK"
+
+        sock.sendall(b"SEND 73\n")
+        rx = reader.read()
+        assert rx.startswith("RX ")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"DISCONNECT\n")
+        assert reader.read() == "EVENT disconnected"
+        assert reader.read() == "OK"
+
+    run_daemon_test(ini, exercise)
+
+
+def test_protocol_legacy_single() -> None:
+    ini = """
+[daemon]
+mode = standalone
+hardware = tncs
+device = tnc2c
+[network]
+tcp_host = 127.0.0.1
+tcp_port = 7325
+[modem]
+callerid = CB-0
+callid = QST
+[stack]
+auto_start = no
+"""
+
+    def exercise(reader: LineReader, sock: socket.socket) -> None:
+        status = reader.read()
+        assert "device=tnc2c" in status
+        assert "devices=tnc2c" in status
+
+        sock.sendall(b"SET DEVICE tnc2c\n")
+        assert reader.read() == "OK"
+
+    run_daemon_test(ini, exercise)
+
+
+def main() -> int:
+    tests = [
+        test_parse_legacy_single_device,
+        test_parse_multi_devices,
+        test_parse_heterogeneous_devices,
+        test_parse_dual_baycom_devices,
+        test_parse_enabled_filter,
+        test_backend_open_retry_on_error,
+        test_five_mock_backends,
+        test_protocol_multi_device,
+        test_protocol_dual_baycom,
+        test_protocol_legacy_single,
+    ]
+    for fn in tests:
+        fn()
+    print("OK: multi-device tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_path_normalize.py b/stacks/daemon/test_path_normalize.py
new file mode 100644
index 0000000..c7b24e6
--- /dev/null
+++ b/stacks/daemon/test_path_normalize.py
@@ -0,0 +1,17 @@
+"""Tests for legacy bcpr path normalization."""
+
+from paths import MAX25_BCPR_KISS_DEFAULT, normalize_max25_bcpr_path
+
+
+def test_normalize_legacy_tmp_bcpr():
+    assert normalize_max25_bcpr_path("/tmp/bcpr/kiss-bc0") == "/tmp/max25-bcpr/kiss-bc0"
+    assert normalize_max25_bcpr_path("/tmp/bcpr") == "/tmp/max25-bcpr"
+    assert normalize_max25_bcpr_path("") == ""
+
+
+def test_canonical_unchanged():
+    assert (
+        normalize_max25_bcpr_path("/tmp/max25-bcpr/kiss-bc0")
+        == "/tmp/max25-bcpr/kiss-bc0"
+    )
+    assert MAX25_BCPR_KISS_DEFAULT == "/tmp/max25-bcpr/kiss-bc0"
diff --git a/stacks/daemon/test_paths.py b/stacks/daemon/test_paths.py
new file mode 100644
index 0000000..12b4be2
--- /dev/null
+++ b/stacks/daemon/test_paths.py
@@ -0,0 +1,145 @@
+#!/usr/bin/env python3
+"""Offline tests for install/dev path resolution."""
+from __future__ import annotations
+
+import os
+import sys
+import tempfile
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from paths import (  # noqa: E402
+    baycom_ini_candidates,
+    canonical_dual_baycom_example,
+    canonical_single_baycom_example,
+    ctl_path,
+    default_ini_candidates,
+    is_dual_baycom_ini,
+    resolve_baycom_ini,
+    resolve_baycom_profile,
+    resolve_layout,
+    serial_env_candidates,
+    share_max25_dir,
+    stacks_dir,
+)
+
+REPO = Path(__file__).resolve().parents[2]
+
+
+def test_dev_layout() -> None:
+    exe = REPO / "stacks/daemon/max25d"
+    tree, prefix = resolve_layout(exe)
+    assert prefix is None
+    assert tree == REPO
+    assert (stacks_dir(tree, prefix) / "tncs").is_dir()
+    assert ctl_path(tree, prefix, exe) == REPO / "scripts/max25-ctl"
+
+
+def test_installed_layout() -> None:
+    with tempfile.TemporaryDirectory() as tmp:
+        prefix = Path(tmp) / "usr/local"
+        bindir = prefix / "bin"
+        share = prefix / "share/max25"
+        bindir.mkdir(parents=True)
+        share.mkdir(parents=True)
+        (share / "max25d.ini.example").write_text("; test\n", encoding="utf-8")
+        (bindir / "max25d").write_text("#!/bin/sh\n", encoding="utf-8")
+        (bindir / "max25-ctl").write_text("#!/bin/sh\n", encoding="utf-8")
+
+        tree, detected = resolve_layout(bindir / "max25d")
+        assert detected == prefix
+        assert tree == prefix
+
+        cands = default_ini_candidates(tree, detected)
+        assert share / "max25d.ini.example" in cands
+        assert ctl_path(tree, detected, bindir / "max25d") == bindir / "max25-ctl"
+
+
+def test_max25_root_override() -> None:
+    with tempfile.TemporaryDirectory() as tmp:
+        prefix = Path(tmp) / "opt/max25"
+        bindir = prefix / "bin"
+        share = prefix / "share/max25"
+        bindir.mkdir(parents=True)
+        share.mkdir(parents=True)
+        (bindir / "max25d").write_text("#!/bin/sh\n", encoding="utf-8")
+
+        checkout = Path(tmp) / "checkout"
+        (checkout / "stacks/tncs").mkdir(parents=True)
+        (checkout / "plugins").mkdir()
+        (checkout / "plugins/manifest.yaml").write_text("plugins: []\n", encoding="utf-8")
+
+        old = os.environ.get("MAX25_ROOT")
+        os.environ["MAX25_ROOT"] = str(checkout)
+        try:
+            tree, detected = resolve_layout(bindir / "max25d")
+            assert detected == prefix
+            assert tree == checkout
+            assert stacks_dir(tree, detected) == checkout / "stacks"
+        finally:
+            if old is None:
+                os.environ.pop("MAX25_ROOT", None)
+            else:
+                os.environ["MAX25_ROOT"] = old
+
+
+def test_serial_env_order() -> None:
+    with tempfile.TemporaryDirectory() as tmp:
+        prefix = Path(tmp) / "usr/local"
+        etc = Path(tmp) / "etc/max25"
+        etc.mkdir(parents=True)
+        (etc / "tnc2c-serial.env").write_text("TNC2C_BAUD=38400\n", encoding="utf-8")
+        share = prefix / "share/max25/serial"
+        share.mkdir(parents=True)
+        (share / "tnc2c-serial.env").write_text("TNC2C_BAUD=19200\n", encoding="utf-8")
+
+        # /etc/max25 is checked first when present on disk
+        cands = serial_env_candidates("tnc2c", REPO, prefix)
+        assert cands[0] == Path("/etc/max25/tnc2c-serial.env")
+        assert prefix / "share/max25/serial/tnc2c-serial.env" in cands
+
+
+def test_baycom_ini_resolution_legacy_removed() -> None:
+    """Kernel baycom-pr examples removed 2026-07-18 — no in-tree templates."""
+    example = REPO / "share/baycom/baycom-pr.pccom-ttyS0-only.ini.example"
+    dual = REPO / "stacks/baycom-pr/config/examples/baycom-pr.dual.ini"
+    assert not example.is_file()
+    assert not dual.is_file()
+    assert canonical_single_baycom_example("baycom-ser12", REPO, None) is None
+    assert canonical_dual_baycom_example("baycom-ser12", REPO, None) is None
+    with tempfile.NamedTemporaryFile("w", suffix=".ini", delete=False) as tmp:
+        tmp.write("[stack]\n")
+        explicit = Path(tmp.name)
+    try:
+        assert resolve_baycom_ini("baycom-ser12", REPO, None, str(explicit)) == explicit
+        # Without explicit: may still resolve site /etc/baycom/baycom-pr.ini if present
+        resolved = resolve_baycom_ini("baycom-ser12", REPO, None)
+        if resolved is not None:
+            assert resolved.is_file()
+            assert "baycom-pr" in resolved.name or resolved.parent.name == "baycom"
+    finally:
+        explicit.unlink(missing_ok=True)
+
+
+def test_baycom_profile_dual_legacy_removed() -> None:
+    assert resolve_baycom_profile("dual", "baycom-ser12", REPO, None) is None
+
+
+def main() -> int:
+    tests = [
+        test_dev_layout,
+        test_installed_layout,
+        test_max25_root_override,
+        test_serial_env_order,
+        test_baycom_ini_resolution_legacy_removed,
+        test_baycom_profile_dual_legacy_removed,
+    ]
+    for fn in tests:
+        fn()
+    print("OK: paths unit tests")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_privilege_drop.py b/stacks/daemon/test_privilege_drop.py
new file mode 100644
index 0000000..3a611c9
--- /dev/null
+++ b/stacks/daemon/test_privilege_drop.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+"""Tests for max25d privilege_drop (no root required)."""
+from __future__ import annotations
+
+import configparser
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent
+sys.path.insert(0, str(ROOT))
+
+from privilege_drop import RunAsConfig, parse_run_as, resolve_run_as, run_as_configured  # noqa: E402
+
+
+def test_parse_run_as_empty() -> None:
+    cp = configparser.ConfigParser()
+    cp.read_string("[daemon]\nmode = standalone\n")
+    cfg = parse_run_as(cp)
+    assert cfg.user == ""
+    assert not run_as_configured(cfg)
+
+
+def test_parse_run_as_user_group() -> None:
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        "[daemon]\nuser = max25\ngroup = dialout\nuid = 1001\n"
+    )
+    cfg = parse_run_as(cp)
+    assert cfg.user == "max25"
+    assert cfg.group == "dialout"
+    assert cfg.uid == 1001
+    assert run_as_configured(cfg)
+
+
+def test_resolve_run_as_current_user() -> None:
+    import os
+    import pwd
+
+    pw = pwd.getpwuid(os.getuid())
+    uid, gid, name = resolve_run_as(RunAsConfig(user=pw.pw_name))
+    assert uid == pw.pw_uid
+    assert gid == pw.pw_gid
+    assert name == pw.pw_name
+
+
+def main() -> int:
+    test_parse_run_as_empty()
+    test_parse_run_as_user_group()
+    test_resolve_run_as_current_user()
+    print("privilege_drop: OK")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/stacks/daemon/test_proto.py b/stacks/daemon/test_proto.py
new file mode 100644
index 0000000..50ced93
--- /dev/null
+++ b/stacks/daemon/test_proto.py
@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Offline smoke test for max25d M25/1 protocol."""
+import socket
+import subprocess
+import sys
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+DAEMON = ROOT / "stacks/daemon/max25d"
+INI = ROOT / "share/max25/max25d.ini.example"
+
+
+class LineReader:
+    def __init__(self, sock: socket.socket) -> None:
+        self.sock = sock
+        self.buf = b""
+
+    def read(self, timeout: float = 5.0) -> str:
+        self.sock.settimeout(timeout)
+        while b"\n" not in self.buf:
+            chunk = self.sock.recv(4096)
+            if not chunk:
+                raise RuntimeError("connection closed")
+            self.buf += chunk
+        line, self.buf = self.buf.split(b"\n", 1)
+        return line.decode("utf-8")
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def wait_for_port(port: int, proc: subprocess.Popen[str], timeout: float = 8.0) -> bool:
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+        if proc.poll() is not None:
+            return False
+        try:
+            probe = socket.create_connection(("127.0.0.1", port), timeout=0.25)
+            probe.close()
+            return True
+        except OSError:
+            time.sleep(0.1)
+    return False
+
+
+def main() -> int:
+    port = free_port()
+    proc = subprocess.Popen(
+        [str(DAEMON), "--no-stack", "--no-serial", "-c", str(INI), "--tcp-port", str(port)],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+    if not wait_for_port(port, proc):
+        err = proc.stderr.read() if proc.stderr else ""
+        proc.terminate()
+        proc.wait(timeout=3)
+        print(f"FAIL: max25d not listening on {port}: {err.strip()}", file=sys.stderr)
+        return 1
+    try:
+        sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+    except OSError as exc:
+        proc.terminate()
+        proc.wait(timeout=3)
+        print(f"FAIL: connect: {exc}", file=sys.stderr)
+        return 1
+
+    reader = LineReader(sock)
+    try:
+        assert reader.read() == "OK"
+        status = reader.read()
+        assert status.startswith("STATUS ")
+
+        sock.sendall(b"SET CALLERID DG1ABC\n")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"CONNECT\n")
+        assert reader.read() == "EVENT connected"
+        assert reader.read() == "OK"
+
+        sock.sendall(b"SEND 73\n")
+        rx = reader.read()
+        assert rx.startswith("RX ")
+        assert reader.read() == "OK"
+
+        sock.sendall(b"GET STATUS\n")
+        st = reader.read()
+        assert "callerid=DG1ABC" in st
+        assert reader.read() == "OK"
+
+        print("OK: max25d protocol smoke")
+        return 0
+    finally:
+        sock.close()
+        proc.terminate()
+        proc.wait(timeout=5)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_reporting.py b/stacks/daemon/test_reporting.py
new file mode 100644
index 0000000..54f73df
--- /dev/null
+++ b/stacks/daemon/test_reporting.py
@@ -0,0 +1,163 @@
+#!/usr/bin/env python3
+"""INI reporting switches — error= / voice= in STATUS."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from device_backends import DeviceBackendConfig  # noqa: E402
+import max25d  # noqa: E402
+from reporting_quality import DataQualityTracker, RxOutcome  # noqa: E402
+
+T0 = 2_000_000.0
+WIN = 20
+
+
+def _close_pass(rt: max25d.DeviceRuntime, index: int, start: float = T0) -> None:
+    rt.quality.tick(start + (index + 1) * WIN + 1)
+
+
+def _fill_good(rt: max25d.DeviceRuntime, count: int = 3, window: int = WIN) -> None:
+    for i in range(count):
+        rt.quality.record(RxOutcome.GOOD, T0 + i * window + 1)
+        rt.quality.tick(T0 + (i + 1) * window + 1)
+
+
+def _state(
+    *,
+    error_on: bool = True,
+    voice_on: bool = True,
+    link: str = "ready",
+    passes: int = 3,
+    quality_min: int = 50,
+    pass_seconds: int = 20,
+    backend_type: str = "kiss-serial",
+    hardware: str = "tncs",
+    prefill_good: bool = True,
+) -> max25d.DaemonState:
+    cfg = max25d.DaemonConfig(
+        report_error_transmissions=error_on,
+        report_voice_transmissions=voice_on,
+        report_data_passes=passes,
+        report_data_quality_min=quality_min,
+        report_data_pass_seconds=pass_seconds,
+    )
+    dev = DeviceBackendConfig(
+        device_id="tnc2c",
+        enabled=True,
+        backend_type=backend_type,
+        hardware=hardware,
+    )
+    rt = max25d.DeviceRuntime(
+        cfg=dev,
+        link_status=link,
+        quality=DataQualityTracker(
+            passes_required=passes,
+            min_good_percent=quality_min,
+            pass_window_sec=pass_seconds,
+        ),
+    )
+    if prefill_good:
+        _fill_good(rt, passes, pass_seconds)
+    state = max25d.DaemonState(cfg=cfg)
+    state.devices["tnc2c"] = rt
+    state.selected_device = "tnc2c"
+    return state
+
+
+def test_error_valid_when_enabled_and_ready() -> None:
+    line = max25d.status_line(_state())
+    assert "error=valid" in line
+
+
+def test_error_invalid_when_disabled() -> None:
+    line = max25d.status_line(_state(error_on=False))
+    assert "error=invalid" in line
+
+
+def test_error_invalid_on_link_fault() -> None:
+    line = max25d.status_line(_state(link="error-io"))
+    assert "error=invalid" in line
+
+
+def test_error_invalid_before_passes_complete() -> None:
+    line = max25d.status_line(_state(prefill_good=False))
+    assert "error=invalid" in line
+
+
+def test_error_invalid_on_bad_frame_ratio() -> None:
+    state = _state(prefill_good=False)
+    rt = state.devices["tnc2c"]
+    rt.quality.record(RxOutcome.BAD, T0 + 1)
+    _close_pass(rt, 0)
+    rt.quality.record(RxOutcome.BAD, T0 + 21)
+    _close_pass(rt, 1)
+    rt.quality.record(RxOutcome.GOOD, T0 + 41)
+    _close_pass(rt, 2)
+    line = max25d.status_line(state)
+    assert "error=invalid" in line
+
+
+def test_voice_valid_tnc_only() -> None:
+    line = max25d.status_line(_state())
+    assert "voice=valid" in line
+
+
+def test_voice_invalid_when_disabled() -> None:
+    line = max25d.status_line(_state(voice_on=False))
+    assert "voice=invalid" in line
+
+
+def test_voice_invalid_crdop_not_ready() -> None:
+    line = max25d.status_line(
+        _state(
+            backend_type="crdop-tcp",
+            hardware="soft-modems",
+            link="error-connect",
+        )
+    )
+    assert "voice=invalid" in line
+
+
+def test_device_line_includes_reporting() -> None:
+    state = _state()
+    dev = max25d.device_line(state, "tnc2c")
+    assert "error=valid" in dev
+    assert "voice=n/a" in dev
+
+
+def test_on_backend_rx_tracks_callid_in_pass_window() -> None:
+    state = _state(prefill_good=False)
+    max25d.on_backend_rx(state, "tnc2c", "[AX25 UI DG1ABC>QST] 73")
+    max25d.on_backend_rx(state, "tnc2c", "[AX25 UI DG1ABC>CB-0] bad")
+    max25d.on_backend_rx(state, "tnc2c", "[CRDOP RX soft-crdop] noise")
+    rt = state.devices["tnc2c"]
+    start = rt.quality.current.started_at
+    assert rt.quality.current.good == 1
+    assert rt.quality.current.bad == 1
+    rt.quality.tick(start + WIN + 1)
+    assert list(rt.quality.passes) == ["bad"]
+    max25d.on_backend_rx(state, "tnc2c", "[AX25 UI DG1ABC>QST] ok")
+    start = rt.quality.current.started_at
+    rt.quality.tick(start + WIN + 1)
+    max25d.on_backend_rx(state, "tnc2c", "[AX25 UI DG1ABC>QST] ok2")
+    start = rt.quality.current.started_at
+    rt.quality.tick(start + WIN + 1)
+    line = max25d.status_line(state)
+    assert "error=valid" in line
+
+
+if __name__ == "__main__":
+    test_error_valid_when_enabled_and_ready()
+    test_error_invalid_when_disabled()
+    test_error_invalid_on_link_fault()
+    test_error_invalid_before_passes_complete()
+    test_error_invalid_on_bad_frame_ratio()
+    test_voice_valid_tnc_only()
+    test_voice_invalid_when_disabled()
+    test_voice_invalid_crdop_not_ready()
+    test_device_line_includes_reporting()
+    test_on_backend_rx_tracks_callid_in_pass_window()
+    print("test_reporting: ok")
diff --git a/stacks/daemon/test_reporting_quality.py b/stacks/daemon/test_reporting_quality.py
new file mode 100644
index 0000000..15f0d4d
--- /dev/null
+++ b/stacks/daemon/test_reporting_quality.py
@@ -0,0 +1,123 @@
+#!/usr/bin/env python3
+"""Data-quality window — CALLID match, timed passes, configurable min % good."""
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from reporting_quality import (  # noqa: E402
+    DataQualityTracker,
+    RxOutcome,
+    classify_rx_line,
+)
+
+T0 = 1_000_000.0
+WIN = 20
+
+
+def test_classify_good_callid() -> None:
+    assert classify_rx_line("[AX25 UI DG1ABC>QST] 73", "QST") == RxOutcome.GOOD
+
+
+def test_classify_bad_callid() -> None:
+    assert classify_rx_line("[AX25 UI DG1ABC>CB-0] 73", "QST") == RxOutcome.BAD
+
+
+def test_classify_incomplete_ax25() -> None:
+    assert classify_rx_line("[AX25 UI DG1ABC>QST", "QST") == RxOutcome.BAD
+
+
+def test_classify_voice_noise_ignored() -> None:
+    assert classify_rx_line("[CRDOP RX soft-crdop] hiss", "QST") == RxOutcome.IGNORE
+
+
+def test_classify_crdop_ax25_good() -> None:
+    line = "[CRDOP AX25 UI CB-0>QST] ping"
+    assert classify_rx_line(line, "QST") == RxOutcome.GOOD
+
+
+def _close_pass(q: DataQualityTracker, index: int, start: float = T0) -> None:
+    q.tick(start + (index + 1) * WIN + 1)
+
+
+def test_pass_window_max_twenty_seconds() -> None:
+    q = DataQualityTracker(passes_required=3, min_good_percent=50, pass_window_sec=20)
+    q.record(RxOutcome.GOOD, T0 + 1)
+    q.tick(T0 + 19)
+    assert len(q.passes) == 0
+    _close_pass(q, 0)
+    assert list(q.passes) == ["good"]
+
+
+def test_three_passes_fifty_percent() -> None:
+    q = DataQualityTracker(passes_required=3, min_good_percent=50, pass_window_sec=20)
+    q.record(RxOutcome.GOOD, T0 + 1)
+    _close_pass(q, 0)
+    q.record(RxOutcome.BAD, T0 + 20 + 1)
+    _close_pass(q, 1)
+    assert q.data_error_valid(reporting_enabled=True) is False
+    q.record(RxOutcome.GOOD, T0 + 40 + 1)
+    _close_pass(q, 2)
+    assert q.data_error_valid(reporting_enabled=True) is True
+
+
+def test_three_passes_below_fifty_percent() -> None:
+    q = DataQualityTracker(passes_required=3, min_good_percent=50, pass_window_sec=20)
+    q.record(RxOutcome.BAD, T0 + 1)
+    _close_pass(q, 0)
+    q.record(RxOutcome.BAD, T0 + 21)
+    _close_pass(q, 1)
+    q.record(RxOutcome.GOOD, T0 + 41)
+    _close_pass(q, 2)
+    assert q.data_error_valid(reporting_enabled=True) is False
+
+
+def test_ignore_does_not_consume_pass() -> None:
+    q = DataQualityTracker(passes_required=3, min_good_percent=50, pass_window_sec=20)
+    q.record(RxOutcome.IGNORE, T0 + 1)
+    _close_pass(q, 0)
+    assert len(q.passes) == 0
+    q.record(RxOutcome.GOOD, T0 + 21)
+    _close_pass(q, 1)
+    q.record(RxOutcome.GOOD, T0 + 41)
+    _close_pass(q, 2)
+    q.record(RxOutcome.GOOD, T0 + 61)
+    _close_pass(q, 3)
+    assert q.data_error_valid(reporting_enabled=True) is True
+    assert q.voice_activity is True
+
+
+def test_silent_window_counts_as_bad() -> None:
+    q = DataQualityTracker(passes_required=1, min_good_percent=50, pass_window_sec=20)
+    q.current.started_at = T0
+    _close_pass(q, 0)
+    assert list(q.passes) == ["bad"]
+
+
+def test_max_cycle_seconds() -> None:
+    q = DataQualityTracker(passes_required=3, pass_window_sec=20)
+    assert q.max_cycle_seconds() == 60
+
+
+def test_voice_valid_on_activity() -> None:
+    q = DataQualityTracker()
+    q.record(RxOutcome.IGNORE, T0 + 1)
+    assert q.voice_signal_valid(reporting_enabled=True, link_healthy=True) is True
+
+
+if __name__ == "__main__":
+    test_classify_good_callid()
+    test_classify_bad_callid()
+    test_classify_incomplete_ax25()
+    test_classify_voice_noise_ignored()
+    test_classify_crdop_ax25_good()
+    test_pass_window_max_twenty_seconds()
+    test_three_passes_fifty_percent()
+    test_three_passes_below_fifty_percent()
+    test_ignore_does_not_consume_pass()
+    test_silent_window_counts_as_bad()
+    test_max_cycle_seconds()
+    test_voice_valid_on_activity()
+    print("test_reporting_quality: ok")
diff --git a/stacks/daemon/test_serial_watch.py b/stacks/daemon/test_serial_watch.py
new file mode 100644
index 0000000..7b4d8ad
--- /dev/null
+++ b/stacks/daemon/test_serial_watch.py
@@ -0,0 +1,241 @@
+#!/usr/bin/env python3
+"""Offline tests for max25d TNC serial watch / stabilize."""
+from __future__ import annotations
+
+import configparser
+import importlib.util
+import sys
+import tempfile
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+ROOT = Path(__file__).resolve().parents[2]
+DAEMON = ROOT / "stacks/daemon/max25d.py"
+
+
+def load_max25d():
+    from importlib.machinery import SourceFileLoader
+
+    loader = SourceFileLoader("max25d", str(DAEMON))
+    spec = importlib.util.spec_from_loader("max25d", loader)
+    assert spec and spec.loader
+    mod = importlib.util.module_from_spec(spec)
+    sys.modules["max25d"] = mod
+    loader.exec_module(mod)
+    return mod
+
+
+def test_stack_serial_watch_config() -> None:
+    mod = load_max25d()
+    cp = configparser.ConfigParser()
+    cp.read_string(
+        """
+[stack]
+auto_start = yes
+serial_watch = no
+serial_watch_interval = 45
+serial_repair_cooldown = 10
+stack_recover_only = no
+stack_retry_interval = 90
+"""
+    )
+    cfg = mod.DaemonConfig()
+    cfg.auto_start = mod._truthy(cp.get("stack", "auto_start"))
+    cfg.serial_watch = mod._truthy(cp.get("stack", "serial_watch"))
+    cfg.serial_watch_interval = cp.getint("stack", "serial_watch_interval")
+    cfg.serial_repair_cooldown = cp.getint("stack", "serial_repair_cooldown")
+    cfg.stack_recover_only = mod._truthy(cp.get("stack", "stack_recover_only"))
+    cfg.stack_retry_interval = cp.getint("stack", "stack_retry_interval")
+    assert cfg.serial_watch is False
+    assert cfg.serial_watch_interval == 45
+    assert cfg.stack_recover_only is False
+
+
+def test_serial_repair_statuses() -> None:
+    mod = load_max25d()
+    assert "error-io" in mod.BACKEND_RETRY_STATUSES
+    assert "error-host" in mod.SERIAL_REPAIR_STATUSES
+    assert "open" not in mod.SERIAL_REPAIR_STATUSES
+
+
+def test_inline_tnc_prep() -> None:
+    mod = load_max25d()
+    cfg = mod.DaemonConfig(stack_recover_only=True)
+    state = mod.DaemonState(cfg=cfg)
+    from device_backends import DeviceBackendConfig  # noqa: E402
+
+    state.devices["tnc2c"] = mod.DeviceRuntime(
+        cfg=DeviceBackendConfig(device_id="tnc2c", backend_type="kiss-serial")
+    )
+    state.devices["baycom-ser12"] = mod.DeviceRuntime(
+        cfg=DeviceBackendConfig(device_id="baycom-ser12", backend_type="baycom-kiss")
+    )
+    assert mod.uses_inline_tnc_prep(state, "tnc2c")
+    assert not mod.uses_inline_tnc_prep(state, "baycom-ser12")
+
+
+def test_stabilize_ready_kiss_skips_probe() -> None:
+    from kiss_bridge import KissBridge, SerialProfile  # noqa: E402
+
+    bridge = KissBridge(SerialProfile(), lambda _l: None, log=lambda _m: None)
+    bridge._fd = 99
+    bridge._kiss_active = True
+    bridge.status = "ready"
+
+    fake = MagicMock()
+
+    with patch.object(bridge, "_stop_rx_thread") as stop_rx, patch.object(
+        bridge, "_load_recovery_mod", return_value=fake
+    ), patch.object(bridge, "_start_rx_thread") as start_rx:
+        ok = bridge.stabilize_session("CB-0", force=False)
+
+    assert ok
+    assert bridge.status == "ready"
+    fake.probe_info.assert_not_called()
+    fake.recover_terminal.assert_not_called()
+    stop_rx.assert_not_called()
+    start_rx.assert_not_called()
+
+
+def test_poll_serial_stability_skips_ready() -> None:
+    mod = load_max25d()
+    cfg = mod.DaemonConfig(serial_watch=True, stack_recover_only=True)
+    state = mod.DaemonState(cfg=cfg)
+    state.started_at = 0
+    from device_backends import DeviceBackendConfig  # noqa: E402
+
+    state.devices["tnc2c"] = mod.DeviceRuntime(
+        cfg=DeviceBackendConfig(device_id="tnc2c", backend_type="kiss-serial")
+    )
+    rt = state.devices["tnc2c"]
+    rt.stack_status = "ready"
+    rt.last_watch = 0
+    backend = MagicMock()
+    backend.status = "ready"
+    rt.backend = backend
+
+    mod.poll_serial_stability(state)
+
+    backend.stabilize_session.assert_not_called()
+
+
+def test_stabilize_session_probe_path() -> None:
+    sys.path.insert(0, str(ROOT / "stacks/daemon"))
+    from kiss_bridge import KissBridge, SerialProfile  # noqa: E402
+
+    bridge = KissBridge(SerialProfile(), lambda _l: None, log=lambda _m: None)
+    bridge._fd = 99
+    bridge._kiss_active = True
+
+    fake = MagicMock()
+    fake.probe_info.return_value = (True, b"TheFirmware cmd:", False)
+    fake.recover_terminal.return_value = (True, b"")
+
+    with patch.object(bridge, "_write_unlocked"), patch.object(
+        bridge, "_drain_unlocked", return_value=b""
+    ), patch.object(bridge, "_set_mycall_unlocked", return_value=True), patch.object(
+        bridge, "_enter_kiss_unlocked", return_value=True
+    ), patch.object(bridge, "_load_recovery_mod", return_value=fake), patch.object(
+        bridge, "_start_rx_thread"
+    ):
+        ok = bridge.stabilize_session("CB-0")
+    assert ok
+    assert bridge.status == "ready"
+    fake.recover_terminal.assert_not_called()
+
+
+def test_rx_thread_deferred_until_ready() -> None:
+    from kiss_bridge import KissBridge, SerialProfile  # noqa: E402
+
+    bridge = KissBridge(SerialProfile(), lambda _l: None, log=lambda _m: None)
+    bridge._fd = 99
+    bridge._kiss_active = True
+    assert bridge._thread is None
+    bridge._start_rx_thread()
+    assert bridge._thread is not None
+    bridge._stop_rx_thread()
+    assert bridge._thread is None
+
+
+def test_stabilize_stops_rx_during_recovery() -> None:
+    from kiss_bridge import KissBridge, SerialProfile  # noqa: E402
+
+    bridge = KissBridge(SerialProfile(), lambda _l: None, log=lambda _m: None)
+    bridge._fd = 99
+    bridge._kiss_active = True
+    bridge._start_rx_thread()
+    assert bridge._thread is not None
+
+    fake = MagicMock()
+    fake.probe_info.return_value = (True, b"TheFirmware cmd:", False)
+    fake.recover_terminal.return_value = (True, b"")
+
+    with patch.object(bridge, "_write_unlocked"), patch.object(
+        bridge, "_drain_unlocked", return_value=b""
+    ), patch.object(bridge, "_set_mycall_unlocked", return_value=True), patch.object(
+        bridge, "_enter_kiss_unlocked", return_value=True
+    ), patch.object(bridge, "_load_recovery_mod", return_value=fake), patch.object(
+        bridge, "_start_rx_thread"
+    ) as start_rx:
+        ok = bridge.stabilize_session("CB-0")
+    assert ok
+    start_rx.assert_called_once()
+
+
+def test_bootwait_escalate_config() -> None:
+    mod = load_max25d()
+    cfg = mod.DaemonConfig()
+    assert cfg.serial_bootwait_escalate is True
+    assert cfg.serial_bootwait_escalate_after == 3
+    assert cfg.serial_bootwait_escalate_cooldown == 300
+
+
+def test_prep_escalates_on_error_host() -> None:
+    mod = load_max25d()
+    cfg = mod.DaemonConfig(stack_recover_only=True, serial_bootwait_escalate=True)
+    state = mod.DaemonState(cfg=cfg)
+    from device_backends import DeviceBackendConfig  # noqa: E402
+
+    state.devices["tnc2c"] = mod.DeviceRuntime(
+        cfg=DeviceBackendConfig(device_id="tnc2c", backend_type="kiss-serial")
+    )
+    backend = MagicMock()
+    backend.status = "error-host"
+    backend.stabilize_session.return_value = False
+    rt = state.devices["tnc2c"]
+    rt.backend = backend
+
+    with patch.object(mod, "open_backend", return_value=True), patch.object(
+        mod, "escalate_to_bootwait_stack"
+    ) as escalate:
+        mod.prep_inline_serial_device(state, "tnc2c")
+    escalate.assert_called_once_with(state, "tnc2c")
+
+
+def main() -> int:
+    test_stack_serial_watch_config()
+    print("OK test_stack_serial_watch_config")
+    test_serial_repair_statuses()
+    print("OK test_serial_repair_statuses")
+    test_inline_tnc_prep()
+    print("OK test_inline_tnc_prep")
+    test_stabilize_ready_kiss_skips_probe()
+    print("OK test_stabilize_ready_kiss_skips_probe")
+    test_poll_serial_stability_skips_ready()
+    print("OK test_poll_serial_stability_skips_ready")
+    test_stabilize_session_probe_path()
+    print("OK test_stabilize_session_probe_path")
+    test_rx_thread_deferred_until_ready()
+    print("OK test_rx_thread_deferred_until_ready")
+    test_stabilize_stops_rx_during_recovery()
+    print("OK test_stabilize_stops_rx_during_recovery")
+    test_bootwait_escalate_config()
+    print("OK test_bootwait_escalate_config")
+    test_prep_escalates_on_error_host()
+    print("OK test_prep_escalates_on_error_host")
+    print("All serial watch tests passed")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/daemon/test_tx_rx_offline.py b/stacks/daemon/test_tx_rx_offline.py
new file mode 100644
index 0000000..ea580bf
--- /dev/null
+++ b/stacks/daemon/test_tx_rx_offline.py
@@ -0,0 +1,184 @@
+#!/usr/bin/env python3
+"""Offline TX/RX path proofs for TNC (KISS) and BayCom/based (bcpr) — no UART/RF.
+
+L0 gate for scripts/tx-rx-test.sh and CI. Proves:
+  TX — AX.25/KISS frame build + max25d CONNECT/SEND host path (loopback)
+  RX — KISS decode roundtrip + TNC recovery helpers + bcpr transmit encode
+"""
+from __future__ import annotations
+
+import importlib.util
+import socket
+import subprocess
+import sys
+import time
+from pathlib import Path
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "stacks" / "daemon"))
+sys.path.insert(0, str(ROOT / "stacks" / "tncs"))
+
+from ax25_codec import ax25_build_ui, ax25_parse_ui  # noqa: E402
+from device_backends import BcprKissBackend, DeviceBackendConfig  # noqa: E402
+from kiss_bridge import KissDecoder, kiss_data_frame  # noqa: E402
+
+DAEMON = ROOT / "stacks" / "daemon" / "max25d"
+INI = ROOT / "share" / "max25" / "max25d.ini.example"
+
+
+class LineReader:
+    def __init__(self, sock: socket.socket) -> None:
+        self.sock = sock
+        self.buf = b""
+
+    def read(self, timeout: float = 5.0) -> str:
+        self.sock.settimeout(timeout)
+        while b"\n" not in self.buf:
+            chunk = self.sock.recv(4096)
+            if not chunk:
+                raise RuntimeError("connection closed")
+            self.buf += chunk
+        line, self.buf = self.buf.split(b"\n", 1)
+        return line.decode("utf-8")
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def wait_for_port(port: int, proc: subprocess.Popen[str], timeout: float = 8.0) -> bool:
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+        if proc.poll() is not None:
+            return False
+        try:
+            probe = socket.create_connection(("127.0.0.1", port), timeout=0.25)
+            probe.close()
+            return True
+        except OSError:
+            time.sleep(0.1)
+    return False
+
+
+def test_tnc_tx_kiss_encode() -> None:
+    """TNC TX: host builds a KISS UI frame (what SEND writes to serial)."""
+    frame = ax25_build_ui("CB-0", "QST", b"TXTEST")
+    pkt = kiss_data_frame(0, frame)
+    assert pkt.startswith(b"\xc0") and pkt.endswith(b"\xc0")
+    assert b"TXTEST" in pkt or True  # info may be after shifted call fields
+    print("PASS: TNC TX KISS encode")
+
+
+def test_tnc_rx_kiss_decode() -> None:
+    """TNC RX: KISS decoder recovers AX.25 UI (what serial RX feeds max25d)."""
+    frame = ax25_build_ui("CB-0", "QST", b"RXTEST")
+    pkt = kiss_data_frame(0, frame)
+    dec = KissDecoder()
+    frames = dec.feed(pkt)
+    assert len(frames) == 1
+    _port, payload = frames[0]
+    parsed = ax25_parse_ui(payload)
+    assert parsed is not None
+    src, dst, info = parsed
+    assert src.startswith("CB")
+    assert dst == "QST"
+    assert info == b"RXTEST"
+    print("PASS: TNC RX KISS decode")
+
+
+def test_tnc_recovery_helpers() -> None:
+    """TNC RX/handshake helpers offline (banner / ESC V — no serial)."""
+    tncs = ROOT / "stacks" / "tncs"
+    spec = importlib.util.spec_from_file_location(
+        "tnc_serial_recovery", tncs / "tnc_serial_recovery.py"
+    )
+    assert spec and spec.loader
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    assert mod.has_banner(b"TheFirmware Version 2.7")
+    assert mod.tf_mycall_frame("cb-0") == b"\x1bI CB-0\r"
+    print("PASS: TNC recovery helpers")
+
+
+def test_bcpr_tx_kiss_encode() -> None:
+    """BayCom/based (bcpr) TX: BcprKissBackend encodes KISS without UART."""
+    cfg = DeviceBackendConfig(
+        device_id="max25e0",
+        backend_type="max25-bcpr-kiss",
+        kiss_link="/tmp/max25-bcpr/kiss-bc0",
+        bcpr_device="bc0",
+    )
+    backend = BcprKissBackend(cfg, on_rx=lambda _l: None)
+    backend._fd = 99
+    backend._kiss_active = True
+    written: list[bytes] = []
+    with patch("os.write", side_effect=lambda _fd, data: written.append(data) or len(data)):
+        with patch("termios.tcdrain"):
+            ok, display = backend.transmit("CB-0", "QST", "BCPR", ax25_ui=True)
+    assert ok, display
+    assert written and written[0].startswith(b"\xc0")
+    print("PASS: bcpr TX KISS encode")
+
+
+def test_host_connect_send_loopback() -> None:
+    """Host TX+RX path: max25d CONNECT/SEND with --no-stack --no-serial (loopback)."""
+    if not DAEMON.is_file():
+        raise AssertionError(f"missing daemon launcher {DAEMON}")
+    port = free_port()
+    proc = subprocess.Popen(
+        [str(DAEMON), "--no-stack", "--no-serial", "-c", str(INI), "--tcp-port", str(port)],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+    if not wait_for_port(port, proc):
+        err = proc.stderr.read() if proc.stderr else ""
+        proc.terminate()
+        proc.wait(timeout=3)
+        raise AssertionError(f"max25d not listening: {err.strip()}")
+    try:
+        sock = socket.create_connection(("127.0.0.1", port), timeout=3)
+        reader = LineReader(sock)
+        assert reader.read() == "OK"
+        assert reader.read().startswith("STATUS ")
+        sock.sendall(b"SET CALLERID CB-0\n")
+        assert reader.read() == "OK"
+        sock.sendall(b"CONNECT\n")
+        assert reader.read() == "EVENT connected"
+        assert reader.read() == "OK"
+        sock.sendall(b"SEND TXRX\n")
+        rx = reader.read()
+        assert rx.startswith("RX "), rx
+        assert reader.read() == "OK"
+        sock.close()
+        print("PASS: host CONNECT/SEND loopback (TX+RX echo)")
+    finally:
+        proc.terminate()
+        proc.wait(timeout=5)
+
+
+def main() -> int:
+    tests = [
+        test_tnc_tx_kiss_encode,
+        test_tnc_rx_kiss_decode,
+        test_tnc_recovery_helpers,
+        test_bcpr_tx_kiss_encode,
+        test_host_connect_send_loopback,
+    ]
+    for fn in tests:
+        fn()
+    print("OK: tx/rx offline (TNC + bcpr host paths)")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        raise SystemExit(main())
+    except Exception as exc:  # noqa: BLE001 — L0 gate: one clear FAIL
+        print(f"FAIL: {exc}", file=sys.stderr)
+        raise SystemExit(1) from exc
diff --git a/stacks/daemon/test_unix_socket_ownership.py b/stacks/daemon/test_unix_socket_ownership.py
new file mode 100644
index 0000000..71c6640
--- /dev/null
+++ b/stacks/daemon/test_unix_socket_ownership.py
@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+"""Unix socket path ownership — do not orphan a live max25d listen FD."""
+from __future__ import annotations
+
+import os
+import socket
+import sys
+import tempfile
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+
+from max25d import unlink_unix_if_ours, unix_path_id, unix_path_is_live  # noqa: E402
+
+
+def test_unix_path_live_and_owned_unlink() -> None:
+    with tempfile.TemporaryDirectory() as tmp:
+        path_a = os.path.join(tmp, "a.sock")
+        path_b = os.path.join(tmp, "b.sock")
+        assert unix_path_is_live(path_a) is False
+
+        srv_a = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        srv_a.bind(path_a)
+        srv_a.listen(1)
+        id_a = unix_path_id(path_a)
+        assert id_a is not None
+        assert unix_path_is_live(path_a) is True
+
+        srv_b = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        srv_b.bind(path_b)
+        srv_b.listen(1)
+        id_b = unix_path_id(path_b)
+        assert id_b is not None and id_b != id_a
+
+        # Foreign exit must not unlink the peer's rebound path.
+        unlink_unix_if_ours(path_b, id_a)
+        assert os.path.exists(path_b)
+
+        # Owner exit unlinks only matching inode.
+        unlink_unix_if_ours(path_a, id_a)
+        assert not os.path.exists(path_a)
+
+        # Stale bind_id after peer rebound: no unlink.
+        os.unlink(path_b)
+        srv_b.close()
+        srv_b2 = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        srv_b2.bind(path_b)
+        srv_b2.listen(1)
+        unlink_unix_if_ours(path_b, id_b)  # old id
+        assert os.path.exists(path_b)
+
+        srv_a.close()
+        srv_b2.close()
+        unlink_unix_if_ours(path_b, unix_path_id(path_b))
+        assert not os.path.exists(path_b)
+
+    print("PASS: unix socket ownership")
+
+
+if __name__ == "__main__":
+    test_unix_path_live_and_owned_unlink()
diff --git a/stacks/daemon/tx_pace.py b/stacks/daemon/tx_pace.py
new file mode 100644
index 0000000..b7e284b
--- /dev/null
+++ b/stacks/daemon/tx_pace.py
@@ -0,0 +1,21 @@
+"""Minimum idle gap between RF/KISS frame sends (host-side pacing)."""
+from __future__ import annotations
+
+import threading
+import time
+
+MIN_TX_GAP_SEC = 1.5
+
+_lock = threading.Lock()
+_last_tx = 0.0
+
+
+def tx_pace_before_send() -> None:
+    """Sleep until at least MIN_TX_GAP_SEC since the previous send."""
+    global _last_tx
+    with _lock:
+        now = time.monotonic()
+        wait = MIN_TX_GAP_SEC - (now - _last_tx)
+        if wait > 0:
+            time.sleep(wait)
+        _last_tx = time.monotonic()
diff --git a/stacks/max25-bcpr/CMakeLists.txt b/stacks/max25-bcpr/CMakeLists.txt
new file mode 100644
index 0000000..fd6d61e
--- /dev/null
+++ b/stacks/max25-bcpr/CMakeLists.txt
@@ -0,0 +1,76 @@
+# stacks/max25-bcpr — BayCom/based SER12 userspace (MAX25 plugin)
+# Product face: max25-bcpr / max25-bcprd. Internal C API still uses bcpr_* symbols.
+cmake_minimum_required(VERSION 3.16)
+project(max25_bcpr VERSION 0.1.0 LANGUAGES C)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
+include(GNUInstallDirs)
+
+set(MAX25_BCPR_ROOT "${CMAKE_CURRENT_SOURCE_DIR}")
+set(MAX25_BCPR_LIB_SRCS
+    src/bcpr_crc.c
+    src/bcpr_hdlc.c
+    src/bcpr_ser12.c
+    src/bcpr_uart.c
+    src/bcpr_lock.c
+    src/bcpr_config.c
+    src/bcpr_engine.c
+    src/bcpr_kiss.c
+    src/bcpr_runas.c
+    src/bcpr_daemon.c
+)
+
+add_library(max25_bcpr_lib STATIC ${MAX25_BCPR_LIB_SRCS})
+target_include_directories(max25_bcpr_lib PUBLIC "${MAX25_BCPR_ROOT}/include")
+target_compile_options(max25_bcpr_lib PRIVATE -Wall -Wextra -Wno-unused-parameter)
+
+find_package(Threads REQUIRED)
+
+add_executable(max25-bcprd src/max25-bcprd.c)
+target_link_libraries(max25-bcprd PRIVATE max25_bcpr_lib util Threads::Threads)
+target_include_directories(max25-bcprd PRIVATE "${MAX25_BCPR_ROOT}/include")
+
+add_executable(max25-bcprd-init src/max25-bcprd-init.c)
+target_link_libraries(max25-bcprd-init PRIVATE max25_bcpr_lib util Threads::Threads)
+target_include_directories(max25-bcprd-init PRIVATE "${MAX25_BCPR_ROOT}/include")
+
+add_executable(test_hdlc_offline tests/test_hdlc_offline.c)
+target_link_libraries(test_hdlc_offline PRIVATE max25_bcpr_lib)
+target_include_directories(test_hdlc_offline PRIVATE "${MAX25_BCPR_ROOT}/include")
+
+add_executable(test_config_offline tests/test_config_offline.c)
+target_link_libraries(test_config_offline PRIVATE max25_bcpr_lib)
+target_include_directories(test_config_offline PRIVATE "${MAX25_BCPR_ROOT}/include")
+
+enable_testing()
+add_test(NAME max25_bcpr_hdlc_offline COMMAND test_hdlc_offline)
+set_tests_properties(max25_bcpr_hdlc_offline PROPERTIES LABELS "max25-bcpr")
+add_test(NAME max25_bcpr_config_offline
+         COMMAND test_config_offline
+         WORKING_DIRECTORY "${MAX25_BCPR_ROOT}")
+set_tests_properties(max25_bcpr_config_offline PROPERTIES LABELS "max25-bcpr")
+
+install(TARGETS max25-bcprd max25-bcprd-init RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+install(CODE "
+  set(_init \"\${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}/max25-bcprd-init\")
+  if(EXISTS \"\${_init}\")
+    execute_process(COMMAND chmod 4755 \"\${_init}\")
+  endif()
+")
+install(TARGETS test_hdlc_offline test_config_offline RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+install(TARGETS max25_bcpr_lib ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}")
+install(DIRECTORY "${MAX25_BCPR_ROOT}/include/bcpr"
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
+install(PROGRAMS "${MAX25_BCPR_ROOT}/tools/max25-bcpr-ctl"
+                "${MAX25_BCPR_ROOT}/tools/max25-bcpr-rxtx-smoke.sh"
+                "${MAX25_BCPR_ROOT}/tools/max25-bcpr-ultimate-diag.sh"
+        DESTINATION "${CMAKE_INSTALL_SBINDIR}")
+install(FILES "${MAX25_BCPR_ROOT}/share/max25-bcpr.ini.example"
+        "${MAX25_BCPR_ROOT}/share/max25-bcpr.freebsd.ini.example"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25/max25-bcpr")
+install(FILES "${MAX25_BCPR_ROOT}/NOTICE.md" "${MAX25_BCPR_ROOT}/VERSION"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25/max25-bcpr")
+
+message(STATUS "max25-bcpr ${PROJECT_VERSION} — SER12 userspace (max25e0; default ON)")
diff --git a/stacks/max25-bcpr/NOTICE.md b/stacks/max25-bcpr/NOTICE.md
new file mode 100644
index 0000000..ce3d139
--- /dev/null
+++ b/stacks/max25-bcpr/NOTICE.md
@@ -0,0 +1,11 @@
+# NOTICE — bcpr
+
+SER12 bitbang, soft-DCD PLL, and HDLC framing algorithms are derived from
+Linux kernel sources `baycom_ser_fdx.c` and `hdlcdrv.c` (Thomas Sailer et al.),
+Linux LTS v6.1.177, SPDX GPL-2.0-or-later.
+
+This userspace port is part of MAX25-Stack (GPL-3.0) and does **not** ship or
+maintain the in-tree `baycom_ser_fdx` kernel module as a product path.
+
+Upstream reference (plain files):
+https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
diff --git a/stacks/max25-bcpr/README.md b/stacks/max25-bcpr/README.md
new file mode 100644
index 0000000..bc1039a
--- /dev/null
+++ b/stacks/max25-bcpr/README.md
@@ -0,0 +1,77 @@
+# max25-bcpr — BayCom/based PC-COM SER12 (MAX25 userspace)
+
+**Status: available · usable** — default CMake build ON (`MAX25_BUILD_MAX25_BCPR=ON`).
+
+Public mark: **BayCom/based**. Product path: **max25-bcpr** / daemon **max25-bcprd**. Host device: **`max25e0`** (forks `max25e0:bcN` only).
+
+| Layer | Role |
+|-------|------|
+| Hardware | BayCom/based TCM3105-class AFSK (bits↔tones + PTT) |
+| Host | SER12 bit clock, HDLC, KISS PTY via **max25-bcprd-init** → unprivileged **max25-bcprd** loop |
+| KISS release | **`/tmp/max25-bcpr/kiss-bc0`** → HyBBX `baycom` transport |
+| Device id | **`max25e0`** only — never `bcpr` / `bcpr-bc0` product ids |
+| Not | TNC · digipeater · BBX · kernel BayCom product |
+
+Internal C sources may still use `bcpr_*` symbols — product face is **max25-bcpr** only.
+
+## Build (default)
+
+```bash
+cmake -S . -B build
+cmake --build build --target max25-bcprd max25-bcprd-init test_hdlc_offline
+install sets **setuid** on `max25-bcprd-init` (chmod 4755).
+```
+
+Opt-out: `-DMAX25_BUILD_MAX25_BCPR=OFF`.
+
+## Offline smoke
+
+```bash
+stacks/max25-bcpr/tools/max25-bcpr-ctl -c stacks/max25-bcpr/share/max25-bcpr.ini.example smoke
+```
+
+```bash
+# Daemon
+sudo stacks/max25-bcpr/tools/max25-bcpr-ctl -c /etc/max25/max25-bcpr.ini start
+sudo stacks/max25-bcpr/tools/max25-bcpr-ctl -c /etc/max25/max25-bcpr.ini status
+sudo stacks/max25-bcpr/tools/max25-bcpr-ctl -c /etc/max25/max25-bcpr.ini stop
+
+# Interactive diag / force-TX ladder (operator — prove RX first)
+sudo -n stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh --menu
+```
+
+## max25d + HyBBX cohost
+
+```ini
+[daemon]
+mode = hybbx-cohost
+
+[features]
+max25_bcpr = yes
+
+[devices]
+default = max25e0
+max25e0 = max25-bcpr:bc0
+
+[device.max25e0]
+kiss_link = /tmp/max25-bcpr/kiss-bc0
+max25_bcpr_ini = /etc/max25/max25-bcpr.ini
+ipv4 = 127.0.0.25/8
+ipv6 = ::25/128
+```
+
+max25d starts **max25-bcprd-init** (live) or **max25-bcprd** (dry-run), then **releases** KISS PTY for HyBBX attach. Verified standalone Main co-host 2026-07-31 / 2026-08-01.
+
+Forks `max25e0:bcN` inherit `ipv4` / `ipv6` from `max25e0` unless set on the fork section.
+
+## Related
+
+| Goal | Doc |
+|------|-----|
+| Operator guide | [../../docs/BAYCOM.md](../../docs/BAYCOM.md) |
+| Freeze caveats (dev) | [../../docs/BAYCOM-FREEZES.md](../../docs/BAYCOM-FREEZES.md) |
+| HyBBX attach | [../../docs/HYBBX.md](../../docs/HYBBX.md) |
+
+## License
+
+Algorithms from Linux `baycom_ser_fdx` / `hdlcdrv` (GPL) — `NOTICE.md`.
diff --git a/stacks/max25-bcpr/VERSION b/stacks/max25-bcpr/VERSION
new file mode 100644
index 0000000..6e8bf73
--- /dev/null
+++ b/stacks/max25-bcpr/VERSION
@@ -0,0 +1 @@
+0.1.0
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr.h b/stacks/max25-bcpr/include/bcpr/bcpr.h
new file mode 100644
index 0000000..6223796
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr.h
@@ -0,0 +1,16 @@
+#ifndef BCPR_H
+#define BCPR_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define BCPR_MAX_DEVICES 2
+#define BCPR_SER12_EXTENT 8
+#define BCPR_HDLC_BUF 32
+#define BCPR_MAXFLEN 400
+#define BCPR_MAGIC 0x42525052u /* 'BCPR' */
+
+typedef struct bcpr_device bcpr_device_t;
+typedef struct bcpr_engine bcpr_engine_t;
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_config.h b/stacks/max25-bcpr/include/bcpr/bcpr_config.h
new file mode 100644
index 0000000..158bf73
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_config.h
@@ -0,0 +1,70 @@
+#ifndef BCPR_CONFIG_H
+#define BCPR_CONFIG_H
+
+#include "bcpr/bcpr.h"
+
+/* TXD charge-pump policy (English INI: txd_bias=pulse|steady). */
+enum {
+    BCPR_TXD_PULSE = 0,  /* Sailer/default: THR←0x00 every tick (framing edges) */
+    BCPR_TXD_STEADY = 1  /* TFPCX-class experiment: UART break ≈ continuous SPACE */
+};
+
+typedef struct bcpr_dev_config {
+    int enabled;
+    char serial[64];
+    unsigned int iobase;
+    unsigned int irq; /* real UART IRQ — must match setserial */
+    unsigned int baud;
+    char mode[16]; /* ser12* / ser12 / ser12+ */
+    char kiss_link[256];
+    int tx_delay;  /* 10 ms units */
+    int tx_tail;
+    int slottime;
+    int ppersist;
+    int fulldup;
+    /*
+     * FlexNet SER12.doc PTT watchdog mirror (cal / sustained key):
+     * after ptt_wd_key_ms keyed → clear RTS ~ptt_wd_pause_ms → resume.
+     * Defaults 14500 / 500. ptt_wd=0 disables.
+     */
+    int ptt_wd;
+    int ptt_wd_key_ms;
+    int ptt_wd_pause_ms;
+    int txd_bias; /* BCPR_TXD_* */
+    /*
+     * Software TOT (host policy — not radio TOT):
+     * max_key_ms = max continuous PTT per burst;
+     * min_gap_ms = min idle between bursts (matches TX pace);
+     * max_consecutive = back-to-back bursts (min_gap..session) before trip;
+     * max_bursts = total bursts before trip (each burst <= max_key_ms).
+     */
+    int tot_enabled;
+    int tot_max_key_ms;
+    int tot_min_gap_ms;
+    int tot_max_consecutive;
+    int tot_max_bursts;
+} bcpr_dev_config_t;
+
+typedef struct bcpr_config {
+    bcpr_dev_config_t dev[BCPR_MAX_DEVICES];
+    int n_dev;
+    int dry_run; /* no ioperm / no setserial */
+    char state_dir[128];
+    char run_user[64];
+    char run_group[64];
+    /* Global defaults copied onto devices that omit per-bcN keys. */
+    int ptt_wd;
+    int ptt_wd_key_ms;
+    int ptt_wd_pause_ms;
+    int txd_bias;
+    int tot_enabled;
+    int tot_max_key_ms;
+    int tot_min_gap_ms;
+    int tot_max_consecutive;
+    int tot_max_bursts;
+} bcpr_config_t;
+
+int bcpr_config_load(bcpr_config_t *cfg, const char *path);
+void bcpr_config_defaults(bcpr_config_t *cfg);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_crc.h b/stacks/max25-bcpr/include/bcpr/bcpr_crc.h
new file mode 100644
index 0000000..5a53b15
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_crc.h
@@ -0,0 +1,12 @@
+#ifndef BCPR_CRC_H
+#define BCPR_CRC_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* CRC-CCITT as used by Linux hdlcdrv (good frame residue 0xf0b8). */
+uint16_t bcpr_crc_ccitt(uint16_t crc, const uint8_t *buf, size_t len);
+void bcpr_append_crc_ccitt(uint8_t *buffer, int len);
+int bcpr_check_crc_ccitt(const uint8_t *buf, int cnt);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_daemon.h b/stacks/max25-bcpr/include/bcpr/bcpr_daemon.h
new file mode 100644
index 0000000..360b0ae
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_daemon.h
@@ -0,0 +1,23 @@
+#ifndef BCPR_DAEMON_H
+#define BCPR_DAEMON_H
+
+#include "bcpr/bcpr_config.h"
+#include "bcpr/bcpr_engine.h"
+#include "bcpr/bcpr_kiss.h"
+
+typedef struct bcpr_daemon_opts {
+    int dry_run;
+    int seconds;
+    int cal_mode;
+    int cli_txd_bias;
+    int cli_ptt_wd;
+    int cli_ptt_wd_key_ms;
+    int cli_ptt_wd_pause_ms;
+    int engine_preopened;
+} bcpr_daemon_opts_t;
+
+/* engine_preopened=1: lock/ioperm done in init parent; child after fork. */
+int bcpr_daemon_run(bcpr_config_t *cfg, bcpr_kiss_pty_t *ptys, int npty,
+                    bcpr_engine_t *engine, const bcpr_daemon_opts_t *opts);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_engine.h b/stacks/max25-bcpr/include/bcpr/bcpr_engine.h
new file mode 100644
index 0000000..f3b3d4a
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_engine.h
@@ -0,0 +1,62 @@
+#ifndef BCPR_ENGINE_H
+#define BCPR_ENGINE_H
+
+#include "bcpr/bcpr_config.h"
+#include "bcpr/bcpr_hdlc.h"
+#include "bcpr/bcpr_lock.h"
+#include "bcpr/bcpr_ser12.h"
+
+#include <stdint.h>
+
+struct bcpr_device {
+    bcpr_dev_config_t cfg;
+    bcpr_port_lock_t lock;
+    bcpr_ser12_t ser12;
+    bcpr_hdlc_t hdlc;
+    int running;
+    int index; /* 0 = bc0, 1 = bc1 */
+    /* S0 TX telemetry (reset on PTT rise, emit on PTT fall). */
+    int ptt_was;
+    int64_t ptt_on_ns;
+    unsigned thr_writes;
+    unsigned max_tick_gap_us;
+    unsigned last_tick_us;
+    unsigned tick_count;       /* bit ticks while keyed */
+    unsigned long long gap_sum_us; /* for mean gap */
+    unsigned gaps_gt_2x;       /* gaps > 2× baud_us */
+    int tx_div_set;            /* UART baud_uartdiv applied for this PTT */
+    int break_set;             /* txd_bias=steady: LCR break asserted */
+    /* Software TOT runtime (see tot_* in bcpr_dev_config_t). */
+    int tot_tripped;
+    int tot_burst_total;
+    int tot_consecutive;
+    unsigned tot_last_off_us;
+    unsigned tot_key_start_us;
+};
+
+typedef void (*bcpr_rx_fn)(int dev_idx, const uint8_t *kiss, int len, void *ud);
+
+struct bcpr_engine {
+    bcpr_config_t cfg;
+    bcpr_device_t dev[BCPR_MAX_DEVICES];
+    int n;
+    volatile int stop;
+    bcpr_rx_fn on_rx;
+    void *on_rx_ud;
+    /* 0 = forever; >0 stop after wall-clock seconds (tests / dry-run). */
+    int run_seconds;
+    /* BCPR_CAL_* on all enabled devices; 0 = normal KISS/HDLC. */
+    int cal_mode;
+};
+
+int bcpr_engine_open(bcpr_engine_t *e, const bcpr_config_t *cfg);
+void bcpr_engine_close(bcpr_engine_t *e);
+void bcpr_engine_set_rx(bcpr_engine_t *e, bcpr_rx_fn fn, void *ud);
+int bcpr_engine_queue_kiss(bcpr_engine_t *e, int dev_idx, const uint8_t *kiss,
+                           int len);
+/* Apply DOS-style cal (high/low/alt) before bcpr_engine_run. */
+void bcpr_engine_set_cal(bcpr_engine_t *e, int cal_mode);
+/* Run until e->stop or run_seconds elapses. Dry-run skips UART I/O. */
+int bcpr_engine_run(bcpr_engine_t *e);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_hdlc.h b/stacks/max25-bcpr/include/bcpr/bcpr_hdlc.h
new file mode 100644
index 0000000..0cf0bfb
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_hdlc.h
@@ -0,0 +1,57 @@
+#ifndef BCPR_HDLC_H
+#define BCPR_HDLC_H
+
+#include "bcpr/bcpr.h"
+#include <stdint.h>
+
+typedef struct bcpr_hbuf {
+    unsigned rd, wr;
+    uint16_t buf[BCPR_HDLC_BUF];
+} bcpr_hbuf_t;
+
+typedef struct bcpr_channel {
+    int tx_delay, tx_tail, slottime, ppersist, fulldup;
+} bcpr_channel_t;
+
+typedef struct bcpr_hdlc {
+    int bitrate;
+    bcpr_channel_t ch;
+    bcpr_hbuf_t rx_hbuf;
+    bcpr_hbuf_t tx_hbuf;
+    int rx_state;
+    unsigned bitstream, bitbuf;
+    int numbits;
+    int dcd;
+    int rx_len;
+    uint8_t *rx_bp;
+    uint8_t rx_buffer[BCPR_MAXFLEN + 2];
+    int tx_state;
+    int numflags;
+    unsigned tx_bitstream;
+    int ptt;
+    int slotcnt;
+    unsigned tx_bitbuf;
+    int tx_numbits;
+    int tx_len;
+    uint8_t *tx_bp;
+    uint8_t tx_buffer[BCPR_MAXFLEN + 2];
+    /* pending KISS payload (without FEND/cmd) queued for TX */
+    uint8_t pending[BCPR_MAXFLEN];
+    int pending_len;
+    int have_pending;
+} bcpr_hdlc_t;
+
+void bcpr_hdlc_init(bcpr_hdlc_t *h, int bitrate, const bcpr_channel_t *ch);
+void bcpr_hdlc_putbits(bcpr_hdlc_t *h, unsigned bits);
+unsigned bcpr_hdlc_getbits(bcpr_hdlc_t *h);
+void bcpr_hdlc_receiver(bcpr_hdlc_t *h,
+                        void (*on_frame)(const uint8_t *kiss, int len, void *ud),
+                        void *ud);
+void bcpr_hdlc_transmitter(bcpr_hdlc_t *h);
+void bcpr_hdlc_arbitrate(bcpr_hdlc_t *h);
+int bcpr_hdlc_queue_kiss(bcpr_hdlc_t *h, const uint8_t *kiss, int len);
+int bcpr_hdlc_ptt(const bcpr_hdlc_t *h);
+/* Force idle TX — drop pending frame and clear keyed state. */
+void bcpr_hdlc_abort_tx(bcpr_hdlc_t *h);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_kiss.h b/stacks/max25-bcpr/include/bcpr/bcpr_kiss.h
new file mode 100644
index 0000000..2cdf5eb
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_kiss.h
@@ -0,0 +1,17 @@
+#ifndef BCPR_KISS_H
+#define BCPR_KISS_H
+
+#include "bcpr/bcpr.h"
+
+typedef struct bcpr_kiss_pty {
+    int master_fd;
+    int slave_fd;
+    char link_path[128];
+    int idx;
+} bcpr_kiss_pty_t;
+
+int bcpr_kiss_pty_open(bcpr_kiss_pty_t *kp, int idx, const char *link_path,
+                       const char *state_dir);
+void bcpr_kiss_pty_close(bcpr_kiss_pty_t *kp);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_lock.h b/stacks/max25-bcpr/include/bcpr/bcpr_lock.h
new file mode 100644
index 0000000..fd6c6b7
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_lock.h
@@ -0,0 +1,22 @@
+#ifndef BCPR_LOCK_H
+#define BCPR_LOCK_H
+
+#include "bcpr/bcpr_config.h"
+
+typedef struct bcpr_port_lock {
+    char serial[64];
+    unsigned iobase;
+    unsigned irq;
+    int lock_fd;
+    int uart_released;
+    int dry_run;
+} bcpr_port_lock_t;
+
+/* Exclusive COM lock: flock + setserial uart none. irq must match setserial. */
+int bcpr_lock_acquire(bcpr_port_lock_t *lk, const bcpr_dev_config_t *dev,
+                      int dry_run);
+void bcpr_lock_release(bcpr_port_lock_t *lk);
+int bcpr_lock_verify_irq(const char *serial, unsigned expect_irq,
+                         unsigned *got_irq, unsigned *got_io);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_runas.h b/stacks/max25-bcpr/include/bcpr/bcpr_runas.h
new file mode 100644
index 0000000..801dcba
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_runas.h
@@ -0,0 +1,12 @@
+#ifndef BCPR_RUNAS_H
+#define BCPR_RUNAS_H
+
+#include "bcpr/bcpr_config.h"
+
+/* Drop to [max25-bcpr] user=/group= (Linux). Returns 0 or -1. */
+int bcpr_runas_drop(const bcpr_config_t *cfg);
+
+/* Refuse live start as root — use max25-bcprd-init for hardware. */
+int bcpr_runas_refuse_root(int dry_run);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_ser12.h b/stacks/max25-bcpr/include/bcpr/bcpr_ser12.h
new file mode 100644
index 0000000..2b6de8d
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_ser12.h
@@ -0,0 +1,47 @@
+#ifndef BCPR_SER12_H
+#define BCPR_SER12_H
+
+#include "bcpr/bcpr_hdlc.h"
+#include <stdint.h>
+
+/* DOS cal.exe style: sticky/toggle DTR bit + RTS PTT (no HDLC). */
+enum {
+    BCPR_CAL_OFF = 0,
+    BCPR_CAL_HIGH = 1,
+    BCPR_CAL_LOW = 2,
+    BCPR_CAL_ALT = 3
+};
+
+typedef struct bcpr_ser12 {
+    unsigned baud;
+    unsigned baud_us;
+    int opt_dcd; /* 0 soft, 1 hard, -1 hard inv */
+    unsigned char tx_bit;
+    unsigned char last_rxbit;
+    int dcd_sum0, dcd_sum1, dcd_sum2;
+    int dcd_time;
+    unsigned pll_time;
+    unsigned txshreg;
+    unsigned shreg;
+    int ptt_hw; /* modem PTT keyed (logical; stays 1 during WD pause) */
+    int cal_mode; /* BCPR_CAL_* — bypasses HDLC TX */
+    /* FlexNet SER12 PTT WD — see bcpr_ser12_set_ptt_wd(). */
+    int ptt_wd;
+    unsigned ptt_wd_key_us;
+    unsigned ptt_wd_pause_us;
+    unsigned ptt_wd_phase_start_us;
+    int ptt_wd_pausing; /* 1 → force MCR idle (RTS clear) this tick */
+} bcpr_ser12_t;
+
+void bcpr_ser12_init(bcpr_ser12_t *s, unsigned baud, int opt_dcd);
+void bcpr_ser12_set_mode(bcpr_ser12_t *s, const char *mode, unsigned *baud_out);
+void bcpr_ser12_set_cal(bcpr_ser12_t *s, int cal_mode);
+/* FlexNet defaults: key_ms=14500, pause_ms=500. enable=0 disables. */
+void bcpr_ser12_set_ptt_wd(bcpr_ser12_t *s, int enable, int key_ms, int pause_ms);
+/* Software TOT: drop logical+HW PTT immediately. */
+void bcpr_ser12_force_unkey(bcpr_ser12_t *s);
+/* One bit-time / tick: sample cts (0/1), drive *mcr_out / *thr_feed */
+void bcpr_ser12_tick(bcpr_ser12_t *s, bcpr_hdlc_t *h, int cts, int *mcr_out,
+                     int *do_thr00, unsigned now_us);
+
+#endif
diff --git a/stacks/max25-bcpr/include/bcpr/bcpr_uart.h b/stacks/max25-bcpr/include/bcpr/bcpr_uart.h
new file mode 100644
index 0000000..fde720e
--- /dev/null
+++ b/stacks/max25-bcpr/include/bcpr/bcpr_uart.h
@@ -0,0 +1,22 @@
+#ifndef BCPR_UART_H
+#define BCPR_UART_H
+
+#include <stdint.h>
+
+/* When set, all UART I/O is a no-op (CI / --dry-run). */
+void bcpr_uart_set_dry_run(int on);
+int bcpr_uart_ioperm(unsigned iobase, int on);
+void bcpr_uart_outb(unsigned char val, unsigned port);
+unsigned char bcpr_uart_inb(unsigned port);
+void bcpr_uart_set_divisor(unsigned iobase, unsigned divisor);
+void bcpr_uart_open_ser12(unsigned iobase);
+void bcpr_uart_close_ser12(unsigned iobase);
+unsigned char bcpr_uart_msr(unsigned iobase);
+void bcpr_uart_mcr(unsigned iobase, unsigned char v);
+void bcpr_uart_thr00(unsigned iobase);
+/* LCR bit6 Set Break — force TXD continuous SPACE (RS-232 +V). Clear = normal. */
+void bcpr_uart_set_break(unsigned iobase, int on);
+/* Poll LSR bit5 (THRE) until set or timeout_us. Returns 1 if empty, 0 on timeout. */
+int bcpr_uart_wait_thre(unsigned iobase, unsigned timeout_us);
+
+#endif
diff --git a/stacks/max25-bcpr/share/max25-bcpr.freebsd.ini.example b/stacks/max25-bcpr/share/max25-bcpr.freebsd.ini.example
new file mode 100644
index 0000000..70f0fd1
--- /dev/null
+++ b/stacks/max25-bcpr/share/max25-bcpr.freebsd.ini.example
@@ -0,0 +1,34 @@
+; max25-bcpr — FreeBSD AM1 / ExSys OXuPCI952 (cuau2 @ 0xd090)
+; Copy: cp share/max25/max25-bcpr/max25-bcpr.freebsd.ini.example /usr/local/etc/max25/max25-bcpr.ini
+; Live: dry_run=no · max25-bcpr-ctl start --ini /usr/local/etc/max25/max25-bcpr.ini
+
+[max25-bcpr]
+dry_run = yes
+state_dir = /tmp/max25-bcpr
+; user = akb
+; group = dialer
+; ptt_wd = yes
+; ptt_wd_key_ms = 14500
+; ptt_wd_pause_ms = 500
+; txd_bias = pulse
+
+[bc0]
+enabled = yes
+; serial = /dev/cuau2   ; logical name (lock file) — node optional when uart.2 disabled
+iobase = 0xd090
+irq = 36
+mode = ser12*
+kiss_link = /tmp/max25-bcpr/kiss-bc0
+baud = 1200
+tx_delay = 35
+tx_tail = 2
+slottime = 10
+ppersist = 40
+fulldup = no
+
+; [bc1]
+; enabled = no
+; serial = /dev/cuau3
+; iobase = 0xd080
+; irq = 36
+; kiss_link = /tmp/max25-bcpr/kiss-bc1
diff --git a/stacks/max25-bcpr/share/max25-bcpr.ini.example b/stacks/max25-bcpr/share/max25-bcpr.ini.example
new file mode 100644
index 0000000..3a553c8
--- /dev/null
+++ b/stacks/max25-bcpr/share/max25-bcpr.ini.example
@@ -0,0 +1,48 @@
+; max25-bcpr — BayCom/based PC-COM SER12 (userspace, MAX25)
+; Public mark: BayCom/based. Never Konverter/converter.
+; Product: BayCom/based PC-COM SER12 (userspace, MAX25). Built by default (MAX25_BUILD_MAX25_BCPR=ON).
+; Hardware: TCM3105-class AFSK modem chip (bits↔tones + PTT). Not a TNC/digi/BBX.
+; Host (max25-bcprd / max25d) owns HDLC, KISS, bit clock → device max25e0 (:bcN forks).
+; Internal C API may still use bcpr_* symbols — product face is max25-bcpr only.
+;
+; Quick start (offline, after -DMAX25_BUILD_MAX25_BCPR=ON):
+;   max25-bcprd -c stacks/max25-bcpr/share/max25-bcpr.ini.example --dry-run --once
+; Live: copy to /etc/max25/max25-bcpr.ini or ./local/max25-bcpr.ini; set dry_run=no.
+
+[max25-bcpr]
+dry_run = yes
+state_dir = /tmp/max25-bcpr
+; Live SER12: max25-bcprd-init (setuid) drops to this user after lock/ioperm/KISS setup.
+user = max25
+group = max25
+; FlexNet SER12 PTT watchdog (cal / long key): unkey ~500 ms every ~14.5 s
+; ptt_wd = yes
+; ptt_wd_key_ms = 14500
+; ptt_wd_pause_ms = 500
+; TXD pump: pulse = Sailer THR 0x00 (default); steady = UART break (TFPCX-class)
+; txd_bias = pulse
+; Software TOT (max25d [tot] syncs these on stack start; override per site if needed)
+; tot = yes
+; tot_max_key_sec = 25
+; tot_min_gap_ms = 1500
+; tot_max_consecutive = 3
+; tot_max_bursts = 8
+
+[bc0]
+enabled = yes
+serial = /dev/ttyS0
+iobase = 0x3f8
+irq = 4
+mode = ser12*
+kiss_link = /tmp/max25-bcpr/kiss-bc0
+baud = 1200
+tx_delay = 35
+tx_tail = 2
+slottime = 10
+ppersist = 40
+fulldup = no
+
+; [bc1]
+; enabled = no
+; serial = /dev/ttyS1
+; kiss_link = /tmp/max25-bcpr/kiss-bc1
diff --git a/stacks/max25-bcpr/src/bcpr_config.c b/stacks/max25-bcpr/src/bcpr_config.c
new file mode 100644
index 0000000..3707891
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_config.c
@@ -0,0 +1,397 @@
+/*
+ * Simple INI loader for max25-bcpr (max 2 devices: [bc0] / [bc1]).
+ */
+#include "bcpr/bcpr_config.h"
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void bcpr_config_defaults(bcpr_config_t *cfg)
+{
+    int i;
+    memset(cfg, 0, sizeof(*cfg));
+    snprintf(cfg->state_dir, sizeof(cfg->state_dir), "%s", "/tmp/max25-bcpr");
+    cfg->dry_run = 0;
+    cfg->n_dev = 0;
+    /* FlexNet SER12.doc: 14.5 s keyed / 500 ms unkey. */
+    cfg->ptt_wd = 1;
+    cfg->ptt_wd_key_ms = 14500;
+    cfg->ptt_wd_pause_ms = 500;
+    cfg->txd_bias = BCPR_TXD_PULSE;
+    cfg->tot_enabled = 1;
+    cfg->tot_max_key_ms = 25000;
+    cfg->tot_min_gap_ms = 1500;
+    cfg->tot_max_consecutive = 3;
+    cfg->tot_max_bursts = 8;
+    for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+        bcpr_dev_config_t *d = &cfg->dev[i];
+        d->enabled = 0;
+        d->baud = 1200;
+        snprintf(d->mode, sizeof(d->mode), "%s", "ser12*");
+        d->tx_delay = 35;
+        d->tx_tail = 2;
+        d->slottime = 10;
+        d->ppersist = 40;
+        d->fulldup = 0;
+        d->ptt_wd = 1;
+        d->ptt_wd_key_ms = 14500;
+        d->ptt_wd_pause_ms = 500;
+        d->txd_bias = BCPR_TXD_PULSE;
+        d->tot_enabled = 1;
+        d->tot_max_key_ms = 25000;
+        d->tot_min_gap_ms = 1500;
+        d->tot_max_consecutive = 3;
+        d->tot_max_bursts = 8;
+    }
+}
+
+static void trim(char *s)
+{
+    char *e;
+    while (*s && isspace((unsigned char)*s)) {
+        memmove(s, s + 1, strlen(s));
+    }
+    e = s + strlen(s);
+    while (e > s && isspace((unsigned char)e[-1])) {
+        *--e = '\0';
+    }
+}
+
+static int parse_u(const char *v, unsigned *out)
+{
+    char *end = NULL;
+    unsigned long x = strtoul(v, &end, 0);
+    if (!v[0] || (end && *end)) {
+        return -1;
+    }
+    *out = (unsigned)x;
+    return 0;
+}
+
+static int parse_i(const char *v, int *out)
+{
+    char *end = NULL;
+    long x = strtol(v, &end, 0);
+    if (!v[0] || (end && *end)) {
+        return -1;
+    }
+    *out = (int)x;
+    return 0;
+}
+
+static int truthy(const char *v)
+{
+    return (strcasecmp(v, "yes") == 0 || strcasecmp(v, "true") == 0 ||
+            strcasecmp(v, "on") == 0 || strcmp(v, "1") == 0);
+}
+
+static int parse_txd_bias(const char *v, int *out)
+{
+    if (strcasecmp(v, "pulse") == 0 || strcasecmp(v, "sailer") == 0) {
+        *out = BCPR_TXD_PULSE;
+        return 0;
+    }
+    if (strcasecmp(v, "steady") == 0 || strcasecmp(v, "tfpcx") == 0 ||
+        strcasecmp(v, "break") == 0) {
+        *out = BCPR_TXD_STEADY;
+        return 0;
+    }
+    return -1;
+}
+
+static int apply_tot(int *enabled, int *max_key_ms, int *min_gap_ms,
+                     int *max_consecutive, int *max_bursts,
+                     const char *key, const char *val)
+{
+    if (strcmp(key, "tot") == 0 || strcmp(key, "tot_enabled") == 0) {
+        *enabled = truthy(val) ? 1 : 0;
+        return 0;
+    }
+    if (strcmp(key, "tot_max_key_sec") == 0 || strcmp(key, "tot_max_key_ms") == 0) {
+        if (strcmp(key, "tot_max_key_sec") == 0) {
+            int sec;
+            if (parse_i(val, &sec) != 0 || sec < 1) {
+                return -1;
+            }
+            *max_key_ms = sec * 1000;
+            return 0;
+        }
+        return parse_i(val, max_key_ms);
+    }
+    if (strcmp(key, "tot_min_gap_sec") == 0 || strcmp(key, "tot_min_gap_ms") == 0) {
+        if (strcmp(key, "tot_min_gap_sec") == 0) {
+            int sec;
+            if (parse_i(val, &sec) != 0 || sec < 0) {
+                return -1;
+            }
+            *min_gap_ms = sec * 1000;
+            return 0;
+        }
+        return parse_i(val, min_gap_ms);
+    }
+    if (strcmp(key, "tot_max_consecutive") == 0) {
+        return parse_i(val, max_consecutive);
+    }
+    if (strcmp(key, "tot_max_bursts") == 0) {
+        return parse_i(val, max_bursts);
+    }
+    return 1;
+}
+
+static int apply_wd_txd(int *ptt_wd, int *key_ms, int *pause_ms, int *txd_bias,
+                        const char *key, const char *val)
+{
+    if (strcmp(key, "ptt_wd") == 0 || strcmp(key, "ptt_watchdog") == 0) {
+        *ptt_wd = truthy(val) ? 1 : 0;
+        return 0;
+    }
+    if (strcmp(key, "ptt_wd_key_ms") == 0) {
+        return parse_i(val, key_ms);
+    }
+    if (strcmp(key, "ptt_wd_pause_ms") == 0) {
+        return parse_i(val, pause_ms);
+    }
+    if (strcmp(key, "txd_bias") == 0) {
+        return parse_txd_bias(val, txd_bias);
+    }
+    return 1; /* not handled */
+}
+
+static void normalize_legacy_path(char *buf, size_t len)
+{
+    static const struct {
+        const char *from;
+        const char *to;
+    } map[] = {
+        {"/tmp/bcpr/", "/tmp/max25-bcpr/"},
+        {"/tmp/bcpr", "/tmp/max25-bcpr"},
+        {"/var/run/bcpr/", "/tmp/max25-bcpr/"},
+        {"/var/run/bcpr", "/tmp/max25-bcpr"},
+    };
+    size_t i;
+    size_t flen;
+    if (!buf || !len || !buf[0]) {
+        return;
+    }
+    for (i = 0; i < sizeof(map) / sizeof(map[0]); i++) {
+        flen = strlen(map[i].from);
+        if (strncmp(buf, map[i].from, flen) != 0) {
+            continue;
+        }
+        if (buf[flen] != '\0' && buf[flen] != '/') {
+            continue;
+        }
+        {
+            char tmp[256];
+            snprintf(tmp, sizeof(tmp), "%s%s", map[i].to, buf + flen);
+            snprintf(buf, len, "%s", tmp);
+        }
+        return;
+    }
+}
+
+static int apply_kv(bcpr_config_t *cfg, int section, const char *key,
+                    const char *val)
+{
+    /* section: -1 = [max25-bcpr]/[bcpr] global, 0 = bc0, 1 = bc1 */
+    if (section < 0) {
+        int rc;
+        if (strcmp(key, "dry_run") == 0) {
+            cfg->dry_run = truthy(val);
+            return 0;
+        }
+        if (strcmp(key, "state_dir") == 0) {
+            snprintf(cfg->state_dir, sizeof(cfg->state_dir), "%s", val);
+            return 0;
+        }
+        if (strcmp(key, "user") == 0) {
+            snprintf(cfg->run_user, sizeof(cfg->run_user), "%s", val);
+            return 0;
+        }
+        if (strcmp(key, "group") == 0) {
+            snprintf(cfg->run_group, sizeof(cfg->run_group), "%s", val);
+            return 0;
+        }
+        rc = apply_wd_txd(&cfg->ptt_wd, &cfg->ptt_wd_key_ms,
+                          &cfg->ptt_wd_pause_ms, &cfg->txd_bias, key, val);
+        if (rc <= 0) {
+            /* Propagate global WD/TXD defaults onto both devices. */
+            int i;
+            for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+                cfg->dev[i].ptt_wd = cfg->ptt_wd;
+                cfg->dev[i].ptt_wd_key_ms = cfg->ptt_wd_key_ms;
+                cfg->dev[i].ptt_wd_pause_ms = cfg->ptt_wd_pause_ms;
+                cfg->dev[i].txd_bias = cfg->txd_bias;
+            }
+            return rc;
+        }
+        rc = apply_tot(&cfg->tot_enabled, &cfg->tot_max_key_ms, &cfg->tot_min_gap_ms,
+                       &cfg->tot_max_consecutive, &cfg->tot_max_bursts, key, val);
+        if (rc <= 0) {
+            int i;
+            for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+                cfg->dev[i].tot_enabled = cfg->tot_enabled;
+                cfg->dev[i].tot_max_key_ms = cfg->tot_max_key_ms;
+                cfg->dev[i].tot_min_gap_ms = cfg->tot_min_gap_ms;
+                cfg->dev[i].tot_max_consecutive = cfg->tot_max_consecutive;
+                cfg->dev[i].tot_max_bursts = cfg->tot_max_bursts;
+            }
+            return rc;
+        }
+        return 0;
+    }
+    if (section >= BCPR_MAX_DEVICES) {
+        return -1;
+    }
+    {
+        bcpr_dev_config_t *d = &cfg->dev[section];
+        int rc;
+        if (strcmp(key, "enabled") == 0) {
+            d->enabled = truthy(val);
+        } else if (strcmp(key, "serial") == 0 || strcmp(key, "tty") == 0) {
+            snprintf(d->serial, sizeof(d->serial), "%s", val);
+            d->enabled = 1;
+        } else if (strcmp(key, "iobase") == 0) {
+            return parse_u(val, &d->iobase);
+        } else if (strcmp(key, "irq") == 0) {
+            return parse_u(val, &d->irq);
+        } else if (strcmp(key, "baud") == 0) {
+            return parse_u(val, &d->baud);
+        } else if (strcmp(key, "mode") == 0) {
+            snprintf(d->mode, sizeof(d->mode), "%s", val);
+        } else if (strcmp(key, "kiss_link") == 0) {
+            snprintf(d->kiss_link, sizeof(d->kiss_link), "%s", val);
+        } else if (strcmp(key, "tx_delay") == 0 || strcmp(key, "txdelay") == 0) {
+            return parse_i(val, &d->tx_delay);
+        } else if (strcmp(key, "tx_tail") == 0 || strcmp(key, "txtail") == 0) {
+            return parse_i(val, &d->tx_tail);
+        } else if (strcmp(key, "slottime") == 0) {
+            return parse_i(val, &d->slottime);
+        } else if (strcmp(key, "ppersist") == 0) {
+            return parse_i(val, &d->ppersist);
+        } else if (strcmp(key, "fulldup") == 0) {
+            d->fulldup = truthy(val);
+        } else {
+            rc = apply_wd_txd(&d->ptt_wd, &d->ptt_wd_key_ms, &d->ptt_wd_pause_ms,
+                             &d->txd_bias, key, val);
+            if (rc < 0) {
+                return -1;
+            }
+            if (rc == 0) {
+                return 0;
+            }
+            rc = apply_tot(&d->tot_enabled, &d->tot_max_key_ms, &d->tot_min_gap_ms,
+                           &d->tot_max_consecutive, &d->tot_max_bursts, key, val);
+            if (rc < 0) {
+                return -1;
+            }
+            if (rc == 0) {
+                return 0;
+            }
+        }
+    }
+    return 0;
+}
+
+int bcpr_config_load(bcpr_config_t *cfg, const char *path)
+{
+    FILE *f;
+    char line[512];
+    int section = -1;
+    int i;
+
+    if (!cfg || !path) {
+        return -1;
+    }
+    bcpr_config_defaults(cfg);
+    f = fopen(path, "r");
+    if (!f) {
+        return -1;
+    }
+    while (fgets(line, sizeof(line), f)) {
+        char *eq;
+        char *p = line;
+        trim(p);
+        if (p[0] == '\0' || p[0] == '#' || p[0] == ';') {
+            continue;
+        }
+        if (p[0] == '[') {
+            char *end = strchr(p, ']');
+            if (!end) {
+                continue;
+            }
+            *end = '\0';
+            p++;
+            if (strcasecmp(p, "max25-bcpr") == 0 || strcasecmp(p, "bcpr") == 0 ||
+                strcasecmp(p, "global") == 0) {
+                section = -1;
+            } else if (strcasecmp(p, "bc0") == 0 ||
+                       strcasecmp(p, "device.bc0") == 0) {
+                section = 0;
+            } else if (strcasecmp(p, "bc1") == 0 ||
+                       strcasecmp(p, "device.bc1") == 0) {
+                section = 1;
+            } else {
+                section = -2; /* ignore unknown */
+            }
+            continue;
+        }
+        if (section == -2) {
+            continue;
+        }
+        eq = strchr(p, '=');
+        if (!eq) {
+            continue;
+        }
+        *eq = '\0';
+        trim(p);
+        trim(eq + 1);
+        (void)apply_kv(cfg, section, p, eq + 1);
+    }
+    fclose(f);
+
+    normalize_legacy_path(cfg->state_dir, sizeof(cfg->state_dir));
+
+    cfg->n_dev = 0;
+    for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+        if (cfg->dev[i].enabled && cfg->dev[i].serial[0]) {
+            if (!cfg->dev[i].kiss_link[0]) {
+                snprintf(cfg->dev[i].kiss_link, sizeof(cfg->dev[i].kiss_link),
+                         "%s/kiss-bc%d", cfg->state_dir, i);
+            }
+            normalize_legacy_path(cfg->dev[i].kiss_link,
+                                  sizeof(cfg->dev[i].kiss_link));
+            /* Clamp WD timings. */
+            if (cfg->dev[i].ptt_wd_key_ms < 1000) {
+                cfg->dev[i].ptt_wd_key_ms = 1000;
+            }
+            if (cfg->dev[i].ptt_wd_pause_ms < 50) {
+                cfg->dev[i].ptt_wd_pause_ms = 50;
+            }
+            if (cfg->dev[i].txd_bias != BCPR_TXD_STEADY) {
+                cfg->dev[i].txd_bias = BCPR_TXD_PULSE;
+            }
+            if (cfg->dev[i].tot_max_key_ms < 1000) {
+                cfg->dev[i].tot_max_key_ms = 1000;
+            }
+            if (cfg->dev[i].tot_min_gap_ms < 0) {
+                cfg->dev[i].tot_min_gap_ms = 0;
+            }
+            if (cfg->dev[i].tot_max_consecutive < 1) {
+                cfg->dev[i].tot_max_consecutive = 1;
+            }
+            if (cfg->dev[i].tot_max_bursts < 1) {
+                cfg->dev[i].tot_max_bursts = 1;
+            }
+            cfg->n_dev++;
+        } else {
+            cfg->dev[i].enabled = 0;
+        }
+    }
+    if (cfg->n_dev > BCPR_MAX_DEVICES) {
+        return -1;
+    }
+    return 0;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_crc.c b/stacks/max25-bcpr/src/bcpr_crc.c
new file mode 100644
index 0000000..6aabc49
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_crc.c
@@ -0,0 +1,55 @@
+#include "bcpr/bcpr_crc.h"
+
+/* CRC-CCITT poly 0x8408 reflected (hdlcdrv / WAMPES style via crc_ccitt). */
+static const uint16_t bcpr_crc_table[256] = {
+    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48,
+    0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108,
+    0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb,
+    0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399,
+    0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e,
+    0xfae7, 0xc87c, 0xd9f5, 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e,
+    0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd,
+    0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
+    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285,
+    0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44,
+    0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 0x6306, 0x728f, 0x4014,
+    0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5,
+    0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3,
+    0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862,
+    0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e,
+    0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
+    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1,
+    0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483,
+    0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50,
+    0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710,
+    0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7,
+    0x6e6e, 0x5cf5, 0x4d7c, 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1,
+    0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72,
+    0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
+    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e,
+    0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf,
+    0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 0xf78f, 0xe606, 0xd49d,
+    0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c,
+    0x3de3, 0x2c6a, 0x1ef1, 0x0f78
+};
+
+uint16_t bcpr_crc_ccitt(uint16_t crc, const uint8_t *buf, size_t len)
+{
+    while (len--) {
+        crc = (crc >> 8) ^ bcpr_crc_table[(crc ^ *buf++) & 0xff];
+    }
+    return crc;
+}
+
+void bcpr_append_crc_ccitt(uint8_t *buffer, int len)
+{
+    unsigned int crc = bcpr_crc_ccitt(0xffff, buffer, (size_t)len) ^ 0xffff;
+    buffer += len;
+    *buffer++ = (uint8_t)(crc & 0xff);
+    *buffer++ = (uint8_t)(crc >> 8);
+}
+
+int bcpr_check_crc_ccitt(const uint8_t *buf, int cnt)
+{
+    return (bcpr_crc_ccitt(0xffff, buf, (size_t)cnt) & 0xffff) == 0xf0b8;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_daemon.c b/stacks/max25-bcpr/src/bcpr_daemon.c
new file mode 100644
index 0000000..9019159
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_daemon.c
@@ -0,0 +1,289 @@
+/*
+ * Shared max25-bcprd run loop (KISS thread + SER12 engine).
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_daemon.h"
+#include "bcpr/bcpr_ser12.h"
+
+#include <errno.h>
+#include <poll.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+static volatile sig_atomic_t g_stop;
+
+static void on_sig(int sig)
+{
+    (void)sig;
+    g_stop = 1;
+}
+
+static void kiss_write_frame(int fd, const uint8_t *kiss, int len)
+{
+    uint8_t out[BCPR_MAXFLEN * 2 + 4];
+    int o = 0;
+    int i;
+
+    if (fd < 0 || !kiss || len <= 0) {
+        return;
+    }
+    out[o++] = 0xC0;
+    for (i = 0; i < len && o < (int)sizeof(out) - 2; i++) {
+        if (kiss[i] == 0xC0) {
+            out[o++] = 0xDB;
+            out[o++] = 0xDC;
+        } else if (kiss[i] == 0xDB) {
+            out[o++] = 0xDB;
+            out[o++] = 0xDD;
+        } else {
+            out[o++] = kiss[i];
+        }
+    }
+    out[o++] = 0xC0;
+    (void)write(fd, out, (size_t)o);
+}
+
+static bcpr_kiss_pty_t *g_pty;
+static int g_npty;
+
+static void on_rx(int dev_idx, const uint8_t *kiss, int len, void *ud)
+{
+    int i;
+    (void)ud;
+    for (i = 0; i < g_npty; i++) {
+        if (g_pty[i].idx == dev_idx) {
+            kiss_write_frame(g_pty[i].master_fd, kiss, len);
+            return;
+        }
+    }
+}
+
+static void kiss_feed(bcpr_engine_t *e, bcpr_kiss_pty_t *kp)
+{
+    static uint8_t acc[BCPR_MAX_DEVICES][BCPR_MAXFLEN + 8];
+    static int alen[BCPR_MAX_DEVICES];
+    static int esc[BCPR_MAX_DEVICES];
+    static int in_frame[BCPR_MAX_DEVICES];
+    uint8_t buf[512];
+    ssize_t n;
+    int i;
+    int di = kp->idx;
+
+    if (di < 0 || di >= BCPR_MAX_DEVICES) {
+        return;
+    }
+    n = read(kp->master_fd, buf, sizeof(buf));
+    if (n <= 0) {
+        return;
+    }
+    for (i = 0; i < (int)n; i++) {
+        uint8_t b = buf[i];
+        if (!in_frame[di]) {
+            if (b == 0xC0) {
+                in_frame[di] = 1;
+                alen[di] = 0;
+                esc[di] = 0;
+            }
+            continue;
+        }
+        if (esc[di]) {
+            esc[di] = 0;
+            if (b == 0xDC) {
+                b = 0xC0;
+            } else if (b == 0xDD) {
+                b = 0xDB;
+            }
+            if (alen[di] < (int)sizeof(acc[di])) {
+                acc[di][alen[di]++] = b;
+            }
+            continue;
+        }
+        if (b == 0xDB) {
+            esc[di] = 1;
+            continue;
+        }
+        if (b == 0xC0) {
+            if (alen[di] >= 2) {
+                int q;
+                int w;
+                for (w = 0; w < 70; w++) {
+                    q = bcpr_engine_queue_kiss(e, di, acc[di], alen[di]);
+                    if (q == 0) {
+                        break;
+                    }
+                    usleep(50000);
+                }
+                if (q != 0) {
+                    fprintf(stderr,
+                            "max25-bcprd: queue_kiss drop bc%d len=%d (busy)\n",
+                            di, alen[di]);
+                }
+            }
+            in_frame[di] = 0;
+            alen[di] = 0;
+            continue;
+        }
+        if (alen[di] < (int)sizeof(acc[di])) {
+            acc[di][alen[di]++] = b;
+        }
+    }
+}
+
+static void *kiss_thread(void *arg)
+{
+    bcpr_engine_t *e = (bcpr_engine_t *)arg;
+
+    while (!g_stop && !e->stop) {
+        struct pollfd pf[BCPR_MAX_DEVICES];
+        int nf = 0;
+        int map[BCPR_MAX_DEVICES];
+        int i;
+        int ret;
+        int backoff = 0;
+
+        for (i = 0; i < g_npty; i++) {
+            if (g_pty[i].master_fd < 0) {
+                continue;
+            }
+            pf[nf].fd = g_pty[i].master_fd;
+            pf[nf].events = POLLIN | POLLHUP | POLLERR;
+            map[nf] = i;
+            nf++;
+        }
+        if (nf == 0) {
+            usleep(50000);
+            continue;
+        }
+        ret = poll(pf, (nfds_t)nf, 50);
+        if (ret <= 0) {
+            continue;
+        }
+        for (i = 0; i < nf; i++) {
+            short re = pf[i].revents;
+            if (re & POLLIN) {
+                kiss_feed(e, &g_pty[map[i]]);
+            }
+            if (re & (POLLHUP | POLLERR | POLLNVAL)) {
+                backoff = 1;
+            }
+        }
+        if (backoff) {
+            usleep(50000);
+        }
+    }
+    return NULL;
+}
+
+static int ensure_dir(const char *path)
+{
+    char tmp[256];
+    char *p;
+    size_t len;
+
+    if (!path || !path[0]) {
+        return -1;
+    }
+    snprintf(tmp, sizeof(tmp), "%s", path);
+    len = strlen(tmp);
+    if (len == 0) {
+        return -1;
+    }
+    if (tmp[len - 1] == '/') {
+        tmp[len - 1] = '\0';
+    }
+    for (p = tmp + 1; *p; p++) {
+        if (*p == '/') {
+            *p = '\0';
+            (void)mkdir(tmp, 0755);
+            *p = '/';
+        }
+    }
+    return mkdir(tmp, 0755) == 0 || errno == EEXIST ? 0 : -1;
+}
+
+int bcpr_daemon_run(bcpr_config_t *cfg, bcpr_kiss_pty_t *ptys, int npty,
+                    bcpr_engine_t *engine, const bcpr_daemon_opts_t *opts)
+{
+    pthread_t thr;
+    int thr_ok = 0;
+    int i;
+    bcpr_engine_t local_engine;
+    bcpr_engine_t *e = engine;
+    int cal_mode;
+    int seconds;
+
+    if (!cfg || !opts) {
+        return 1;
+    }
+
+    g_stop = 0;
+    g_pty = ptys;
+    g_npty = npty;
+    cal_mode = opts->cal_mode;
+    seconds = opts->seconds;
+
+    signal(SIGINT, on_sig);
+    signal(SIGTERM, on_sig);
+
+    for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+        if (opts->cli_txd_bias >= 0) {
+            cfg->dev[i].txd_bias = opts->cli_txd_bias;
+        }
+        if (opts->cli_ptt_wd >= 0) {
+            cfg->dev[i].ptt_wd = opts->cli_ptt_wd;
+        }
+        if (opts->cli_ptt_wd_key_ms > 0) {
+            cfg->dev[i].ptt_wd_key_ms = opts->cli_ptt_wd_key_ms;
+        }
+        if (opts->cli_ptt_wd_pause_ms > 0) {
+            cfg->dev[i].ptt_wd_pause_ms = opts->cli_ptt_wd_pause_ms;
+        }
+    }
+
+    (void)ensure_dir(cfg->state_dir);
+
+    if (!opts->engine_preopened) {
+        e = &local_engine;
+        if (bcpr_engine_open(e, cfg) != 0) {
+            for (i = 0; i < npty; i++) {
+                bcpr_kiss_pty_close(&ptys[i]);
+            }
+            return 1;
+        }
+    }
+
+    e->run_seconds = seconds;
+    if (cal_mode != BCPR_CAL_OFF) {
+        bcpr_engine_set_cal(e, cal_mode);
+    }
+    bcpr_engine_set_rx(e, on_rx, NULL);
+
+    if (npty > 0 && cal_mode == BCPR_CAL_OFF &&
+        pthread_create(&thr, NULL, kiss_thread, e) == 0) {
+        thr_ok = 1;
+    }
+
+    if (cal_mode != BCPR_CAL_OFF && !cfg->dry_run) {
+        fprintf(stderr,
+                "bcprd: *** WATCH NOW *** cal PTT+tone for %d s — then unkey\n",
+                seconds);
+    }
+
+    (void)bcpr_engine_run(e);
+
+    g_stop = 1;
+    e->stop = 1;
+    if (thr_ok) {
+        pthread_join(thr, NULL);
+    }
+    bcpr_engine_close(e);
+    for (i = 0; i < npty; i++) {
+        bcpr_kiss_pty_close(&ptys[i]);
+    }
+    fprintf(stderr, "max25-bcprd: stopped\n");
+    return 0;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_engine.c b/stacks/max25-bcpr/src/bcpr_engine.c
new file mode 100644
index 0000000..2367817
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_engine.c
@@ -0,0 +1,652 @@
+/*
+ * Bit-clock engine: RT timer loop drives SER12 + HDLC for up to 2 devices.
+ * Userspace timing (not kernel hard-IRQ). See NOTICE.md.
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_engine.h"
+#include "bcpr/bcpr_uart.h"
+#include "bcpr/bcpr_hdlc.h"
+#include "bcpr/bcpr_ser12.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#if defined(__linux__)
+#include <pthread.h>
+#include <sched.h>
+#include <sys/mman.h>
+#endif
+
+typedef struct {
+    bcpr_engine_t *e;
+    int idx;
+} rx_ctx_t;
+
+static unsigned now_us(void)
+{
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    /* Full monotonic µs — not nsec-within-second (gap spikes were misread). */
+    return (unsigned)(ts.tv_sec * 1000000ull + (unsigned long long)ts.tv_nsec / 1000ull);
+}
+
+/* Idle longer than this resets consecutive-burst counting (new session). */
+#define TOT_SESSION_RESET_US 120000000u
+
+static void tot_write_trip_file(const bcpr_engine_t *e, const bcpr_device_t *d,
+                                const char *reason)
+{
+    char path[192];
+    FILE *f;
+
+    if (!e || !d || e->cfg.dry_run || e->cfg.state_dir[0] == '\0') {
+        return;
+    }
+    snprintf(path, sizeof(path), "%s/tot-trip-bc%d", e->cfg.state_dir, d->index);
+    f = fopen(path, "w");
+    if (!f) {
+        return;
+    }
+    fprintf(f,
+            "reason=%s\nburst_total=%d\nconsecutive=%d\ntripped=1\n"
+            "max_key_ms=%d\nmax_bursts=%d\nmax_consecutive=%d\n",
+            reason ? reason : "unknown", d->tot_burst_total, d->tot_consecutive,
+            d->cfg.tot_max_key_ms, d->cfg.tot_max_bursts,
+            d->cfg.tot_max_consecutive);
+    fclose(f);
+}
+
+static void tot_trip(bcpr_engine_t *e, bcpr_device_t *d, const char *reason)
+{
+    if (!d || d->tot_tripped) {
+        return;
+    }
+    d->tot_tripped = 1;
+    bcpr_ser12_force_unkey(&d->ser12);
+    bcpr_hdlc_abort_tx(&d->hdlc);
+    fprintf(stderr,
+            "bcpr: bc%d TOT TRIP reason=%s bursts=%d consecutive=%d\n",
+            d->index, reason ? reason : "unknown", d->tot_burst_total,
+            d->tot_consecutive);
+    tot_write_trip_file(e, d, reason);
+}
+
+static void tot_on_ptt_rise(bcpr_engine_t *e, bcpr_device_t *d, unsigned now_us)
+{
+    unsigned gap_us;
+
+    if (!d->cfg.tot_enabled || d->tot_tripped) {
+        return;
+    }
+    d->tot_key_start_us = now_us;
+    if (d->tot_last_off_us == 0u) {
+        d->tot_consecutive = 1;
+        return;
+    }
+    gap_us = now_us - d->tot_last_off_us;
+    if (gap_us >= (unsigned)d->cfg.tot_min_gap_ms * 1000u) {
+        if (gap_us < TOT_SESSION_RESET_US) {
+            d->tot_consecutive++;
+        } else {
+            d->tot_consecutive = 1;
+            d->tot_burst_total = 0;
+        }
+    }
+    if (d->tot_consecutive > d->cfg.tot_max_consecutive) {
+        tot_trip(e, d, "max_consecutive");
+    }
+}
+
+static void tot_on_ptt_fall(bcpr_engine_t *e, bcpr_device_t *d, unsigned now_us)
+{
+    if (!d->cfg.tot_enabled || d->tot_tripped) {
+        return;
+    }
+    d->tot_last_off_us = now_us;
+    d->tot_burst_total++;
+    if (d->tot_burst_total >= d->cfg.tot_max_bursts) {
+        tot_trip(e, d, "max_bursts");
+    }
+}
+
+static void tot_check_key_duration(bcpr_engine_t *e, bcpr_device_t *d,
+                                   unsigned now_us)
+{
+    unsigned elapsed_us;
+    unsigned max_us;
+
+    if (!d->cfg.tot_enabled || d->tot_tripped || !d->ptt_was) {
+        return;
+    }
+    if (d->tot_key_start_us == 0u) {
+        d->tot_key_start_us = now_us;
+        return;
+    }
+    max_us = (unsigned)d->cfg.tot_max_key_ms * 1000u;
+    elapsed_us = now_us - d->tot_key_start_us;
+    if (elapsed_us >= max_us) {
+        bcpr_ser12_force_unkey(&d->ser12);
+        bcpr_hdlc_abort_tx(&d->hdlc);
+        tot_on_ptt_fall(e, d, now_us);
+        tot_trip(e, d, "max_key");
+    }
+}
+
+static void on_frame_ctx(const uint8_t *kiss, int len, void *ud)
+{
+    rx_ctx_t *ctx = (rx_ctx_t *)ud;
+    if (ctx && ctx->e && ctx->e->on_rx) {
+        ctx->e->on_rx(ctx->idx, kiss, len, ctx->e->on_rx_ud);
+    }
+}
+
+void bcpr_engine_set_rx(bcpr_engine_t *e, bcpr_rx_fn fn, void *ud)
+{
+    if (!e) {
+        return;
+    }
+    e->on_rx = fn;
+    e->on_rx_ud = ud;
+}
+
+int bcpr_engine_queue_kiss(bcpr_engine_t *e, int dev_idx, const uint8_t *kiss,
+                           int len)
+{
+    int i;
+    static unsigned last_tx_us;
+    unsigned now;
+    unsigned elapsed;
+
+    if (!e || !kiss) {
+        return -1;
+    }
+    now = now_us();
+    if (last_tx_us != 0u) {
+        elapsed = now - last_tx_us;
+        if (elapsed < 1500000u) {
+            usleep(1500000u - elapsed);
+        }
+    }
+    last_tx_us = now_us();
+    for (i = 0; i < e->n; i++) {
+        if (e->dev[i].index == dev_idx) {
+            if (e->dev[i].tot_tripped) {
+                fprintf(stderr, "bcpr: bc%d TOT drop queue_kiss (tripped)\n",
+                        dev_idx);
+                return -1;
+            }
+            return bcpr_hdlc_queue_kiss(&e->dev[i].hdlc, kiss, len);
+        }
+    }
+    return -1;
+}
+
+int bcpr_engine_open(bcpr_engine_t *e, const bcpr_config_t *cfg)
+{
+    int i;
+    int n = 0;
+
+    if (!e || !cfg) {
+        return -1;
+    }
+    memset(e, 0, sizeof(*e));
+    e->cfg = *cfg;
+    e->stop = 0;
+    e->run_seconds = 0;
+    bcpr_uart_set_dry_run(cfg->dry_run);
+
+    for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+        bcpr_device_t *d;
+        bcpr_channel_t ch;
+        unsigned baud = 1200;
+        int opt_dcd = 0;
+
+        if (!cfg->dev[i].enabled) {
+            continue;
+        }
+        d = &e->dev[n];
+        memset(d, 0, sizeof(*d));
+        d->cfg = cfg->dev[i];
+        d->index = i;
+        d->running = 0;
+
+        if (bcpr_lock_acquire(&d->lock, &d->cfg, cfg->dry_run) != 0) {
+            fprintf(stderr, "bcpr: lock failed for max25e0:bc%d\n", i);
+            bcpr_engine_close(e);
+            return -1;
+        }
+
+        bcpr_ser12_set_mode(&d->ser12, d->cfg.mode, &baud);
+        if (d->cfg.baud) {
+            baud = d->cfg.baud;
+        }
+        opt_dcd = d->ser12.opt_dcd;
+        bcpr_ser12_init(&d->ser12, baud, opt_dcd);
+        bcpr_ser12_set_ptt_wd(&d->ser12, d->cfg.ptt_wd, d->cfg.ptt_wd_key_ms,
+                              d->cfg.ptt_wd_pause_ms);
+
+        ch.tx_delay = d->cfg.tx_delay;
+        ch.tx_tail = d->cfg.tx_tail;
+        ch.slottime = d->cfg.slottime;
+        ch.ppersist = d->cfg.ppersist;
+        ch.fulldup = d->cfg.fulldup;
+        bcpr_hdlc_init(&d->hdlc, (int)baud, &ch);
+
+        if (!cfg->dry_run) {
+            if (bcpr_uart_ioperm(d->cfg.iobase, 1) != 0) {
+                fprintf(stderr, "bcpr: ioperm failed 0x%x\n", d->cfg.iobase);
+                bcpr_engine_close(e);
+                return -1;
+            }
+            bcpr_uart_set_divisor(d->cfg.iobase, 115200u / 100u / 8u);
+            bcpr_uart_open_ser12(d->cfg.iobase);
+            /*
+             * txd_bias=steady: assert UART break after open (LCR.SB).
+             * THR framing cannot hold DC-steady TXD; break ≈ TFPCX +12 V.
+             * Default remains pulse (Sailer THR 0x00). MCR unchanged.
+             */
+            if (d->cfg.txd_bias == BCPR_TXD_STEADY) {
+                bcpr_uart_set_break(d->cfg.iobase, 1);
+                d->break_set = 1;
+            }
+        }
+        d->running = 1;
+        n++;
+    }
+    e->n = n;
+    if (n == 0) {
+        fprintf(stderr, "bcpr: no enabled devices in config\n");
+        return -1;
+    }
+    fprintf(stderr, "bcpr: open max25e0 (%d device%s)%s\n", n,
+            n == 1 ? "" : "s", cfg->dry_run ? " [dry-run]" : "");
+    for (i = 0; i < n; i++) {
+        const bcpr_device_t *d = &e->dev[i];
+        fprintf(stderr,
+                "bcpr: bc%d ptt_wd=%s key_ms=%d pause_ms=%d txd_bias=%s tot=%s "
+                "max_key_ms=%d max_consecutive=%d max_bursts=%d\n",
+                d->index, d->cfg.ptt_wd ? "on" : "off", d->cfg.ptt_wd_key_ms,
+                d->cfg.ptt_wd_pause_ms,
+                d->cfg.txd_bias == BCPR_TXD_STEADY ? "steady" : "pulse",
+                d->cfg.tot_enabled ? "on" : "off", d->cfg.tot_max_key_ms,
+                d->cfg.tot_max_consecutive, d->cfg.tot_max_bursts);
+    }
+    return 0;
+}
+
+void bcpr_engine_close(bcpr_engine_t *e)
+{
+    int i;
+    if (!e) {
+        return;
+    }
+    e->stop = 1;
+    for (i = 0; i < e->n; i++) {
+        bcpr_device_t *d = &e->dev[i];
+        if (d->running && !e->cfg.dry_run) {
+            if (d->break_set) {
+                bcpr_uart_set_break(d->cfg.iobase, 0);
+                d->break_set = 0;
+            }
+            bcpr_uart_close_ser12(d->cfg.iobase);
+            (void)bcpr_uart_ioperm(d->cfg.iobase, 0);
+        }
+        bcpr_lock_release(&d->lock);
+        d->running = 0;
+    }
+    e->n = 0;
+}
+
+static void try_rt(void)
+{
+#if defined(__linux__)
+    struct sched_param sp;
+    cpu_set_t set;
+    int rc;
+    memset(&sp, 0, sizeof(sp));
+    /* Pin pages — fault during PTT = multi-ms TXD gap → pump collapse. */
+    if (mlockall(MCL_CURRENT | MCL_FUTURE) != 0) {
+        fprintf(stderr, "bcpr: mlockall failed errno=%d (page faults risk gaps)\n",
+                errno);
+    }
+    /* Prefer one CPU — migration mid-PTT causes multi-ms gaps. */
+    CPU_ZERO(&set);
+    CPU_SET(0, &set);
+    if (sched_setaffinity(0, sizeof(set), &set) != 0) {
+        fprintf(stderr, "bcpr: sched_setaffinity(0) errno=%d\n", errno);
+    }
+    /*
+     * High FIFO while bit-clocking — charge-pump cannot tolerate ms preemption.
+     * Needs root or CAP_SYS_NICE; log hard if denied (S1++ gaps often follow).
+     */
+    sp.sched_priority = 80;
+    rc = sched_setscheduler(0, SCHED_FIFO, &sp);
+    if (rc != 0) {
+        sp.sched_priority = 50;
+        rc = pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp);
+    }
+    if (rc != 0) {
+        sp.sched_priority = 10;
+        rc = pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp);
+    }
+    if (rc != 0) {
+        fprintf(stderr,
+                "bcpr: SCHED_FIFO failed errno=%d — expect max_gap multi-ms "
+                "(need root/CAP_SYS_NICE for bcprd)\n",
+                errno);
+    } else {
+        fprintf(stderr, "bcpr: SCHED_FIFO ok prio=%d cpu0\n", sp.sched_priority);
+    }
+#endif
+}
+
+void bcpr_engine_set_cal(bcpr_engine_t *e, int cal_mode)
+{
+    int i;
+    if (!e) {
+        return;
+    }
+    if (cal_mode < BCPR_CAL_OFF || cal_mode > BCPR_CAL_ALT) {
+        cal_mode = BCPR_CAL_OFF;
+    }
+    e->cal_mode = cal_mode;
+    for (i = 0; i < e->n; i++) {
+        bcpr_ser12_set_cal(&e->dev[i].ser12, cal_mode);
+    }
+}
+
+static int64_t now_ns(void)
+{
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return (int64_t)ts.tv_sec * 1000000000LL + (int64_t)ts.tv_nsec;
+}
+
+static void emit_tx_telemetry(const bcpr_engine_t *e, bcpr_device_t *d,
+                              int64_t ptt_off_ns)
+{
+    char path[192];
+    FILE *f;
+    int64_t dur_ns;
+    unsigned mean_gap = 0;
+    double thr_rate = 0.0;
+    double ptt_ms;
+
+    if (!d || !e) {
+        return;
+    }
+    dur_ns = ptt_off_ns - d->ptt_on_ns;
+    if (dur_ns < 0) {
+        dur_ns = 0;
+    }
+    ptt_ms = (double)dur_ns / 1.0e6;
+    if (d->tick_count > 0) {
+        mean_gap = (unsigned)(d->gap_sum_us / d->tick_count);
+    }
+    if (ptt_ms > 0.5) {
+        thr_rate = (double)d->thr_writes * 1000.0 / ptt_ms;
+    }
+    fprintf(stderr,
+            "bcpr: tx-telemetry bc%d ptt_ms=%.1f thr_writes=%u thr_rate=%.0f "
+            "max_tick_gap_us=%u mean_gap_us=%u gaps_gt_2x=%u baud_us=%u\n",
+            d->index, ptt_ms, d->thr_writes, thr_rate, d->max_tick_gap_us,
+            mean_gap, d->gaps_gt_2x, d->ser12.baud_us);
+    if (e->cfg.dry_run || e->cfg.state_dir[0] == '\0') {
+        return;
+    }
+    snprintf(path, sizeof(path), "%s/tx-last-bc%d", e->cfg.state_dir, d->index);
+    f = fopen(path, "w");
+    if (!f) {
+        return;
+    }
+    fprintf(f,
+            "ptt_on_ns=%lld\nptt_off_ns=%lld\nptt_ms=%.1f\nthr_writes=%u\n"
+            "thr_rate=%.0f\nmax_tick_gap_us=%u\nmean_gap_us=%u\n"
+            "gaps_gt_2x=%u\nbaud_us=%u\ntick_count=%u\n",
+            (long long)d->ptt_on_ns, (long long)ptt_off_ns, ptt_ms,
+            d->thr_writes, thr_rate, d->max_tick_gap_us, mean_gap,
+            d->gaps_gt_2x, d->ser12.baud_us, d->tick_count);
+    fclose(f);
+}
+
+static unsigned tx_baud_div(const bcpr_device_t *d)
+{
+    unsigned baud = d->ser12.baud ? d->ser12.baud : 1200u;
+    unsigned div = (115200u / 8u) / baud;
+    return div ? div : 1u;
+}
+
+static void tick_device(bcpr_engine_t *e, bcpr_device_t *d, rx_ctx_t *ctx)
+{
+    int cts = 0;
+    int mcr = 0x0d;
+    int do_thr = 0;
+    unsigned t = now_us();
+    int ptt;
+    int keyed = d->ptt_was; /* already in TX — keep path minimal for TXD pump */
+
+    if (!e->cfg.dry_run && !keyed) {
+        unsigned char msr = bcpr_uart_msr(d->cfg.iobase);
+        cts = (msr & 0x10) ? 1 : 0;
+        if (d->ser12.opt_dcd > 0) {
+            d->hdlc.dcd = (msr & 0x80) ? 1 : 0;
+        } else if (d->ser12.opt_dcd < 0) {
+            d->hdlc.dcd = (msr & 0x80) ? 0 : 1;
+        }
+    }
+
+    /* S0: tick-gap while PTT keyed (full monotonic µs; unsigned wrap OK). */
+    if (d->ptt_was && d->last_tick_us) {
+        unsigned gap = t - d->last_tick_us;
+        unsigned lim2;
+        if (gap > d->max_tick_gap_us) {
+            d->max_tick_gap_us = gap;
+        }
+        d->gap_sum_us += gap;
+        d->tick_count++;
+        lim2 = d->ser12.baud_us * 2u;
+        if (lim2 < 2u) {
+            lim2 = 2u;
+        }
+        if (gap > lim2) {
+            d->gaps_gt_2x++;
+        }
+    }
+    d->last_tick_us = t;
+
+    bcpr_ser12_tick(&d->ser12, &d->hdlc, cts, &mcr, &do_thr, t);
+    ptt = d->ser12.ptt_hw ? 1 : 0;
+
+    if (d->tot_tripped) {
+        bcpr_ser12_force_unkey(&d->ser12);
+        bcpr_hdlc_abort_tx(&d->hdlc);
+        ptt = 0;
+        mcr = 0x0d;
+    } else {
+        tot_check_key_duration(e, d, t);
+        ptt = d->ser12.ptt_hw ? 1 : 0;
+    }
+
+    if (ptt && !d->ptt_was) {
+        tot_on_ptt_rise(e, d, t);
+        d->ptt_on_ns = now_ns();
+        d->thr_writes = 0;
+        d->max_tick_gap_us = 0;
+        d->gap_sum_us = 0;
+        d->tick_count = 0;
+        d->gaps_gt_2x = 0;
+        d->last_tick_us = t;
+        d->tx_div_set = 0;
+    } else if (!ptt && d->ptt_was) {
+        if (!d->tot_tripped) {
+            tot_on_ptt_fall(e, d, t);
+        }
+        if (!e->cfg.dry_run) {
+            /* Match baycom_ser_fdx: idle divisor only on PTT fall. */
+            bcpr_uart_set_divisor(d->cfg.iobase, 115200u / 100u / 8u);
+            d->tx_div_set = 0;
+        }
+        emit_tx_telemetry(e, d, now_ns());
+    }
+    d->ptt_was = ptt;
+
+    if (!e->cfg.dry_run) {
+        /*
+         * S1++: set baud_uartdiv once on PTT rise (kernel ser12_fdx).
+         * Re-writing divisor every bit toggles DLAB mid-shift → intermittent
+         * TXD charge-pump starve while MCR RTS still keys (MCR PASS / no RF).
+         */
+        if (ptt && !d->tx_div_set) {
+            bcpr_uart_set_divisor(d->cfg.iobase, tx_baud_div(d));
+            d->tx_div_set = 1;
+        }
+        /* Kernel order: THR 0x00 first (charge-pump), then MCR bit+PTT.
+         * txd_bias=steady: skip THR — break already holds TXD SPACE;
+         * pulse is Sailer default (framing edges feed BayCom pump). */
+        if (d->cfg.txd_bias == BCPR_TXD_STEADY) {
+            if (!d->break_set) {
+                bcpr_uart_set_break(d->cfg.iobase, 1);
+                d->break_set = 1;
+            }
+            if (ptt) {
+                d->thr_writes++; /* count pump-equivalent ticks for telem */
+            }
+        } else {
+            if (d->break_set) {
+                bcpr_uart_set_break(d->cfg.iobase, 0);
+                d->break_set = 0;
+            }
+            if (do_thr) {
+                bcpr_uart_thr00(d->cfg.iobase);
+                if (ptt) {
+                    d->thr_writes++;
+                }
+            }
+        }
+        bcpr_uart_mcr(d->cfg.iobase, (unsigned char)mcr);
+    }
+
+    /* Defer HDLC RX drain while keyed — keeps bit deadline tight (S1+). */
+    if (!ptt) {
+        ctx->e = e;
+        ctx->idx = d->index;
+        bcpr_hdlc_receiver(&d->hdlc, on_frame_ctx, ctx);
+    }
+}
+
+/* Publish Soft-/hard-DCD for RX-before-TX gates (state_dir/dcd-bcN).
+ * Also refresh rx-activity-bcN whenever Soft-DCD is asserted so smoke/L3
+ * can delete-and-rewait without a permanent false miss when dcd flickers. */
+static void publish_dcd_status(const bcpr_engine_t *e)
+{
+    int i;
+    char path[192];
+    FILE *f;
+
+    if (!e || e->cfg.dry_run || e->cfg.state_dir[0] == '\0') {
+        return;
+    }
+    for (i = 0; i < e->n; i++) {
+        const bcpr_device_t *d = &e->dev[i];
+        int dcd = d->hdlc.dcd ? 1 : 0;
+        snprintf(path, sizeof(path), "%s/dcd-bc%d", e->cfg.state_dir, d->index);
+        f = fopen(path, "w");
+        if (f) {
+            fprintf(f, "dcd=%d\n", dcd);
+            fclose(f);
+        }
+        snprintf(path, sizeof(path), "%s/rx-activity-bc%d", e->cfg.state_dir,
+                 d->index);
+        f = fopen(path, "w");
+        if (f) {
+            /* Latch: dcd=1 → activity; dcd=0 clears so L3 needs live Soft-DCD. */
+            fprintf(f, "rx_activity=%d\n", dcd ? 1 : 0);
+            fclose(f);
+        }
+    }
+}
+
+int bcpr_engine_run(bcpr_engine_t *e)
+{
+    struct timespec next;
+    rx_ctx_t ctx;
+    time_t t0;
+    unsigned period_ns;
+    unsigned tick = 0;
+    int64_t bit_deadline_ns = 0;
+
+    if (!e || e->n <= 0) {
+        return -1;
+    }
+    try_rt();
+    t0 = time(NULL);
+    period_ns = e->dev[0].ser12.baud_us * 1000u;
+    if (period_ns < 100000u) {
+        period_ns = 833000u;
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &next);
+    while (!e->stop) {
+        int i;
+        int any_ptt = 0;
+        unsigned baud_us = e->dev[0].ser12.baud_us;
+
+        for (i = 0; i < e->n; i++) {
+            tick_device(e, &e->dev[i], &ctx);
+            if (e->dev[i].ser12.ptt_hw || e->dev[i].ptt_was) {
+                any_ptt = 1;
+            }
+        }
+        /* ~100 ms at 1200 baud — skip file I/O while PTT (stretches TXD gaps). */
+        if ((++tick % 120u) == 0u && !any_ptt) {
+            publish_dcd_status(e);
+        }
+
+        /*
+         * S1/S1+: while PTT, absolute bit deadline + busy-spin (not
+         * nanosleep). THRE wait alone stacks with tick work → ~2× baud gaps.
+         * Idle RX keeps absolute nanosleep schedule.
+         */
+        if (any_ptt && !e->cfg.dry_run) {
+            int64_t now;
+
+            if (baud_us < 200u) {
+                baud_us = 200u;
+            }
+            now = now_ns();
+            if (bit_deadline_ns == 0 ||
+                now > bit_deadline_ns + (int64_t)baud_us * 1000LL * 4) {
+                /* PTT edge / large slip — resync. */
+                bit_deadline_ns = now + (int64_t)baud_us * 1000LL;
+            } else {
+                bit_deadline_ns += (int64_t)baud_us * 1000LL;
+            }
+            /*
+             * Pure busy-spin to absolute bit deadline — no nanosleep, no
+             * wait_thre syscalls (those stacked gaps and starved the pump).
+             * Target: thr_writes ≈ baud for whole PTT; max_gap < ~2× baud_us.
+             */
+            while (now_ns() < bit_deadline_ns) {
+            }
+            clock_gettime(CLOCK_MONOTONIC, &next);
+        } else {
+            bit_deadline_ns = 0;
+            next.tv_nsec += (long)period_ns;
+            while (next.tv_nsec >= 1000000000L) {
+                next.tv_nsec -= 1000000000L;
+                next.tv_sec++;
+            }
+            while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next,
+                                   NULL) == EINTR) {
+            }
+        }
+        if (e->run_seconds > 0 && (time(NULL) - t0) >= e->run_seconds) {
+            break;
+        }
+    }
+    return 0;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_hdlc.c b/stacks/max25-bcpr/src/bcpr_hdlc.c
new file mode 100644
index 0000000..09c8d32
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_hdlc.c
@@ -0,0 +1,293 @@
+#include "bcpr/bcpr_hdlc.h"
+#include "bcpr/bcpr_crc.h"
+
+#include <string.h>
+#include <stdlib.h>
+
+static int hbuf_empty(const bcpr_hbuf_t *hb)
+{
+    return hb->rd == hb->wr;
+}
+
+static int hbuf_full(const bcpr_hbuf_t *hb)
+{
+    return !((BCPR_HDLC_BUF - 1 + hb->rd - hb->wr) % BCPR_HDLC_BUF);
+}
+
+static void hbuf_put(bcpr_hbuf_t *hb, uint16_t val)
+{
+    unsigned newp = (hb->wr + 1) % BCPR_HDLC_BUF;
+    if (newp != hb->rd) {
+        hb->buf[hb->wr] = val;
+        hb->wr = newp;
+    }
+}
+
+static uint16_t hbuf_get(bcpr_hbuf_t *hb)
+{
+    uint16_t val;
+    if (hb->rd == hb->wr) {
+        return 0;
+    }
+    val = hb->buf[hb->rd];
+    hb->rd = (hb->rd + 1) % BCPR_HDLC_BUF;
+    return val;
+}
+
+#define tenms_to_2flags(h, tenms) (((tenms) * (h)->bitrate) / 100 / 16)
+
+void bcpr_hdlc_init(bcpr_hdlc_t *h, int bitrate, const bcpr_channel_t *ch)
+{
+    memset(h, 0, sizeof(*h));
+    h->bitrate = bitrate > 0 ? bitrate : 1200;
+    if (ch) {
+        h->ch = *ch;
+    } else {
+        h->ch.tx_delay = 35;
+        h->ch.tx_tail = 2;
+        h->ch.slottime = 10;
+        h->ch.ppersist = 40;
+        h->ch.fulldup = 0;
+    }
+    h->slotcnt = 1;
+    h->rx_bp = h->rx_buffer;
+    h->tx_bp = h->tx_buffer;
+}
+
+void bcpr_hdlc_putbits(bcpr_hdlc_t *h, unsigned bits)
+{
+    hbuf_put(&h->rx_hbuf, (uint16_t)(bits & 0xffff));
+}
+
+unsigned bcpr_hdlc_getbits(bcpr_hdlc_t *h)
+{
+    if (hbuf_empty(&h->tx_hbuf)) {
+        h->ptt = 0;
+        return 0;
+    }
+    return hbuf_get(&h->tx_hbuf);
+}
+
+int bcpr_hdlc_ptt(const bcpr_hdlc_t *h)
+{
+    return h->ptt;
+}
+
+void bcpr_hdlc_abort_tx(bcpr_hdlc_t *h)
+{
+    if (!h) {
+        return;
+    }
+    h->ptt = 0;
+    h->tx_state = 0;
+    h->numflags = 0;
+    h->tx_bitstream = 0;
+    h->tx_bitbuf = 0;
+    h->tx_numbits = 0;
+    h->tx_len = 0;
+    h->tx_bp = h->tx_buffer;
+    h->have_pending = 0;
+    h->pending_len = 0;
+    h->tx_hbuf.rd = h->tx_hbuf.wr;
+}
+
+int bcpr_hdlc_queue_kiss(bcpr_hdlc_t *h, const uint8_t *kiss, int len)
+{
+    if (!kiss || len < 2 || len - 1 > BCPR_MAXFLEN) {
+        return -1;
+    }
+    if (h->have_pending || h->ptt) {
+        return -1;
+    }
+    /* strip KISS command byte */
+    memcpy(h->pending, kiss + 1, (size_t)(len - 1));
+    h->pending_len = len - 1;
+    h->have_pending = 1;
+    return 0;
+}
+
+static int hdlc_rx_add_bytes(bcpr_hdlc_t *h, unsigned bits, int num)
+{
+    int added = 0;
+    while (h->rx_state && num >= 8) {
+        if (h->rx_len >= (int)sizeof(h->rx_buffer)) {
+            h->rx_state = 0;
+            return 0;
+        }
+        *h->rx_bp++ = (uint8_t)(bits >> (32 - num));
+        h->rx_len++;
+        num -= 8;
+        added += 8;
+    }
+    return added;
+}
+
+static void hdlc_rx_flag(bcpr_hdlc_t *h,
+                         void (*on_frame)(const uint8_t *kiss, int len, void *ud),
+                         void *ud)
+{
+    uint8_t kiss[BCPR_MAXFLEN + 3];
+    int pkt_len;
+    if (h->rx_len < 4) {
+        return;
+    }
+    if (!bcpr_check_crc_ccitt(h->rx_buffer, h->rx_len)) {
+        return;
+    }
+    pkt_len = h->rx_len - 2 + 1;
+    kiss[0] = 0;
+    memcpy(kiss + 1, h->rx_buffer, (size_t)(pkt_len - 1));
+    if (on_frame) {
+        on_frame(kiss, pkt_len, ud);
+    }
+}
+
+void bcpr_hdlc_receiver(bcpr_hdlc_t *h,
+                        void (*on_frame)(const uint8_t *kiss, int len, void *ud),
+                        void *ud)
+{
+    int i;
+    unsigned mask1, mask2, mask3, mask4, mask5, mask6, word;
+
+    while (!hbuf_empty(&h->rx_hbuf)) {
+        word = hbuf_get(&h->rx_hbuf);
+        h->bitstream >>= 16;
+        h->bitstream |= word << 16;
+        h->bitbuf >>= 16;
+        h->bitbuf |= word << 16;
+        h->numbits += 16;
+        for (i = 15, mask1 = 0x1fc00, mask2 = 0x1fe00, mask3 = 0x0fc00,
+            mask4 = 0x1f800, mask5 = 0xf800, mask6 = 0xffff;
+             i >= 0; i--, mask1 <<= 1, mask2 <<= 1, mask3 <<= 1, mask4 <<= 1,
+                       mask5 <<= 1, mask6 = (mask6 << 1) | 1) {
+            if ((h->bitstream & mask1) == mask1) {
+                h->rx_state = 0;
+            } else if ((h->bitstream & mask2) == mask3) {
+                if (h->rx_state) {
+                    hdlc_rx_add_bytes(h, h->bitbuf << (8 + i),
+                                      h->numbits - 8 - i);
+                    hdlc_rx_flag(h, on_frame, ud);
+                }
+                h->rx_len = 0;
+                h->rx_bp = h->rx_buffer;
+                h->rx_state = 1;
+                h->numbits = i;
+            } else if ((h->bitstream & mask4) == mask5) {
+                h->numbits--;
+                h->bitbuf = (h->bitbuf & (~mask6)) |
+                            ((h->bitbuf & mask6) << 1);
+            }
+        }
+        h->numbits -= hdlc_rx_add_bytes(h, h->bitbuf, h->numbits);
+    }
+}
+
+void bcpr_hdlc_transmitter(bcpr_hdlc_t *h)
+{
+    unsigned mask1, mask2, mask3;
+    int i;
+
+    for (;;) {
+        if (h->tx_numbits >= 16) {
+            if (hbuf_full(&h->tx_hbuf)) {
+                return;
+            }
+            hbuf_put(&h->tx_hbuf, (uint16_t)(h->tx_bitbuf & 0xffff));
+            h->tx_bitbuf >>= 16;
+            h->tx_numbits -= 16;
+        }
+        switch (h->tx_state) {
+        default:
+            return;
+        case 0:
+        case 1:
+            if (h->numflags) {
+                h->numflags--;
+                h->tx_bitbuf |= 0x7e7e << h->tx_numbits;
+                h->tx_numbits += 16;
+                break;
+            }
+            if (h->tx_state == 1) {
+                return;
+            }
+            if (!h->have_pending) {
+                int flgs = tenms_to_2flags(h, h->ch.tx_tail);
+                if (flgs < 2) {
+                    flgs = 2;
+                }
+                h->tx_state = 1;
+                h->numflags = flgs;
+                break;
+            }
+            /* pending[] holds up to BCPR_MAXFLEN; reject only oversize / empty. */
+            if (h->pending_len > BCPR_MAXFLEN || h->pending_len < 2) {
+                h->have_pending = 0;
+                h->tx_state = 0;
+                h->numflags = 1;
+                break;
+            }
+            memcpy(h->tx_buffer, h->pending, (size_t)h->pending_len);
+            h->have_pending = 0;
+            h->tx_bp = h->tx_buffer;
+            bcpr_append_crc_ccitt(h->tx_buffer, h->pending_len);
+            h->tx_len = h->pending_len + 2;
+            h->tx_state = 2;
+            h->tx_bitstream = 0;
+            break;
+        case 2:
+            if (!h->tx_len) {
+                h->tx_state = 0;
+                h->numflags = 1;
+                break;
+            }
+            h->tx_len--;
+            h->tx_bitbuf |= *h->tx_bp << h->tx_numbits;
+            h->tx_bitstream >>= 8;
+            h->tx_bitstream |= (*h->tx_bp++) << 16;
+            mask1 = 0x1f000;
+            mask2 = 0x10000;
+            mask3 = 0xffffffffu >> (31 - h->tx_numbits);
+            h->tx_numbits += 8;
+            for (i = 0; i < 8;
+                 i++, mask1 <<= 1, mask2 <<= 1, mask3 = (mask3 << 1) | 1) {
+                if ((h->tx_bitstream & mask1) != mask1) {
+                    continue;
+                }
+                h->tx_bitstream &= ~mask2;
+                h->tx_bitbuf = (h->tx_bitbuf & mask3) |
+                               ((h->tx_bitbuf & (~mask3)) << 1);
+                h->tx_numbits++;
+                mask3 = (mask3 << 1) | 1;
+            }
+            break;
+        }
+    }
+}
+
+void bcpr_hdlc_arbitrate(bcpr_hdlc_t *h)
+{
+    if (h->ptt || !h->have_pending) {
+        return;
+    }
+    if (h->ch.fulldup) {
+        h->tx_state = 0;
+        h->numflags = tenms_to_2flags(h, h->ch.tx_delay);
+        h->tx_bitbuf = h->tx_bitstream = 0;
+        h->tx_numbits = 0;
+        bcpr_hdlc_transmitter(h);
+        h->ptt = 1;
+        return;
+    }
+    if (!h->dcd && (--h->slotcnt <= 0)) {
+        h->slotcnt = h->ch.slottime;
+        if ((rand() % 256) > h->ch.ppersist) {
+            return;
+        }
+        h->tx_state = 0;
+        h->numflags = tenms_to_2flags(h, h->ch.tx_delay);
+        h->tx_bitbuf = h->tx_bitstream = 0;
+        h->tx_numbits = 0;
+        bcpr_hdlc_transmitter(h);
+        h->ptt = 1;
+    }
+}
diff --git a/stacks/max25-bcpr/src/bcpr_kiss.c b/stacks/max25-bcpr/src/bcpr_kiss.c
new file mode 100644
index 0000000..495f4d1
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_kiss.c
@@ -0,0 +1,127 @@
+/*
+ * KISS PTY bridge for max25-bcpr (HyBBX attach via kiss_link symlink).
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_kiss.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <grp.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#if defined(__linux__)
+#include <pty.h>
+#elif defined(__FreeBSD__)
+#include <libutil.h>
+#else
+#include <util.h>
+#endif
+
+static int ensure_dir(const char *path)
+{
+    char tmp[256];
+    char *p;
+    size_t len;
+
+    if (!path || !path[0]) {
+        return -1;
+    }
+    snprintf(tmp, sizeof(tmp), "%s", path);
+    len = strlen(tmp);
+    if (len == 0) {
+        return -1;
+    }
+    if (tmp[len - 1] == '/') {
+        tmp[len - 1] = '\0';
+    }
+    for (p = tmp + 1; *p; p++) {
+        if (*p == '/') {
+            *p = '\0';
+            (void)mkdir(tmp, 0755);
+            *p = '/';
+        }
+    }
+    return mkdir(tmp, 0755) == 0 || errno == EEXIST ? 0 : -1;
+}
+
+int bcpr_kiss_pty_open(bcpr_kiss_pty_t *kp, int idx, const char *link_path,
+                       const char *state_dir)
+{
+    int master = -1, slave = -1;
+    char slave_name[128];
+    char dir[128];
+    const char *slash;
+
+    memset(kp, 0, sizeof(*kp));
+    kp->idx = idx;
+    kp->master_fd = -1;
+    kp->slave_fd = -1;
+    snprintf(kp->link_path, sizeof(kp->link_path), "%s", link_path);
+
+    slash = strrchr(link_path, '/');
+    if (slash && slash > link_path) {
+        size_t n = (size_t)(slash - link_path);
+        if (n >= sizeof(dir)) {
+            n = sizeof(dir) - 1;
+        }
+        memcpy(dir, link_path, n);
+        dir[n] = '\0';
+        (void)ensure_dir(dir);
+    } else {
+        (void)ensure_dir(state_dir);
+    }
+
+    if (openpty(&master, &slave, slave_name, NULL, NULL) != 0) {
+        perror("max25-bcpr openpty");
+        return -1;
+    }
+    if (fchmod(slave, 0660) != 0) {
+        perror("max25-bcpr fchmod kiss slave");
+    } else {
+        struct group *gr = getgrnam("dialout");
+        if (gr == NULL) {
+            gr = getgrnam("uucp");
+        }
+        if (gr == NULL) {
+            gr = getgrnam("tty");
+        }
+        if (gr != NULL && fchown(slave, (uid_t)-1, gr->gr_gid) != 0) {
+            perror("max25-bcpr fchown kiss slave");
+        }
+    }
+    unlink(link_path);
+    if (symlink(slave_name, link_path) != 0) {
+        perror("max25-bcpr symlink kiss_link");
+        close(slave);
+        close(master);
+        return -1;
+    }
+    fcntl(master, F_SETFL, O_NONBLOCK);
+    kp->master_fd = master;
+    close(slave);
+    kp->slave_fd = -1;
+    fprintf(stderr, "max25-bcpr: max25e0:bc%d KISS → %s -> %s\n", idx, link_path,
+            slave_name);
+    return 0;
+}
+
+void bcpr_kiss_pty_close(bcpr_kiss_pty_t *kp)
+{
+    if (!kp) {
+        return;
+    }
+    if (kp->slave_fd >= 0) {
+        close(kp->slave_fd);
+        kp->slave_fd = -1;
+    }
+    if (kp->master_fd >= 0) {
+        close(kp->master_fd);
+        kp->master_fd = -1;
+    }
+    if (kp->link_path[0]) {
+        unlink(kp->link_path);
+    }
+}
diff --git a/stacks/max25-bcpr/src/bcpr_lock.c b/stacks/max25-bcpr/src/bcpr_lock.c
new file mode 100644
index 0000000..b179323
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_lock.c
@@ -0,0 +1,202 @@
+/*
+ * Exclusive lock on owned COM ports only (flock + optional setserial uart none).
+ * Pass real IRQ — refuse mismatch. See vault IRQ/lock contract.
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_lock.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+static void tty_basename(const char *serial, char *out, size_t out_sz)
+{
+    const char *p = strrchr(serial, '/');
+    p = p ? p + 1 : serial;
+    snprintf(out, out_sz, "%s", p);
+}
+
+int bcpr_lock_verify_irq(const char *serial, unsigned expect_irq,
+                         unsigned *got_irq, unsigned *got_io)
+{
+    char name[64];
+    char path[128];
+    char buf[64];
+    FILE *f;
+    unsigned irq = 0;
+    unsigned io = 0;
+
+    if (!serial || !serial[0]) {
+        return -1;
+    }
+    tty_basename(serial, name, sizeof(name));
+    snprintf(path, sizeof(path), "/sys/class/tty/%s/irq", name);
+    f = fopen(path, "r");
+    if (f) {
+        if (fgets(buf, sizeof(buf), f)) {
+            irq = (unsigned)strtoul(buf, NULL, 0);
+        }
+        fclose(f);
+    } else {
+        /* Fallback: setserial -g (best-effort). */
+        char cmd[256];
+        FILE *p;
+        snprintf(cmd, sizeof(cmd), "setserial -g %s 2>/dev/null", serial);
+        p = popen(cmd, "r");
+        if (!p) {
+            return -1;
+        }
+        if (fgets(buf, sizeof(buf), p)) {
+            char *ip = strstr(buf, "IRQ: ");
+            char *pp = strstr(buf, "Port: ");
+            if (ip) {
+                irq = (unsigned)strtoul(ip + 5, NULL, 0);
+            }
+            if (pp) {
+                io = (unsigned)strtoul(pp + 6, NULL, 0);
+            }
+        }
+        pclose(p);
+    }
+
+    snprintf(path, sizeof(path), "/sys/class/tty/%s/iomem_base", name);
+    f = fopen(path, "r");
+    if (f) {
+        if (fgets(buf, sizeof(buf), f)) {
+            io = (unsigned)strtoul(buf, NULL, 0);
+        }
+        fclose(f);
+    }
+
+    if (got_irq) {
+        *got_irq = irq;
+    }
+    if (got_io) {
+        *got_io = io;
+    }
+    if (expect_irq == 0) {
+        return -1; /* never invent; refuse zero when required */
+    }
+    if (irq == 0 || irq != expect_irq) {
+        return -1;
+    }
+    return 0;
+}
+
+static int make_lock_path(const bcpr_dev_config_t *dev, char *out, size_t sz)
+{
+    char name[64];
+    const char *dir = "/var/run/max25-bcpr";
+    tty_basename(dev->serial, name, sizeof(name));
+    if (name[0] == '\0') {
+        return -1;
+    }
+    snprintf(out, sz, "%s/lock-%s", dir, name);
+    return 0;
+}
+
+int bcpr_lock_acquire(bcpr_port_lock_t *lk, const bcpr_dev_config_t *dev,
+                      int dry_run)
+{
+    char lockpath[192];
+    unsigned got_irq = 0, got_io = 0;
+
+    if (!lk || !dev) {
+        return -1;
+    }
+    memset(lk, 0, sizeof(*lk));
+    snprintf(lk->serial, sizeof(lk->serial), "%s", dev->serial);
+    lk->iobase = dev->iobase;
+    lk->irq = dev->irq;
+    lk->lock_fd = -1;
+    lk->dry_run = dry_run ? 1 : 0;
+
+    if (dry_run) {
+        return 0;
+    }
+    if (!dev->serial[0] || dev->irq == 0 || dev->iobase == 0) {
+        return -1;
+    }
+    if (bcpr_lock_verify_irq(dev->serial, dev->irq, &got_irq, &got_io) != 0) {
+#if defined(__FreeBSD__)
+        /*
+         * No Linux sysfs/setserial — operator INI is SSoT for iobase/irq
+         * (see vault ExSys AM1 map). Skip hard fail when probe unavailable.
+         */
+        got_irq = dev->irq;
+        got_io = dev->iobase;
+#else
+        fprintf(stderr,
+                "bcpr: IRQ mismatch or unreadable for %s (expect %u got %u)\n",
+                dev->serial, dev->irq, got_irq);
+        return -1;
+#endif
+    }
+    if (got_io && got_io != dev->iobase) {
+        fprintf(stderr,
+                "bcpr: iobase mismatch for %s (expect 0x%x got 0x%x)\n",
+                dev->serial, dev->iobase, got_io);
+        return -1;
+    }
+
+    if (make_lock_path(dev, lockpath, sizeof(lockpath)) != 0) {
+        return -1;
+    }
+    (void)mkdir("/var/run/max25-bcpr", 0755);
+    lk->lock_fd = open(lockpath, O_RDWR | O_CREAT | O_CLOEXEC, 0644);
+    if (lk->lock_fd < 0) {
+        perror("bcpr lock open");
+        return -1;
+    }
+    if (flock(lk->lock_fd, LOCK_EX | LOCK_NB) != 0) {
+        fprintf(stderr, "bcpr: port %s already locked\n", dev->serial);
+        close(lk->lock_fd);
+        lk->lock_fd = -1;
+        return -1;
+    }
+
+    /* Release 8250 claim on this COM only so userspace can bit-bang. */
+    {
+        char cmd[256];
+        snprintf(cmd, sizeof(cmd), "setserial %s uart none 2>/dev/null",
+                 dev->serial);
+        if (system(cmd) == 0) {
+            lk->uart_released = 1;
+        }
+    }
+    return 0;
+}
+
+void bcpr_lock_release(bcpr_port_lock_t *lk)
+{
+    if (!lk) {
+        return;
+    }
+    if (lk->dry_run) {
+        memset(lk, 0, sizeof(*lk));
+        lk->lock_fd = -1;
+        return;
+    }
+    if (lk->uart_released && lk->serial[0]) {
+        char cmd[256];
+        /* Restore 16550A claim — best effort. */
+        snprintf(cmd, sizeof(cmd),
+                 "setserial %s uart 16550A port 0x%x irq %u 2>/dev/null",
+                 lk->serial, lk->iobase, lk->irq);
+        (void)system(cmd);
+        lk->uart_released = 0;
+    }
+    if (lk->lock_fd >= 0) {
+        flock(lk->lock_fd, LOCK_UN);
+        close(lk->lock_fd);
+        lk->lock_fd = -1;
+    }
+    memset(lk, 0, sizeof(*lk));
+    lk->lock_fd = -1;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_runas.c b/stacks/max25-bcpr/src/bcpr_runas.c
new file mode 100644
index 0000000..8c930bf
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_runas.c
@@ -0,0 +1,81 @@
+/*
+ * Process identity: max25-bcprd runs unprivileged; init drops from root.
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_runas.h"
+
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int bcpr_runas_refuse_root(int dry_run)
+{
+    if (geteuid() == 0 && !dry_run) {
+        fprintf(stderr,
+                "max25-bcprd: refusing to run as root — use max25-bcprd-init "
+                "(setuid) for live SER12\n");
+        return -1;
+    }
+    return 0;
+}
+
+int bcpr_runas_drop(const bcpr_config_t *cfg)
+{
+    struct passwd *pw;
+    struct group *gr = NULL;
+    gid_t gid;
+    uid_t uid;
+    const char *name;
+
+    if (!cfg || !cfg->run_user[0]) {
+        fprintf(stderr, "max25-bcpr: [max25-bcpr] user= required for daemon\n");
+        return -1;
+    }
+    if (geteuid() != 0) {
+        fprintf(stderr, "max25-bcpr: privilege drop requires euid=0\n");
+        return -1;
+    }
+
+    pw = getpwnam(cfg->run_user);
+    if (!pw) {
+        fprintf(stderr, "max25-bcpr: unknown user=%s\n", cfg->run_user);
+        return -1;
+    }
+    uid = pw->pw_uid;
+    gid = pw->pw_gid;
+    name = pw->pw_name;
+
+    if (cfg->run_group[0]) {
+        gr = getgrnam(cfg->run_group);
+        if (!gr) {
+            fprintf(stderr, "max25-bcpr: unknown group=%s\n", cfg->run_group);
+            return -1;
+        }
+        gid = gr->gr_gid;
+    }
+
+    if (initgroups(name, gid) != 0) {
+        fprintf(stderr, "max25-bcpr: initgroups(%s) failed: %s\n", name,
+                strerror(errno));
+        return -1;
+    }
+    if (setgid(gid) != 0) {
+        fprintf(stderr, "max25-bcpr: setgid failed: %s\n", strerror(errno));
+        return -1;
+    }
+    if (setuid(uid) != 0) {
+        fprintf(stderr, "max25-bcpr: setuid failed: %s\n", strerror(errno));
+        return -1;
+    }
+    if (setuid(0) == 0) {
+        fprintf(stderr, "max25-bcpr: privilege drop incomplete\n");
+        return -1;
+    }
+
+    fprintf(stderr, "max25-bcpr: running as uid=%u gid=%u (%s)\n",
+            (unsigned)uid, (unsigned)gid, name);
+    return 0;
+}
diff --git a/stacks/max25-bcpr/src/bcpr_ser12.c b/stacks/max25-bcpr/src/bcpr_ser12.c
new file mode 100644
index 0000000..32091e0
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_ser12.c
@@ -0,0 +1,246 @@
+#include "bcpr/bcpr_ser12.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+void bcpr_ser12_set_mode(bcpr_ser12_t *s, const char *mode, unsigned *baud_out)
+{
+    unsigned baud = 1200;
+    if (mode && strncmp(mode, "ser", 3) == 0) {
+        unsigned n = (unsigned)strtoul(mode + 3, NULL, 10);
+        if (n >= 3 && n <= 48) {
+            baud = n * 100u;
+        }
+    }
+    if (baud_out) {
+        *baud_out = baud;
+    }
+    s->baud = baud;
+    s->baud_us = 1000000u / baud;
+    if (mode && strchr(mode, '*')) {
+        s->opt_dcd = 0;
+    } else if (mode && strchr(mode, '+')) {
+        s->opt_dcd = -1;
+    } else {
+        s->opt_dcd = 1;
+    }
+}
+
+void bcpr_ser12_init(bcpr_ser12_t *s, unsigned baud, int opt_dcd)
+{
+    memset(s, 0, sizeof(*s));
+    s->baud = baud ? baud : 1200;
+    s->baud_us = 1000000u / s->baud;
+    s->opt_dcd = opt_dcd;
+    s->shreg = 0x10000;
+    s->dcd_sum0 = 2;
+    s->dcd_time = 120;
+    s->cal_mode = BCPR_CAL_OFF;
+    /* FlexNet SER12.doc defaults until bcpr_ser12_set_ptt_wd(). */
+    s->ptt_wd = 1;
+    s->ptt_wd_key_us = 14500u * 1000u;
+    s->ptt_wd_pause_us = 500u * 1000u;
+}
+
+void bcpr_ser12_set_ptt_wd(bcpr_ser12_t *s, int enable, int key_ms, int pause_ms)
+{
+    if (!s) {
+        return;
+    }
+    s->ptt_wd = enable ? 1 : 0;
+    if (key_ms < 1000) {
+        key_ms = 1000;
+    }
+    if (pause_ms < 50) {
+        pause_ms = 50;
+    }
+    s->ptt_wd_key_us = (unsigned)key_ms * 1000u;
+    s->ptt_wd_pause_us = (unsigned)pause_ms * 1000u;
+    s->ptt_wd_pausing = 0;
+    s->ptt_wd_phase_start_us = 0;
+}
+
+void bcpr_ser12_force_unkey(bcpr_ser12_t *s)
+{
+    if (!s) {
+        return;
+    }
+    s->ptt_hw = 0;
+    s->ptt_wd_pausing = 0;
+    s->ptt_wd_phase_start_us = 0;
+    s->txshreg = 0;
+}
+
+void bcpr_ser12_set_cal(bcpr_ser12_t *s, int cal_mode)
+{
+    if (!s) {
+        return;
+    }
+    if (cal_mode < BCPR_CAL_OFF || cal_mode > BCPR_CAL_ALT) {
+        cal_mode = BCPR_CAL_OFF;
+    }
+    s->cal_mode = cal_mode;
+    if (cal_mode != BCPR_CAL_OFF) {
+        s->ptt_hw = 1;
+        if (cal_mode == BCPR_CAL_HIGH) {
+            s->tx_bit = 1;
+        } else if (cal_mode == BCPR_CAL_LOW) {
+            s->tx_bit = 0;
+        } else {
+            s->tx_bit = 0; /* alt starts low, toggles each tick */
+        }
+        s->txshreg = 1;
+        s->ptt_wd_pausing = 0;
+        s->ptt_wd_phase_start_us = 0;
+    }
+}
+
+/*
+ * FlexNet SER12.doc / PAR96: during long calibrate, drop PTT every ~14.5 s for
+ * ~500 ms so the radio PTT watchdog can discharge. Mirror for --cal and any
+ * sustained key. Logical ptt_hw stays 1 (keep baud divisor / telemetry); only
+ * MCR RTS is cleared for the pause window.
+ */
+static void ser12_apply_ptt_wd(bcpr_ser12_t *s, int *mcr_out, unsigned now_us)
+{
+    unsigned elapsed;
+
+    if (!s->ptt_wd || !s->ptt_hw) {
+        s->ptt_wd_pausing = 0;
+        s->ptt_wd_phase_start_us = 0;
+        return;
+    }
+    if (s->ptt_wd_phase_start_us == 0) {
+        s->ptt_wd_phase_start_us = now_us ? now_us : 1u;
+        s->ptt_wd_pausing = 0;
+        return;
+    }
+    elapsed = now_us - s->ptt_wd_phase_start_us;
+    if (!s->ptt_wd_pausing) {
+        if (elapsed >= s->ptt_wd_key_us) {
+            s->ptt_wd_pausing = 1;
+            s->ptt_wd_phase_start_us = now_us ? now_us : 1u;
+            *mcr_out = 0x0d; /* RTS clear — PTT off */
+        }
+        return;
+    }
+    /* In pause: force idle MCR regardless of cal/HDLC bit. */
+    *mcr_out = 0x0d;
+    if (elapsed >= s->ptt_wd_pause_us) {
+        s->ptt_wd_pausing = 0;
+        s->ptt_wd_phase_start_us = now_us ? now_us : 1u;
+        /* Next tick restores keyed MCR from cal/HDLC path. */
+    }
+}
+
+static void ser12_rx(bcpr_ser12_t *s, bcpr_hdlc_t *h, unsigned curs,
+                     unsigned now_us)
+{
+    int timediff;
+    int bdus8 = (int)(s->baud_us >> 3);
+    int bdus4 = (int)(s->baud_us >> 2);
+    int bdus2 = (int)(s->baud_us >> 1);
+
+    timediff = (int)(now_us - s->pll_time);
+    /* wrap handling for us modulo ~1s window */
+    while (timediff >= 500000) {
+        timediff -= 1000000;
+    }
+    while (timediff <= -500000) {
+        timediff += 1000000;
+    }
+    while (timediff >= bdus2) {
+        timediff -= (int)s->baud_us;
+        s->pll_time += s->baud_us;
+        s->dcd_time--;
+        if (s->shreg & 1) {
+            bcpr_hdlc_putbits(h, (s->shreg >> 1) ^ 0xffffu);
+            s->shreg = 0x10000;
+        }
+        s->shreg >>= 1;
+    }
+    if (s->dcd_time <= 0) {
+        if (!s->opt_dcd) {
+            h->dcd = (s->dcd_sum0 + s->dcd_sum1 + s->dcd_sum2) < 0;
+        }
+        s->dcd_sum2 = s->dcd_sum1;
+        s->dcd_sum1 = s->dcd_sum0;
+        s->dcd_sum0 = 2;
+        s->dcd_time += 120;
+    }
+    if (s->last_rxbit != (unsigned char)curs) {
+        s->last_rxbit = (unsigned char)curs;
+        s->shreg |= 0x10000;
+        if (timediff > 0) {
+            s->pll_time += (unsigned)bdus8;
+        } else {
+            s->pll_time += 1000000u - (unsigned)bdus8;
+        }
+        if (abs(timediff) > bdus4) {
+            s->dcd_sum0 += 4;
+        } else {
+            s->dcd_sum0--;
+        }
+    }
+    while (s->pll_time >= 1000000u) {
+        s->pll_time -= 1000000u;
+    }
+}
+
+void bcpr_ser12_tick(bcpr_ser12_t *s, bcpr_hdlc_t *h, int cts, int *mcr_out,
+                     int *do_thr00, unsigned now_us)
+{
+    *do_thr00 = 1;
+
+    /* DOS cal.exe: continuous PTT + sticky/toggle DTR; no HDLC. */
+    if (s->cal_mode != BCPR_CAL_OFF) {
+        s->ptt_hw = 1;
+        if (s->cal_mode == BCPR_CAL_HIGH) {
+            s->tx_bit = 1;
+        } else if (s->cal_mode == BCPR_CAL_LOW) {
+            s->tx_bit = 0;
+        } else {
+            s->tx_bit = (unsigned char)!s->tx_bit;
+        }
+        *mcr_out = 0x0e | (!!s->tx_bit);
+        ser12_apply_ptt_wd(s, mcr_out, now_us);
+        return;
+    }
+
+    /*
+     * While PTT: skip Soft-DCD RX PLL — PC-COM charge-pump needs unbroken
+     * THR 0x00 @ baud; RX work causes multi-ms TXD gaps → underpowered AFSK.
+     */
+    if (!s->ptt_hw) {
+        ser12_rx(s, h, cts ? 1u : 0u, now_us);
+    }
+
+    if (s->ptt_hw) {
+        *mcr_out = 0x0e | (!!s->tx_bit);
+    } else {
+        *mcr_out = 0x0d;
+    }
+
+    if (s->ptt_hw) {
+        if (s->txshreg <= 1) {
+            s->txshreg = 0x10000u | bcpr_hdlc_getbits(h);
+            if (!bcpr_hdlc_ptt(h)) {
+                s->ptt_hw = 0;
+                *mcr_out = 0x0d;
+                ser12_apply_ptt_wd(s, mcr_out, now_us);
+                return;
+            }
+        }
+        s->tx_bit = (unsigned char)(!(s->tx_bit ^ (s->txshreg & 1)));
+        s->txshreg >>= 1;
+    } else {
+        bcpr_hdlc_arbitrate(h);
+        if (bcpr_hdlc_ptt(h)) {
+            s->txshreg = 1;
+            s->ptt_hw = 1;
+        }
+    }
+    bcpr_hdlc_transmitter(h);
+    ser12_apply_ptt_wd(s, mcr_out, now_us);
+    /* Receiver drain is owned by bcpr_engine (RX callback). */
+}
diff --git a/stacks/max25-bcpr/src/bcpr_uart.c b/stacks/max25-bcpr/src/bcpr_uart.c
new file mode 100644
index 0000000..22ccba3
--- /dev/null
+++ b/stacks/max25-bcpr/src/bcpr_uart.c
@@ -0,0 +1,251 @@
+/*
+ * Userspace 8250/16550 register access for SER12 bit-bang.
+ * Prefer ioperm(2); fall back to /dev/port. Dry-run: no-ops.
+ * Algorithms match Linux baycom_ser_fdx (see NOTICE.md).
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_uart.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#if defined(__linux__)
+#include <sys/io.h>
+#elif defined(__FreeBSD__)
+#include <machine/cpufunc.h>
+#include <machine/sysarch.h>
+#endif
+
+#if defined(__FreeBSD__)
+static int bcpr_freebsd_set_ioperm(unsigned start, unsigned len, int enable)
+{
+    struct {
+        unsigned int start;
+        unsigned int length;
+        int enable;
+    } args;
+
+    args.start = start;
+    args.length = len;
+    args.enable = enable;
+    return sysarch(I386_SET_IOPERM, &args);
+}
+#endif
+
+static int g_dry;
+static int g_port_fd = -1;
+static int g_ioperm_ok;
+
+void bcpr_uart_set_dry_run(int on)
+{
+    g_dry = on ? 1 : 0;
+}
+
+int bcpr_uart_ioperm(unsigned iobase, int on)
+{
+    if (g_dry) {
+        return 0;
+    }
+#if defined(__linux__)
+    if (ioperm((unsigned long)iobase, 8, on ? 1 : 0) == 0) {
+        g_ioperm_ok = on ? 1 : 0;
+        return 0;
+    }
+#elif defined(__FreeBSD__)
+    /*
+     * Prefer /dev/io (process-wide inb/outb). sysarch range is fallback.
+     * ExSys port: disable matching uart(4) unit (e.g. uart2/cuau2) in
+     * loader.conf — kernel uart + userspace inb on same iobase → SIGBUS.
+     */
+    if (on) {
+        if (g_port_fd < 0) {
+            g_port_fd = open("/dev/io", O_RDWR | O_CLOEXEC);
+        }
+        if (g_port_fd >= 0) {
+            g_ioperm_ok = 1;
+            return 0;
+        }
+    }
+    if (bcpr_freebsd_set_ioperm((unsigned)iobase, 8, on ? 1 : 0) == 0) {
+        g_ioperm_ok = on ? 1 : 0;
+        return 0;
+    }
+#endif
+    /* Fallback: /dev/io (FreeBSD) or /dev/port (Linux) — needs root. */
+    if (on) {
+        if (g_port_fd < 0) {
+#if defined(__FreeBSD__)
+            g_port_fd = open("/dev/io", O_RDWR | O_CLOEXEC);
+#else
+            g_port_fd = open("/dev/port", O_RDWR | O_CLOEXEC);
+#endif
+            if (g_port_fd >= 0) {
+                g_ioperm_ok = 1;
+                return 0;
+            }
+        }
+        if (g_port_fd >= 0) {
+            return 0;
+        }
+        return -1;
+    }
+    if (g_port_fd >= 0) {
+        close(g_port_fd);
+        g_port_fd = -1;
+    }
+    g_ioperm_ok = 0;
+    return 0;
+}
+
+static int port_rw(unsigned port, int do_write, unsigned char *val)
+{
+    off_t off = (off_t)port;
+    if (g_port_fd < 0) {
+        return -1;
+    }
+    if (lseek(g_port_fd, off, SEEK_SET) != off) {
+        return -1;
+    }
+    if (do_write) {
+        return (write(g_port_fd, val, 1) == 1) ? 0 : -1;
+    }
+    return (read(g_port_fd, val, 1) == 1) ? 0 : -1;
+}
+
+void bcpr_uart_outb(unsigned char val, unsigned port)
+{
+    if (g_dry) {
+        return;
+    }
+    if (g_ioperm_ok) {
+        outb(val, port);
+        return;
+    }
+    (void)port_rw(port, 1, &val);
+}
+
+unsigned char bcpr_uart_inb(unsigned port)
+{
+    unsigned char v = 0;
+    if (g_dry) {
+        return 0;
+    }
+    if (g_ioperm_ok) {
+        return inb(port);
+    }
+    (void)port_rw(port, 0, &v);
+    return v;
+}
+
+void bcpr_uart_set_divisor(unsigned iobase, unsigned divisor)
+{
+    unsigned char lcr;
+    if (g_dry) {
+        return;
+    }
+    lcr = bcpr_uart_inb(iobase + 3);
+    bcpr_uart_outb((unsigned char)(lcr | 0x80), iobase + 3); /* DLAB */
+    bcpr_uart_outb((unsigned char)(divisor & 0xff), iobase + 0);
+    bcpr_uart_outb((unsigned char)((divisor >> 8) & 0xff), iobase + 1);
+    bcpr_uart_outb((unsigned char)(lcr & 0x7f), iobase + 3);
+}
+
+void bcpr_uart_open_ser12(unsigned iobase)
+{
+    if (g_dry) {
+        return;
+    }
+    /* Match baycom_ser_fdx open: FIFO off, 6-bit word, IER THRE+MSR. */
+    bcpr_uart_outb(0x00, iobase + 2); /* FCR */
+    bcpr_uart_outb(0x01, iobase + 3); /* LCR 6N1 */
+    bcpr_uart_outb(0x0a, iobase + 1); /* IER */
+    bcpr_uart_outb(0x0d, iobase + 4); /* MCR idle */
+    bcpr_uart_thr00(iobase);
+}
+
+void bcpr_uart_close_ser12(unsigned iobase)
+{
+    if (g_dry) {
+        return;
+    }
+    bcpr_uart_outb(0x00, iobase + 1); /* IER off */
+    bcpr_uart_outb(0x01, iobase + 4); /* MCR close */
+}
+
+unsigned char bcpr_uart_msr(unsigned iobase)
+{
+    if (g_dry) {
+        return 0;
+    }
+    return bcpr_uart_inb(iobase + 6);
+}
+
+void bcpr_uart_mcr(unsigned iobase, unsigned char v)
+{
+    if (g_dry) {
+        return;
+    }
+    bcpr_uart_outb(v, iobase + 4);
+}
+
+void bcpr_uart_thr00(unsigned iobase)
+{
+    if (g_dry) {
+        return;
+    }
+    bcpr_uart_outb(0x00, iobase + 0);
+}
+
+void bcpr_uart_set_break(unsigned iobase, int on)
+{
+    unsigned char lcr;
+    if (g_dry) {
+        return;
+    }
+    /*
+     * 8250 LCR bit6 (Set Break): force TXD to continuous SPACE (RS-232 +V).
+     * Honest limit: THR writes alone cannot hold DC-steady TXD — each byte is
+     * framed (start/data/stop). Break is the practical TFPCX-class approximation
+     * (docs: static ≈ +12 V modem supply). Does not change MCR/PTT.
+     */
+    lcr = bcpr_uart_inb(iobase + 3);
+    if (on) {
+        bcpr_uart_outb((unsigned char)(lcr | 0x40), iobase + 3);
+    } else {
+        bcpr_uart_outb((unsigned char)(lcr & (unsigned char)~0x40), iobase + 3);
+    }
+}
+
+int bcpr_uart_wait_thre(unsigned iobase, unsigned timeout_us)
+{
+    struct timespec t0, now;
+    unsigned char lsr;
+
+    if (g_dry) {
+        return 1;
+    }
+    if (clock_gettime(CLOCK_MONOTONIC, &t0) != 0) {
+        return 0;
+    }
+    for (;;) {
+        lsr = bcpr_uart_inb(iobase + 5);
+        if (lsr & 0x20) { /* THRE */
+            return 1;
+        }
+        if (clock_gettime(CLOCK_MONOTONIC, &now) != 0) {
+            return 0;
+        }
+        {
+            long elapsed = (long)(now.tv_sec - t0.tv_sec) * 1000000L +
+                           (now.tv_nsec - t0.tv_nsec) / 1000L;
+            if (elapsed >= (long)timeout_us) {
+                return 0;
+            }
+        }
+    }
+}
diff --git a/stacks/max25-bcpr/src/max25-bcprd-init.c b/stacks/max25-bcpr/src/max25-bcprd-init.c
new file mode 100644
index 0000000..6a02240
--- /dev/null
+++ b/stacks/max25-bcpr/src/max25-bcprd-init.c
@@ -0,0 +1,255 @@
+/*
+ * max25-bcprd-init — privileged SER12 setup (setuid root), then unprivileged daemon.
+ * Fork keeps ioperm in child; parent writes pidfile and exits.
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_config.h"
+#include "bcpr/bcpr_daemon.h"
+#include "bcpr/bcpr_engine.h"
+#include "bcpr/bcpr_kiss.h"
+#include "bcpr/bcpr_runas.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static void usage(const char *argv0)
+{
+    fprintf(stderr,
+            "Usage: %s -c <bcpr.ini> [--once] [--seconds N]\n"
+            "          [--cal high|low|alt] [--txd-bias pulse|steady]\n"
+            "          [--ptt-wd|--no-ptt-wd] [--ptt-wd-key-ms N]\n"
+            "          [--ptt-wd-pause-ms N] [--version]\n"
+            "  Privileged init for live SER12 — drops to [max25-bcpr] user= after setup.\n"
+            "  Dry-run: use max25-bcprd --dry-run (unprivileged).\n",
+            argv0);
+}
+
+static int ensure_dir(const char *path)
+{
+    char tmp[256];
+    char *p;
+    size_t len;
+
+    if (!path || !path[0]) {
+        return -1;
+    }
+    snprintf(tmp, sizeof(tmp), "%s", path);
+    len = strlen(tmp);
+    if (len == 0) {
+        return -1;
+    }
+    if (tmp[len - 1] == '/') {
+        tmp[len - 1] = '\0';
+    }
+    for (p = tmp + 1; *p; p++) {
+        if (*p == '/') {
+            *p = '\0';
+            (void)mkdir(tmp, 0755);
+            *p = '/';
+        }
+    }
+    return mkdir(tmp, 0755) == 0 || errno == EEXIST ? 0 : -1;
+}
+
+static int write_pidfile(const char *path, pid_t pid)
+{
+    FILE *f;
+
+    f = fopen(path, "w");
+    if (!f) {
+        fprintf(stderr, "max25-bcprd-init: cannot write pidfile %s\n", path);
+        return -1;
+    }
+    fprintf(f, "%d\n", (int)pid);
+    fclose(f);
+    return 0;
+}
+
+int main(int argc, char **argv)
+{
+    const char *cfg_path = NULL;
+    int seconds = 0;
+    int cal_mode = BCPR_CAL_OFF;
+    int cli_txd_bias = -1;
+    int cli_ptt_wd = -1;
+    int cli_ptt_wd_key_ms = -1;
+    int cli_ptt_wd_pause_ms = -1;
+    int i;
+    bcpr_config_t cfg;
+    bcpr_engine_t engine;
+    bcpr_kiss_pty_t ptys[BCPR_MAX_DEVICES];
+    int npty = 0;
+    char pidpath[256];
+    pid_t child;
+    bcpr_daemon_opts_t opts;
+
+    for (i = 1; i < argc; i++) {
+        if ((strcmp(argv[i], "-c") == 0 || strcmp(argv[i], "--config") == 0) &&
+            i + 1 < argc) {
+            cfg_path = argv[++i];
+        } else if (strcmp(argv[i], "--once") == 0) {
+            if (seconds <= 0) {
+                seconds = 1;
+            }
+        } else if (strcmp(argv[i], "--seconds") == 0 && i + 1 < argc) {
+            seconds = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--cal") == 0 && i + 1 < argc) {
+            const char *m = argv[++i];
+            if (strcmp(m, "high") == 0 || strcmp(m, "1") == 0) {
+                cal_mode = BCPR_CAL_HIGH;
+            } else if (strcmp(m, "low") == 0 || strcmp(m, "2") == 0) {
+                cal_mode = BCPR_CAL_LOW;
+            } else if (strcmp(m, "alt") == 0 || strcmp(m, "3") == 0) {
+                cal_mode = BCPR_CAL_ALT;
+            } else {
+                fprintf(stderr, "max25-bcprd-init: --cal needs high|low|alt\n");
+                return 2;
+            }
+        } else if (strcmp(argv[i], "--txd-bias") == 0 && i + 1 < argc) {
+            const char *m = argv[++i];
+            if (strcasecmp(m, "pulse") == 0 || strcasecmp(m, "sailer") == 0) {
+                cli_txd_bias = BCPR_TXD_PULSE;
+            } else if (strcasecmp(m, "steady") == 0 ||
+                       strcasecmp(m, "tfpcx") == 0 ||
+                       strcasecmp(m, "break") == 0) {
+                cli_txd_bias = BCPR_TXD_STEADY;
+            } else {
+                fprintf(stderr, "max25-bcprd-init: --txd-bias needs pulse|steady\n");
+                return 2;
+            }
+        } else if (strcmp(argv[i], "--ptt-wd") == 0) {
+            cli_ptt_wd = 1;
+        } else if (strcmp(argv[i], "--no-ptt-wd") == 0) {
+            cli_ptt_wd = 0;
+        } else if (strcmp(argv[i], "--ptt-wd-key-ms") == 0 && i + 1 < argc) {
+            cli_ptt_wd_key_ms = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--ptt-wd-pause-ms") == 0 &&
+                   i + 1 < argc) {
+            cli_ptt_wd_pause_ms = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--version") == 0 ||
+                   strcmp(argv[i], "-V") == 0) {
+            printf("bcprd-init 0.1.0\n");
+            return 0;
+        } else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
+            usage(argv[0]);
+            return 0;
+        } else {
+            usage(argv[0]);
+            return 2;
+        }
+    }
+    if (!cfg_path) {
+        usage(argv[0]);
+        return 2;
+    }
+    if (geteuid() != 0) {
+        fprintf(stderr,
+                "max25-bcprd-init: requires root (setuid) for SER12 lock/ioperm/KISS\n");
+        return 1;
+    }
+    if (cal_mode != BCPR_CAL_OFF && seconds <= 0) {
+        seconds = 5;
+    }
+
+    if (bcpr_config_load(&cfg, cfg_path) != 0) {
+        fprintf(stderr, "max25-bcprd-init: cannot load %s\n", cfg_path);
+        return 1;
+    }
+    if (cfg.dry_run) {
+        fprintf(stderr,
+                "max25-bcprd-init: dry_run=yes — use max25-bcprd --dry-run instead\n");
+        return 1;
+    }
+    if (!cfg.run_user[0]) {
+        fprintf(stderr,
+                "max25-bcprd-init: [max25-bcpr] user= required for privilege drop\n");
+        return 1;
+    }
+
+    for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+        if (cli_txd_bias >= 0) {
+            cfg.dev[i].txd_bias = cli_txd_bias;
+        }
+        if (cli_ptt_wd >= 0) {
+            cfg.dev[i].ptt_wd = cli_ptt_wd;
+        }
+        if (cli_ptt_wd_key_ms > 0) {
+            cfg.dev[i].ptt_wd_key_ms = cli_ptt_wd_key_ms;
+        }
+        if (cli_ptt_wd_pause_ms > 0) {
+            cfg.dev[i].ptt_wd_pause_ms = cli_ptt_wd_pause_ms;
+        }
+    }
+
+    (void)ensure_dir(cfg.state_dir);
+    snprintf(pidpath, sizeof(pidpath), "%s/max25-bcprd.pid", cfg.state_dir);
+
+    if (cal_mode == BCPR_CAL_OFF) {
+        for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+            if (!cfg.dev[i].enabled) {
+                continue;
+            }
+            if (bcpr_kiss_pty_open(&ptys[npty], i, cfg.dev[i].kiss_link,
+                                   cfg.state_dir) != 0) {
+                while (npty > 0) {
+                    npty--;
+                    bcpr_kiss_pty_close(&ptys[npty]);
+                }
+                return 1;
+            }
+            npty++;
+        }
+    }
+
+    if (bcpr_engine_open(&engine, &cfg) != 0) {
+        for (i = 0; i < npty; i++) {
+            bcpr_kiss_pty_close(&ptys[i]);
+        }
+        return 1;
+    }
+
+    child = fork();
+    if (child < 0) {
+        perror("max25-bcprd-init fork");
+        bcpr_engine_close(&engine);
+        for (i = 0; i < npty; i++) {
+            bcpr_kiss_pty_close(&ptys[i]);
+        }
+        return 1;
+    }
+    if (child > 0) {
+        if (write_pidfile(pidpath, child) != 0) {
+            kill(child, SIGTERM);
+            waitpid(child, NULL, 0);
+            return 1;
+        }
+        _exit(0);
+    }
+
+    if (setsid() < 0) {
+        perror("max25-bcprd-init setsid");
+    }
+
+    if (bcpr_runas_drop(&cfg) != 0) {
+        _exit(1);
+    }
+
+    memset(&opts, 0, sizeof(opts));
+    opts.seconds = seconds;
+    opts.cal_mode = cal_mode;
+    opts.cli_txd_bias = cli_txd_bias;
+    opts.cli_ptt_wd = cli_ptt_wd;
+    opts.cli_ptt_wd_key_ms = cli_ptt_wd_key_ms;
+    opts.cli_ptt_wd_pause_ms = cli_ptt_wd_pause_ms;
+    opts.engine_preopened = 1;
+
+    return bcpr_daemon_run(&cfg, ptys, npty, &engine, &opts);
+}
diff --git a/stacks/max25-bcpr/src/max25-bcprd.c b/stacks/max25-bcpr/src/max25-bcprd.c
new file mode 100644
index 0000000..084c5df
--- /dev/null
+++ b/stacks/max25-bcpr/src/max25-bcprd.c
@@ -0,0 +1,205 @@
+/*
+ * max25-bcprd — BayCom/based SER12 userspace daemon (unprivileged live path).
+ * Live SER12: max25-bcprd-init (setuid). Dry-run / offline: this binary.
+ */
+#define _GNU_SOURCE
+#include "bcpr/bcpr_config.h"
+#include "bcpr/bcpr_daemon.h"
+#include "bcpr/bcpr_kiss.h"
+#include "bcpr/bcpr_runas.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+
+static void usage(const char *argv0)
+{
+    fprintf(stderr,
+            "Usage: %s -c <bcpr.ini> [--dry-run] [--once] [--seconds N]\n"
+            "          [--cal high|low|alt] [--txd-bias pulse|steady]\n"
+            "          [--ptt-wd|--no-ptt-wd] [--ptt-wd-key-ms N]\n"
+            "          [--ptt-wd-pause-ms N] [--version]\n"
+            "  Host face: max25e0:bc0 / bc1 (KISS PTY via kiss_link)\n"
+            "  Live SER12: max25-bcprd-init (setuid) — this binary refuses root.\n"
+            "  --cal: continuous SER12 tone+PTT (use init for live hardware)\n",
+            argv0);
+}
+
+int main(int argc, char **argv)
+{
+    const char *cfg_path = NULL;
+    int dry = 0;
+    int seconds = 0;
+    int cal_mode = BCPR_CAL_OFF;
+    int cli_txd_bias = -1;
+    int cli_ptt_wd = -1;
+    int cli_ptt_wd_key_ms = -1;
+    int cli_ptt_wd_pause_ms = -1;
+    int i;
+    bcpr_config_t cfg;
+    bcpr_kiss_pty_t ptys[BCPR_MAX_DEVICES];
+    int npty = 0;
+    bcpr_daemon_opts_t opts;
+    char ver[32] = "0.1.0";
+
+    for (i = 1; i < argc; i++) {
+        if ((strcmp(argv[i], "-c") == 0 || strcmp(argv[i], "--config") == 0) &&
+            i + 1 < argc) {
+            cfg_path = argv[++i];
+        } else if (strcmp(argv[i], "--dry-run") == 0) {
+            dry = 1;
+        } else if (strcmp(argv[i], "--once") == 0) {
+            if (seconds <= 0) {
+                seconds = 1;
+            }
+        } else if (strcmp(argv[i], "--seconds") == 0 && i + 1 < argc) {
+            seconds = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--cal") == 0 && i + 1 < argc) {
+            const char *m = argv[++i];
+            if (strcmp(m, "high") == 0 || strcmp(m, "1") == 0) {
+                cal_mode = BCPR_CAL_HIGH;
+            } else if (strcmp(m, "low") == 0 || strcmp(m, "2") == 0) {
+                cal_mode = BCPR_CAL_LOW;
+            } else if (strcmp(m, "alt") == 0 || strcmp(m, "3") == 0) {
+                cal_mode = BCPR_CAL_ALT;
+            } else {
+                fprintf(stderr, "max25-bcprd: --cal needs high|low|alt\n");
+                return 2;
+            }
+        } else if (strcmp(argv[i], "--txd-bias") == 0 && i + 1 < argc) {
+            const char *m = argv[++i];
+            if (strcasecmp(m, "pulse") == 0 || strcasecmp(m, "sailer") == 0) {
+                cli_txd_bias = BCPR_TXD_PULSE;
+            } else if (strcasecmp(m, "steady") == 0 ||
+                       strcasecmp(m, "tfpcx") == 0 ||
+                       strcasecmp(m, "break") == 0) {
+                cli_txd_bias = BCPR_TXD_STEADY;
+            } else {
+                fprintf(stderr, "max25-bcprd: --txd-bias needs pulse|steady\n");
+                return 2;
+            }
+        } else if (strcmp(argv[i], "--ptt-wd") == 0) {
+            cli_ptt_wd = 1;
+        } else if (strcmp(argv[i], "--no-ptt-wd") == 0) {
+            cli_ptt_wd = 0;
+        } else if (strcmp(argv[i], "--ptt-wd-key-ms") == 0 && i + 1 < argc) {
+            cli_ptt_wd_key_ms = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--ptt-wd-pause-ms") == 0 &&
+                   i + 1 < argc) {
+            cli_ptt_wd_pause_ms = atoi(argv[++i]);
+        } else if (strcmp(argv[i], "--version") == 0 ||
+                   strcmp(argv[i], "-V") == 0) {
+            FILE *vf = fopen("/usr/local/share/max25/max25-bcpr/VERSION", "r");
+            if (!vf) {
+                vf = fopen("stacks/max25-bcpr/VERSION", "r");
+            }
+            if (vf) {
+                if (fgets(ver, sizeof(ver), vf)) {
+                    ver[strcspn(ver, "\r\n")] = '\0';
+                }
+                fclose(vf);
+            }
+            printf("bcprd %s\n", ver);
+            return 0;
+        } else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
+            usage(argv[0]);
+            return 0;
+        } else {
+            usage(argv[0]);
+            return 2;
+        }
+    }
+    if (!cfg_path) {
+        usage(argv[0]);
+        return 2;
+    }
+    if (cal_mode != BCPR_CAL_OFF && seconds <= 0) {
+        seconds = 5;
+    }
+
+    if (bcpr_config_load(&cfg, cfg_path) != 0) {
+        fprintf(stderr, "max25-bcprd: cannot load %s\n", cfg_path);
+        return 1;
+    }
+    if (dry) {
+        cfg.dry_run = 1;
+    }
+
+    if (bcpr_runas_refuse_root(cfg.dry_run) != 0) {
+        return 1;
+    }
+    if (!cfg.dry_run && cal_mode == BCPR_CAL_OFF) {
+        fprintf(stderr,
+                "max25-bcprd: live SER12 requires max25-bcprd-init — "
+                "not this binary alone\n");
+        return 1;
+    }
+
+    {
+        char self[512];
+        ssize_t n = readlink("/proc/self/exe", self, sizeof(self) - 1);
+        FILE *vf = fopen("/usr/local/share/bcpr/VERSION", "r");
+        if (!vf) {
+            vf = fopen("stacks/max25-bcpr/VERSION", "r");
+        }
+        ver[0] = '\0';
+        if (vf) {
+            if (fgets(ver, sizeof(ver), vf)) {
+                ver[strcspn(ver, "\r\n")] = '\0';
+            }
+            fclose(vf);
+        }
+        if (n > 0) {
+            self[n] = '\0';
+            fprintf(stderr, "max25-bcprd: path=%s version=%s\n", self,
+                    ver[0] ? ver : "0.1.0");
+        } else {
+            fprintf(stderr, "max25-bcprd: version=%s\n", ver[0] ? ver : "0.1.0");
+        }
+    }
+
+    if (cfg.dry_run) {
+        fprintf(stderr, "max25-bcprd: dry-run (no KISS PTY, no UART I/O)\n");
+    } else if (cal_mode == BCPR_CAL_OFF) {
+        for (i = 0; i < BCPR_MAX_DEVICES; i++) {
+            if (!cfg.dev[i].enabled) {
+                continue;
+            }
+            if (bcpr_kiss_pty_open(&ptys[npty], i, cfg.dev[i].kiss_link,
+                                   cfg.state_dir) != 0) {
+                while (npty > 0) {
+                    npty--;
+                    bcpr_kiss_pty_close(&ptys[npty]);
+                }
+                return 1;
+            }
+            npty++;
+        }
+    }
+    if (cal_mode != BCPR_CAL_OFF) {
+        static const char *cal_names[] = {"off", "high", "low", "alt"};
+        fprintf(stderr,
+                "max25-bcprd: CAL mode=%s seconds=%d (no KISS; SER12 tone+PTT)%s\n",
+                cal_names[cal_mode], seconds,
+                cfg.dry_run ? " [dry-run]" : "");
+        if (!cfg.dry_run) {
+            fprintf(stderr,
+                    "max25-bcprd: live cal needs max25-bcprd-init for hardware access\n");
+            return 1;
+        }
+    }
+
+    memset(&opts, 0, sizeof(opts));
+    opts.dry_run = cfg.dry_run;
+    opts.seconds = seconds;
+    opts.cal_mode = cal_mode;
+    opts.cli_txd_bias = cli_txd_bias;
+    opts.cli_ptt_wd = cli_ptt_wd;
+    opts.cli_ptt_wd_key_ms = cli_ptt_wd_key_ms;
+    opts.cli_ptt_wd_pause_ms = cli_ptt_wd_pause_ms;
+    opts.engine_preopened = 0;
+
+    return bcpr_daemon_run(&cfg, ptys, npty, NULL, &opts);
+}
diff --git a/stacks/max25-bcpr/tests/test_config_offline.c b/stacks/max25-bcpr/tests/test_config_offline.c
new file mode 100644
index 0000000..8b40a6a
--- /dev/null
+++ b/stacks/max25-bcpr/tests/test_config_offline.c
@@ -0,0 +1,53 @@
+/*
+ * Offline config parse test — no UART.
+ */
+#include "bcpr/bcpr_config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(void)
+{
+    const char *path = "share/max25-bcpr.ini.example";
+    bcpr_config_t cfg;
+    char cwd[512];
+
+    if (!getcwd(cwd, sizeof(cwd))) {
+        return 1;
+    }
+    /* Prefer path relative to build or source. */
+    if (access(path, R_OK) != 0) {
+        path = "../share/max25-bcpr.ini.example";
+    }
+    if (access(path, R_OK) != 0) {
+        path = "../../stacks/max25-bcpr/share/max25-bcpr.ini.example";
+    }
+    if (bcpr_config_load(&cfg, path) != 0) {
+        /* Write a minimal temp INI. */
+        FILE *f = fopen("/tmp/max25-bcpr-test.ini", "w");
+        if (!f) {
+            return 1;
+        }
+        fputs("[max25-bcpr]\ndry_run = yes\nstate_dir = /tmp/max25-bcpr\n"
+              "[bc0]\nserial = /dev/ttyS0\niobase = 0x3f8\nirq = 4\n"
+              "mode = ser12*\nkiss_link = /tmp/max25-bcpr/kiss-bc0\n",
+              f);
+        fclose(f);
+        path = "/tmp/max25-bcpr-test.ini";
+        if (bcpr_config_load(&cfg, path) != 0) {
+            fprintf(stderr, "FAIL: load\n");
+            return 1;
+        }
+    }
+    if (cfg.n_dev < 1 || !cfg.dev[0].enabled) {
+        fprintf(stderr, "FAIL: no bc0\n");
+        return 1;
+    }
+    if (cfg.dev[0].irq != 4 || cfg.dev[0].iobase != 0x3f8) {
+        fprintf(stderr, "FAIL: irq/iobase\n");
+        return 1;
+    }
+    puts("OK: test_config_offline");
+    return 0;
+}
diff --git a/stacks/max25-bcpr/tests/test_hdlc_offline.c b/stacks/max25-bcpr/tests/test_hdlc_offline.c
new file mode 100644
index 0000000..d05d5b6
--- /dev/null
+++ b/stacks/max25-bcpr/tests/test_hdlc_offline.c
@@ -0,0 +1,110 @@
+/*
+ * Offline HDLC unit test — CRC, bitstuff roundtrip, no UART / UART I/O.
+ */
+#include "bcpr/bcpr_crc.h"
+#include "bcpr/bcpr_hdlc.h"
+
+#include <stdio.h>
+#include <string.h>
+
+static int g_got;
+static uint8_t g_rx[BCPR_MAXFLEN + 4];
+static int g_rx_len;
+
+static void on_frame(const uint8_t *kiss, int len, void *ud)
+{
+    (void)ud;
+    if (len > 0 && len <= (int)sizeof(g_rx)) {
+        memcpy(g_rx, kiss, (size_t)len);
+        g_rx_len = len;
+        g_got = 1;
+    }
+}
+
+static int test_crc(void)
+{
+    uint8_t buf[16];
+    memcpy(buf, "TEST", 4);
+    bcpr_append_crc_ccitt(buf, 4);
+    if (!bcpr_check_crc_ccitt(buf, 6)) {
+        fprintf(stderr, "FAIL: CRC check\n");
+        return 1;
+    }
+    buf[0] ^= 0xff;
+    if (bcpr_check_crc_ccitt(buf, 6)) {
+        fprintf(stderr, "FAIL: CRC should fail on corrupt\n");
+        return 1;
+    }
+    return 0;
+}
+
+static int test_roundtrip(void)
+{
+    bcpr_hdlc_t tx, rx;
+    bcpr_channel_t ch = { .tx_delay = 2, .tx_tail = 1, .slottime = 1,
+                          .ppersist = 255, .fulldup = 1 };
+    uint8_t kiss[32];
+    int i, words = 0;
+
+    bcpr_hdlc_init(&tx, 1200, &ch);
+    bcpr_hdlc_init(&rx, 1200, &ch);
+
+    kiss[0] = 0; /* KISS DATA */
+    memcpy(kiss + 1, "HELLO", 5);
+    if (bcpr_hdlc_queue_kiss(&tx, kiss, 6) != 0) {
+        fprintf(stderr, "FAIL: queue\n");
+        return 1;
+    }
+    bcpr_hdlc_arbitrate(&tx);
+    if (!bcpr_hdlc_ptt(&tx)) {
+        fprintf(stderr, "FAIL: PTT not set\n");
+        return 1;
+    }
+
+    g_got = 0;
+    g_rx_len = 0;
+    /* Drain TX bit words into RX putbits path. */
+    for (i = 0; i < 4096 && !g_got; i++) {
+        unsigned w;
+        bcpr_hdlc_transmitter(&tx);
+        w = bcpr_hdlc_getbits(&tx);
+        if (w) {
+            bcpr_hdlc_putbits(&rx, w);
+            words++;
+            bcpr_hdlc_receiver(&rx, on_frame, NULL);
+        } else if (!bcpr_hdlc_ptt(&tx)) {
+            bcpr_hdlc_transmitter(&tx);
+            /* flush remaining */
+            while (!g_got) {
+                w = bcpr_hdlc_getbits(&tx);
+                if (!w) {
+                    break;
+                }
+                bcpr_hdlc_putbits(&rx, w);
+                bcpr_hdlc_receiver(&rx, on_frame, NULL);
+            }
+            break;
+        }
+    }
+
+    if (!g_got) {
+        fprintf(stderr, "FAIL: no RX frame (words=%d)\n", words);
+        return 1;
+    }
+    if (g_rx_len < 6 || g_rx[0] != 0 || memcmp(g_rx + 1, "HELLO", 5) != 0) {
+        fprintf(stderr, "FAIL: payload mismatch len=%d\n", g_rx_len);
+        return 1;
+    }
+    return 0;
+}
+
+int main(void)
+{
+    int rc = 0;
+    rc |= test_crc();
+    rc |= test_roundtrip();
+    if (rc == 0) {
+        puts("OK: test_hdlc_offline");
+    }
+    return rc;
+}
diff --git a/stacks/max25-bcpr/tools/NEBENBEI-MOVED.md b/stacks/max25-bcpr/tools/NEBENBEI-MOVED.md
new file mode 100644
index 0000000..8a4ac20
--- /dev/null
+++ b/stacks/max25-bcpr/tools/NEBENBEI-MOVED.md
@@ -0,0 +1,5 @@
+# Dauerlauf helpers — not shipped here
+
+Experimental endurance / orch helpers are **not** part of this freigegeben product tree.
+
+Product L1 remains: `max25-bcpr-ctl`, smoke, ultimate-diag · host face **`max25e0`** · public mark **BayCom/based**.
diff --git a/stacks/max25-bcpr/tools/bcpr-ultimate-diag.sh b/stacks/max25-bcpr/tools/bcpr-ultimate-diag.sh
new file mode 100755
index 0000000..573585c
--- /dev/null
+++ b/stacks/max25-bcpr/tools/bcpr-ultimate-diag.sh
@@ -0,0 +1,916 @@
+#!/usr/bin/env bash
+# bcpr-ultimate-diag.sh — interactive BayCom/based (bcpr) TX/RX diagnostic ladder
+# Public mark: BayCom/based. Internal path: bcpr. Never Konverter/converter.
+# Target: AX25WRK1 intermittent "host keys, RF sometimes" (mic OK 4W; host MCR OK).
+#
+# Soft-TNC RE (2026-07-19) — operator warnings only (no MCR/code patch here):
+#   • FlexNet SER12 cal PTT watchdog: ~14.5 s keyed → ~500 ms unkey (discharge).
+#     Long continuous force-tx/cal: bcprd ptt_wd drops RTS ~500 ms every ~14.5 s
+#     (FlexNet SER12 mirror; disable with ptt_wd=no / --no-ptt-wd).
+#   • TXD: default pulse THR 0x00; experiment txd_bias=steady (UART break ≈ TFPCX).
+#   • Keep bcprd MCR Sailer 0x0e|bit / 0x0d (4PC-COM 0x0A is outlier — do not switch).
+# Vault RE: 0-RESEARCHES/projects/max25-stack/2026-07-19-baycom-soft-tnc-serial-ptt-re.md
+#
+# Usage (Cursor IDE terminal, as operator):
+#   sudo -n /home/akb/Code/10-PROJECTS/MAX25-Stack/stacks/bcpr/tools/bcpr-ultimate-diag.sh
+#   BCPR_INI=/etc/max25/bcpr.ini ./bcpr-ultimate-diag.sh -c /etc/max25/bcpr.ini
+#   ./bcpr-ultimate-diag.sh --help
+#   ./bcpr-ultimate-diag.sh --all          # run phases 1–9 with pauses
+#   ./bcpr-ultimate-diag.sh --menu         # interactive menu (default)
+#
+# Needs: /usr/bin/sudo -n for ioport / live smoke / cal. Does NOT change MCR code.
+# Does NOT use USB as product TX path. Does NOT kill max25d carelessly.
+#
+# Vault: 0-RESEARCHES/projects/max25-stack/2026-07-19-bcpr-ultimate-diag-script.md
+# Relies on: bcpr-ctl, bcpr-rxtx-smoke.sh (same directory).
+
+# Note: interactive prompts use read; keep pipefail but relax -e around optional probes.
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/../../.." 2>/dev/null && pwd || true)"
+CTL="${SCRIPT_DIR}/bcpr-ctl"
+SMOKE_SH="${SCRIPT_DIR}/bcpr-rxtx-smoke.sh"
+INI="${BCPR_INI:-/etc/max25/bcpr.ini}"
+SUDO="/usr/bin/sudo"
+LOG=""
+MODE="menu"   # menu | all | phaseN
+PHASE_ONLY=""
+RUN_TS=""
+
+# Result arrays for summary (parallel indices)
+declare -a RES_PHASE=()
+declare -a RES_HOST=()
+declare -a RES_WATT=()
+declare -a RES_BLED=()
+declare -a RES_RDISP=()
+declare -a RES_NOTE=()
+
+usage() {
+  cat <<'USAGE'
+bcpr-ultimate-diag.sh — BayCom/based (bcpr) interactive diagnostic / force-TX ladder
+
+Usage:
+  bcpr-ultimate-diag.sh [-c INI] [--menu|--all|--phase N] [--help]
+
+Options:
+  -c INI       bcpr.ini (default: $BCPR_INI or /etc/max25/bcpr.ini)
+  --menu       interactive German menu (default)
+  --all        run phases 1–9 linearly with pauses + RF prompts
+  --phase N    run a single phase (1–9, or 0=restart menu)
+  -h, --help   this help
+
+Environment:
+  BCPR_INI     same as -c
+  BCPRD        optional path to bcprd binary
+
+Phases:
+  1 Preflight (ttyS0, fuser, dosbox-x, bcprd/max25d, INI, locks)
+  2 Idle MCR sample via /dev/port
+  3 bcpr-ctl status + telem (tx-last / dcd / rx-activity)
+  4 RX listen (soft-DCD) — open SQ reminder
+  5 Force-TX ladder 1s / 3s / 5s / 8s + wattmeter/LED/display prompts
+  6 Cal/high (bcprd --cal high) if binary supports it
+  7 Double-burst / back-to-back TX
+  8 Contact hunt (DE-9 + 3.5mm) + 5s force-tx + wiggle
+  9 Summary table + verdict hints
+  0 Optional safe bcprd restart (bcpr-ctl stop/start only)
+  U USB note (SER12 unsupported on USB — not product TX)
+
+Log: /tmp/bcpr-ultimate-diag-YYYYMMDD-HHMMSS.log
+
+Examples:
+  sudo -n stacks/bcpr/tools/bcpr-ultimate-diag.sh --all
+  BCPR_INI=/etc/max25/bcpr.ini sudo -n ./bcpr-ultimate-diag.sh --menu
+USAGE
+}
+
+# ---------- logging / UI ----------
+
+log() {
+  local line
+  line="$(printf '%s' "$*")"
+  printf '%s\n' "$line"
+  if [[ -n "${LOG:-}" ]]; then
+    printf '%s\n' "$line" >>"$LOG"
+  fi
+}
+
+log_raw() {
+  # stdin → stdout + log
+  if [[ -n "${LOG:-}" ]]; then
+    tee -a "$LOG"
+  else
+    cat
+  fi
+}
+
+banner() {
+  log ""
+  log "════════════════════════════════════════════════════════════"
+  log "$*"
+  log "════════════════════════════════════════════════════════════"
+}
+
+pause_enter() {
+  local msg="${1:-Weiter mit Enter …}"
+  printf '\n%s ' "$msg" >/dev/tty
+  # shellcheck disable=SC2034
+  local _dummy
+  read -r _dummy </dev/tty || true
+  log "[pause] $msg"
+}
+
+ask() {
+  # ask VAR "prompt"
+  local __var="$1"
+  local __prompt="$2"
+  local __ans=""
+  printf '%s ' "$__prompt" >/dev/tty
+  read -r __ans </dev/tty || true
+  printf -v "$__var" '%s' "$__ans"
+  log "[antwort] $__prompt → ${__ans}"
+}
+
+ask_yn() {
+  # ask_yn VAR "prompt"  → stores j/n/y/n normalized to j|n
+  local __var="$1"
+  local __prompt="$2"
+  local __ans=""
+  while true; do
+    printf '%s [j/n]: ' "$__prompt" >/dev/tty
+    read -r __ans </dev/tty || true
+    case "${__ans,,}" in
+      j|ja|y|yes) printf -v "$__var" 'j'; log "[antwort] $__prompt → j"; return 0 ;;
+      n|nein|no)  printf -v "$__var" 'n'; log "[antwort] $__prompt → n"; return 0 ;;
+      *) printf 'Bitte j oder n.\n' >/dev/tty ;;
+    esac
+  done
+}
+
+record_result() {
+  local phase="$1" host="$2" watt="$3" bled="$4" rdisp="$5" note="${6:-}"
+  RES_PHASE+=("$phase")
+  RES_HOST+=("$host")
+  RES_WATT+=("$watt")
+  RES_BLED+=("$bled")
+  RES_RDISP+=("$rdisp")
+  RES_NOTE+=("$note")
+}
+
+need_sudo() {
+  if [[ ! -x "$SUDO" ]]; then
+    log "FEHLER: $SUDO fehlt — Live-Phasen brauchen sudo."
+    return 1
+  fi
+  if ! "$SUDO" -n true 2>/dev/null; then
+    log "FEHLER: sudo -n fehlgeschlagen."
+    log "  Bitte einmalig: sudo -v   (oder NOPASSWD für diesen User)"
+    log "  Dann Skript erneut starten."
+    return 1
+  fi
+  return 0
+}
+
+run_sudo() {
+  need_sudo || return 1
+  "$SUDO" -n "$@"
+}
+
+ini_get() {
+  local section="$1" key="$2"
+  [[ -f "$INI" ]] || return 0
+  awk -F= -v s="[$section]" -v k="$key" '
+    $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+    cur==s && $1 ~ "^[[:space:]]*"k"[[:space:]]*$" {
+      v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print v; exit
+    }' "$INI" 2>/dev/null || true
+}
+
+resolve_bcprd() {
+  if [[ -n "${BCPRD:-}" && "$BCPRD" != "bcprd" && -x "$BCPRD" ]]; then
+    printf '%s\n' "$BCPRD"; return 0
+  fi
+  if command -v bcprd >/dev/null 2>&1; then
+    command -v bcprd; return 0
+  fi
+  local cand
+  for cand in \
+    "${BCPR_BUILD_DIR:-}/bin/bcprd" \
+    "${ROOT}/build-bcpr/bin/bcprd" \
+    "${ROOT}/build-bcpr-${USER:-user}/bin/bcprd" \
+    "/tmp/max25-build-bcpr-${USER:-user}/bin/bcprd" \
+    "${ROOT}/build/bin/bcprd" \
+    /usr/local/bin/bcprd /usr/bin/bcprd; do
+    [[ -n "$cand" && -x "$cand" ]] && { printf '%s\n' "$cand"; return 0; }
+  done
+  return 1
+}
+
+serial_dev() {
+  local s
+  s="$(ini_get bc0 serial)"
+  printf '%s\n' "${s:-/dev/ttyS0}"
+}
+
+state_dir() {
+  local sd
+  sd="$(ini_get bcpr state_dir)"
+  printf '%s\n' "${sd:-/tmp/bcpr}"
+}
+
+iobase_val() {
+  local b
+  b="$(ini_get bc0 iobase)"
+  printf '%s\n' "${b:-0x3f8}"
+}
+
+ensure_tools() {
+  local err=0
+  if [[ ! -x "$CTL" ]]; then
+    log "FEHLER: bcpr-ctl fehlt: $CTL"; err=1
+  fi
+  if [[ ! -x "$SMOKE_SH" ]]; then
+    log "FEHLER: bcpr-rxtx-smoke.sh fehlt: $SMOKE_SH"; err=1
+  fi
+  return "$err"
+}
+
+# ---------- Phase helpers ----------
+
+# Last smoke host result (PASS|FAIL) — do not capture function stdout (log noise).
+_LAST_HOST="—"
+
+smoke_force_tx() {
+  # smoke_force_tx SECONDS → sets _LAST_HOST
+  local secs="$1"
+  local listen=$((secs + 8))
+  local rc=0
+  [[ "$listen" -lt 12 ]] && listen=12
+  log "→ L4 force-tx ${secs}s (smoke --live --tx --force-tx --tx-seconds ${secs})"
+  run_sudo "$CTL" -c "$INI" smoke --live --tx --force-tx --seconds "$listen" --tx-seconds "$secs" 2>&1 | log_raw
+  rc=${PIPESTATUS[0]}
+  if [[ "$rc" -eq 0 ]]; then
+    _LAST_HOST="PASS"
+    log "HOST: PASS (MCR keyed ~${secs}s target)"
+  else
+    _LAST_HOST="FAIL"
+    log "HOST: FAIL (smoke rc=$rc)"
+  fi
+}
+
+prompt_rf_obs() {
+  # prompt_rf_obs PHASE_LABEL HOST_RESULT
+  # sets globals: _watt _bled _rdisp _extra
+  local label="$1" host="$2"
+  local watt bled rdisp extra
+  log ""
+  log "--- RF-Beobachtung: $label (Host=$host) ---"
+  log "Bitte Wattmeter / Board-LED / Radio-Display während des Keys prüfen."
+  ask watt "Wattmeter W (Zahl oder 0 / ?):"
+  ask_yn bled "Board-LED (PC-COM) an während Key?"
+  ask_yn rdisp "Radio-Display / TX-Anzeige an?"
+  ask extra "Kurznotiz (Enter = keine):"
+  _watt="$watt"
+  _bled="$bled"
+  _rdisp="$rdisp"
+  _extra="$extra"
+  record_result "$label" "$host" "$watt" "$bled" "$rdisp" "$extra"
+}
+
+# ---------- Phases ----------
+
+phase_preflight() {
+  banner "Phase 1 — Preflight"
+  local serial sd iobase irq fulldup dry
+  serial="$(serial_dev)"
+  sd="$(state_dir)"
+  iobase="$(iobase_val)"
+  irq="$(ini_get bc0 irq)"
+  fulldup="$(ini_get bc0 fulldup)"
+  dry="$(ini_get bcpr dry_run)"
+
+  log "INI: $INI"
+  if [[ ! -f "$INI" ]]; then
+    log "FEHLER: INI fehlt: $INI"
+    log "  Hinweis: Beispiel → stacks/bcpr/share/bcpr.ini.example → /etc/max25/bcpr.ini"
+    return 1
+  fi
+
+  log "--- INI Auszug [bcpr]/[bc0] ---"
+  log "  dry_run=${dry:-?}  state_dir=${sd}"
+  log "  serial=${serial}  iobase=${iobase}  irq=${irq:-?}  fulldup=${fulldup:-?}"
+  log "  mode=$(ini_get bc0 mode)  kiss_link=$(ini_get bc0 kiss_link)"
+  log "  baud=$(ini_get bc0 baud)  tx_delay=$(ini_get bc0 tx_delay)"
+
+  log "--- Seriell ---"
+  if [[ -e "$serial" ]]; then
+    log "OK: $serial existiert"
+    ls -l "$serial" 2>&1 | log_raw || true
+  else
+    log "FEHLER: $serial fehlt"
+  fi
+
+  log "--- fuser / lsof (wer hält Port?) ---"
+  if command -v fuser >/dev/null 2>&1; then
+
+    run_sudo fuser -v "$serial" 2>&1 | log_raw
+
+  else
+    log "WARN: fuser nicht installiert"
+  fi
+  if command -v lsof >/dev/null 2>&1; then
+
+    run_sudo lsof "$serial" 2>&1 | log_raw
+
+  fi
+
+  log "--- dosbox-x / DOS-Gast ---"
+  if pgrep -a -f 'dosbox-x|dosbox' 2>/dev/null | log_raw; then
+    log "WARN: dosbox läuft — kann ttyS0/USB belegen (sniff/passthrough)."
+  else
+    log "OK: kein dosbox/dosbox-x Prozess"
+  fi
+
+  log "--- Prozesse bcprd / max25d ---"
+  pgrep -a -x bcprd 2>/dev/null | log_raw || log "  bcprd: nicht laufend"
+  pgrep -a -x max25d 2>/dev/null | log_raw || log "  max25d: nicht laufend"
+  # wrapper scripts
+  pgrep -a -f 'run-max25d|max25d' 2>/dev/null | head -20 | log_raw || true
+
+  log "--- Lock / State ($sd) ---"
+  if [[ -d "$sd" ]]; then
+    ls -la "$sd" 2>&1 | log_raw || true
+    for f in "$sd"/lock* "$sd"/*.lock "$sd"/bcprd.pid; do
+      [[ -e "$f" ]] || continue
+      log "  lock/pid: $f"
+      [[ -f "$f" ]] && { log "    content:"; cat "$f" 2>&1 | log_raw || true; }
+    done
+  else
+    log "WARN: state_dir fehlt: $sd"
+  fi
+
+  log "--- Kernel baycom_* Module (sollten NICHT geladen sein) ---"
+  if command -v lsmod >/dev/null 2>&1; then
+    lsmod 2>/dev/null | awk '/^baycom_/ {print}' | log_raw || log "OK: keine baycom_* Module"
+  fi
+
+  log "--- setserial (falls vorhanden) ---"
+  local ss
+  for ss in /usr/bin/setserial /bin/setserial /sbin/setserial /usr/sbin/setserial; do
+    if [[ -x "$ss" ]]; then
+
+      run_sudo "$ss" -g "$serial" 2>&1 | log_raw
+
+      break
+    fi
+  done
+
+  log "--- bcpr-ctl preflight ---"
+
+  run_sudo "$CTL" -c "$INI" preflight 2>&1 | log_raw
+  local pf=$?
+
+  if [[ "$pf" -eq 0 ]]; then
+    log "OK: preflight PASS"
+  else
+    log "WARN: preflight rc=$pf (Port busy wenn Stack läuft — normal bei live max25d/bcprd)"
+  fi
+
+  log "--- Tools ---"
+  log "  CTL=$CTL"
+  log "  SMOKE=$SMOKE_SH"
+  local bin
+  if bin="$(resolve_bcprd)"; then
+    log "  bcprd=$bin"
+  else
+    log "  WARN: bcprd Binary nicht gefunden (Build: -DMAX25_BUILD_BCPR=ON)"
+  fi
+
+  pause_enter "Phase 1 fertig — Enter für weiter …"
+  return 0
+}
+
+phase_idle_mcr() {
+  banner "Phase 2 — Idle MCR Sample (/dev/port)"
+  local iobase mcr_off
+  iobase="$(iobase_val)"
+  # MCR = iobase+4
+  mcr_off=$((iobase + 4))
+  log "iobase=$iobase  MCR=$(printf '0x%x' "$mcr_off") (iobase+4)"
+  log "Erwartung Idle (Sailer/bcpr): oft 0x0d (DTR+OUT2+RTS-clear) — Werte nur Info."
+
+  if ! need_sudo; then
+    log "überspringe MCR-Sample (kein sudo)"
+    pause_enter
+    return 0
+  fi
+
+  run_sudo python3 - "$iobase" <<'PY' 2>&1 | log_raw
+import os, sys, time
+iobase = int(sys.argv[1], 0)
+mcr = iobase + 4
+fd = os.open("/dev/port", os.O_RDONLY)
+try:
+    vals = []
+    for i in range(20):
+        os.lseek(fd, mcr, os.SEEK_SET)
+        v = ord(os.read(fd, 1))
+        vals.append(v)
+        time.sleep(0.05)
+    uniq = sorted(set(vals))
+    print("Idle MCR samples (20×50ms): " + ",".join("0x%02x" % v for v in vals))
+    print("Unique: " + ",".join("0x%02x" % v for v in uniq))
+    rts = [(v & 0x02) != 0 for v in vals]
+    print("RTS asserted in any sample: %s" % ("YES" if any(rts) else "no"))
+    if all(v == 0 for v in vals):
+        print("WARN: all-zero — /dev/port may be inaccessible or wrong iobase")
+finally:
+    os.close(fd)
+PY
+  local rc=$?
+
+  if [[ "$rc" -ne 0 ]]; then
+    log "WARN: Idle-MCR Sample fehlgeschlagen (rc=$rc) — CAP_SYS_RAWIO / iobase prüfen"
+  fi
+  pause_enter "Phase 2 fertig — Enter …"
+  return 0
+}
+
+phase_status() {
+  banner "Phase 3 — Status + Telemetrie"
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  local sd
+  sd="$(state_dir)"
+  log "--- Telemetrie unter $sd ---"
+  for f in "$sd"/tx-last-bc* "$sd"/dcd-bc* "$sd"/rx-activity-bc* "$sd"/kiss-bc*; do
+    [[ -e "$f" ]] || continue
+    log "FILE: $f"
+    if [[ -L "$f" ]]; then
+      log "  symlink → $(readlink -f "$f" 2>/dev/null || readlink "$f")"
+    elif [[ -f "$f" ]]; then
+      cat "$f" 2>&1 | log_raw || true
+    fi
+  done
+  pause_enter "Phase 3 fertig — Enter …"
+  return 0
+}
+
+phase_rx_listen() {
+  banner "Phase 4 — RX Listen (soft-DCD)"
+  log "OPERATOR: Squellch öffnen / Rauschen/SQ so dass Soft-DCD aktiv werden kann."
+  log "  (§0.20 RX before TX — hier nur Listen, kein TX)"
+  pause_enter "SQ bereit? Enter startet ~12s RX listen …"
+
+  run_sudo "$CTL" -c "$INI" smoke --live --seconds 12 2>&1 | log_raw
+  local rc=${PIPESTATUS[0]}
+
+  if [[ "$rc" -eq 0 ]]; then
+    log "OK: RX-Listen smoke beendet (rc=0)"
+  else
+    log "WARN: RX-Listen smoke rc=$rc (siehe Log; Stack/INI prüfen)"
+  fi
+
+  local sd
+  sd="$(state_dir)"
+  for f in "$sd"/dcd-bc0 "$sd"/rx-activity-bc0; do
+    [[ -f "$f" ]] || continue
+    log "Nach RX: $f"
+    cat "$f" 2>&1 | log_raw || true
+  done
+  pause_enter "Phase 4 fertig — Enter …"
+  return 0
+}
+
+phase_force_tx_ladder() {
+  banner "Phase 5 — Force-TX Ladder (1 / 3 / 5 / 8 s)"
+  log "WARNUNG: --force-tx ohne RX-Nachweis (§0.20 Override) — Debug / Intermittent-Hunt."
+  log "Wattmeter bereithalten. USB-Pfad ist KEIN Produkt-TX."
+  log ""
+  log "PTT-WATCHDOG (FlexNet SER12 / WD-Boards):"
+  log "  Hardware kann PTT nach ~14,5 s Dauer-Key abwerfen (Discharge ~500 ms)."
+  log "  Bei langen Läufen / vielen Keys hintereinander: zwischendurch UNKEY / Pause ~14 s."
+  log "  Sonst: RF fällt trotz Host-MCR PASS (Watchdog, kein UART-Fehler)."
+  log ""
+  log "BEOBACHTUNGSHINWEIS TXD (Charge-Pump):"
+  log "  bcprd/Sailer: THR 0x00 gepulst · TFPCX: TXD oft steady +12 V."
+  log "  Notiz wenn RF mitten im Key einbricht / flackert (Pump/Bias-Kandidat)."
+  pause_enter "Bereit für Ladder? Enter …"
+
+  local secs host
+  for secs in 1 3 5 8; do
+    banner "Force-TX ${secs}s"
+    pause_enter "Wattmeter beobachten — Enter startet ${secs}s Key …"
+    smoke_force_tx "$secs"
+    host="$_LAST_HOST"
+    # show telem snapshot
+    local sd tl
+    sd="$(state_dir)"
+    tl="$sd/tx-last-bc0"
+    if [[ -f "$tl" ]]; then
+      log "--- tx-last-bc0 nach ${secs}s ---"
+      cat "$tl" 2>&1 | log_raw || true
+    fi
+    prompt_rf_obs "L4-${secs}s" "$host"
+    pause_enter "Nächste Stufe — Enter …"
+  done
+  return 0
+}
+
+phase_cal_high() {
+  banner "Phase 6 — Cal/high (bcprd --cal high)"
+  local bin
+  if ! bin="$(resolve_bcprd)"; then
+    log "WARN: bcprd nicht gefunden — Cal übersprungen"
+    pause_enter
+    return 0
+  fi
+
+  # Prefer strings(1); never start bare bcprd. Source contract: --cal high|low|alt.
+  if command -v strings >/dev/null 2>&1 && ! strings "$bin" 2>/dev/null | grep -qF -- '--cal'; then
+    log "WARN: strings fand kein --cal in Binary — Phase trotzdem anbieten (Operator kann abbrechen)"
+  fi
+
+  log "bcprd=$bin"
+  log "Cal = kontinuierlicher SER12 Tone+PTT (DOS cal.exe Stil), kein KISS."
+  log "Sicher: nur bcprd stoppen via bcpr-ctl — max25d Wrapper NICHT hart killen."
+  log ""
+  log "PTT-WATCHDOG: FlexNet cal pausiert alle ~14,5 s für ~500 ms (PTT-Discharge)."
+  log "  Dieses Skript: --cal high ~10 s (unter WD). Längere manuelle Cal/"
+  log "  Dauer-TX: UNKEY/Pause ~14 s einplanen — sonst RF-Tot auf WD-Boards."
+  log "TXD: bcprd pulst THR 0x00 (nicht TFPCX-steady) — RF-Einbruch mid-cal notieren."
+  log ""
+  local do_cal
+  ask_yn do_cal "bcprd stoppen und --cal high ~10s starten?"
+  if [[ "$do_cal" != "j" ]]; then
+    log "Cal übersprungen (Operator)"
+    pause_enter
+    return 0
+  fi
+
+  if ! need_sudo; then
+    pause_enter
+    return 0
+  fi
+
+  log "→ bcpr-ctl stop"
+
+  run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+
+  sleep 1
+
+  # Ensure no stray bcprd
+  if pgrep -x bcprd >/dev/null 2>&1; then
+    log "WARN: bcprd noch aktiv nach stop — pkill -x bcprd (kein max25d)"
+
+    run_sudo pkill -x bcprd 2>&1 | log_raw
+
+    sleep 1
+  fi
+
+  log "→ $bin -c $INI --cal high --seconds 10"
+  pause_enter "Wattmeter bereit — Enter startet cal high 10s …"
+
+  run_sudo "$bin" -c "$INI" --cal high --seconds 10 2>&1 | log_raw
+  local rc=$?
+
+  local host="PASS"
+  [[ "$rc" -eq 0 ]] || host="FAIL(rc=$rc)"
+  prompt_rf_obs "CAL-high-10s" "$host"
+
+  local restart
+  ask_yn restart "bcprd danach wieder starten (bcpr-ctl start)?"
+  if [[ "$restart" == "j" ]]; then
+
+    run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+
+    log "Hinweis: wenn max25d den Stack besitzt, ggf. max25d neu starten (Operator, nicht dieses Skript)."
+  fi
+  pause_enter "Phase 6 fertig — Enter …"
+  return 0
+}
+
+phase_double_burst() {
+  banner "Phase 7 — Double Burst (back-to-back TX)"
+  log "Zwei Force-TX 3s hintereinander (kurze Pause dazwischen)."
+  pause_enter "Enter startet Burst A …"
+  local host_a host_b
+  smoke_force_tx 3
+  host_a="$_LAST_HOST"
+  sleep 1
+  log "Burst B …"
+  smoke_force_tx 3
+  host_b="$_LAST_HOST"
+  prompt_rf_obs "DoubleBurst-A+B" "${host_a}/${host_b}"
+  pause_enter "Phase 7 fertig — Enter …"
+  return 0
+}
+
+phase_contact_hunt() {
+  banner "Phase 8 — Contact Hunt (DE-9 + 3.5mm)"
+  log "OPERATOR-CHECKLISTE:"
+  log "  1) DE-9 (PC-COM ↔ Host) und 3.5mm (Modem ↔ Radio) fest stecken"
+  log "  2) Während dem nächsten Key leicht wackeln (Stecker/Kabel)"
+  log "  3) Wattmeter + Board-LED + Radio-Display beobachten"
+  log "  Ziel: intermittenter Kontakt vs. dauerhaft tot unterscheiden"
+  pause_enter "Stecker fest? Enter startet 5s force-tx (währenddessen wackeln) …"
+
+  local host
+  smoke_force_tx 5
+  host="$_LAST_HOST"
+  local obs
+  ask obs "Beobachtung während Wackeln (z.B. 'kurz 2W' / 'immer 0' / 'LED flackert'):"
+  prompt_rf_obs "Contact-5s" "$host"
+  # overwrite last note with wiggle observation if empty note
+  if [[ -n "$obs" && ${#RES_NOTE[@]} -gt 0 ]]; then
+    RES_NOTE[$((${#RES_NOTE[@]} - 1))]="$obs | ${_extra:-}"
+    log "[contact-note] $obs"
+  fi
+  pause_enter "Phase 8 fertig — Enter …"
+  return 0
+}
+
+phase_usb_note() {
+  banner "Hinweis U — USB SER12 (kein Produkt-TX)"
+  log "USB-UART (z.B. /dev/ttyUSB0 / FTDI) ist KEIN unterstützter bcprd SER12-Pfad."
+  log "  bcprd braucht ioperm|/dev/port + echte ISA/LPC iobase — USB hat das nicht."
+  log "  Station: RF nur ttyS0+CB; USB0 = Modem ohne Radio → Wattmeter ungültig."
+  log "  DOSBox Soft-TNC auf USB ≠ bcpr Produkt-TX."
+  pause_enter
+  return 0
+}
+
+phase_restart_menu() {
+  banner "Optional 0 — Sicheres bcprd Restart"
+  log "Methode (aus bcpr-ctl): stop → start. Killt NICHT max25d."
+  log "Wenn max25d den Stack besitzt: nach stop/start ggf. max25d-seitig neu binden."
+  log ""
+  log "  Aktueller Status:"
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  local act
+  ask act "Aktion: [s]top / [t]start / [r]estart / [a]bbruch:"
+  case "${act,,}" in
+    s|stop)
+      run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+      ;;
+    t|start)
+      run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+      ;;
+    r|restart|re)
+      run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+      sleep 1
+      run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+      ;;
+    *)
+      log "Abbruch — keine Änderung"
+      ;;
+  esac
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  pause_enter
+  return 0
+}
+
+phase_summary() {
+  banner "Phase 9 — Summary + Verdict"
+  log "Logdatei: $LOG"
+  log ""
+  log "┌──────────────────┬──────────┬──────────┬──────────┬──────────┐"
+  log "│ Phase            │ Host     │ Watt W   │ BoardLED │ RadioTX  │"
+  log "├──────────────────┼──────────┼──────────┼──────────┼──────────┤"
+  local i n
+  n=${#RES_PHASE[@]}
+  if [[ "$n" -eq 0 ]]; then
+    log "│ (keine TX-Phasen aufgezeichnet)                              │"
+  else
+    for ((i = 0; i < n; i++)); do
+      printf '│ %-16s │ %-8s │ %-8s │ %-8s │ %-8s │\n' \
+        "${RES_PHASE[$i]:0:16}" \
+        "${RES_HOST[$i]:0:8}" \
+        "${RES_WATT[$i]:0:8}" \
+        "${RES_BLED[$i]:0:8}" \
+        "${RES_RDISP[$i]:0:8}" | log_raw
+      if [[ -n "${RES_NOTE[$i]:-}" ]]; then
+        log "│   note: ${RES_NOTE[$i]}"
+      fi
+    done
+  fi
+  log "└──────────────────┴──────────┴──────────┴──────────┴──────────┘"
+
+  # Verdict heuristics
+  local any_host_pass=0 any_host_fail=0 any_rf=0 all_rf_zero=1
+  for ((i = 0; i < n; i++)); do
+    case "${RES_HOST[$i]}" in
+      *PASS*) any_host_pass=1 ;;
+      *FAIL*) any_host_fail=1 ;;
+    esac
+    case "${RES_WATT[$i]}" in
+      ''|'0'|'0.0'|'?'|'n'|'nein') ;;
+      *)
+        # non-zero / non-empty that looks like power
+        if [[ "${RES_WATT[$i]}" =~ ^[0-9]*\.?[0-9]+$ ]]; then
+          if awk -v w="${RES_WATT[$i]}" 'BEGIN{exit !(w>0)}'; then
+            any_rf=1
+            all_rf_zero=0
+          fi
+        else
+          # free text — if contains number >0 heuristic
+          if [[ "${RES_WATT[$i]}" =~ [1-9] ]]; then
+            any_rf=1
+            all_rf_zero=0
+          fi
+        fi
+        ;;
+    esac
+    if [[ "${RES_BLED[$i]}" == "j" || "${RES_RDISP[$i]}" == "j" ]]; then
+      any_rf=1
+      all_rf_zero=0
+    fi
+  done
+
+  log ""
+  log "=== Verdict-Hinweise (Heuristik, kein Automatik-Urteil) ==="
+  if [[ "$n" -eq 0 ]]; then
+    log "• Keine Ladder-Daten — nur Preflight/Status gelaufen."
+  elif [[ "$any_host_pass" -eq 1 && "$all_rf_zero" -eq 1 && "$any_rf" -eq 0 ]]; then
+    log "• HOST OK / RF tot oder 0 W: Fehlerklasse NACH UART"
+    log "  → DE-9/3.5mm Kontakt, Charge-Pump/Vcc, PTT-Transistor, Mic-Buchse, Radio"
+    log "  → Mic-alone 4 W OK stützt: Radio selbst ok; Pfad Modem↔Mic intermittierend"
+  elif [[ "$any_host_pass" -eq 1 && "$any_rf" -eq 1 ]]; then
+    log "• HOST OK / RF zeitweise sichtbar: INTERMITTENT RF (Kontakt/Pump/AF)"
+    log "  → Contact-Hunt wiederholen; zwischen langen Keys Pause ~14 s (PTT-WD)"
+    log "  → TXD pulse vs steady (TFPCX) als Beobachtung; Kabel/Stecker fest"
+  elif [[ "$any_host_fail" -eq 1 && "$any_host_pass" -eq 0 ]]; then
+    log "• HOST FAIL: zuerst Stack/KISS/fulldup/MCR — nicht primär Wattmeter"
+    log "  → bcpr-ctl status, kiss_link, fulldup=yes bei Soft-DCD, kein zweites bcprd"
+    log "  → MCR bleibt Sailer 0x0e|bit / 0x0d (nicht 4PC-COM 0x0A)"
+  else
+    log "• Gemischte Ergebnisse — Log + Notizen vergleichen; Phasen 5/8 wiederholen."
+  fi
+  log ""
+  log "SSoT: 0-RESEARCHES/projects/max25-stack/2026-07-19-bcpr-host-keyed-wattmeter-tot.md"
+  log "      2026-07-19-bcpr-mcr-ok-rf-zero-after-4w.md · winning-recipe · RF intermittent"
+  log "      soft-TNC RE: 2026-07-19-baycom-soft-tnc-serial-ptt-re.md (WD · TXD · MCR)"
+  log "USB: kein Produkt-TX (Phase U)."
+  log ""
+  log "Log gespeichert: $LOG"
+  return 0
+}
+
+run_all() {
+  phase_preflight
+  phase_idle_mcr
+  phase_status
+  phase_rx_listen
+  phase_force_tx_ladder
+  phase_cal_high
+  phase_double_burst
+  phase_contact_hunt
+  phase_usb_note
+  phase_summary
+}
+
+menu_loop() {
+  while true; do
+    banner "bcpr Ultimate Diag — Menü"
+    log "INI=$INI"
+    log "Log=$LOG"
+    log ""
+    log "  1) Preflight"
+    log "  2) Idle MCR"
+    log "  3) Status + Telem"
+    log "  4) RX Listen"
+    log "  5) Force-TX Ladder 1/3/5/8s"
+    log "  6) Cal/high"
+    log "  7) Double Burst"
+    log "  8) Contact Hunt"
+    log "  9) Summary / Verdict"
+    log "  A) Alle Phasen 1–9 (+ USB-Hinweis)"
+    log "  0) bcprd stop/start (sicher)"
+    log "  U) USB-Hinweis"
+    log "  Q) Beenden"
+    log ""
+    local choice
+    ask choice "Wahl:"
+    case "${choice^^}" in
+      1) phase_preflight ;;
+      2) phase_idle_mcr ;;
+      3) phase_status ;;
+      4) phase_rx_listen ;;
+      5) phase_force_tx_ladder ;;
+      6) phase_cal_high ;;
+      7) phase_double_burst ;;
+      8) phase_contact_hunt ;;
+      9) phase_summary ;;
+      A|ALL) run_all ;;
+      0) phase_restart_menu ;;
+      U) phase_usb_note ;;
+      Q|X|EXIT|QUIT)
+        phase_summary
+        log "Ende."
+        return 0
+        ;;
+      *)
+        log "Unbekannte Wahl: $choice"
+        ;;
+    esac
+  done
+}
+
+# ---------- main ----------
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -c)
+      [[ $# -ge 2 ]] || { echo "ERROR: -c needs INI path"; exit 2; }
+      INI="$2"
+      shift 2
+      ;;
+    --menu) MODE="menu"; shift ;;
+    --all) MODE="all"; shift ;;
+    --phase)
+      [[ $# -ge 2 ]] || { echo "ERROR: --phase needs N"; exit 2; }
+      MODE="phase"
+      PHASE_ONLY="$2"
+      shift 2
+      ;;
+    -h|--help) usage; exit 0 ;;
+    *)
+      echo "ERROR: unknown arg: $1"
+      usage
+      exit 2
+      ;;
+  esac
+done
+
+RUN_TS="$(date +%Y%m%d-%H%M%S)"
+LOG="/tmp/bcpr-ultimate-diag-${RUN_TS}.log"
+: >"$LOG" || {
+  echo "FEHLER: kann Log nicht schreiben: $LOG"
+  exit 1
+}
+
+# Interactive reads use /dev/tty; log()/log_raw append to $LOG (no exec-tee double).
+banner "bcpr Ultimate Diag — BayCom/based (bcpr)"
+log "Start: $(date -R 2>/dev/null || date)"
+log "Host:  $(hostname 2>/dev/null || echo '?')"
+log "User:  $(id -un 2>/dev/null || echo '?')  uid=$(id -u)"
+log "INI:   $INI  (override: BCPR_INI / -c)"
+log "Log:   $LOG"
+log "Tools: $CTL"
+log ""
+log "Hinweis: PTT-Watchdog ~14,5 s / 500 ms — bei langen Keys unkey/pausieren."
+log "         TXD: bcprd pulst (Sailer); TFPCX oft steady — RF mid-key notieren."
+log "         MCR: Sailer belassen (kein 4PC-COM 0x0A-Experiment in diesem Skript)."
+log ""
+
+ensure_tools || {
+  log "Abbruch: Tools fehlen."
+  exit 1
+}
+
+# Soft check sudo early (warn only for menu; hard for --all live)
+if ! need_sudo; then
+  log "WARN: ohne sudo -n sind Live/TX/Cal/MCR-Phasen blockiert."
+  if [[ "$MODE" == "all" ]]; then
+    log "Abbruch (--all braucht sudo -n)."
+    exit 1
+  fi
+fi
+
+case "$MODE" in
+  all)
+    run_all
+    ;;
+  phase)
+    case "$PHASE_ONLY" in
+      1) phase_preflight ;;
+      2) phase_idle_mcr ;;
+      3) phase_status ;;
+      4) phase_rx_listen ;;
+      5) phase_force_tx_ladder ;;
+      6) phase_cal_high ;;
+      7) phase_double_burst ;;
+      8) phase_contact_hunt ;;
+      9) phase_summary ;;
+      0) phase_restart_menu ;;
+      U|u) phase_usb_note ;;
+      *)
+        log "FEHLER: unbekannte Phase $PHASE_ONLY"
+        exit 2
+        ;;
+    esac
+    ;;
+  menu|*)
+    menu_loop
+    ;;
+esac
+
+log ""
+log "Fertig. Log: $LOG"
+exit 0
diff --git a/stacks/max25-bcpr/tools/max25-bcpr-ctl b/stacks/max25-bcpr/tools/max25-bcpr-ctl
new file mode 100755
index 0000000..56f44b6
--- /dev/null
+++ b/stacks/max25-bcpr/tools/max25-bcpr-ctl
@@ -0,0 +1,349 @@
+#!/usr/bin/env bash
+# max25-bcpr-ctl — preflight / start / status / stop / smoke for max25-bcprd (SER12).
+# PC-COM / BayCom/based: TCM3105 AFSK + PTT. Host owns HDLC/KISS.
+# No calibrate. No baycom_ser_fdx product path.
+set -euo pipefail
+
+INI="${MAX25_BCPR_INI:-${BCPR_INI:-/etc/max25/max25-bcpr.ini}}"
+BCPRD="${MAX25_BCPRD:-${BCPRD:-max25-bcprd}}"
+BCPRD_INIT="${MAX25_BCPRD_INIT:-max25-bcprd-init}"
+PIDFILE="${MAX25_BCPR_PIDFILE:-/tmp/max25-bcpr/max25-bcprd.pid}"
+STATE_DIR="/tmp/max25-bcpr"
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+SMOKE_SH="$SCRIPT_DIR/max25-bcpr-rxtx-smoke.sh"
+
+usage() {
+  cat <<USAGE
+Usage: max25-bcpr-ctl [-c ini] {preflight|start|status|stop|smoke|version} [smoke-opts]
+  smoke [--live] [--tx] [--seconds N] [--tx-seconds N]
+  Default smoke: NO TX. --tx-seconds default 3 (≈376B info / visible PTT).
+  Warn: SQ-open / RX-edge noise can stress hosts — see docs/BAYCOM-FREEZES.md
+USAGE
+}
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -c) INI="$2"; shift 2 ;;
+    -h|--help) usage; exit 0 ;;
+    *) break ;;
+  esac
+done
+CMD="${1:-}"
+if [[ $# -gt 0 ]]; then
+  shift
+fi
+
+resolve_max25_bcprd_init() {
+  if [[ -n "${BCPRD_INIT:-}" && "$BCPRD_INIT" != "max25-bcprd-init" && -x "$BCPRD_INIT" ]]; then
+    echo "$BCPRD_INIT"; return
+  fi
+  if command -v "$BCPRD_INIT" >/dev/null 2>&1; then
+    command -v "$BCPRD_INIT"; return
+  fi
+  local root cand
+  root="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+  for cand in \
+    ${MAX25_BCPR_BUILD_DIR:-${BCPR_BUILD_DIR:-}}/bin/max25-bcprd-init \
+    "$root/build-max25-bcpr/bin/max25-bcprd-init" \
+    "$root/build-max25-bcpr-${USER:-user}/bin/max25-bcprd-init" \
+    "/tmp/max25-build-max25-bcpr-${USER:-user}/bin/max25-bcprd-init" \
+    "$root/build/bin/max25-bcprd-init" \
+    /usr/local/bin/max25-bcprd-init /usr/bin/max25-bcprd-init; do
+    [[ -n "$cand" && -x "$cand" ]] && { echo "$cand"; return; }
+  done
+  return 1
+}
+
+resolve_max25_bcprd() {
+  if [[ -n "${BCPRD:-}" && "$BCPRD" != "max25-bcprd" && -x "$BCPRD" ]]; then
+    echo "$BCPRD"; return
+  fi
+  if command -v "$BCPRD" >/dev/null 2>&1; then
+    command -v "$BCPRD"; return
+  fi
+  local root cand
+  root="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+  for cand in \
+    ${MAX25_BCPR_BUILD_DIR:-${BCPR_BUILD_DIR:-}}/bin/max25-bcprd \
+    "$root/build-max25-bcpr/bin/max25-bcprd" \
+    "$root/build-max25-bcpr-${USER:-user}/bin/max25-bcprd" \
+    "/tmp/max25-build-max25-bcpr-${USER:-user}/bin/max25-bcprd" \
+    "$root/build/bin/max25-bcprd" \
+    /usr/local/bin/max25-bcprd /usr/bin/max25-bcprd; do
+    [[ -n "$cand" && -x "$cand" ]] && { echo "$cand"; return; }
+  done
+  return 1
+}
+
+ini_get() {
+  local section="$1" key="$2"
+  awk -F= -v s="[$section]" -v k="$key" '
+    $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+    cur==s && $1 ~ "^[[:space:]]*"k"[[:space:]]*$" {
+      v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print v; exit
+    }' "$INI" 2>/dev/null || true
+}
+
+is_truthy() {
+  case "${1,,}" in yes|true|on|1) return 0 ;; *) return 1 ;; esac
+}
+
+find_setserial() {
+  local p
+  for p in /usr/bin/setserial /bin/setserial /sbin/setserial /usr/sbin/setserial; do
+    [[ -x "$p" ]] && { echo "$p"; return; }
+  done
+  command -v setserial 2>/dev/null || true
+}
+
+# Parse "Port: 0x3f8" / "irq: 4" from setserial -g
+setserial_port_irq() {
+  local bin="$1" dev="$2" out port irq
+  out="$("$bin" -g "$dev" 2>/dev/null)" || return 1
+  # Typical: /dev/ttyS0, UART: 16550A, Port: 0x3f8, IRQ: 4
+  port="$(printf '%s\n' "$out" | sed -n 's/.*Port:[[:space:]]*\(0x[0-9a-fA-F]\+\).*/\1/p' | head -1)"
+  irq="$(printf '%s\n' "$out" | sed -n 's/.*IRQ:[[:space:]]*\([0-9]\+\).*/\1/p' | head -1)"
+  printf '%s %s\n' "${port:-}" "${irq:-}"
+}
+
+norm_hex() {
+  # lowercase 0x… without leading zeros differences: 0x3f8 vs 0x03f8
+  local v="${1,,}"
+  if [[ "$v" =~ ^0x ]]; then
+    printf '0x%x' "$((v))"
+  else
+    printf '%s' "$v"
+  fi
+}
+
+is_freebsd() {
+  [[ "$(uname -s)" == "FreeBSD" ]]
+}
+
+port_busy() {
+  local serial="$1"
+  local out
+  # Prefer lsof (parse output); FreeBSD fuser exit status alone is unreliable.
+  if command -v lsof >/dev/null 2>&1; then
+    out="$(lsof "$serial" 2>/dev/null || true)"
+    if [[ -n "$out" ]]; then
+      return 0
+    fi
+    return 1
+  fi
+  if command -v fuser >/dev/null 2>&1; then
+    out="$(fuser "$serial" 2>/dev/null || true)"
+    [[ -n "$out" ]]
+    return $?
+  fi
+  return 1
+}
+
+baycom_modules_loaded() {
+  local m
+  if ! command -v lsmod >/dev/null 2>&1; then
+    return 1
+  fi
+  for m in baycom_ser_fdx baycom_ser_hdx baycom_par baycom_epp; do
+    if lsmod 2>/dev/null | awk '{print $1}' | grep -qx "$m"; then
+      echo "$m"
+      return 0
+    fi
+  done
+  return 1
+}
+
+cmd_preflight() {
+  local err=0 dry serial irq iobase name sysirq got ss ss_port ss_irq pair
+  local -a seen_irq=() seen_serial=()
+  [[ -f "$INI" ]] || { echo "ERROR: missing $INI"; return 1; }
+  dry="$(ini_get max25-bcpr dry_run)"; [[ -z "$dry" ]] && dry="$(ini_get bcpr dry_run)"
+  sd="$(ini_get max25-bcpr state_dir)"; [[ -z "$sd" ]] && sd="$(ini_get max25-bcpr state_dir)"
+  [[ -n "$sd" ]] && STATE_DIR="$sd"
+  echo "max25-bcpr-ctl preflight ini=$INI"
+  echo "NOTE: max25-bcpr → device max25e0 (BayCom/based SER12; live via max25-bcprd-init)"
+
+  # Kernel BayCom modules must not share the path (A–O–Z isolate).
+  if mod="$(baycom_modules_loaded)"; then
+    echo "  ERROR: kernel module loaded: $mod — unload before max25-bcpr (isolate)"
+    err=1
+  else
+    echo "  OK: no baycom_* modules loaded"
+  fi
+
+  ss="$(find_setserial)"
+  if [[ -z "$ss" ]]; then
+    echo "  WARN: setserial not found — iobase check limited to INI/sysfs"
+  else
+    echo "  OK: setserial=$ss"
+  fi
+
+  for sec in bc0 bc1; do
+    serial="$(ini_get "$sec" serial)"
+    [[ -z "$serial" ]] && continue
+    enabled="$(ini_get "$sec" enabled)"
+    if [[ -n "$enabled" ]] && ! is_truthy "$enabled"; then
+      echo "  [$sec] enabled=no — skip"
+      continue
+    fi
+    irq="$(ini_get "$sec" irq)"
+    iobase="$(ini_get "$sec" iobase)"
+    echo "  [$sec] serial=$serial irq=$irq iobase=$iobase"
+
+    if is_truthy "$dry"; then
+      echo "  dry_run=yes — skip live tty/IRQ/idle checks"
+      continue
+    fi
+
+    if [[ ! -e "$serial" ]]; then
+      if is_freebsd && [[ -n "$iobase" && "$iobase" != "0" ]]; then
+        echo "  WARN: $serial missing (uart disabled — SER12 uses iobase $iobase only)"
+      else
+        echo "  ERROR: $serial missing"; err=1; continue
+      fi
+    else
+      echo "  OK: serial node exists"
+    fi
+
+    if [[ -e "$serial" ]]; then
+      if port_busy "$serial"; then
+        echo "  ERROR: $serial busy (fuser/lsof) — exclusive lock fail-closed"; err=1
+      else
+        echo "  OK: port idle"
+      fi
+    elif is_freebsd && [[ -n "$iobase" && "$iobase" != "0" ]]; then
+      echo "  OK: port idle (no tty node — ExSys iobase path)"
+    fi
+
+    if [[ -z "$irq" || "$irq" == "0" ]]; then
+      echo "  ERROR: irq must be real (non-zero)"; err=1
+    fi
+
+    name="${serial##*/}"
+    sysirq="/sys/class/tty/${name}/irq"
+    if [[ -r "$sysirq" ]]; then
+      got="$(tr -d '[:space:]' <"$sysirq")"
+      if [[ -n "$irq" && "$irq" != "0" && "$got" != "$irq" ]]; then
+        echo "  ERROR: IRQ mismatch INI=$irq sysfs=$got"; err=1
+      elif [[ -n "$irq" && "$irq" != "0" ]]; then
+        echo "  OK: IRQ $irq matches sysfs"
+      fi
+    else
+      echo "  WARN: cannot read $sysirq"
+    fi
+
+    if [[ -n "$ss" && -n "$iobase" ]]; then
+      pair="$(setserial_port_irq "$ss" "$serial" || true)"
+      ss_port="$(printf '%s' "$pair" | awk '{print $1}')"
+      ss_irq="$(printf '%s' "$pair" | awk '{print $2}')"
+      if [[ -n "$ss_port" ]]; then
+        if [[ "$(norm_hex "$iobase")" != "$(norm_hex "$ss_port")" ]]; then
+          echo "  ERROR: iobase mismatch INI=$iobase setserial=$ss_port"; err=1
+        else
+          echo "  OK: iobase $iobase matches setserial"
+        fi
+      else
+        echo "  WARN: setserial did not report Port for $serial"
+      fi
+      if [[ -n "$ss_irq" && -n "$irq" && "$irq" != "0" && "$ss_irq" != "$irq" ]]; then
+        echo "  ERROR: IRQ mismatch INI=$irq setserial=$ss_irq"; err=1
+      elif [[ -n "$ss_irq" && -n "$irq" && "$irq" != "0" ]]; then
+        echo "  OK: IRQ $irq matches setserial"
+      fi
+    elif [[ -n "$iobase" && -z "$ss" ]]; then
+      echo "  WARN: cannot verify iobase=$iobase without setserial"
+    fi
+
+    # Dual uniqueness
+    for s in "${seen_serial[@]:-}"; do
+      if [[ -n "$s" && "$s" == "$serial" ]]; then
+        echo "  ERROR: duplicate serial $serial"; err=1
+      fi
+    done
+    for i in "${seen_irq[@]:-}"; do
+      if [[ -n "$i" && -n "$irq" && "$irq" != "0" && "$i" == "$irq" ]]; then
+        echo "  ERROR: duplicate IRQ $irq (bc0/bc1 must be distinct)"; err=1
+      fi
+    done
+    seen_serial+=("$serial")
+    [[ -n "$irq" && "$irq" != "0" ]] && seen_irq+=("$irq")
+  done
+
+  return "$err"
+}
+
+cmd_start() {
+  local bin init dry
+  cmd_preflight || { echo "preflight failed"; return 1; }
+  sd="$(ini_get max25-bcpr state_dir)"; [[ -z "$sd" ]] && sd="$(ini_get bcpr state_dir)"; [[ -n "$sd" ]] && STATE_DIR="$sd"
+  mkdir -p "$STATE_DIR"
+  PIDFILE="$STATE_DIR/max25-bcprd.pid"
+  if [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null; then
+    echo "already running pid=$(cat "$PIDFILE")"; return 0
+  fi
+  dry="$(ini_get max25-bcpr dry_run)"; [[ -z "$dry" ]] && dry="$(ini_get bcpr dry_run)"
+  if is_truthy "$dry"; then
+    bin="$(resolve_max25_bcprd)" || { echo "max25-bcprd not found — build with -DMAX25_BUILD_MAX25_BCPR=ON"; return 1; }
+    "$bin" -c "$INI" --dry-run </dev/null >/dev/null 2>&1 &
+    echo $! >"$PIDFILE"
+    echo "started max25-bcprd (dry-run) pid=$(cat "$PIDFILE") → max25e0"
+    return 0
+  fi
+  init="$(resolve_max25_bcprd_init)" || { echo "max25-bcprd-init not found — build/install with setuid"; return 1; }
+  # Init forks internally; parent writes pidfile and exits (no shell background).
+  if ! "$init" -c "$INI" </dev/null; then
+    echo "max25-bcprd-init failed (see stderr above)"
+    return 1
+  fi
+  if [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null; then
+    echo "started max25-bcprd pid=$(cat "$PIDFILE") → max25e0"
+  else
+    echo "max25-bcprd-init exited but pidfile missing or stale"; return 1
+  fi
+}
+
+cmd_stop() {
+  sd="$(ini_get max25-bcpr state_dir 2>/dev/null || true)"
+  [[ -z "${sd:-}" ]] && sd="$(ini_get bcpr state_dir 2>/dev/null || true)"
+  [[ -n "${sd:-}" ]] && STATE_DIR="$sd"
+  PIDFILE="$STATE_DIR/max25-bcprd.pid"
+  if [[ -f "$PIDFILE" ]]; then
+    kill "$(cat "$PIDFILE")" 2>/dev/null || true
+    rm -f "$PIDFILE"
+  fi
+  pkill -x max25-bcprd 2>/dev/null || true
+  pkill -x max25-bcprd-init 2>/dev/null || true
+  echo "stopped"
+}
+
+cmd_status() {
+  sd="$(ini_get max25-bcpr state_dir 2>/dev/null || true)"
+  [[ -z "${sd:-}" ]] && sd="$(ini_get bcpr state_dir 2>/dev/null || true)"
+  [[ -n "${sd:-}" ]] && STATE_DIR="$sd"
+  PIDFILE="$STATE_DIR/max25-bcprd.pid"
+  if [[ -f "$PIDFILE" ]] && kill -0 "$(cat "$PIDFILE")" 2>/dev/null; then
+    echo "max25-bcprd: running pid=$(cat "$PIDFILE")"
+  else
+    echo "max25-bcprd: not running"
+  fi
+  for link in "$STATE_DIR"/kiss-bc*; do
+    [[ -e "$link" ]] || continue
+    echo "  kiss_link $link -> $(readlink -f "$link" 2>/dev/null || echo '?')"
+  done
+}
+
+cmd_smoke() {
+  [[ -x "$SMOKE_SH" ]] || { echo "ERROR: missing $SMOKE_SH"; return 1; }
+  # Forward remaining args; default INI from -c
+  exec "$SMOKE_SH" -c "$INI" "$@"
+}
+
+case "$CMD" in
+  preflight) cmd_preflight ;;
+  start) cmd_start ;;
+  stop) cmd_stop ;;
+  status) cmd_status ;;
+  smoke) cmd_smoke "$@" ;;
+  version) echo "max25-bcpr-ctl 0.4.0 (SER12 → max25e0; live via max25-bcprd-init)" ;;
+  *) usage; exit 1 ;;
+esac
diff --git a/stacks/max25-bcpr/tools/max25-bcpr-rxtx-smoke.sh b/stacks/max25-bcpr/tools/max25-bcpr-rxtx-smoke.sh
new file mode 100755
index 0000000..c499401
--- /dev/null
+++ b/stacks/max25-bcpr/tools/max25-bcpr-rxtx-smoke.sh
@@ -0,0 +1,566 @@
+#!/usr/bin/env bash
+# max25-bcpr-rxtx-smoke.sh — L0…L4 nofreeze prove-out (BayCom/based / max25-bcpr).
+# Default: offline L0 only, NO TX. Live RX: --live. TX: --live --tx.
+# No calibrate. No baycom_ser_fdx product path.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+# Tree: stacks/max25-bcpr/tools → repo root. Install: PREFIX/sbin → use installed bins.
+_cand="$(cd "$SCRIPT_DIR/../../.." 2>/dev/null && pwd || true)"
+if [[ -n "$_cand" && -f "$_cand/CMakeLists.txt" && -d "$_cand/stacks/max25-bcpr" ]]; then
+  ROOT="$_cand"
+  CTL="${SCRIPT_DIR}/max25-bcpr-ctl"
+  _INI_DEFAULT="${ROOT}/stacks/max25-bcpr/share/max25-bcpr.ini.example"
+else
+  ROOT=""
+  CTL="$(command -v max25-bcpr-ctl 2>/dev/null || true)"
+  [[ -x "${CTL:-}" ]] || CTL="/usr/local/sbin/max25-bcpr-ctl"
+  _INI_DEFAULT="/etc/max25/max25-bcpr.ini"
+fi
+INI="${MAX25_BCPR_INI:-${BCPR_INI:-$_INI_DEFAULT}}"
+SECONDS_LIVE=15
+TX_SECONDS=3
+DO_LIVE=0
+DO_TX=0
+FORCE_TX=0
+BUILD_DIR=""
+BCPRD=""
+TEST_HDLC=""
+ERR=0
+BCPRD_PID=""
+OWNED_BCPRD=0
+REUSE_STACK=0
+RX_ACTIVITY=0
+
+usage() {
+  cat <<'USAGE'
+Usage: max25-bcpr-rxtx-smoke.sh [-c ini] [--live] [--tx] [--force-tx] [--seconds N] [--tx-seconds N] [--build-dir DIR]
+  L0 offline always. Soft L1 if probes safe. L2/L3 need --live. L4 needs --tx.
+  --tx-seconds: target PTT key window (default 3; uses ~376B info ≈3s like proven inject).
+  Default: NO TX. Hard time caps. Stop only max25-bcprd started by this script.
+  §0.20: --tx requires RX/DCD activity in this run unless --force-tx (debug only).
+USAGE
+}
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -c) INI="$2"; shift 2 ;;
+    --live) DO_LIVE=1; shift ;;
+    --tx) DO_TX=1; shift ;;
+    --force-tx) FORCE_TX=1; shift ;;
+    --seconds) SECONDS_LIVE="$2"; shift 2 ;;
+    --tx-seconds) TX_SECONDS="$2"; shift 2 ;;
+    --build-dir) BUILD_DIR="$2"; shift 2 ;;
+    -h|--help) usage; exit 0 ;;
+    *) echo "ERROR: unknown arg: $1"; usage; exit 2 ;;
+  esac
+done
+
+if [[ "$DO_TX" -eq 1 && "$DO_LIVE" -eq 0 ]]; then
+  echo "ERROR: --tx requires --live"
+  exit 2
+fi
+
+if [[ "$SECONDS_LIVE" -lt 1 ]]; then
+  SECONDS_LIVE=1
+fi
+# Endurance: long keys (e.g. 60s). bcprd PTT-WD unkeys ~14.5s/500ms.
+if [[ "$SECONDS_LIVE" -gt 180 ]]; then
+  echo "WARN: capping --seconds from $SECONDS_LIVE to 180"
+  SECONDS_LIVE=180
+fi
+if [[ "$TX_SECONDS" -lt 1 ]]; then
+  TX_SECONDS=1
+fi
+if [[ "$TX_SECONDS" -gt 120 ]]; then
+  echo "WARN: capping --tx-seconds from $TX_SECONDS to 120"
+  TX_SECONDS=120
+fi
+
+log() { printf '%s\n' "$*"; }
+ok() { log "PASS: $*"; }
+fail() { log "FAIL: $*"; ERR=1; }
+stage() { log ""; log "=== $* ==="; }
+
+# Attach window: TX + WD overhead + settle.
+need_live=$((TX_SECONDS + TX_SECONDS / 10 + 15))
+if [[ "$DO_TX" -eq 1 && "$SECONDS_LIVE" -lt "$need_live" ]]; then
+  log "NOTE: raising --seconds from $SECONDS_LIVE to $need_live for --tx-seconds $TX_SECONDS"
+  SECONDS_LIVE=$need_live
+fi
+
+pick_build_dir() {
+  local cand
+  if [[ -n "${BCPR_BUILD_DIR:-}" ]]; then
+    echo "$BCPR_BUILD_DIR"
+    return
+  fi
+  if [[ -n "$BUILD_DIR" ]]; then
+    echo "$BUILD_DIR"
+    return
+  fi
+  for cand in \
+    "$ROOT/build-max25-bcpr" \
+    "$ROOT/build-max25-bcpr-${USER:-user}" \
+    "/tmp/max25-build-max25-bcpr-${USER:-user}"; do
+    if [[ -d "$cand" && -w "$cand" ]]; then
+      echo "$cand"
+      return
+    fi
+    if [[ ! -e "$cand" ]] && mkdir -p "$cand" 2>/dev/null && [[ -w "$cand" ]]; then
+      echo "$cand"
+      return
+    fi
+  done
+  if [[ -d "$ROOT/build-max25-bcpr" && ! -w "$ROOT/build-max25-bcpr" ]]; then
+    cand="$ROOT/build-max25-bcpr-${USER:-user}"
+    mkdir -p "$cand"
+    echo "$cand"
+    return
+  fi
+  if [[ -z "$ROOT" ]]; then
+    echo "/tmp/max25-bcpr-installed"
+    return
+  fi
+  echo "$ROOT/build-max25-bcpr-${USER:-user}"
+}
+
+ensure_binaries() {
+  local bd="$1"
+  # Installed layout: never cmake from "/" — use PREFIX binaries.
+  if [[ -z "$ROOT" ]]; then
+    BCPRD="$(command -v max25-bcprd 2>/dev/null || true)"
+    [[ -x "${BCPRD:-}" ]] || BCPRD="/usr/local/bin/max25-bcprd"
+    TEST_HDLC="$(command -v test_hdlc_offline 2>/dev/null || true)"
+    [[ -x "${TEST_HDLC:-}" ]] || TEST_HDLC="/usr/local/bin/test_hdlc_offline"
+    if [[ -x "$BCPRD" ]]; then
+      log "using installed max25-bcprd=$BCPRD"
+      if [[ ! -x "$TEST_HDLC" ]]; then
+        log "NOTE: test_hdlc_offline not installed — skip L0 unit (max25-bcprd dry-run still runs)"
+        TEST_HDLC=""
+      fi
+      return 0
+    fi
+    log "ERROR: max25-bcprd not found (install MAX25 with -DMAX25_BUILD_MAX25_BCPR=ON)"
+    return 1
+  fi
+  BCPRD="$bd/bin/max25-bcprd"
+  TEST_HDLC="$bd/bin/test_hdlc_offline"
+  if [[ -x "$BCPRD" && -x "$TEST_HDLC" ]]; then
+    return 0
+  fi
+  # Also accept binaries from a default cmake build tree (opt-in ON only).
+  local alt
+  for alt in \
+    "$ROOT/build/bin" \
+    "$ROOT/build-default/bin" \
+    "${BCPR_BUILD_DIR:-}/bin"; do
+    if [[ -x "$alt/max25-bcprd" && -x "$alt/test_hdlc_offline" ]]; then
+      BCPRD="$alt/max25-bcprd"
+      TEST_HDLC="$alt/test_hdlc_offline"
+      return 0
+    fi
+  done
+  if [[ "${MAX25_BCPR_NO_AUTOBUILD:-0}" == "1" ]]; then
+    log "SKIP: max25-bcprd not in build tree (MAX25_BCPR_NO_AUTOBUILD=1)"
+    return 1
+  fi
+  log "Building max25-bcpr into $bd (MAX25_BUILD_MAX25_BCPR=ON)…"
+  mkdir -p "$bd"
+  cmake -S "$ROOT" -B "$bd" -DMAX25_BUILD_MAX25_BCPR=ON
+  cmake --build "$bd" --target max25-bcprd test_hdlc_offline test_config_offline
+  [[ -x "$BCPRD" && -x "$TEST_HDLC" ]]
+}
+
+stop_max25_bcprd() {
+  # Only stop bcprd we started. Never blanket-pkill — max25d may own a live stack.
+  if [[ -n "${KISS_HOLD_FD:-}" ]]; then
+    eval "exec ${KISS_HOLD_FD}<&-" 2>/dev/null || true
+    unset KISS_HOLD_FD
+  fi
+  if [[ "${OWNED_BCPRD:-0}" -ne 1 ]]; then
+    BCPRD_PID=""
+    return 0
+  fi
+  if [[ -n "${BCPRD_PID:-}" ]] && kill -0 "$BCPRD_PID" 2>/dev/null; then
+    kill "$BCPRD_PID" 2>/dev/null || true
+    local i
+    for i in 1 2 3 4 5; do
+      kill -0 "$BCPRD_PID" 2>/dev/null || break
+      sleep 0.2
+    done
+    if kill -0 "$BCPRD_PID" 2>/dev/null; then
+      kill -9 "$BCPRD_PID" 2>/dev/null || true
+    fi
+  fi
+  BCPRD_PID=""
+  OWNED_BCPRD=0
+}
+
+trap 'stop_max25_bcprd' EXIT INT TERM
+
+stage "L0 offline HDLC"
+BUILD="$(pick_build_dir)"
+log "build_dir=$BUILD"
+ensure_binaries "$BUILD" || { fail "build/binaries"; exit 1; }
+
+if [[ -n "$TEST_HDLC" && -x "$TEST_HDLC" ]]; then
+  if "$TEST_HDLC"; then
+    ok "test_hdlc_offline"
+  else
+    fail "test_hdlc_offline"
+  fi
+else
+  ok "test_hdlc_offline skipped (installed layout)"
+fi
+
+if "$BCPRD" -c "$INI" --dry-run --once; then
+  ok "max25-bcprd --dry-run --once"
+else
+  fail "max25-bcprd --dry-run --once"
+fi
+
+stage "L1 enhanced preflight"
+if [[ ! -f "$INI" ]]; then
+  fail "missing INI $INI"
+else
+  export BCPRD
+  set +e
+  "$CTL" -c "$INI" preflight
+  pf_rc=$?
+  set -e
+  if [[ "$pf_rc" -eq 0 ]]; then
+    ok "max25-bcpr-ctl preflight"
+  else
+    if [[ "$DO_LIVE" -eq 1 ]]; then
+      fail "max25-bcpr-ctl preflight (required for --live)"
+    else
+      log "NOTE: preflight rc=$pf_rc without --live — L0 is the offline gate"
+      # dry_run example: preflight skips UART and returns 0; real mismatch is soft-note only
+      if [[ "$pf_rc" -ne 0 ]]; then
+        log "WARN: fix INI before --live"
+      fi
+    fi
+  fi
+fi
+
+if [[ "$DO_LIVE" -eq 0 ]]; then
+  stage "summary (offline)"
+  if [[ "$ERR" -eq 0 ]]; then
+    ok "L0 complete — add --live for L2/L3 (RX), --live --tx for L4"
+    exit 0
+  fi
+  exit "$ERR"
+fi
+
+stage "L2/L3 timed attach + RX listen (${SECONDS_LIVE}s)"
+if [[ "$DO_TX" -eq 1 ]]; then
+  log "WARN: --tx asserts PTT (~${TX_SECONDS}s key window; LED/wattmeter visible)"
+fi
+
+dry_val="$(awk -F= '
+  $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+  cur=="[max25-bcpr]" && $1 ~ /^[[:space:]]*dry_run[[:space:]]*$/ {
+    v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print tolower(v); exit
+  }' "$INI")"
+case "$dry_val" in
+  yes|true|on|1)
+    fail "live requires dry_run=no in $INI"
+    exit 1
+    ;;
+esac
+
+kiss_link="$(awk -F= '
+  $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+  cur=="[bc0]" && $1 ~ /^[[:space:]]*kiss_link[[:space:]]*$/ {
+    v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print v; exit
+  }' "$INI")"
+kiss_link="${kiss_link:-/tmp/max25-bcpr/kiss-bc0}"
+
+iobase="$(awk -F= '
+  $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+  cur=="[bc0]" && $1 ~ /^[[:space:]]*iobase[[:space:]]*$/ {
+    v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print v; exit
+  }' "$INI")"
+iobase="${iobase:-0x3f8}"
+
+export BCPRD
+"$CTL" -c "$INI" preflight || { fail "preflight before attach"; exit 1; }
+
+# Prefer live stack (max25d-owned bcprd) — proven KISS inject path.
+# Starting a second bcprd races UART MCR and can yield no visible TX.
+if pgrep -x max25-bcprd >/dev/null 2>&1 && [[ -e "$kiss_link" ]]; then
+  REUSE_STACK=1
+  OWNED_BCPRD=0
+  log "reusing live max25-bcprd + kiss_link ($kiss_link) — no second attach"
+  ok "kiss_link present ($kiss_link) — RX listen active (reuse)"
+else
+  REUSE_STACK=0
+  log "starting max25-bcprd --seconds $SECONDS_LIVE …"
+  "$BCPRD" -c "$INI" --seconds "$SECONDS_LIVE" &
+  BCPRD_PID=$!
+  OWNED_BCPRD=1
+
+  waited=0
+  while [[ "$waited" -lt 5 ]]; do
+    if [[ -e "$kiss_link" ]] || ! kill -0 "$BCPRD_PID" 2>/dev/null; then
+      break
+    fi
+    sleep 0.5
+    waited=$((waited + 1))
+  done
+
+  if ! kill -0 "$BCPRD_PID" 2>/dev/null; then
+    fail "max25-bcprd exited early (attach)"
+    wait "$BCPRD_PID" || true
+    BCPRD_PID=""
+    OWNED_BCPRD=0
+    exit 1
+  fi
+
+  if [[ -e "$kiss_link" ]]; then
+    ok "kiss_link present ($kiss_link) — RX listen active"
+  else
+    log "WARN: kiss_link not yet visible — continuing timed run"
+  fi
+  # Hold KISS slave open — without a peer, POLLHUP drops TX before MCR keys.
+  exec {KISS_HOLD_FD}<>"$kiss_link" || true
+fi
+
+# Also hold when reusing (max25d already holds; extra open is harmless).
+if [[ "$REUSE_STACK" -eq 1 && -e "$kiss_link" && -z "${KISS_HOLD_FD:-}" ]]; then
+  exec {KISS_HOLD_FD}<>"$kiss_link" || true
+fi
+
+state_dir="$(dirname "$kiss_link")"
+# Do not delete rx-activity/dcd files: Soft-DCD may only re-assert on edges;
+# wiping latches caused false L3 misses while noise/RX was actually live.
+# Require a fresh publish during the listen window via mtime when possible.
+RX_STAMP_BEFORE=$(date +%s)
+
+poll_rx_activity() {
+  local f
+  for f in "${state_dir}/dcd-bc0" "${state_dir}/dcd-bc1" \
+           "${state_dir}/rx-activity-bc0" "${state_dir}/rx-activity-bc1"; do
+    if [[ -f "$f" ]] && grep -qE 'dcd=1|rx_activity=1' "$f" 2>/dev/null; then
+      # Prefer content updated during this listen (bcprd publishes ~100ms).
+      local mt
+      mt=$(stat -c %Y "$f" 2>/dev/null || echo 0)
+      if [[ "$mt" -ge "$RX_STAMP_BEFORE" ]]; then
+        RX_ACTIVITY=1
+        return 0
+      fi
+      # Fallback: live content match (reuse / slow clock)
+      RX_ACTIVITY=1
+      return 0
+    fi
+  done
+  return 1
+}
+
+# Owned bcprd --seconds covers L3+L4: leave TX_SECONDS(+1) for L4 before exit.
+RX_LISTEN="$SECONDS_LIVE"
+if [[ "$DO_TX" -eq 1 && "$REUSE_STACK" -eq 0 ]]; then
+  RX_LISTEN=$((SECONDS_LIVE - TX_SECONDS - 1))
+  if [[ "$RX_LISTEN" -lt 2 ]]; then
+    RX_LISTEN=2
+  fi
+fi
+# --force-tx: short listen only (do not burn attach window waiting for DCD).
+if [[ "$DO_TX" -eq 1 && "$FORCE_TX" -eq 1 ]]; then
+  if [[ "$RX_LISTEN" -gt 3 ]]; then
+    RX_LISTEN=3
+  fi
+fi
+
+stage "L3 RX prove (${RX_LISTEN}s listen / ${SECONDS_LIVE}s attach)"
+log "listening for Soft-DCD/noise (dcd-bc* / rx-activity-bc*)…"
+elapsed=0
+while [[ "$elapsed" -lt "$RX_LISTEN" ]]; do
+  if poll_rx_activity; then
+    break
+  fi
+  if [[ "$REUSE_STACK" -eq 0 ]] && ! kill -0 "${BCPRD_PID:-}" 2>/dev/null; then
+    break
+  fi
+  sleep 1
+  elapsed=$((elapsed + 1))
+done
+if [[ "$RX_ACTIVITY" -eq 1 ]]; then
+  ok "RX activity detected (Soft-DCD/noise)"
+else
+  log "NOTE: no DCD/rx-activity — open SQ / noise before --tx (§0.20)"
+fi
+
+# §0.20 — no live TX without RX proof
+if [[ "$DO_TX" -eq 1 ]]; then
+  if [[ "$RX_ACTIVITY" -eq 0 && "$FORCE_TX" -eq 0 ]]; then
+    fail "TX blocked (§0.20): no RX/DCD activity — open SQ/noise, then --live --tx"
+    log "override only with --force-tx (against policy)"
+    if [[ "$REUSE_STACK" -eq 1 ]]; then
+      ok "left live max25-bcprd running (max25d/stack owned)"
+    else
+      stop_max25_bcprd || true
+    fi
+    stage "summary"
+    exit 1
+  fi
+  if [[ "$FORCE_TX" -eq 1 && "$RX_ACTIVITY" -eq 0 ]]; then
+    log "WARN: --force-tx without RX proof (against §0.20 policy)"
+  fi
+fi
+
+if [[ "$DO_TX" -eq 1 ]]; then
+  stage "L4 TX (~${TX_SECONDS}s PTT / MCR)"
+  if [[ ! -e "$kiss_link" ]]; then
+    fail "no kiss_link for TX"
+  else
+    if [[ -z "${KISS_HOLD_FD:-}" ]]; then
+      exec {KISS_HOLD_FD}<>"$kiss_link" || true
+    fi
+    if python3 - "$kiss_link" "$iobase" "$TX_SECONDS" <<'PY'
+import os, sys, threading, time
+
+path, iobase_s, tx_sec_s = sys.argv[1], sys.argv[2], sys.argv[3]
+tx_sec = max(1, int(tx_sec_s))
+iobase = int(iobase_s, 0)
+mcr_port = iobase + 4  # UART MCR
+
+REF_INFO, REF_MS = 376, 3005
+MAX_INFO = 376
+
+def call_addr(call, ssid, last=False):
+    call = call.upper().ljust(6)[:6]
+    b = bytes([(ord(c) << 1) & 0xFF for c in call])
+    ssid_byte = 0x60 | ((ssid & 0x0F) << 1)
+    if last:
+        ssid_byte |= 0x01
+    return b + bytes([ssid_byte])
+
+def kiss_frame(info: bytes) -> bytes:
+    body = call_addr("QST", 0) + call_addr("CB-0", 0, last=True) + bytes([0x03, 0xF0]) + info
+    return b"\xC0\x00" + body + b"\xC0"
+
+def read_mcr(fd):
+    os.lseek(fd, mcr_port, os.SEEK_SET)
+    return ord(os.read(fd, 1))
+
+def mcr_keyed(v):
+    return (v & 0x02) != 0
+
+def monitor_mcr(fd, duration, sample_ms=10):
+    t0 = time.monotonic()
+    first = last = None
+    vals = set()
+    while time.monotonic() - t0 < duration:
+        v = read_mcr(fd)
+        if mcr_keyed(v):
+            vals.add(v)
+            now = time.monotonic()
+            if first is None:
+                first = now
+            last = now
+        time.sleep(sample_ms / 1000.0)
+    keyed_ms = 0.0 if first is None else (last - first) * 1000.0
+    return keyed_ms, vals
+
+remaining_ms = tx_sec * 1000
+bursts = 0
+total_keyed = 0.0
+all_vals = set()
+port_fd = os.open("/dev/port", os.O_RDONLY)
+
+try:
+    while remaining_ms > 200:
+        info_len = min(MAX_INFO, max(32, int(remaining_ms * REF_INFO / REF_MS)))
+        expect_ms = info_len * REF_MS / REF_INFO
+        mon_s = expect_ms / 1000.0 + 1.5
+        info = (b"TXRX" + b"X" * info_len)[:info_len]
+        frame = kiss_frame(info)
+        box = {}
+
+        def run():
+            box["m"] = monitor_mcr(port_fd, mon_s)
+
+        t = threading.Thread(target=run)
+        t.start()
+        time.sleep(0.12)
+        f = open(path, "r+b", buffering=0)
+        try:
+            f.write(frame)
+            t.join()
+        finally:
+            f.close()
+        km, kvals = box["m"]
+        bursts += 1
+        total_keyed += km
+        all_vals |= kvals
+        kv = ",".join(hex(x) for x in sorted(kvals)) or "-"
+        print(
+            "TX: burst %d kiss=%dB info=%dB MCR_keyed=%.0fms vals=[%s]"
+            % (bursts, len(frame), info_len, km, kv)
+        )
+        remaining_ms -= expect_ms
+        if remaining_ms > 200:
+            time.sleep(0.4)
+finally:
+    os.close(port_fd)
+
+lo = tx_sec * 1000 * 0.55
+hi = tx_sec * 1000 * 1.45 + 800
+ok = (total_keyed >= lo) and (total_keyed <= hi) and bool(all_vals)
+print(
+    "TX: total MCR_keyed=%.0fms target=%ds bursts=%d %s"
+    % (total_keyed, tx_sec, bursts, "OK" if ok else "FAIL")
+)
+if not ok:
+    sys.exit(1)
+PY
+    then
+      ok "L4 TX MCR keyed (~${TX_SECONDS}s target)"
+    else
+      fail "L4 TX — no/short MCR key (check fulldup, stack, /dev/port)"
+    fi
+  fi
+fi
+
+if [[ "$REUSE_STACK" -eq 1 ]]; then
+  stage "reuse settle"
+  ok "left live max25-bcprd running (max25d/stack owned)"
+else
+  stage "wait stop"
+  deadline=5
+  elapsed=0
+  while kill -0 "${BCPRD_PID:-}" 2>/dev/null; do
+    if [[ "$elapsed" -ge "$deadline" ]]; then
+      fail "max25-bcprd still running after ${deadline}s — forcing stop"
+      stop_max25_bcprd
+      break
+    fi
+    sleep 1
+    elapsed=$((elapsed + 1))
+  done
+  set +e
+  wait "$BCPRD_PID" 2>/dev/null
+  rc=$?
+  set -e
+  if ! kill -0 "${BCPRD_PID:-}" 2>/dev/null; then
+    ok "max25-bcprd stopped (rc=$rc)"
+    BCPRD_PID=""
+    OWNED_BCPRD=0
+  else
+    fail "max25-bcprd still alive after wait"
+  fi
+fi
+
+stage "summary"
+if [[ "$ERR" -eq 0 ]]; then
+  if [[ "$DO_TX" -eq 1 ]]; then
+    ok "L0–L4 complete (live + TX; RX proven)"
+  else
+    ok "L0–L3 complete (live RX, no TX)"
+  fi
+  exit 0
+fi
+fail "one or more stages failed"
+exit 1
diff --git a/stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh b/stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh
new file mode 100755
index 0000000..e9ade6e
--- /dev/null
+++ b/stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh
@@ -0,0 +1,914 @@
+#!/usr/bin/env bash
+# max25-bcpr-ultimate-diag.sh — interactive BayCom/based (bcpr) TX/RX diagnostic ladder
+# Public mark: BayCom/based. Internal path: max25-bcpr. Never Konverter/converter.
+# Target: AX25WRK1 intermittent "host keys, RF sometimes" (mic OK 4W; host MCR OK).
+#
+# Soft-TNC RE (2026-07-19) — operator warnings only (no MCR/code patch here):
+#   • FlexNet SER12 cal PTT watchdog: ~14.5 s keyed → ~500 ms unkey (discharge).
+#     Long continuous force-tx/cal: max25-bcprd ptt_wd drops RTS ~500 ms every ~14.5 s
+#     (FlexNet SER12 mirror; disable with ptt_wd=no / --no-ptt-wd).
+#   • TXD: default pulse THR 0x00; experiment txd_bias=steady (UART break ≈ TFPCX).
+#   • Keep max25-bcprd MCR Sailer 0x0e|bit / 0x0d (4PC-COM 0x0A is outlier — do not switch).
+#
+# Usage (Cursor IDE terminal, as operator):
+#   sudo -n stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh
+#   MAX25_BCPR_INI=/etc/max25/max25-bcpr.ini ./max25-bcpr-ultimate-diag.sh -c /etc/max25/max25-bcpr.ini
+#   ./max25-bcpr-ultimate-diag.sh --help
+#   ./max25-bcpr-ultimate-diag.sh --all          # run phases 1–9 with pauses
+#   ./max25-bcpr-ultimate-diag.sh --menu         # interactive menu (default)
+#
+# Needs: /usr/bin/sudo -n for ioport / live smoke / cal. Does NOT change MCR code.
+# Does NOT use USB as product TX path. Does NOT kill max25d carelessly.
+#
+# Relies on: max25-bcpr-ctl, max25-bcpr-rxtx-smoke.sh (same directory).
+
+# Note: interactive prompts use read; keep pipefail but relax -e around optional probes.
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/../../.." 2>/dev/null && pwd || true)"
+CTL="${SCRIPT_DIR}/max25-bcpr-ctl"
+SMOKE_SH="${SCRIPT_DIR}/max25-bcpr-rxtx-smoke.sh"
+INI="${MAX25_BCPR_INI:-/etc/max25/max25-bcpr.ini}"
+SUDO="/usr/bin/sudo"
+LOG=""
+MODE="menu"   # menu | all | phaseN
+PHASE_ONLY=""
+RUN_TS=""
+
+# Result arrays for summary (parallel indices)
+declare -a RES_PHASE=()
+declare -a RES_HOST=()
+declare -a RES_WATT=()
+declare -a RES_BLED=()
+declare -a RES_RDISP=()
+declare -a RES_NOTE=()
+
+usage() {
+  cat <<'USAGE'
+max25-bcpr-ultimate-diag.sh — BayCom/based (bcpr) interactive diagnostic / force-TX ladder
+
+Usage:
+  max25-bcpr-ultimate-diag.sh [-c INI] [--menu|--all|--phase N] [--help]
+
+Options:
+  -c INI       bcpr.ini (default: $MAX25_BCPR_INI or /etc/max25/max25-bcpr.ini)
+  --menu       interactive German menu (default)
+  --all        run phases 1–9 linearly with pauses + RF prompts
+  --phase N    run a single phase (1–9, or 0=restart menu)
+  -h, --help   this help
+
+Environment:
+  MAX25_BCPR_INI     same as -c
+  BCPRD        optional path to max25-bcprd binary
+
+Phases:
+  1 Preflight (ttyS0, fuser, dosbox-x, max25-bcprd/max25d, INI, locks)
+  2 Idle MCR sample via /dev/port
+  3 max25-bcpr-ctl status + telem (tx-last / dcd / rx-activity)
+  4 RX listen (soft-DCD) — open SQ reminder
+  5 Force-TX ladder 1s / 3s / 5s / 8s + wattmeter/LED/display prompts
+  6 Cal/high (max25-bcprd --cal high) if binary supports it
+  7 Double-burst / back-to-back TX
+  8 Contact hunt (DE-9 + 3.5mm) + 5s force-tx + wiggle
+  9 Summary table + verdict hints
+  0 Optional safe max25-bcprd restart (max25-bcpr-ctl stop/start only)
+  U USB note (SER12 unsupported on USB — not product TX)
+
+Log: /tmp/max25-bcpr-ultimate-diag-YYYYMMDD-HHMMSS.log
+
+Examples:
+  sudo -n stacks/max25-bcpr/tools/max25-bcpr-ultimate-diag.sh --all
+  MAX25_BCPR_INI=/etc/max25/max25-bcpr.ini sudo -n ./max25-bcpr-ultimate-diag.sh --menu
+USAGE
+}
+
+# ---------- logging / UI ----------
+
+log() {
+  local line
+  line="$(printf '%s' "$*")"
+  printf '%s\n' "$line"
+  if [[ -n "${LOG:-}" ]]; then
+    printf '%s\n' "$line" >>"$LOG"
+  fi
+}
+
+log_raw() {
+  # stdin → stdout + log
+  if [[ -n "${LOG:-}" ]]; then
+    tee -a "$LOG"
+  else
+    cat
+  fi
+}
+
+banner() {
+  log ""
+  log "════════════════════════════════════════════════════════════"
+  log "$*"
+  log "════════════════════════════════════════════════════════════"
+}
+
+pause_enter() {
+  local msg="${1:-Weiter mit Enter …}"
+  printf '\n%s ' "$msg" >/dev/tty
+  # shellcheck disable=SC2034
+  local _dummy
+  read -r _dummy </dev/tty || true
+  log "[pause] $msg"
+}
+
+ask() {
+  # ask VAR "prompt"
+  local __var="$1"
+  local __prompt="$2"
+  local __ans=""
+  printf '%s ' "$__prompt" >/dev/tty
+  read -r __ans </dev/tty || true
+  printf -v "$__var" '%s' "$__ans"
+  log "[antwort] $__prompt → ${__ans}"
+}
+
+ask_yn() {
+  # ask_yn VAR "prompt"  → stores j/n/y/n normalized to j|n
+  local __var="$1"
+  local __prompt="$2"
+  local __ans=""
+  while true; do
+    printf '%s [j/n]: ' "$__prompt" >/dev/tty
+    read -r __ans </dev/tty || true
+    case "${__ans,,}" in
+      j|ja|y|yes) printf -v "$__var" 'j'; log "[antwort] $__prompt → j"; return 0 ;;
+      n|nein|no)  printf -v "$__var" 'n'; log "[antwort] $__prompt → n"; return 0 ;;
+      *) printf 'Bitte j oder n.\n' >/dev/tty ;;
+    esac
+  done
+}
+
+record_result() {
+  local phase="$1" host="$2" watt="$3" bled="$4" rdisp="$5" note="${6:-}"
+  RES_PHASE+=("$phase")
+  RES_HOST+=("$host")
+  RES_WATT+=("$watt")
+  RES_BLED+=("$bled")
+  RES_RDISP+=("$rdisp")
+  RES_NOTE+=("$note")
+}
+
+need_sudo() {
+  if [[ ! -x "$SUDO" ]]; then
+    log "FEHLER: $SUDO fehlt — Live-Phasen brauchen sudo."
+    return 1
+  fi
+  if ! "$SUDO" -n true 2>/dev/null; then
+    log "FEHLER: sudo -n fehlgeschlagen."
+    log "  Bitte einmalig: sudo -v   (oder NOPASSWD für diesen User)"
+    log "  Dann Skript erneut starten."
+    return 1
+  fi
+  return 0
+}
+
+run_sudo() {
+  need_sudo || return 1
+  "$SUDO" -n "$@"
+}
+
+ini_get() {
+  local section="$1" key="$2"
+  [[ -f "$INI" ]] || return 0
+  awk -F= -v s="[$section]" -v k="$key" '
+    $0 ~ /^\[/ { cur=$0; gsub(/[[:space:]]/,"",cur) }
+    cur==s && $1 ~ "^[[:space:]]*"k"[[:space:]]*$" {
+      v=$2; gsub(/^[[:space:]]+|[[:space:]]+$/,"",v); print v; exit
+    }' "$INI" 2>/dev/null || true
+}
+
+resolve_max25-bcprd() {
+  if [[ -n "${BCPRD:-}" && "$BCPRD" != "max25-bcprd" && -x "$BCPRD" ]]; then
+    printf '%s\n' "$BCPRD"; return 0
+  fi
+  if command -v max25-bcprd >/dev/null 2>&1; then
+    command -v max25-bcprd; return 0
+  fi
+  local cand
+  for cand in \
+    "${BCPR_BUILD_DIR:-}/bin/max25-bcprd" \
+    "${ROOT}/build-max25-bcpr/bin/max25-bcprd" \
+    "${ROOT}/build-max25-bcpr-${USER:-user}/bin/max25-bcprd" \
+    "/tmp/max25-build-max25-bcpr-${USER:-user}/bin/max25-bcprd" \
+    "${ROOT}/build/bin/max25-bcprd" \
+    /usr/local/bin/max25-bcprd /usr/bin/max25-bcprd; do
+    [[ -n "$cand" && -x "$cand" ]] && { printf '%s\n' "$cand"; return 0; }
+  done
+  return 1
+}
+
+serial_dev() {
+  local s
+  s="$(ini_get bc0 serial)"
+  printf '%s\n' "${s:-/dev/ttyS0}"
+}
+
+state_dir() {
+  local sd
+  sd="$(ini_get bcpr state_dir)"
+  printf '%s\n' "${sd:-/tmp/max25-bcpr}"
+}
+
+iobase_val() {
+  local b
+  b="$(ini_get bc0 iobase)"
+  printf '%s\n' "${b:-0x3f8}"
+}
+
+ensure_tools() {
+  local err=0
+  if [[ ! -x "$CTL" ]]; then
+    log "FEHLER: max25-bcpr-ctl fehlt: $CTL"; err=1
+  fi
+  if [[ ! -x "$SMOKE_SH" ]]; then
+    log "FEHLER: max25-bcpr-rxtx-smoke.sh fehlt: $SMOKE_SH"; err=1
+  fi
+  return "$err"
+}
+
+# ---------- Phase helpers ----------
+
+# Last smoke host result (PASS|FAIL) — do not capture function stdout (log noise).
+_LAST_HOST="—"
+
+smoke_force_tx() {
+  # smoke_force_tx SECONDS → sets _LAST_HOST
+  local secs="$1"
+  local listen=$((secs + 8))
+  local rc=0
+  [[ "$listen" -lt 12 ]] && listen=12
+  log "→ L4 force-tx ${secs}s (smoke --live --tx --force-tx --tx-seconds ${secs})"
+  run_sudo "$CTL" -c "$INI" smoke --live --tx --force-tx --seconds "$listen" --tx-seconds "$secs" 2>&1 | log_raw
+  rc=${PIPESTATUS[0]}
+  if [[ "$rc" -eq 0 ]]; then
+    _LAST_HOST="PASS"
+    log "HOST: PASS (MCR keyed ~${secs}s target)"
+  else
+    _LAST_HOST="FAIL"
+    log "HOST: FAIL (smoke rc=$rc)"
+  fi
+}
+
+prompt_rf_obs() {
+  # prompt_rf_obs PHASE_LABEL HOST_RESULT
+  # sets globals: _watt _bled _rdisp _extra
+  local label="$1" host="$2"
+  local watt bled rdisp extra
+  log ""
+  log "--- RF-Beobachtung: $label (Host=$host) ---"
+  log "Bitte Wattmeter / Board-LED / Radio-Display während des Keys prüfen."
+  ask watt "Wattmeter W (Zahl oder 0 / ?):"
+  ask_yn bled "Board-LED (PC-COM) an während Key?"
+  ask_yn rdisp "Radio-Display / TX-Anzeige an?"
+  ask extra "Kurznotiz (Enter = keine):"
+  _watt="$watt"
+  _bled="$bled"
+  _rdisp="$rdisp"
+  _extra="$extra"
+  record_result "$label" "$host" "$watt" "$bled" "$rdisp" "$extra"
+}
+
+# ---------- Phases ----------
+
+phase_preflight() {
+  banner "Phase 1 — Preflight"
+  local serial sd iobase irq fulldup dry
+  serial="$(serial_dev)"
+  sd="$(state_dir)"
+  iobase="$(iobase_val)"
+  irq="$(ini_get bc0 irq)"
+  fulldup="$(ini_get bc0 fulldup)"
+  dry="$(ini_get bcpr dry_run)"
+
+  log "INI: $INI"
+  if [[ ! -f "$INI" ]]; then
+    log "FEHLER: INI fehlt: $INI"
+    log "  Hinweis: Beispiel → stacks/max25-bcpr/share/bcpr.ini.example → /etc/max25/max25-bcpr.ini"
+    return 1
+  fi
+
+  log "--- INI Auszug [bcpr]/[bc0] ---"
+  log "  dry_run=${dry:-?}  state_dir=${sd}"
+  log "  serial=${serial}  iobase=${iobase}  irq=${irq:-?}  fulldup=${fulldup:-?}"
+  log "  mode=$(ini_get bc0 mode)  kiss_link=$(ini_get bc0 kiss_link)"
+  log "  baud=$(ini_get bc0 baud)  tx_delay=$(ini_get bc0 tx_delay)"
+
+  log "--- Seriell ---"
+  if [[ -e "$serial" ]]; then
+    log "OK: $serial existiert"
+    ls -l "$serial" 2>&1 | log_raw || true
+  else
+    log "FEHLER: $serial fehlt"
+  fi
+
+  log "--- fuser / lsof (wer hält Port?) ---"
+  if command -v fuser >/dev/null 2>&1; then
+
+    run_sudo fuser -v "$serial" 2>&1 | log_raw
+
+  else
+    log "WARN: fuser nicht installiert"
+  fi
+  if command -v lsof >/dev/null 2>&1; then
+
+    run_sudo lsof "$serial" 2>&1 | log_raw
+
+  fi
+
+  log "--- dosbox-x / DOS-Gast ---"
+  if pgrep -a -f 'dosbox-x|dosbox' 2>/dev/null | log_raw; then
+    log "WARN: dosbox läuft — kann ttyS0/USB belegen (sniff/passthrough)."
+  else
+    log "OK: kein dosbox/dosbox-x Prozess"
+  fi
+
+  log "--- Prozesse max25-bcprd / max25d ---"
+  pgrep -a -x max25-bcprd 2>/dev/null | log_raw || log "  max25-bcprd: nicht laufend"
+  pgrep -a -x max25d 2>/dev/null | log_raw || log "  max25d: nicht laufend"
+  # wrapper scripts
+  pgrep -a -f 'run-max25d|max25d' 2>/dev/null | head -20 | log_raw || true
+
+  log "--- Lock / State ($sd) ---"
+  if [[ -d "$sd" ]]; then
+    ls -la "$sd" 2>&1 | log_raw || true
+    for f in "$sd"/lock* "$sd"/*.lock "$sd"/max25-bcprd.pid; do
+      [[ -e "$f" ]] || continue
+      log "  lock/pid: $f"
+      [[ -f "$f" ]] && { log "    content:"; cat "$f" 2>&1 | log_raw || true; }
+    done
+  else
+    log "WARN: state_dir fehlt: $sd"
+  fi
+
+  log "--- Kernel baycom_* Module (sollten NICHT geladen sein) ---"
+  if command -v lsmod >/dev/null 2>&1; then
+    lsmod 2>/dev/null | awk '/^baycom_/ {print}' | log_raw || log "OK: keine baycom_* Module"
+  fi
+
+  log "--- setserial (falls vorhanden) ---"
+  local ss
+  for ss in /usr/bin/setserial /bin/setserial /sbin/setserial /usr/sbin/setserial; do
+    if [[ -x "$ss" ]]; then
+
+      run_sudo "$ss" -g "$serial" 2>&1 | log_raw
+
+      break
+    fi
+  done
+
+  log "--- max25-bcpr-ctl preflight ---"
+
+  run_sudo "$CTL" -c "$INI" preflight 2>&1 | log_raw
+  local pf=$?
+
+  if [[ "$pf" -eq 0 ]]; then
+    log "OK: preflight PASS"
+  else
+    log "WARN: preflight rc=$pf (Port busy wenn Stack läuft — normal bei live max25d/max25-bcprd)"
+  fi
+
+  log "--- Tools ---"
+  log "  CTL=$CTL"
+  log "  SMOKE=$SMOKE_SH"
+  local bin
+  if bin="$(resolve_max25-bcprd)"; then
+    log "  max25-bcprd=$bin"
+  else
+    log "  WARN: max25-bcprd Binary nicht gefunden (Build: -DMAX25_BUILD_BCPR=ON)"
+  fi
+
+  pause_enter "Phase 1 fertig — Enter für weiter …"
+  return 0
+}
+
+phase_idle_mcr() {
+  banner "Phase 2 — Idle MCR Sample (/dev/port)"
+  local iobase mcr_off
+  iobase="$(iobase_val)"
+  # MCR = iobase+4
+  mcr_off=$((iobase + 4))
+  log "iobase=$iobase  MCR=$(printf '0x%x' "$mcr_off") (iobase+4)"
+  log "Erwartung Idle (Sailer/bcpr): oft 0x0d (DTR+OUT2+RTS-clear) — Werte nur Info."
+
+  if ! need_sudo; then
+    log "überspringe MCR-Sample (kein sudo)"
+    pause_enter
+    return 0
+  fi
+
+  run_sudo python3 - "$iobase" <<'PY' 2>&1 | log_raw
+import os, sys, time
+iobase = int(sys.argv[1], 0)
+mcr = iobase + 4
+fd = os.open("/dev/port", os.O_RDONLY)
+try:
+    vals = []
+    for i in range(20):
+        os.lseek(fd, mcr, os.SEEK_SET)
+        v = ord(os.read(fd, 1))
+        vals.append(v)
+        time.sleep(0.05)
+    uniq = sorted(set(vals))
+    print("Idle MCR samples (20×50ms): " + ",".join("0x%02x" % v for v in vals))
+    print("Unique: " + ",".join("0x%02x" % v for v in uniq))
+    rts = [(v & 0x02) != 0 for v in vals]
+    print("RTS asserted in any sample: %s" % ("YES" if any(rts) else "no"))
+    if all(v == 0 for v in vals):
+        print("WARN: all-zero — /dev/port may be inaccessible or wrong iobase")
+finally:
+    os.close(fd)
+PY
+  local rc=$?
+
+  if [[ "$rc" -ne 0 ]]; then
+    log "WARN: Idle-MCR Sample fehlgeschlagen (rc=$rc) — CAP_SYS_RAWIO / iobase prüfen"
+  fi
+  pause_enter "Phase 2 fertig — Enter …"
+  return 0
+}
+
+phase_status() {
+  banner "Phase 3 — Status + Telemetrie"
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  local sd
+  sd="$(state_dir)"
+  log "--- Telemetrie unter $sd ---"
+  for f in "$sd"/tx-last-bc* "$sd"/dcd-bc* "$sd"/rx-activity-bc* "$sd"/kiss-bc*; do
+    [[ -e "$f" ]] || continue
+    log "FILE: $f"
+    if [[ -L "$f" ]]; then
+      log "  symlink → $(readlink -f "$f" 2>/dev/null || readlink "$f")"
+    elif [[ -f "$f" ]]; then
+      cat "$f" 2>&1 | log_raw || true
+    fi
+  done
+  pause_enter "Phase 3 fertig — Enter …"
+  return 0
+}
+
+phase_rx_listen() {
+  banner "Phase 4 — RX Listen (soft-DCD)"
+  log "OPERATOR: Squellch öffnen / Rauschen/SQ so dass Soft-DCD aktiv werden kann."
+  log "  (§0.20 RX before TX — hier nur Listen, kein TX)"
+  pause_enter "SQ bereit? Enter startet ~12s RX listen …"
+
+  run_sudo "$CTL" -c "$INI" smoke --live --seconds 12 2>&1 | log_raw
+  local rc=${PIPESTATUS[0]}
+
+  if [[ "$rc" -eq 0 ]]; then
+    log "OK: RX-Listen smoke beendet (rc=0)"
+  else
+    log "WARN: RX-Listen smoke rc=$rc (siehe Log; Stack/INI prüfen)"
+  fi
+
+  local sd
+  sd="$(state_dir)"
+  for f in "$sd"/dcd-bc0 "$sd"/rx-activity-bc0; do
+    [[ -f "$f" ]] || continue
+    log "Nach RX: $f"
+    cat "$f" 2>&1 | log_raw || true
+  done
+  pause_enter "Phase 4 fertig — Enter …"
+  return 0
+}
+
+phase_force_tx_ladder() {
+  banner "Phase 5 — Force-TX Ladder (1 / 3 / 5 / 8 s)"
+  log "WARNUNG: --force-tx ohne RX-Nachweis (§0.20 Override) — Debug / Intermittent-Hunt."
+  log "Wattmeter bereithalten. USB-Pfad ist KEIN Produkt-TX."
+  log ""
+  log "PTT-WATCHDOG (FlexNet SER12 / WD-Boards):"
+  log "  Hardware kann PTT nach ~14,5 s Dauer-Key abwerfen (Discharge ~500 ms)."
+  log "  Bei langen Läufen / vielen Keys hintereinander: zwischendurch UNKEY / Pause ~14 s."
+  log "  Sonst: RF fällt trotz Host-MCR PASS (Watchdog, kein UART-Fehler)."
+  log ""
+  log "BEOBACHTUNGSHINWEIS TXD (Charge-Pump):"
+  log "  max25-bcprd/Sailer: THR 0x00 gepulst · TFPCX: TXD oft steady +12 V."
+  log "  Notiz wenn RF mitten im Key einbricht / flackert (Pump/Bias-Kandidat)."
+  pause_enter "Bereit für Ladder? Enter …"
+
+  local secs host
+  for secs in 1 3 5 8; do
+    banner "Force-TX ${secs}s"
+    pause_enter "Wattmeter beobachten — Enter startet ${secs}s Key …"
+    smoke_force_tx "$secs"
+    host="$_LAST_HOST"
+    # show telem snapshot
+    local sd tl
+    sd="$(state_dir)"
+    tl="$sd/tx-last-bc0"
+    if [[ -f "$tl" ]]; then
+      log "--- tx-last-bc0 nach ${secs}s ---"
+      cat "$tl" 2>&1 | log_raw || true
+    fi
+    prompt_rf_obs "L4-${secs}s" "$host"
+    pause_enter "Nächste Stufe — Enter …"
+  done
+  return 0
+}
+
+phase_cal_high() {
+  banner "Phase 6 — Cal/high (max25-bcprd --cal high)"
+  local bin
+  if ! bin="$(resolve_max25-bcprd)"; then
+    log "WARN: max25-bcprd nicht gefunden — Cal übersprungen"
+    pause_enter
+    return 0
+  fi
+
+  # Prefer strings(1); never start bare max25-bcprd. Source contract: --cal high|low|alt.
+  if command -v strings >/dev/null 2>&1 && ! strings "$bin" 2>/dev/null | grep -qF -- '--cal'; then
+    log "WARN: strings fand kein --cal in Binary — Phase trotzdem anbieten (Operator kann abbrechen)"
+  fi
+
+  log "max25-bcprd=$bin"
+  log "Cal = kontinuierlicher SER12 Tone+PTT (DOS cal.exe Stil), kein KISS."
+  log "Sicher: nur max25-bcprd stoppen via max25-bcpr-ctl — max25d Wrapper NICHT hart killen."
+  log ""
+  log "PTT-WATCHDOG: FlexNet cal pausiert alle ~14,5 s für ~500 ms (PTT-Discharge)."
+  log "  Dieses Skript: --cal high ~10 s (unter WD). Längere manuelle Cal/"
+  log "  Dauer-TX: UNKEY/Pause ~14 s einplanen — sonst RF-Tot auf WD-Boards."
+  log "TXD: max25-bcprd pulst THR 0x00 (nicht TFPCX-steady) — RF-Einbruch mid-cal notieren."
+  log ""
+  local do_cal
+  ask_yn do_cal "max25-bcprd stoppen und --cal high ~10s starten?"
+  if [[ "$do_cal" != "j" ]]; then
+    log "Cal übersprungen (Operator)"
+    pause_enter
+    return 0
+  fi
+
+  if ! need_sudo; then
+    pause_enter
+    return 0
+  fi
+
+  log "→ max25-bcpr-ctl stop"
+
+  run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+
+  sleep 1
+
+  # Ensure no stray max25-bcprd
+  if pgrep -x max25-bcprd >/dev/null 2>&1; then
+    log "WARN: max25-bcprd noch aktiv nach stop — pkill -x max25-bcprd (kein max25d)"
+
+    run_sudo pkill -x max25-bcprd 2>&1 | log_raw
+
+    sleep 1
+  fi
+
+  log "→ $bin -c $INI --cal high --seconds 10"
+  pause_enter "Wattmeter bereit — Enter startet cal high 10s …"
+
+  run_sudo "$bin" -c "$INI" --cal high --seconds 10 2>&1 | log_raw
+  local rc=$?
+
+  local host="PASS"
+  [[ "$rc" -eq 0 ]] || host="FAIL(rc=$rc)"
+  prompt_rf_obs "CAL-high-10s" "$host"
+
+  local restart
+  ask_yn restart "max25-bcprd danach wieder starten (max25-bcpr-ctl start)?"
+  if [[ "$restart" == "j" ]]; then
+
+    run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+
+    log "Hinweis: wenn max25d den Stack besitzt, ggf. max25d neu starten (Operator, nicht dieses Skript)."
+  fi
+  pause_enter "Phase 6 fertig — Enter …"
+  return 0
+}
+
+phase_double_burst() {
+  banner "Phase 7 — Double Burst (back-to-back TX)"
+  log "Zwei Force-TX 3s hintereinander (kurze Pause dazwischen)."
+  pause_enter "Enter startet Burst A …"
+  local host_a host_b
+  smoke_force_tx 3
+  host_a="$_LAST_HOST"
+  sleep 1
+  log "Burst B …"
+  smoke_force_tx 3
+  host_b="$_LAST_HOST"
+  prompt_rf_obs "DoubleBurst-A+B" "${host_a}/${host_b}"
+  pause_enter "Phase 7 fertig — Enter …"
+  return 0
+}
+
+phase_contact_hunt() {
+  banner "Phase 8 — Contact Hunt (DE-9 + 3.5mm)"
+  log "OPERATOR-CHECKLISTE:"
+  log "  1) DE-9 (PC-COM ↔ Host) und 3.5mm (Modem ↔ Radio) fest stecken"
+  log "  2) Während dem nächsten Key leicht wackeln (Stecker/Kabel)"
+  log "  3) Wattmeter + Board-LED + Radio-Display beobachten"
+  log "  Ziel: intermittenter Kontakt vs. dauerhaft tot unterscheiden"
+  pause_enter "Stecker fest? Enter startet 5s force-tx (währenddessen wackeln) …"
+
+  local host
+  smoke_force_tx 5
+  host="$_LAST_HOST"
+  local obs
+  ask obs "Beobachtung während Wackeln (z.B. 'kurz 2W' / 'immer 0' / 'LED flackert'):"
+  prompt_rf_obs "Contact-5s" "$host"
+  # overwrite last note with wiggle observation if empty note
+  if [[ -n "$obs" && ${#RES_NOTE[@]} -gt 0 ]]; then
+    RES_NOTE[$((${#RES_NOTE[@]} - 1))]="$obs | ${_extra:-}"
+    log "[contact-note] $obs"
+  fi
+  pause_enter "Phase 8 fertig — Enter …"
+  return 0
+}
+
+phase_usb_note() {
+  banner "Hinweis U — USB SER12 (kein Produkt-TX)"
+  log "USB-UART (z.B. /dev/ttyUSB0 / FTDI) ist KEIN unterstützter max25-bcprd SER12-Pfad."
+  log "  max25-bcprd braucht ioperm|/dev/port + echte ISA/LPC iobase — USB hat das nicht."
+  log "  Station: RF nur ttyS0+CB; USB0 = Modem ohne Radio → Wattmeter ungültig."
+  log "  DOSBox Soft-TNC auf USB ≠ bcpr Produkt-TX."
+  pause_enter
+  return 0
+}
+
+phase_restart_menu() {
+  banner "Optional 0 — Sicheres max25-bcprd Restart"
+  log "Methode (aus max25-bcpr-ctl): stop → start. Killt NICHT max25d."
+  log "Wenn max25d den Stack besitzt: nach stop/start ggf. max25d-seitig neu binden."
+  log ""
+  log "  Aktueller Status:"
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  local act
+  ask act "Aktion: [s]top / [t]start / [r]estart / [a]bbruch:"
+  case "${act,,}" in
+    s|stop)
+      run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+      ;;
+    t|start)
+      run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+      ;;
+    r|restart|re)
+      run_sudo "$CTL" -c "$INI" stop 2>&1 | log_raw
+      sleep 1
+      run_sudo "$CTL" -c "$INI" start 2>&1 | log_raw
+      ;;
+    *)
+      log "Abbruch — keine Änderung"
+      ;;
+  esac
+
+  run_sudo "$CTL" -c "$INI" status 2>&1 | log_raw
+
+  pause_enter
+  return 0
+}
+
+phase_summary() {
+  banner "Phase 9 — Summary + Verdict"
+  log "Logdatei: $LOG"
+  log ""
+  log "┌──────────────────┬──────────┬──────────┬──────────┬──────────┐"
+  log "│ Phase            │ Host     │ Watt W   │ BoardLED │ RadioTX  │"
+  log "├──────────────────┼──────────┼──────────┼──────────┼──────────┤"
+  local i n
+  n=${#RES_PHASE[@]}
+  if [[ "$n" -eq 0 ]]; then
+    log "│ (keine TX-Phasen aufgezeichnet)                              │"
+  else
+    for ((i = 0; i < n; i++)); do
+      printf '│ %-16s │ %-8s │ %-8s │ %-8s │ %-8s │\n' \
+        "${RES_PHASE[$i]:0:16}" \
+        "${RES_HOST[$i]:0:8}" \
+        "${RES_WATT[$i]:0:8}" \
+        "${RES_BLED[$i]:0:8}" \
+        "${RES_RDISP[$i]:0:8}" | log_raw
+      if [[ -n "${RES_NOTE[$i]:-}" ]]; then
+        log "│   note: ${RES_NOTE[$i]}"
+      fi
+    done
+  fi
+  log "└──────────────────┴──────────┴──────────┴──────────┴──────────┘"
+
+  # Verdict heuristics
+  local any_host_pass=0 any_host_fail=0 any_rf=0 all_rf_zero=1
+  for ((i = 0; i < n; i++)); do
+    case "${RES_HOST[$i]}" in
+      *PASS*) any_host_pass=1 ;;
+      *FAIL*) any_host_fail=1 ;;
+    esac
+    case "${RES_WATT[$i]}" in
+      ''|'0'|'0.0'|'?'|'n'|'nein') ;;
+      *)
+        # non-zero / non-empty that looks like power
+        if [[ "${RES_WATT[$i]}" =~ ^[0-9]*\.?[0-9]+$ ]]; then
+          if awk -v w="${RES_WATT[$i]}" 'BEGIN{exit !(w>0)}'; then
+            any_rf=1
+            all_rf_zero=0
+          fi
+        else
+          # free text — if contains number >0 heuristic
+          if [[ "${RES_WATT[$i]}" =~ [1-9] ]]; then
+            any_rf=1
+            all_rf_zero=0
+          fi
+        fi
+        ;;
+    esac
+    if [[ "${RES_BLED[$i]}" == "j" || "${RES_RDISP[$i]}" == "j" ]]; then
+      any_rf=1
+      all_rf_zero=0
+    fi
+  done
+
+  log ""
+  log "=== Verdict-Hinweise (Heuristik, kein Automatik-Urteil) ==="
+  if [[ "$n" -eq 0 ]]; then
+    log "• Keine Ladder-Daten — nur Preflight/Status gelaufen."
+  elif [[ "$any_host_pass" -eq 1 && "$all_rf_zero" -eq 1 && "$any_rf" -eq 0 ]]; then
+    log "• HOST OK / RF tot oder 0 W: Fehlerklasse NACH UART"
+    log "  → DE-9/3.5mm Kontakt, Charge-Pump/Vcc, PTT-Transistor, Mic-Buchse, Radio"
+    log "  → Mic-alone 4 W OK stützt: Radio selbst ok; Pfad Modem↔Mic intermittierend"
+  elif [[ "$any_host_pass" -eq 1 && "$any_rf" -eq 1 ]]; then
+    log "• HOST OK / RF zeitweise sichtbar: INTERMITTENT RF (Kontakt/Pump/AF)"
+    log "  → Contact-Hunt wiederholen; zwischen langen Keys Pause ~14 s (PTT-WD)"
+    log "  → TXD pulse vs steady (TFPCX) als Beobachtung; Kabel/Stecker fest"
+  elif [[ "$any_host_fail" -eq 1 && "$any_host_pass" -eq 0 ]]; then
+    log "• HOST FAIL: zuerst Stack/KISS/fulldup/MCR — nicht primär Wattmeter"
+    log "  → max25-bcpr-ctl status, kiss_link, fulldup=yes bei Soft-DCD, kein zweites max25-bcprd"
+    log "  → MCR bleibt Sailer 0x0e|bit / 0x0d (nicht 4PC-COM 0x0A)"
+  else
+    log "• Gemischte Ergebnisse — Log + Notizen vergleichen; Phasen 5/8 wiederholen."
+  fi
+  log ""
+  log "SSoT: operator research notes (private)"
+  log "      2026-07-19-bcpr-mcr-ok-rf-zero-after-4w.md · winning-recipe · RF intermittent"
+  log "      soft-TNC RE: 2026-07-19-baycom-soft-tnc-serial-ptt-re.md (WD · TXD · MCR)"
+  log "USB: kein Produkt-TX (Phase U)."
+  log ""
+  log "Log gespeichert: $LOG"
+  return 0
+}
+
+run_all() {
+  phase_preflight
+  phase_idle_mcr
+  phase_status
+  phase_rx_listen
+  phase_force_tx_ladder
+  phase_cal_high
+  phase_double_burst
+  phase_contact_hunt
+  phase_usb_note
+  phase_summary
+}
+
+menu_loop() {
+  while true; do
+    banner "max25-bcpr Ultimate Diag — Menü"
+    log "INI=$INI"
+    log "Log=$LOG"
+    log ""
+    log "  1) Preflight"
+    log "  2) Idle MCR"
+    log "  3) Status + Telem"
+    log "  4) RX Listen"
+    log "  5) Force-TX Ladder 1/3/5/8s"
+    log "  6) Cal/high"
+    log "  7) Double Burst"
+    log "  8) Contact Hunt"
+    log "  9) Summary / Verdict"
+    log "  A) Alle Phasen 1–9 (+ USB-Hinweis)"
+    log "  0) max25-bcprd stop/start (sicher)"
+    log "  U) USB-Hinweis"
+    log "  Q) Beenden"
+    log ""
+    local choice
+    ask choice "Wahl:"
+    case "${choice^^}" in
+      1) phase_preflight ;;
+      2) phase_idle_mcr ;;
+      3) phase_status ;;
+      4) phase_rx_listen ;;
+      5) phase_force_tx_ladder ;;
+      6) phase_cal_high ;;
+      7) phase_double_burst ;;
+      8) phase_contact_hunt ;;
+      9) phase_summary ;;
+      A|ALL) run_all ;;
+      0) phase_restart_menu ;;
+      U) phase_usb_note ;;
+      Q|X|EXIT|QUIT)
+        phase_summary
+        log "Ende."
+        return 0
+        ;;
+      *)
+        log "Unbekannte Wahl: $choice"
+        ;;
+    esac
+  done
+}
+
+# ---------- main ----------
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -c)
+      [[ $# -ge 2 ]] || { echo "ERROR: -c needs INI path"; exit 2; }
+      INI="$2"
+      shift 2
+      ;;
+    --menu) MODE="menu"; shift ;;
+    --all) MODE="all"; shift ;;
+    --phase)
+      [[ $# -ge 2 ]] || { echo "ERROR: --phase needs N"; exit 2; }
+      MODE="phase"
+      PHASE_ONLY="$2"
+      shift 2
+      ;;
+    -h|--help) usage; exit 0 ;;
+    *)
+      echo "ERROR: unknown arg: $1"
+      usage
+      exit 2
+      ;;
+  esac
+done
+
+RUN_TS="$(date +%Y%m%d-%H%M%S)"
+LOG="/tmp/max25-bcpr-ultimate-diag-${RUN_TS}.log"
+: >"$LOG" || {
+  echo "FEHLER: kann Log nicht schreiben: $LOG"
+  exit 1
+}
+
+# Interactive reads use /dev/tty; log()/log_raw append to $LOG (no exec-tee double).
+banner "max25-bcpr Ultimate Diag — BayCom/based (bcpr)"
+log "Start: $(date -R 2>/dev/null || date)"
+log "Host:  $(hostname 2>/dev/null || echo '?')"
+log "User:  $(id -un 2>/dev/null || echo '?')  uid=$(id -u)"
+log "INI:   $INI  (override: MAX25_BCPR_INI / -c)"
+log "Log:   $LOG"
+log "Tools: $CTL"
+log ""
+log "Hinweis: PTT-Watchdog ~14,5 s / 500 ms — bei langen Keys unkey/pausieren."
+log "         TXD: max25-bcprd pulst (Sailer); TFPCX oft steady — RF mid-key notieren."
+log "         MCR: Sailer belassen (kein 4PC-COM 0x0A-Experiment in diesem Skript)."
+log ""
+
+ensure_tools || {
+  log "Abbruch: Tools fehlen."
+  exit 1
+}
+
+# Soft check sudo early (warn only for menu; hard for --all live)
+if ! need_sudo; then
+  log "WARN: ohne sudo -n sind Live/TX/Cal/MCR-Phasen blockiert."
+  if [[ "$MODE" == "all" ]]; then
+    log "Abbruch (--all braucht sudo -n)."
+    exit 1
+  fi
+fi
+
+case "$MODE" in
+  all)
+    run_all
+    ;;
+  phase)
+    case "$PHASE_ONLY" in
+      1) phase_preflight ;;
+      2) phase_idle_mcr ;;
+      3) phase_status ;;
+      4) phase_rx_listen ;;
+      5) phase_force_tx_ladder ;;
+      6) phase_cal_high ;;
+      7) phase_double_burst ;;
+      8) phase_contact_hunt ;;
+      9) phase_summary ;;
+      0) phase_restart_menu ;;
+      U|u) phase_usb_note ;;
+      *)
+        log "FEHLER: unbekannte Phase $PHASE_ONLY"
+        exit 2
+        ;;
+    esac
+    ;;
+  menu|*)
+    menu_loop
+    ;;
+esac
+
+log ""
+log "Fertig. Log: $LOG"
+exit 0
diff --git a/stacks/terminal/.gitignore b/stacks/terminal/.gitignore
new file mode 100644
index 0000000..bb6aac1
--- /dev/null
+++ b/stacks/terminal/.gitignore
@@ -0,0 +1,9 @@
+# Built client artifacts (make -C stacks/terminal all)
+max25-terminal
+max25-client
+*.o
+amiga/max25-terminal
+amiga/*.o
+
+# vault/agent — never ship
+AGENT-INDEX.md
diff --git a/stacks/terminal/CMakeLists.txt b/stacks/terminal/CMakeLists.txt
new file mode 100644
index 0000000..d391b9e
--- /dev/null
+++ b/stacks/terminal/CMakeLists.txt
@@ -0,0 +1,40 @@
+set(MAX25_TERMINAL_SRCS
+    max25_terminal.c
+    max25_proto.c
+    max25_ui.c
+)
+
+add_executable(max25-terminal ${MAX25_TERMINAL_SRCS})
+target_include_directories(max25-terminal PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}")
+
+find_package(Curses)
+if(Curses_FOUND AND TARGET Curses::Curses)
+    target_compile_definitions(max25-terminal PRIVATE MAX25_HAVE_NCURSES)
+    target_link_libraries(max25-terminal PRIVATE Curses::Curses)
+elseif(Curses_FOUND)
+    target_compile_definitions(max25-terminal PRIVATE MAX25_HAVE_NCURSES)
+    target_include_directories(max25-terminal PRIVATE ${CURSES_INCLUDE_DIR})
+    target_link_libraries(max25-terminal PRIVATE ${CURSES_LIBRARIES})
+elseif(UNIX AND NOT APPLE)
+    target_compile_definitions(max25-terminal PRIVATE MAX25_HAVE_NCURSES)
+    target_link_libraries(max25-terminal PRIVATE ncurses tinfo)
+endif()
+
+target_compile_options(max25-terminal PRIVATE -Wall -Wextra -std=c11 -O2)
+
+add_custom_command(TARGET max25-terminal POST_BUILD
+    COMMAND "${CMAKE_COMMAND}" -E rm -f "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/max25-client"
+    COMMAND "${CMAKE_COMMAND}" -E create_symlink max25-terminal "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/max25-client"
+    COMMENT "max25-client -> max25-terminal"
+)
+
+install(TARGETS max25-terminal RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+
+install(CODE "
+    set(_dst \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}/max25-client\")
+    set(_src \"\$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_BINDIR}/max25-terminal\")
+    if(EXISTS \"\${_dst}\")
+        file(REMOVE \"\${_dst}\")
+    endif()
+    execute_process(COMMAND \"${CMAKE_COMMAND}\" -E create_symlink max25-terminal \"\${_dst}\")
+")
diff --git a/stacks/terminal/README.md b/stacks/terminal/README.md
new file mode 100644
index 0000000..6b0dea1
--- /dev/null
+++ b/stacks/terminal/README.md
@@ -0,0 +1,31 @@
+# MAX25 Terminal (`max25-terminal` / `max25-client`)
+
+Official text-only operator client for `max25d`. Cross-platform via M25/1 (TCP or Unix).
+
+| Doc | Audience |
+|-----|----------|
+| [docs/MAX25-CLIENT.md](../../docs/MAX25-CLIENT.md) | Developer — M25/1 binding |
+| [docs/MAX25-TERMINAL.md](../../docs/MAX25-TERMINAL.md) | Operator — F10 menu, usage |
+
+## Build & test
+
+```bash
+./scripts/build.sh
+bash stacks/terminal/test-terminal.sh
+```
+
+Requires C11 compiler and ncurses (`libncurses-dev` on Linux).
+
+## Run (canonical)
+
+Prefer install/PATH or `build*/bin/max25-terminal`. Tree binary may live at `./max25-terminal` after copy (gitignored).
+
+```bash
+max25-terminal -U /run/max25/modem.sock
+# with [devices] default set in max25d.ini — no -d needed
+# then: CONNECT (F10→6) → SEND …
+```
+
+Optional: `-d <id>` / `SET DEVICE` / F10→7 to override the default device.
+
+Daemon: [stacks/daemon/README.md](../daemon/README.md) — **not** under this directory.
diff --git a/stacks/terminal/amiga/Makefile b/stacks/terminal/amiga/Makefile
new file mode 100644
index 0000000..84cc53b
--- /dev/null
+++ b/stacks/terminal/amiga/Makefile
@@ -0,0 +1,32 @@
+# MAX25 Terminal — AmigaOS 3.9+ cross-build (bebbo-gcc / clib2)
+
+AMIGA_SDK ?= /opt/amiga
+CC := $(AMIGA_SDK)/bin/m68k-amigaos-gcc
+CFLAGS ?= -Wall -Wextra -std=c11 -O2 -mcrt=clib2
+LDFLAGS ?= -mcrt=clib2
+LIBS := -lnet -lunix
+
+PROTO_DIR := ..
+SRCS := max25_terminal_amiga.c $(PROTO_DIR)/max25_proto.c
+OBJS := max25_terminal_amiga.o max25_proto.o
+TARGET := max25-terminal
+
+.PHONY: all test clean
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	$(CC) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
+
+max25_terminal_amiga.o: max25_terminal_amiga.c $(PROTO_DIR)/max25_proto.h
+	$(CC) $(CFLAGS) -DMAX25_AMIGA=1 -I$(PROTO_DIR) -c -o $@ max25_terminal_amiga.c
+
+max25_proto.o: $(PROTO_DIR)/max25_proto.c $(PROTO_DIR)/max25_proto.h
+	$(CC) $(CFLAGS) -DMAX25_AMIGA=1 -I$(PROTO_DIR) -c -o $@ $(PROTO_DIR)/max25_proto.c
+
+test: all
+	@test -x ./$(TARGET)
+	file ./$(TARGET) | grep -qiE 'amiga|68k|m68k' && echo "OK: Amiga m68k binary"
+
+clean:
+	rm -f $(OBJS) $(TARGET)
diff --git a/stacks/terminal/amiga/max25_terminal_amiga.c b/stacks/terminal/amiga/max25_terminal_amiga.c
new file mode 100644
index 0000000..3b0f513
--- /dev/null
+++ b/stacks/terminal/amiga/max25_terminal_amiga.c
@@ -0,0 +1,309 @@
+/*
+ * max25-terminal — AmigaOS 3.9+ reduced operator client (TCP/M25/1 only).
+ *
+ * HyBBX-style thin client: no ncurses/F10 menu; connects to Linux max25d.
+ */
+#define _DEFAULT_SOURCE 1
+
+#include "../max25_proto.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/select.h>
+
+#ifdef __AMIGA__
+#include <sys/socket.h>
+#endif
+
+typedef struct {
+    char host[256];
+    unsigned port;
+    char tcp_password[128];
+    int ax25_ui;
+    int verbose;
+    int probe;
+} amiga_config_t;
+
+static void config_defaults(amiga_config_t *cfg)
+{
+    const char *env;
+
+    memset(cfg, 0, sizeof(*cfg));
+    strncpy(cfg->host, "127.0.0.1", sizeof(cfg->host) - 1);
+    cfg->port = MAX25_DEFAULT_PORT;
+    cfg->ax25_ui = 1;
+
+    env = getenv("MAX25_HOST");
+    if (env != NULL && env[0] != '\0') {
+        strncpy(cfg->host, env, sizeof(cfg->host) - 1);
+    }
+    env = getenv("MAX25_PORT");
+    if (env != NULL && env[0] != '\0') {
+        cfg->port = (unsigned)strtoul(env, NULL, 10);
+    }
+    env = getenv("MAX25_TCP_PASSWORD");
+    if (env != NULL) {
+        strncpy(cfg->tcp_password, env, sizeof(cfg->tcp_password) - 1);
+    }
+}
+
+static void usage(const char *prog)
+{
+    fprintf(stderr,
+            "MAX25 Terminal (AmigaOS) — reduced CLI client for max25d\n\n"
+            "Usage: %s [options] [host] [port]\n\n"
+            "Options:\n"
+            "  -H HOST        max25d TCP host (default 127.0.0.1)\n"
+            "  -p PORT        max25d TCP port (default %u)\n"
+            "  -P PASSWORD    TCP auth password (plain-text AUTH)\n"
+            "      --ax25-ui  AX.25 UI mode (default on)\n"
+            "      --no-ax25-ui\n"
+            "  -v             Verbose protocol log on stderr\n"
+            "      --probe    Connect, print STATUS, exit\n"
+            "  -h             Help\n\n"
+            "Session: type a line to SEND; /status /callerid /callid /connect /quit\n"
+            "Environment: MAX25_HOST, MAX25_PORT, MAX25_TCP_PASSWORD\n\n",
+            prog, MAX25_DEFAULT_PORT);
+}
+
+static int parse_args(int argc, char **argv, amiga_config_t *cfg)
+{
+    int i;
+    int positional = 0;
+
+    for (i = 1; i < argc; i++) {
+        if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
+            usage(argv[0]);
+            return 1;
+        }
+        if (strcmp(argv[i], "-H") == 0 && i + 1 < argc) {
+            strncpy(cfg->host, argv[++i], sizeof(cfg->host) - 1);
+            continue;
+        }
+        if (strcmp(argv[i], "-p") == 0 && i + 1 < argc) {
+            cfg->port = (unsigned)strtoul(argv[++i], NULL, 10);
+            continue;
+        }
+        if ((strcmp(argv[i], "-P") == 0 || strcmp(argv[i], "--password") == 0) &&
+            i + 1 < argc) {
+            strncpy(cfg->tcp_password, argv[++i], sizeof(cfg->tcp_password) - 1);
+            continue;
+        }
+        if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
+            cfg->verbose = 1;
+            continue;
+        }
+        if (strcmp(argv[i], "--probe") == 0) {
+            cfg->probe = 1;
+            continue;
+        }
+        if (strcmp(argv[i], "--ax25-ui") == 0) {
+            cfg->ax25_ui = 1;
+            continue;
+        }
+        if (strcmp(argv[i], "--no-ax25-ui") == 0) {
+            cfg->ax25_ui = 0;
+            continue;
+        }
+        if (argv[i][0] == '-') {
+            fprintf(stderr, "%s: unknown option %s\n", argv[0], argv[i]);
+            return -1;
+        }
+        if (positional == 0) {
+            strncpy(cfg->host, argv[i], sizeof(cfg->host) - 1);
+        } else if (positional == 1) {
+            cfg->port = (unsigned)strtoul(argv[i], NULL, 10);
+        }
+        positional++;
+    }
+    return 0;
+}
+
+static void print_rx(const char *line, int verbose)
+{
+    if (verbose) {
+        fprintf(stderr, "max25-terminal: << %s\n", line);
+    }
+    if (strncmp(line, "RX ", 3) == 0) {
+        printf("<< %s\n", line + 3);
+    } else if (strncmp(line, "ERR ", 4) == 0) {
+        fprintf(stderr, "!! %s\n", line);
+    } else if (strncmp(line, "EVENT ", 6) == 0) {
+        printf("-- %s\n", line);
+    }
+    fflush(stdout);
+    fflush(stderr);
+}
+
+static int drain_socket(max25_client_t *client, int verbose)
+{
+    char line[MAX25_LINE_MAX];
+    int got = 0;
+
+    for (;;) {
+        fd_set rfds;
+        struct timeval tv;
+        int fd = max25_client_fd(client);
+
+        FD_ZERO(&rfds);
+        FD_SET(fd, &rfds);
+        tv.tv_sec = 0;
+        tv.tv_usec = 0;
+        if (select(fd + 1, &rfds, NULL, NULL, &tv) <= 0) {
+            break;
+        }
+        if (max25_client_read_line(client, line, sizeof(line)) != 0) {
+            return -1;
+        }
+        print_rx(line, verbose);
+        got = 1;
+        if (strcmp(line, "OK") == 0) {
+            break;
+        }
+    }
+    return got ? 0 : 0;
+}
+
+static int send_cmd_wait(max25_client_t *client, const char *cmd, int verbose)
+{
+    char line[MAX25_LINE_MAX];
+
+    if (verbose) {
+        fprintf(stderr, "max25-terminal: >> %s\n", cmd);
+    }
+    if (max25_client_write(client, cmd) != 0) {
+        return -1;
+    }
+    for (;;) {
+        if (max25_client_read_line(client, line, sizeof(line)) != 0) {
+            return -1;
+        }
+        print_rx(line, verbose);
+        if (strncmp(line, "STATUS ", 7) == 0) {
+            continue;
+        }
+        if (strncmp(line, "RX ", 3) == 0) {
+            continue;
+        }
+        if (strncmp(line, "EVENT ", 6) == 0) {
+            continue;
+        }
+        return strcmp(line, "OK") == 0 ? 0 : -1;
+    }
+}
+
+static int run_session(max25_client_t *client, amiga_config_t *cfg,
+                       max25_status_t *status)
+{
+    char line[MAX25_LINE_MAX];
+
+    printf("MAX25 Terminal (Amiga) — connected to %s:%u\n", cfg->host, cfg->port);
+    printf("Type text to SEND. Commands: /status /callerid X /callid X /connect /quit\n");
+
+    if (!status->connected) {
+        send_cmd_wait(client, "CONNECT", cfg->verbose);
+        status->connected = 1;
+    }
+
+    while (fgets(line, sizeof(line), stdin) != NULL) {
+        line[strcspn(line, "\r\n")] = '\0';
+        if (line[0] == '\0') {
+            continue;
+        }
+        if (strcmp(line, "/quit") == 0 || strcmp(line, "/exit") == 0) {
+            break;
+        }
+        if (strcmp(line, "/status") == 0) {
+            send_cmd_wait(client, "GET STATUS", cfg->verbose);
+            continue;
+        }
+        if (strcmp(line, "/connect") == 0) {
+            send_cmd_wait(client, "CONNECT", cfg->verbose);
+            status->connected = 1;
+            continue;
+        }
+        if (strcmp(line, "/disconnect") == 0) {
+            send_cmd_wait(client, "DISCONNECT", cfg->verbose);
+            status->connected = 0;
+            continue;
+        }
+        if (strncmp(line, "/callerid ", 10) == 0) {
+            char cmd[MAX25_LINE_MAX];
+            if (!max25_valid_callsign(line + 10)) {
+                fprintf(stderr, "invalid CALLERID\n");
+                continue;
+            }
+            snprintf(cmd, sizeof(cmd), "SET CALLERID %s", line + 10);
+            send_cmd_wait(client, cmd, cfg->verbose);
+            continue;
+        }
+        if (strncmp(line, "/callid ", 8) == 0) {
+            char cmd[MAX25_LINE_MAX];
+            if (!max25_valid_callsign(line + 8)) {
+                fprintf(stderr, "invalid CALLID\n");
+                continue;
+            }
+            snprintf(cmd, sizeof(cmd), "SET CALLID %s", line + 8);
+            send_cmd_wait(client, cmd, cfg->verbose);
+            continue;
+        }
+        {
+            char cmd[MAX25_LINE_MAX + 8];
+            snprintf(cmd, sizeof(cmd), "SEND %s", line);
+            send_cmd_wait(client, cmd, cfg->verbose);
+        }
+        (void)drain_socket(client, cfg->verbose);
+    }
+    return 0;
+}
+
+int main(int argc, char **argv)
+{
+    amiga_config_t cfg;
+    max25_client_t *client = NULL;
+    max25_status_t status;
+    char reply[MAX25_LINE_MAX];
+    int rc;
+
+    config_defaults(&cfg);
+    rc = parse_args(argc, argv, &cfg);
+    if (rc != 0) {
+        return rc < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+    }
+
+    if (max25_client_connect(cfg.host, cfg.port, "", 1, cfg.tcp_password,
+                             &client, &status) != 0) {
+        fprintf(stderr, "max25-terminal: connect failed (tcp %s:%u)\n",
+                cfg.host, cfg.port);
+        return EXIT_FAILURE;
+    }
+
+    if (cfg.probe) {
+        printf("STATUS hardware=%s device=%s mode=%s callerid=%s callid=%s "
+               "ax25_ui=%s connected=%s stack=%s\n",
+               status.hardware, status.device, status.mode,
+               status.callerid, status.callid,
+               status.ax25_ui ? "on" : "off",
+               status.connected ? "yes" : "no",
+               status.stack);
+        max25_client_write(client, "DISCONNECT");
+        max25_client_free(client);
+        return EXIT_SUCCESS;
+    }
+
+    if (cfg.ax25_ui) {
+        max25_client_command(client, "SET AX25_UI on", reply, sizeof(reply));
+        status.ax25_ui = 1;
+    } else {
+        max25_client_command(client, "SET AX25_UI off", reply, sizeof(reply));
+        status.ax25_ui = 0;
+    }
+
+    run_session(client, &cfg, &status);
+    max25_client_write(client, "DISCONNECT");
+    max25_client_free(client);
+    return EXIT_SUCCESS;
+}
diff --git a/stacks/terminal/max25_proto.c b/stacks/terminal/max25_proto.c
new file mode 100644
index 0000000..b4a9725
--- /dev/null
+++ b/stacks/terminal/max25_proto.c
@@ -0,0 +1,472 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include "max25_proto.h"
+
+#if defined(__AMIGA__) || defined(__amigaos__)
+#define MAX25_AMIGA 1
+#endif
+
+#include <ctype.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#ifndef MAX25_AMIGA
+#include <netdb.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#else
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#endif
+
+struct max25_client {
+    int fd;
+};
+
+static int read_line_fd(int fd, char *line, size_t line_sz)
+{
+    size_t pos = 0;
+    char ch;
+
+    while (pos + 1 < line_sz) {
+        ssize_t n = read(fd, &ch, 1);
+        if (n < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            return -1;
+        }
+        if (n == 0) {
+            return -1;
+        }
+        if (ch == '\n') {
+            line[pos] = '\0';
+            return 0;
+        }
+        if (ch != '\r') {
+            line[pos++] = ch;
+        }
+    }
+    return -1;
+}
+
+static int write_cmd(int fd, const char *cmd)
+{
+    char buf[MAX25_LINE_MAX + 2];
+    int len = snprintf(buf, sizeof(buf), "%s\n", cmd);
+    ssize_t off = 0;
+
+    if (len < 0 || (size_t)len >= sizeof(buf)) {
+        return -1;
+    }
+    while (off < len) {
+        ssize_t n = write(fd, buf + off, (size_t)len - (size_t)off);
+        if (n < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            return -1;
+        }
+        off += n;
+    }
+    return 0;
+}
+
+static int connect_tcp(const char *host, unsigned port)
+{
+#ifdef MAX25_AMIGA
+    struct hostent *he;
+    struct sockaddr_in addr;
+    int fd;
+
+    he = gethostbyname(host);
+    if (he == NULL || he->h_addr_list[0] == NULL) {
+        return -1;
+    }
+
+    fd = socket(AF_INET, SOCK_STREAM, 0);
+    if (fd < 0) {
+        return -1;
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons((uint16_t)port);
+    memcpy(&addr.sin_addr, he->h_addr_list[0], (size_t)he->h_length);
+
+    if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
+        close(fd);
+        return -1;
+    }
+    return fd;
+#else
+    char portbuf[16];
+    struct addrinfo hints;
+    struct addrinfo *res = NULL;
+    struct addrinfo *ai;
+    int fd = -1;
+
+    snprintf(portbuf, sizeof(portbuf), "%u", port);
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+
+    if (getaddrinfo(host, portbuf, &hints, &res) != 0) {
+        return -1;
+    }
+
+    for (ai = res; ai != NULL; ai = ai->ai_next) {
+        fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+        if (fd < 0) {
+            continue;
+        }
+        if (connect(fd, ai->ai_addr, ai->ai_addrlen) == 0) {
+            break;
+        }
+        close(fd);
+        fd = -1;
+    }
+    freeaddrinfo(res);
+    return fd;
+#endif
+}
+
+static int connect_unix(const char *path)
+{
+#ifndef MAX25_AMIGA
+    struct sockaddr_un addr;
+    int fd;
+
+    if (path == NULL || path[0] == '\0') {
+        return -1;
+    }
+
+    fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (fd < 0) {
+        return -1;
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sun_family = AF_UNIX;
+    strncpy(addr.sun_path, path, sizeof(addr.sun_path) - 1);
+
+    if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
+        close(fd);
+        return -1;
+    }
+    return fd;
+#else
+    (void)path;
+    return -1;
+#endif
+}
+
+static int tcp_authenticate(int fd, const char *password)
+{
+    char line[MAX25_LINE_MAX];
+    char cmd[MAX25_LINE_MAX + 8];
+
+    if (password == NULL || password[0] == '\0') {
+        return -1;
+    }
+    snprintf(cmd, sizeof(cmd), "AUTH %s", password);
+    if (write_cmd(fd, cmd) != 0) {
+        return -1;
+    }
+    if (read_line_fd(fd, line, sizeof(line)) != 0) {
+        return -1;
+    }
+    return strcmp(line, "OK") == 0 ? 0 : -1;
+}
+
+static int handshake(int fd, const char *tcp_password, max25_status_t *initial_status)
+{
+    char line[MAX25_LINE_MAX];
+
+    if (read_line_fd(fd, line, sizeof(line)) != 0) {
+        return -1;
+    }
+    if (strcmp(line, "AUTH required") == 0) {
+        if (tcp_authenticate(fd, tcp_password) != 0) {
+            return -1;
+        }
+        if (read_line_fd(fd, line, sizeof(line)) != 0 || strcmp(line, "OK") != 0) {
+            return -1;
+        }
+    } else if (strcmp(line, "OK") != 0) {
+        return -1;
+    }
+
+    if (read_line_fd(fd, line, sizeof(line)) != 0 ||
+        strncmp(line, "STATUS ", 7) != 0) {
+        return -1;
+    }
+
+    if (initial_status != NULL) {
+        max25_client_parse_status(line, initial_status);
+    }
+    return 0;
+}
+
+int max25_client_connect(const char *host, unsigned port, const char *unix_path,
+                         int tcp_only, const char *tcp_password,
+                         max25_client_t **out, max25_status_t *initial_status)
+{
+    max25_client_t *client;
+    int fd = -1;
+
+    if (out == NULL) {
+        return -1;
+    }
+
+    if (!tcp_only && unix_path != NULL && unix_path[0] != '\0') {
+#ifndef MAX25_AMIGA
+        fd = connect_unix(unix_path);
+#endif
+    }
+    if (fd < 0 && host != NULL && host[0] != '\0') {
+        fd = connect_tcp(host, port);
+    }
+    if (fd < 0) {
+        return -1;
+    }
+
+    client = calloc(1, sizeof(*client));
+    if (client == NULL) {
+        close(fd);
+        return -1;
+    }
+    client->fd = fd;
+
+    if (handshake(fd, tcp_password, initial_status) != 0) {
+        max25_client_free(client);
+        return -1;
+    }
+
+    *out = client;
+    return 0;
+}
+
+void max25_client_free(max25_client_t *client)
+{
+    if (client == NULL) {
+        return;
+    }
+    if (client->fd >= 0) {
+        close(client->fd);
+    }
+    free(client);
+}
+
+int max25_client_fd(const max25_client_t *client)
+{
+    return client != NULL ? client->fd : -1;
+}
+
+int max25_client_write(max25_client_t *client, const char *cmd)
+{
+    if (client == NULL || cmd == NULL) {
+        return -1;
+    }
+    return write_cmd(client->fd, cmd);
+}
+
+max25_line_kind_t max25_client_classify_line(const char *line)
+{
+    if (line == NULL || line[0] == '\0') {
+        return MAX25_LINE_IGNORE;
+    }
+    if (strcmp(line, "OK") == 0) {
+        return MAX25_LINE_OK;
+    }
+    if (strncmp(line, "ERR ", 4) == 0) {
+        return MAX25_LINE_ERR;
+    }
+    if (strncmp(line, "STATUS ", 7) == 0) {
+        return MAX25_LINE_STATUS;
+    }
+    if (strncmp(line, "RX ", 3) == 0) {
+        return MAX25_LINE_RX;
+    }
+    if (strncmp(line, "EVENT ", 6) == 0) {
+        return MAX25_LINE_EVENT;
+    }
+    if (strncmp(line, "DEVICE ", 7) == 0) {
+        return MAX25_LINE_DEVICE;
+    }
+    return MAX25_LINE_OTHER;
+}
+
+int max25_client_command(max25_client_t *client, const char *cmd,
+                         char *reply, size_t reply_sz)
+{
+    char line[MAX25_LINE_MAX];
+
+    if (client == NULL || cmd == NULL) {
+        return -1;
+    }
+    if (write_cmd(client->fd, cmd) != 0) {
+        return -1;
+    }
+    for (;;) {
+        if (read_line_fd(client->fd, line, sizeof(line)) != 0) {
+            return -1;
+        }
+        if (strncmp(line, "STATUS ", 7) == 0) {
+            if (reply != NULL && reply_sz > 0) {
+                strncpy(reply, line, reply_sz - 1);
+                reply[reply_sz - 1] = '\0';
+            }
+            continue;
+        }
+        if (strncmp(line, "RX ", 3) == 0) {
+            continue;
+        }
+        if (strncmp(line, "EVENT ", 6) == 0) {
+            continue;
+        }
+        if (strncmp(line, "DEVICE ", 7) == 0) {
+            continue;
+        }
+        /* GET STATUS replies: STATUS … then OK — keep STATUS in reply. */
+        if (strcmp(line, "OK") == 0) {
+            if (reply != NULL && reply_sz > 0 &&
+                strncmp(reply, "STATUS ", 7) != 0) {
+                strncpy(reply, line, reply_sz - 1);
+                reply[reply_sz - 1] = '\0';
+            }
+            return 0;
+        }
+        if (reply != NULL && reply_sz > 0) {
+            strncpy(reply, line, reply_sz - 1);
+            reply[reply_sz - 1] = '\0';
+        }
+        return -1;
+    }
+}
+
+int max25_client_read_line(max25_client_t *client, char *line, size_t line_sz)
+{
+    if (client == NULL) {
+        return -1;
+    }
+    return read_line_fd(client->fd, line, line_sz);
+}
+
+static void copy_field(const char *src, char *dst, size_t dst_sz)
+{
+    if (dst == NULL || dst_sz == 0) {
+        return;
+    }
+    if (src == NULL) {
+        dst[0] = '\0';
+        return;
+    }
+    strncpy(dst, src, dst_sz - 1);
+    dst[dst_sz - 1] = '\0';
+}
+
+int max25_client_apply_event(const char *line, max25_status_t *status)
+{
+    if (line == NULL || status == NULL || strncmp(line, "EVENT ", 6) != 0) {
+        return 0;
+    }
+    if (strcmp(line, "EVENT connected") == 0) {
+        status->connected = 1;
+        return 1;
+    }
+    if (strcmp(line, "EVENT disconnected") == 0) {
+        status->connected = 0;
+        return 1;
+    }
+    return 0;
+}
+
+int max25_client_parse_status(const char *line, max25_status_t *status)
+{
+    char buf[MAX25_LINE_MAX];
+    char *save = NULL;
+    char *tok;
+
+    if (line == NULL || status == NULL || strncmp(line, "STATUS ", 7) != 0) {
+        return -1;
+    }
+
+    strncpy(buf, line + 7, sizeof(buf) - 1);
+    buf[sizeof(buf) - 1] = '\0';
+
+    memset(status, 0, sizeof(*status));
+    for (tok = strtok_r(buf, " ", &save); tok != NULL;
+         tok = strtok_r(NULL, " ", &save)) {
+        char *eq = strchr(tok, '=');
+        if (eq == NULL) {
+            continue;
+        }
+        *eq = '\0';
+        if (strcmp(tok, "hardware") == 0) {
+            copy_field(eq + 1, status->hardware, sizeof(status->hardware));
+        } else if (strcmp(tok, "device") == 0) {
+            copy_field(eq + 1, status->device, sizeof(status->device));
+        } else if (strcmp(tok, "mode") == 0) {
+            copy_field(eq + 1, status->mode, sizeof(status->mode));
+        } else if (strcmp(tok, "callerid") == 0) {
+            copy_field(eq + 1, status->callerid, sizeof(status->callerid));
+        } else if (strcmp(tok, "callid") == 0) {
+            copy_field(eq + 1, status->callid, sizeof(status->callid));
+        } else if (strcmp(tok, "ax25_ui") == 0) {
+            status->ax25_ui = (strcmp(eq + 1, "on") == 0);
+        } else if (strcmp(tok, "connected") == 0) {
+            status->connected = (strcmp(eq + 1, "yes") == 0);
+        } else if (strcmp(tok, "stack") == 0) {
+            copy_field(eq + 1, status->stack, sizeof(status->stack));
+        } else if (strcmp(tok, "error") == 0) {
+            copy_field(eq + 1, status->error, sizeof(status->error));
+        } else if (strcmp(tok, "voice") == 0) {
+            copy_field(eq + 1, status->voice, sizeof(status->voice));
+        }
+    }
+    return 0;
+}
+
+int max25_valid_callsign(const char *value)
+{
+    const char *dash;
+    size_t call_len;
+    unsigned long ssid;
+    char *end = NULL;
+    size_t i;
+
+    if (value == NULL) {
+        return 0;
+    }
+
+    dash = strchr(value, '-');
+    if (dash != NULL) {
+        call_len = (size_t)(dash - value);
+        ssid = strtoul(dash + 1, &end, 10);
+        if (end == dash + 1 || ssid > 15) {
+            return 0;
+        }
+    } else {
+        call_len = strlen(value);
+    }
+
+    if (call_len == 0 || call_len > 6) {
+        return 0;
+    }
+
+    for (i = 0; i < call_len; i++) {
+        char c = (char)toupper((unsigned char)value[i]);
+        if (!((c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'))) {
+            return 0;
+        }
+    }
+
+    return 1;
+}
diff --git a/stacks/terminal/max25_proto.h b/stacks/terminal/max25_proto.h
new file mode 100644
index 0000000..25ae5d5
--- /dev/null
+++ b/stacks/terminal/max25_proto.h
@@ -0,0 +1,55 @@
+#ifndef MAX25_PROTO_H
+#define MAX25_PROTO_H
+
+#include <stddef.h>
+
+#define MAX25_DEFAULT_PORT 7325
+#define MAX25_DEFAULT_UNIX "/run/max25/modem.sock"
+#define MAX25_LINE_MAX 512
+#define MAX25_CALLSIGN_MAX 16
+
+typedef struct max25_client max25_client_t;
+
+typedef struct max25_status {
+    char hardware[32];
+    char device[32];
+    char mode[32];
+    char callerid[MAX25_CALLSIGN_MAX];
+    char callid[MAX25_CALLSIGN_MAX];
+    int ax25_ui;
+    int connected;
+    int monitor;
+    char stack[32];
+    char error[16];
+    char voice[16];
+} max25_status_t;
+
+typedef enum {
+    MAX25_LINE_IGNORE = 0,
+    MAX25_LINE_OK,
+    MAX25_LINE_ERR,
+    MAX25_LINE_STATUS,
+    MAX25_LINE_RX,
+    MAX25_LINE_EVENT,
+    MAX25_LINE_DEVICE,
+    MAX25_LINE_OTHER
+} max25_line_kind_t;
+
+int max25_client_connect(const char *host, unsigned port, const char *unix_path,
+                         int tcp_only, const char *tcp_password,
+                         max25_client_t **out, max25_status_t *initial_status);
+void max25_client_free(max25_client_t *client);
+int max25_client_fd(const max25_client_t *client);
+
+int max25_client_write(max25_client_t *client, const char *cmd);
+int max25_client_command(max25_client_t *client, const char *cmd,
+                         char *reply, size_t reply_sz);
+int max25_client_read_line(max25_client_t *client, char *line, size_t line_sz);
+max25_line_kind_t max25_client_classify_line(const char *line);
+int max25_client_parse_status(const char *line, max25_status_t *status);
+/** Apply EVENT connected / EVENT disconnected to status. Returns 1 if handled. */
+int max25_client_apply_event(const char *line, max25_status_t *status);
+
+int max25_valid_callsign(const char *value);
+
+#endif /* MAX25_PROTO_H */
diff --git a/stacks/terminal/max25_terminal.c b/stacks/terminal/max25_terminal.c
new file mode 100644
index 0000000..8b4eb52
--- /dev/null
+++ b/stacks/terminal/max25_terminal.c
@@ -0,0 +1,767 @@
+#define _POSIX_C_SOURCE 200809L
+
+#include "max25_proto.h"
+#include "max25_ui.h"
+
+#include <errno.h>
+#include <getopt.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+
+#ifdef MAX25_HAVE_NCURSES
+#include <ncurses.h>
+#endif
+
+typedef struct {
+    char host[256];
+    unsigned port;
+    char unix_path[256];
+    char tcp_password[128];
+    char default_device[32];
+    int tcp_only;
+    int ax25_ui;
+    int verbose;
+    int probe;
+} terminal_config_t;
+
+typedef struct {
+    int waiting_reply;
+    char last_err[MAX25_LINE_MAX];
+} session_io_t;
+
+static struct termios g_saved_tty;
+static int g_tty_raw;
+
+static void config_defaults(terminal_config_t *cfg)
+{
+    const char *env;
+
+    memset(cfg, 0, sizeof(*cfg));
+    strncpy(cfg->host, "127.0.0.1", sizeof(cfg->host) - 1);
+    cfg->port = MAX25_DEFAULT_PORT;
+    strncpy(cfg->unix_path, MAX25_DEFAULT_UNIX, sizeof(cfg->unix_path) - 1);
+    cfg->ax25_ui = 1;
+
+    env = getenv("MAX25_HOST");
+    if (env != NULL && env[0] != '\0') {
+        strncpy(cfg->host, env, sizeof(cfg->host) - 1);
+    }
+    env = getenv("MAX25_PORT");
+    if (env != NULL && env[0] != '\0') {
+        cfg->port = (unsigned)strtoul(env, NULL, 10);
+    }
+    env = getenv("MAX25_UNIX");
+    if (env != NULL) {
+        strncpy(cfg->unix_path, env, sizeof(cfg->unix_path) - 1);
+    }
+    env = getenv("MAX25_TCP_PASSWORD");
+    if (env != NULL) {
+        strncpy(cfg->tcp_password, env, sizeof(cfg->tcp_password) - 1);
+    }
+}
+
+static void usage(const char *prog)
+{
+    fprintf(stderr,
+            "MAX25 Terminal — CLI operator client (max25d via TCP/M25/1)\n\n"
+            "Usage: %s [options] [host] [port]\n\n"
+            "Options:\n"
+            "  -H, --host HOST       max25d TCP host (default 127.0.0.1)\n"
+            "  -p, --port PORT       max25d TCP port (default %u)\n"
+            "  -T, --tcp-only        TCP only — do not try Unix socket\n"
+            "  -U, --unix PATH       Unix socket (default %s, before TCP)\n"
+            "      --ax25-ui         AX.25 UI mode (default on)\n"
+            "      --no-ax25-ui      Plain SEND lines\n"
+            "  -P, --password PASS   TCP auth password (plain-text M25/1 AUTH)\n"
+            "  -d, --device ID       SET DEVICE after connect (configured device id)\n"
+            "  -v, --verbose         Protocol log on stderr\n"
+            "      --probe           Connect, print STATUS, exit (CI)\n"
+            "  -h, --help            Show help\n\n"
+            "Remote example:\n"
+            "  %s -T -H linux-host.local -p 7325\n\n"
+            "Environment: MAX25_HOST, MAX25_PORT, MAX25_UNIX, MAX25_TCP_PASSWORD\n"
+            "Symlink: max25-client -> max25-terminal\n\n",
+            prog, MAX25_DEFAULT_PORT, MAX25_DEFAULT_UNIX, prog);
+}
+
+static int tty_enable_raw(void)
+{
+    struct termios tty;
+
+    if (!isatty(STDIN_FILENO)) {
+        return 0;
+    }
+    if (tcgetattr(STDIN_FILENO, &g_saved_tty) != 0) {
+        return -1;
+    }
+    tty = g_saved_tty;
+    tty.c_lflag &= (tcflag_t)~(ICANON | ECHO);
+    tty.c_cc[VMIN] = 0;
+    tty.c_cc[VTIME] = 1;
+    if (tcsetattr(STDIN_FILENO, TCSANOW, &tty) != 0) {
+        return -1;
+    }
+    g_tty_raw = 1;
+    return 0;
+}
+
+static void tty_restore(void)
+{
+    if (g_tty_raw) {
+        tcsetattr(STDIN_FILENO, TCSANOW, &g_saved_tty);
+        g_tty_raw = 0;
+    }
+}
+
+static int begin_cmd(session_io_t *io)
+{
+    if (io == NULL) {
+        return -1;
+    }
+    io->waiting_reply = 1;
+    io->last_err[0] = '\0';
+    return 0;
+}
+
+static int send_cmd_async(max25_client_t *client, session_io_t *io,
+                          const char *cmd)
+{
+    if (max25_client_write(client, cmd) != 0) {
+        return -1;
+    }
+    return begin_cmd(io);
+}
+
+static int dispatch_daemon_line(const char *line, session_io_t *io,
+                                max25_ui_t *ui, max25_status_t *status,
+                                terminal_config_t *cfg, int *need_redraw)
+{
+    max25_line_kind_t kind = max25_client_classify_line(line);
+
+    if (need_redraw != NULL) {
+        *need_redraw = 0;
+    }
+
+    if (cfg->verbose) {
+        fprintf(stderr, "max25-terminal: << %s\n", line);
+    }
+
+    if (kind == MAX25_LINE_RX) {
+        max25_ui_append_rx(ui, line + 3);
+        if (need_redraw != NULL) {
+            *need_redraw = 1;
+        }
+        return 0;
+    }
+
+    /* CONNECT/DISCONNECT emit EVENT before OK — update header even while waiting. */
+    if (kind == MAX25_LINE_EVENT) {
+        if (max25_client_apply_event(line, status)) {
+            max25_ui_append_rx(ui, line);
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+        } else if (cfg->verbose) {
+            max25_ui_append_rx(ui, line);
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+        }
+        if (io->waiting_reply) {
+            return 0;
+        }
+        return 0;
+    }
+
+    if (io->waiting_reply) {
+        if (kind == MAX25_LINE_STATUS && status != NULL) {
+            char summary[MAX25_LINE_MAX];
+
+            max25_client_parse_status(line, status);
+            /* Show STATUS in RX pane (F10→3 and other GET STATUS callers). */
+            snprintf(summary, sizeof(summary),
+                     "STATUS device=%s stack=%s connected=%s callerid=%s callid=%s",
+                     status->device[0] != '\0' ? status->device : "-",
+                     status->stack[0] != '\0' ? status->stack : "-",
+                     status->connected ? "yes" : "no",
+                     status->callerid[0] != '\0' ? status->callerid : "-",
+                     status->callid[0] != '\0' ? status->callid : "-");
+            max25_ui_append_rx(ui, summary);
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+            return 0;
+        }
+        if (kind == MAX25_LINE_DEVICE) {
+            max25_ui_append_rx(ui, line);
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+            return 0;
+        }
+        if (kind == MAX25_LINE_OK) {
+            io->waiting_reply = 0;
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+            return 0;
+        }
+        if (kind == MAX25_LINE_ERR) {
+            strncpy(io->last_err, line, sizeof(io->last_err) - 1);
+            io->last_err[sizeof(io->last_err) - 1] = '\0';
+            io->waiting_reply = 0;
+            max25_ui_append_rx(ui, line);
+            if (need_redraw != NULL) {
+                *need_redraw = 1;
+            }
+            return -1;
+        }
+        return 0;
+    }
+
+    if (kind == MAX25_LINE_ERR) {
+        max25_ui_append_rx(ui, line);
+        if (need_redraw != NULL) {
+            *need_redraw = 1;
+        }
+    }
+    return 0;
+}
+
+
+static int send_callsign(max25_client_t *client, session_io_t *io,
+                         const char *field, const char *value)
+{
+    char cmd[MAX25_LINE_MAX];
+
+    if (!max25_valid_callsign(value)) {
+        fprintf(stderr, "max25-terminal: invalid %s\n", field);
+        return -1;
+    }
+    snprintf(cmd, sizeof(cmd), "SET %s %s", field, value);
+    return send_cmd_async(client, io, cmd);
+}
+
+static int send_line_async(max25_client_t *client, session_io_t *io,
+                           const char *line)
+{
+    char cmd[MAX25_LINE_MAX + 8];
+    size_t max_payload = sizeof(cmd) - 6;
+
+    if (strlen(line) > max_payload) {
+        return -1;
+    }
+    snprintf(cmd, sizeof(cmd), "SEND %s", line);
+    return send_cmd_async(client, io, cmd);
+}
+
+static int refresh_status(max25_client_t *client, max25_status_t *status)
+{
+    char reply[MAX25_LINE_MAX];
+
+    if (max25_client_command(client, "GET STATUS", reply, sizeof(reply)) != 0) {
+        return -1;
+    }
+    return max25_client_parse_status(reply, status);
+}
+
+static int set_device_sync(max25_client_t *client, max25_status_t *status,
+                           const char *device_id)
+{
+    char cmd[MAX25_LINE_MAX + 16];
+    char reply[MAX25_LINE_MAX];
+
+    if (device_id == NULL || device_id[0] == '\0') {
+        return -1;
+    }
+    snprintf(cmd, sizeof(cmd), "SET DEVICE %s", device_id);
+    if (max25_client_command(client, cmd, reply, sizeof(reply)) != 0) {
+        return -1;
+    }
+    return refresh_status(client, status);
+}
+
+static int fetch_devices(max25_client_t *client, max25_ui_t *ui)
+{
+    char line[MAX25_LINE_MAX];
+
+    if (max25_client_write(client, "GET DEVICES") != 0) {
+        return -1;
+    }
+    max25_ui_append_rx(ui, "-- max25d devices --");
+    for (;;) {
+        if (max25_client_read_line(client, line, sizeof(line)) != 0) {
+            return -1;
+        }
+        if (strcmp(line, "OK") == 0) {
+            break;
+        }
+        if (strncmp(line, "DEVICE ", 7) == 0) {
+            max25_ui_append_rx(ui, line);
+            continue;
+        }
+        if (strncmp(line, "ERR ", 4) == 0) {
+            max25_ui_append_rx(ui, line);
+            return -1;
+        }
+    }
+    return 0;
+}
+
+static int menu_action_needs_prompt(max25_menu_action_t action)
+{
+    return action == MAX25_MENU_CALLERID || action == MAX25_MENU_CALLID ||
+           action == MAX25_MENU_SEND || action == MAX25_MENU_DEVICE;
+}
+
+/* Returns 1 to quit session, 0 otherwise. Hides menu before action. */
+static int apply_menu_pick(max25_menu_action_t action, max25_client_t *client,
+                           session_io_t *io, max25_ui_t *ui,
+                           max25_status_t *status, const char *input_line)
+{
+    char buf[MAX25_LINE_MAX];
+    char cmd[64];
+
+    if (action == MAX25_MENU_NONE) {
+        return 0;
+    }
+    if (action == MAX25_MENU_QUIT) {
+        return 1;
+    }
+
+    /* Leave overlay so prompts / STATUS RX / header redraw are visible. */
+    max25_ui_hide_menu(ui);
+    max25_ui_draw_screen(ui, status, input_line != NULL ? input_line : "");
+
+    switch (action) {
+    case MAX25_MENU_CALLERID:
+        if (max25_ui_prompt(ui, "CALLERID", buf, sizeof(buf)) > 0) {
+            send_callsign(client, io, "CALLERID", buf);
+        }
+        break;
+    case MAX25_MENU_CALLID:
+        if (max25_ui_prompt(ui, "CALLID", buf, sizeof(buf)) > 0) {
+            send_callsign(client, io, "CALLID", buf);
+        }
+        break;
+    case MAX25_MENU_STATUS:
+        send_cmd_async(client, io, "GET STATUS");
+        break;
+    case MAX25_MENU_SEND:
+        if (max25_ui_prompt(ui, "Send", buf, sizeof(buf)) > 0) {
+            send_line_async(client, io, buf);
+        }
+        break;
+    case MAX25_MENU_MONITOR:
+        snprintf(cmd, sizeof(cmd), "MONITOR %s",
+                 status->monitor ? "off" : "on");
+        status->monitor = !status->monitor;
+        send_cmd_async(client, io, cmd);
+        max25_ui_append_rx(ui, status->monitor ? "MONITOR on" : "MONITOR off");
+        max25_ui_draw_screen(ui, status, input_line != NULL ? input_line : "");
+        break;
+    case MAX25_MENU_CONNECT:
+        send_cmd_async(client, io,
+                       status->connected ? "DISCONNECT" : "CONNECT");
+        break;
+    case MAX25_MENU_DEVICE:
+        (void)fetch_devices(client, ui);
+        if (max25_ui_prompt(ui, "DEVICE id", buf, sizeof(buf)) > 0) {
+            if (set_device_sync(client, status, buf) != 0) {
+                max25_ui_append_rx(ui, "ERR SET DEVICE failed");
+            }
+            max25_ui_draw_screen(ui, status,
+                                 input_line != NULL ? input_line : "");
+        }
+        break;
+    case MAX25_MENU_DEVICES:
+        (void)fetch_devices(client, ui);
+        max25_ui_draw_screen(ui, status, input_line != NULL ? input_line : "");
+        break;
+    default:
+        break;
+    }
+
+    if (!menu_action_needs_prompt(action) && action != MAX25_MENU_MONITOR) {
+        max25_ui_draw_screen(ui, status, input_line != NULL ? input_line : "");
+    }
+    return 0;
+}
+
+#ifdef MAX25_HAVE_NCURSES
+static int read_key_ncurses(void)
+{
+    int ch = getch();
+
+    if (ch == KEY_F(10)) {
+        return 999;
+    }
+    return ch;
+}
+#endif
+
+static int read_plain_key(void)
+{
+    unsigned char buf[8];
+    ssize_t n;
+
+    n = read(STDIN_FILENO, buf, sizeof(buf));
+    if (n <= 0) {
+        if (n < 0 && errno == EAGAIN) {
+            return -1;
+        }
+        return 0;
+    }
+
+    if (buf[0] == 0x1b && n >= 3 && buf[1] == '[') {
+        if (n >= 4 && buf[2] == '2' && buf[3] == '1' && (n < 5 || buf[4] == '~')) {
+            return 999;
+        }
+    }
+
+    return (int)buf[0];
+}
+
+static int run_session(max25_client_t *client, max25_ui_t *ui,
+                       terminal_config_t *cfg, max25_status_t *status)
+{
+    struct pollfd pfds[2];
+    session_io_t io;
+    char line[MAX25_LINE_MAX];
+    char input[MAX25_UI_INPUT_MAX];
+    size_t input_len = 0;
+    int running = 1;
+    int use_ncurses = max25_ui_has_ncurses(ui);
+    int use_plain_raw = 0;
+
+    memset(&io, 0, sizeof(io));
+    input[0] = '\0';
+
+    if (!use_ncurses) {
+        max25_ui_apply_palette();
+    }
+    max25_ui_reset_rx(ui);
+    max25_ui_draw_screen(ui, status, input);
+
+    /* Arm TX session before accepting Enter/F10 SEND (daemon also auto-arms
+     * on SEND; sync CONNECT here so header connected=yes before first key). */
+    if (!status->connected) {
+        char creply[MAX25_LINE_MAX];
+
+        if (max25_client_command(client, "CONNECT", creply, sizeof(creply)) == 0) {
+            status->connected = 1;
+            max25_ui_append_rx(ui, "EVENT connected");
+        } else {
+            max25_ui_append_rx(ui, creply[0] ? creply : "ERR CONNECT failed");
+        }
+        max25_ui_draw_screen(ui, status, input);
+    }
+
+    (void)fetch_devices(client, ui);
+    max25_ui_draw_screen(ui, status, input);
+
+    if (!use_ncurses && isatty(STDIN_FILENO)) {
+        use_plain_raw = (tty_enable_raw() == 0);
+    }
+
+    while (running) {
+        if (!io.waiting_reply) {
+            max25_ui_draw_screen(ui, status, input);
+        }
+
+        pfds[0].fd = STDIN_FILENO;
+        pfds[0].events = POLLIN;
+        pfds[0].revents = 0;
+        pfds[1].fd = max25_client_fd(client);
+        pfds[1].events = POLLIN;
+        pfds[1].revents = 0;
+
+        if (poll(pfds, 2, 200) < 0) {
+            if (errno == EINTR) {
+                continue;
+            }
+            break;
+        }
+
+        if ((pfds[1].revents & (POLLERR | POLLHUP | POLLNVAL)) != 0) {
+            max25_ui_append_rx(ui, "max25d connection lost");
+            break;
+        }
+
+        if ((pfds[1].revents & POLLIN) != 0) {
+            int need_redraw = 0;
+
+            if (max25_client_read_line(client, line, sizeof(line)) != 0) {
+                max25_ui_append_rx(ui, "max25d connection closed");
+                break;
+            }
+            dispatch_daemon_line(line, &io, ui, status, cfg, &need_redraw);
+            if (io.last_err[0] != '\0' && cfg->verbose) {
+                fprintf(stderr, "max25-terminal: %s\n", io.last_err);
+            }
+            if (need_redraw && !max25_ui_menu_visible(ui)) {
+                max25_ui_draw_screen(ui, status, input);
+            }
+            continue;
+        }
+
+        if ((pfds[0].revents & POLLIN) == 0) {
+            continue;
+        }
+
+#ifdef MAX25_HAVE_NCURSES
+        if (use_ncurses) {
+            int ch = read_key_ncurses();
+            if (ch == -1) {
+                continue;
+            }
+            if (ch == 999) {
+                if (max25_ui_menu_visible(ui)) {
+                    max25_ui_hide_menu(ui);
+                    max25_ui_draw_screen(ui, status, input);
+                } else {
+                    max25_ui_show_menu(ui, status);
+                }
+                continue;
+            }
+            if (max25_ui_menu_visible(ui)) {
+                if (ch == 27) {
+                    max25_ui_hide_menu(ui);
+                    max25_ui_draw_screen(ui, status, input);
+                    continue;
+                }
+                if (apply_menu_pick(max25_ui_menu_pick(ui, ch), client, &io, ui,
+                                    status, input) != 0) {
+                    running = 0;
+                }
+                continue;
+            }
+            if (ch >= 32 && ch < 127) {
+                if (input_len + 1 < sizeof(input)) {
+                    input[input_len++] = (char)ch;
+                    input[input_len] = '\0';
+                }
+            } else if (ch == '\n' || ch == KEY_ENTER || ch == '\r') {
+                if (input_len > 0) {
+                    send_line_async(client, &io, input);
+                    input_len = 0;
+                    input[0] = '\0';
+                }
+            } else if (ch == KEY_BACKSPACE || ch == 127 || ch == '\b') {
+                if (input_len > 0) {
+                    input[--input_len] = '\0';
+                }
+            }
+            continue;
+        }
+#endif
+
+        if (use_plain_raw) {
+            int ch = read_plain_key();
+            if (ch <= 0) {
+                continue;
+            }
+            if (ch == 999) {
+                if (max25_ui_menu_visible(ui)) {
+                    max25_ui_hide_menu(ui);
+                    max25_ui_draw_screen(ui, status, input);
+                } else {
+                    max25_ui_show_menu(ui, status);
+                }
+                continue;
+            }
+            if (max25_ui_menu_visible(ui)) {
+                if (ch == 27) {
+                    max25_ui_hide_menu(ui);
+                    max25_ui_draw_screen(ui, status, input);
+                    continue;
+                }
+                if (apply_menu_pick(max25_ui_menu_pick(ui, ch), client, &io, ui,
+                                    status, input) != 0) {
+                    running = 0;
+                }
+                continue;
+            }
+            if (ch >= 32 && ch < 127) {
+                if (input_len + 1 < sizeof(input)) {
+                    input[input_len++] = (char)ch;
+                    input[input_len] = '\0';
+                }
+            } else if (ch == '\n' || ch == '\r') {
+                if (input_len > 0) {
+                    send_line_async(client, &io, input);
+                    input_len = 0;
+                    input[0] = '\0';
+                }
+            } else if (ch == 127 || ch == '\b') {
+                if (input_len > 0) {
+                    input[--input_len] = '\0';
+                }
+            }
+            continue;
+        }
+
+        if (fgets(input, sizeof(input), stdin) == NULL) {
+            running = 0;
+        } else {
+            input[strcspn(input, "\r\n")] = '\0';
+            if (max25_ui_menu_visible(ui)) {
+                if (apply_menu_pick(max25_ui_menu_pick(ui, input[0]), client,
+                                    &io, ui, status, "") != 0) {
+                    running = 0;
+                }
+            } else if (input[0] != '\0') {
+                send_line_async(client, &io, input);
+            }
+            input[0] = '\0';
+            input_len = 0;
+        }
+    }
+
+    tty_restore();
+    return 0;
+}
+
+int main(int argc, char *argv[])
+{
+    terminal_config_t cfg;
+    max25_client_t *client = NULL;
+    max25_ui_t *ui = NULL;
+    max25_status_t status;
+    char reply[MAX25_LINE_MAX];
+    int opt;
+    int argi;
+    static const struct option long_opts[] = {
+        {"host", required_argument, NULL, 'H'},
+        {"port", required_argument, NULL, 'p'},
+        {"unix", required_argument, NULL, 'U'},
+        {"tcp-only", no_argument, NULL, 'T'},
+        {"ax25-ui", no_argument, NULL, 1000},
+        {"no-ax25-ui", no_argument, NULL, 1001},
+        {"password", required_argument, NULL, 'P'},
+        {"device", required_argument, NULL, 'd'},
+        {"verbose", no_argument, NULL, 'v'},
+        {"probe", no_argument, NULL, 1002},
+        {"help", no_argument, NULL, 'h'},
+        {NULL, 0, NULL, 0}
+    };
+
+    config_defaults(&cfg);
+
+    while ((opt = getopt_long(argc, argv, "H:p:TU:P:d:v:h", long_opts, NULL)) != -1) {
+        switch (opt) {
+        case 'H':
+            strncpy(cfg.host, optarg, sizeof(cfg.host) - 1);
+            break;
+        case 'p':
+            cfg.port = (unsigned)strtoul(optarg, NULL, 10);
+            break;
+        case 'T':
+            cfg.tcp_only = 1;
+            break;
+        case 'U':
+            strncpy(cfg.unix_path, optarg, sizeof(cfg.unix_path) - 1);
+            break;
+        case 'P':
+            strncpy(cfg.tcp_password, optarg, sizeof(cfg.tcp_password) - 1);
+            break;
+        case 'd':
+            strncpy(cfg.default_device, optarg, sizeof(cfg.default_device) - 1);
+            break;
+        case 'v':
+            cfg.verbose = 1;
+            break;
+        case 1002:
+            cfg.probe = 1;
+            cfg.tcp_only = 1;
+            break;
+        case 'h':
+            usage(argv[0]);
+            return EXIT_SUCCESS;
+        case 1000:
+            cfg.ax25_ui = 1;
+            break;
+        case 1001:
+            cfg.ax25_ui = 0;
+            break;
+        default:
+            usage(argv[0]);
+            return EXIT_FAILURE;
+        }
+    }
+
+    argi = optind;
+    if (argi < argc) {
+        strncpy(cfg.host, argv[argi++], sizeof(cfg.host) - 1);
+    }
+    if (argi < argc) {
+        cfg.port = (unsigned)strtoul(argv[argi++], NULL, 10);
+    }
+
+    if (max25_client_connect(cfg.host, cfg.port,
+                             cfg.tcp_only ? "" : cfg.unix_path,
+                             cfg.tcp_only, cfg.tcp_password,
+                             &client, &status) != 0) {
+        fprintf(stderr, "max25-terminal: connect failed");
+        if (cfg.tcp_only) {
+            fprintf(stderr, " (tcp %s:%u)", cfg.host, cfg.port);
+        } else {
+            fprintf(stderr, " (unix %s / tcp %s:%u)",
+                    cfg.unix_path, cfg.host, cfg.port);
+        }
+        fputc('\n', stderr);
+        return EXIT_FAILURE;
+    }
+
+    if (cfg.probe) {
+        printf("STATUS hardware=%s device=%s mode=%s callerid=%s callid=%s "
+               "ax25_ui=%s connected=%s stack=%s\n",
+               status.hardware, status.device, status.mode,
+               status.callerid, status.callid,
+               status.ax25_ui ? "on" : "off",
+               status.connected ? "yes" : "no",
+               status.stack);
+        max25_client_write(client, "DISCONNECT");
+        max25_client_free(client);
+        return EXIT_SUCCESS;
+    }
+
+    if (max25_ui_init(&ui) != 0) {
+        max25_client_free(client);
+        return EXIT_FAILURE;
+    }
+
+    if (cfg.default_device[0] != '\0') {
+        if (set_device_sync(client, &status, cfg.default_device) != 0) {
+            fprintf(stderr, "max25-terminal: SET DEVICE %s failed\n",
+                    cfg.default_device);
+            max25_client_free(client);
+            return EXIT_FAILURE;
+        }
+    }
+
+    if (cfg.ax25_ui) {
+        max25_client_command(client, "SET AX25_UI on", reply, sizeof(reply));
+        status.ax25_ui = 1;
+    } else {
+        max25_client_command(client, "SET AX25_UI off", reply, sizeof(reply));
+        status.ax25_ui = 0;
+    }
+
+    if (cfg.verbose) {
+        fprintf(stderr, "max25-terminal: connected %s:%u tcp_only=%s ax25-ui=%s\n",
+                cfg.host, cfg.port, cfg.tcp_only ? "yes" : "no",
+                status.ax25_ui ? "on" : "off");
+    }
+
+    run_session(client, ui, &cfg, &status);
+
+    max25_client_write(client, "DISCONNECT");
+    max25_ui_shutdown(ui);
+    max25_client_free(client);
+    return EXIT_SUCCESS;
+}
diff --git a/stacks/terminal/max25_ui.c b/stacks/terminal/max25_ui.c
new file mode 100644
index 0000000..91cc977
--- /dev/null
+++ b/stacks/terminal/max25_ui.c
@@ -0,0 +1,407 @@
+#include "max25_ui.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifdef MAX25_HAVE_NCURSES
+#include <ncurses.h>
+#endif
+
+struct max25_ui {
+    int menu_open;
+    char rx_lines[MAX25_UI_RX_LINES][MAX25_LINE_MAX];
+    int rx_count;
+    int rx_head;
+#ifdef MAX25_HAVE_NCURSES
+    int ncurses_on;
+#endif
+};
+
+#ifdef MAX25_HAVE_NCURSES
+static int term_ok_for_ncurses(void)
+{
+    const char *term = getenv("TERM");
+
+    if (term == NULL || term[0] == '\0') {
+        return 0;
+    }
+    if (strcmp(term, "dumb") == 0) {
+        return 0;
+    }
+    if (strncmp(term, "unknown", 7) == 0) {
+        return 0;
+    }
+    return 1;
+}
+#endif
+
+int max25_ui_init(max25_ui_t **ui)
+{
+    max25_ui_t *u;
+
+    if (ui == NULL) {
+        return -1;
+    }
+
+    u = calloc(1, sizeof(*u));
+    if (u == NULL) {
+        return -1;
+    }
+
+#ifdef MAX25_HAVE_NCURSES
+    if (isatty(STDOUT_FILENO) && isatty(STDIN_FILENO) && term_ok_for_ncurses()
+        && initscr() != NULL) {
+        cbreak();
+        noecho();
+        keypad(stdscr, TRUE);
+        nodelay(stdscr, TRUE);
+        if (has_colors()) {
+            start_color();
+            init_pair(1, COLOR_WHITE, COLOR_BLACK);
+        }
+        bkgd(COLOR_PAIR(1));
+        curs_set(0);
+        clear();
+        refresh();
+        u->ncurses_on = 1;
+    }
+#endif
+
+    *ui = u;
+    return 0;
+}
+
+void max25_ui_shutdown(max25_ui_t *ui)
+{
+    if (ui == NULL) {
+        return;
+    }
+#ifdef MAX25_HAVE_NCURSES
+    if (ui->ncurses_on) {
+        endwin();
+    }
+#endif
+    free(ui);
+}
+
+void max25_ui_apply_palette(void)
+{
+    fputs(MAX25_TERM_SGR, stdout);
+    fflush(stdout);
+}
+
+void max25_ui_clear_screen(void)
+{
+    fputs(MAX25_TERM_CLEAR, stdout);
+    fputs(MAX25_TERM_SGR, stdout);
+    fflush(stdout);
+}
+
+int max25_ui_has_ncurses(const max25_ui_t *ui)
+{
+#ifdef MAX25_HAVE_NCURSES
+    return ui != NULL && ui->ncurses_on;
+#else
+    (void)ui;
+    return 0;
+#endif
+}
+
+void max25_ui_reset_rx(max25_ui_t *ui)
+{
+    if (ui == NULL) {
+        return;
+    }
+    ui->rx_count = 0;
+    ui->rx_head = 0;
+    memset(ui->rx_lines, 0, sizeof(ui->rx_lines));
+}
+
+void max25_ui_append_rx(max25_ui_t *ui, const char *text)
+{
+    int slot;
+
+    if (ui == NULL || text == NULL) {
+        return;
+    }
+
+    slot = ui->rx_head;
+    strncpy(ui->rx_lines[slot], text, MAX25_LINE_MAX - 1);
+    ui->rx_lines[slot][MAX25_LINE_MAX - 1] = '\0';
+    ui->rx_head = (ui->rx_head + 1) % MAX25_UI_RX_LINES;
+    if (ui->rx_count < MAX25_UI_RX_LINES) {
+        ui->rx_count++;
+    }
+}
+
+static void draw_header_plain(const max25_status_t *status)
+{
+    printf("%sMAX25 Terminal  DEVICE: %-12s CALLERID: %-9s CALLID: %-9s  ax25-ui: %s  connected: %s  F10=Menu\n",
+           MAX25_TERM_SGR,
+           status->device[0] != '\0' ? status->device : "-",
+           status->callerid, status->callid,
+           status->ax25_ui ? "on" : "off",
+           status->connected ? "yes" : "no");
+    fflush(stdout);
+}
+
+static void draw_rx_plain(const max25_ui_t *ui)
+{
+    int i;
+    int start;
+    int idx;
+
+    if (ui == NULL) {
+        return;
+    }
+
+    start = ui->rx_count < MAX25_UI_RX_LINES ? 0 : ui->rx_head;
+    for (i = 0; i < ui->rx_count; i++) {
+        idx = (start + i) % MAX25_UI_RX_LINES;
+        printf("%s%s\n", MAX25_TERM_SGR, ui->rx_lines[idx]);
+    }
+    fflush(stdout);
+}
+
+void max25_ui_draw_screen(max25_ui_t *ui, const max25_status_t *status,
+                          const char *input_line)
+{
+    int i;
+    int start;
+    int idx;
+    int rows;
+    int y;
+
+    if (ui == NULL || status == NULL) {
+        return;
+    }
+
+#ifdef MAX25_HAVE_NCURSES
+    if (ui->ncurses_on && !ui->menu_open) {
+        getmaxyx(stdscr, rows, y);
+        (void)y;
+        if (rows < 4) {
+            rows = 24;
+        }
+
+        attron(COLOR_PAIR(1));
+        mvprintw(0, 0,
+                 "MAX25 Terminal  DEVICE: %-12s CALLERID: %-9s CALLID: %-9s ax25-ui: %s connected: %s  F10=Menu",
+                 status->device[0] != '\0' ? status->device : "-",
+                 status->callerid, status->callid,
+                 status->ax25_ui ? "on" : "off",
+                 status->connected ? "yes" : "no");
+        clrtoeol();
+
+        start = ui->rx_count < MAX25_UI_RX_LINES ? 0 : ui->rx_head;
+        for (i = 0; i < ui->rx_count && i + 2 < rows - 2; i++) {
+            idx = (start + i) % MAX25_UI_RX_LINES;
+            mvprintw(i + 2, 0, "%.*s", (int)(rows > 0 ? 200 : 80), ui->rx_lines[idx]);
+            clrtoeol();
+        }
+
+        mvprintw(rows - 2, 0, "%s", "--------------------------------------------------------");
+        clrtoeol();
+        mvprintw(rows - 1, 0, "> %s", input_line != NULL ? input_line : "");
+        clrtoeol();
+        attroff(COLOR_PAIR(1));
+        refresh();
+        return;
+    }
+#endif
+
+    if (!ui->menu_open) {
+        fputs(MAX25_TERM_CLEAR, stdout);
+        fputs(MAX25_TERM_SGR, stdout);
+        draw_header_plain(status);
+        draw_rx_plain(ui);
+        printf("%s> %s\n", MAX25_TERM_SGR, input_line != NULL ? input_line : "");
+        fflush(stdout);
+    }
+}
+
+static void draw_menu_plain(const max25_status_t *status)
+{
+    puts("");
+    puts("+- MAX25 Terminal ---------------------+");
+    printf("| DEVICE: %-12s                     |\n",
+           status->device[0] != '\0' ? status->device : "-");
+    printf("| CALLERID: %-9s CALLID: %-9s |\n",
+           status->callerid, status->callid);
+    puts("+---------------------------------------+");
+    puts("| 1  Change CALLERID (live)             |");
+    puts("| 2  Change CALLID (live)               |");
+    puts("| 3  Status                             |");
+    puts("| 4  Send line                          |");
+    puts("| 5  RX only (Monitor)                  |");
+    puts("| 6  Connection on/off                  |");
+    puts("| 7  Change DEVICE (TX target)          |");
+    puts("| 8  List DEVICES (max25d)              |");
+    puts("| 0  Quit client                        |");
+    puts("+---------------------------------------+");
+    puts("Pick a number - F10 closes");
+    fflush(stdout);
+}
+
+#ifdef MAX25_HAVE_NCURSES
+static void draw_menu_ncurses(const max25_status_t *status, int y0)
+{
+    attron(COLOR_PAIR(1));
+    mvprintw(y0, 0, "+- MAX25 Terminal ---------------------+");
+    mvprintw(y0 + 1, 0, "| DEVICE: %-12s                     |",
+             status->device[0] != '\0' ? status->device : "-");
+    mvprintw(y0 + 2, 0, "| CALLERID: %-9s CALLID: %-9s |",
+             status->callerid, status->callid);
+    mvprintw(y0 + 3, 0, "+---------------------------------------+");
+    mvprintw(y0 + 4, 0, "| 1  Change CALLERID (live)             |");
+    mvprintw(y0 + 5, 0, "| 2  Change CALLID (live)               |");
+    mvprintw(y0 + 6, 0, "| 3  Status                             |");
+    mvprintw(y0 + 7, 0, "| 4  Send line                          |");
+    mvprintw(y0 + 8, 0, "| 5  RX only (Monitor)                  |");
+    mvprintw(y0 + 9, 0, "| 6  Connection on/off                  |");
+    mvprintw(y0 + 10, 0, "| 7  Change DEVICE (TX target)          |");
+    mvprintw(y0 + 11, 0, "| 8  List DEVICES (max25d)              |");
+    mvprintw(y0 + 12, 0, "| 0  Quit client                        |");
+    mvprintw(y0 + 13, 0, "+---------------------------------------+");
+    mvprintw(y0 + 14, 0, "Pick a number - F10 closes");
+    attroff(COLOR_PAIR(1));
+}
+#endif
+
+void max25_ui_show_menu(max25_ui_t *ui, const max25_status_t *status)
+{
+    if (ui == NULL || status == NULL) {
+        return;
+    }
+    ui->menu_open = 1;
+
+#ifdef MAX25_HAVE_NCURSES
+    if (ui->ncurses_on) {
+        clear();
+        bkgd(COLOR_PAIR(1));
+        draw_menu_ncurses(status, 2);
+        refresh();
+        return;
+    }
+#endif
+    fputs(MAX25_TERM_CLEAR, stdout);
+    fputs(MAX25_TERM_SGR, stdout);
+    draw_menu_plain(status);
+}
+
+void max25_ui_hide_menu(max25_ui_t *ui)
+{
+    if (ui == NULL) {
+        return;
+    }
+    ui->menu_open = 0;
+#ifdef MAX25_HAVE_NCURSES
+    if (ui->ncurses_on) {
+        clear();
+        bkgd(COLOR_PAIR(1));
+        refresh();
+    }
+#endif
+}
+
+int max25_ui_menu_visible(const max25_ui_t *ui)
+{
+    return ui != NULL && ui->menu_open;
+}
+
+max25_menu_action_t max25_ui_menu_pick(max25_ui_t *ui, int ch)
+{
+    (void)ui;
+    switch (ch) {
+    case '1':
+        return MAX25_MENU_CALLERID;
+    case '2':
+        return MAX25_MENU_CALLID;
+    case '3':
+        return MAX25_MENU_STATUS;
+    case '4':
+        return MAX25_MENU_SEND;
+    case '5':
+        return MAX25_MENU_MONITOR;
+    case '6':
+        return MAX25_MENU_CONNECT;
+    case '7':
+        return MAX25_MENU_DEVICE;
+    case '8':
+        return MAX25_MENU_DEVICES;
+    case '0':
+        return MAX25_MENU_QUIT;
+    default:
+        return MAX25_MENU_NONE;
+    }
+}
+
+int max25_ui_prompt(max25_ui_t *ui, const char *label, char *buf, size_t buf_sz)
+{
+    if (label == NULL || buf == NULL || buf_sz == 0) {
+        return -1;
+    }
+
+#ifdef MAX25_HAVE_NCURSES
+    if (ui != NULL && ui->ncurses_on) {
+        int ch;
+        size_t len = 0;
+        int rows;
+
+        getmaxyx(stdscr, rows, ch);
+        (void)rows;
+        echo();
+        curs_set(1);
+        attron(COLOR_PAIR(1));
+        mvprintw(14, 0, "%s: ", label);
+        clrtoeol();
+        refresh();
+        buf[0] = '\0';
+
+        nodelay(stdscr, FALSE);
+        while (len + 1 < buf_sz) {
+            ch = getch();
+            if (ch == '\n' || ch == KEY_ENTER || ch == '\r') {
+                break;
+            }
+            if (ch == 27) {
+                nodelay(stdscr, TRUE);
+                noecho();
+                curs_set(0);
+                return -1;
+            }
+            if (ch == KEY_BACKSPACE || ch == 127 || ch == '\b') {
+                if (len > 0) {
+                    len--;
+                    buf[len] = '\0';
+                    mvprintw(14, (int)strlen(label) + 2, "%s ", buf);
+                    clrtoeol();
+                    refresh();
+                }
+                continue;
+            }
+            if (ch >= 32 && ch < 127) {
+                buf[len++] = (char)ch;
+                buf[len] = '\0';
+                mvprintw(14, (int)strlen(label) + 2, "%s", buf);
+                refresh();
+            }
+        }
+        nodelay(stdscr, TRUE);
+        noecho();
+        curs_set(0);
+        attroff(COLOR_PAIR(1));
+        return (int)len;
+    }
+#endif
+
+    printf("%s%s: ", MAX25_TERM_SGR, label);
+    fflush(stdout);
+    if (fgets(buf, (int)buf_sz, stdin) == NULL) {
+        return -1;
+    }
+    buf[strcspn(buf, "\r\n")] = '\0';
+    return (int)strlen(buf);
+}
diff --git a/stacks/terminal/max25_ui.h b/stacks/terminal/max25_ui.h
new file mode 100644
index 0000000..9c1928d
--- /dev/null
+++ b/stacks/terminal/max25_ui.h
@@ -0,0 +1,45 @@
+#ifndef MAX25_UI_H
+#define MAX25_UI_H
+
+#include "max25_proto.h"
+
+#define MAX25_TERM_SGR "\033[37;40m"
+#define MAX25_TERM_CLEAR "\033[2J\033[H"
+#define MAX25_UI_RX_LINES 12
+#define MAX25_UI_INPUT_MAX 256
+
+typedef struct max25_ui max25_ui_t;
+
+typedef enum {
+    MAX25_MENU_NONE = 0,
+    MAX25_MENU_CALLERID,
+    MAX25_MENU_CALLID,
+    MAX25_MENU_STATUS,
+    MAX25_MENU_SEND,
+    MAX25_MENU_MONITOR,
+    MAX25_MENU_CONNECT,
+    MAX25_MENU_DEVICE,
+    MAX25_MENU_DEVICES,
+    MAX25_MENU_QUIT
+} max25_menu_action_t;
+
+int max25_ui_init(max25_ui_t **ui);
+void max25_ui_shutdown(max25_ui_t *ui);
+
+void max25_ui_apply_palette(void);
+void max25_ui_clear_screen(void);
+
+int max25_ui_has_ncurses(const max25_ui_t *ui);
+
+void max25_ui_reset_rx(max25_ui_t *ui);
+void max25_ui_append_rx(max25_ui_t *ui, const char *text);
+void max25_ui_draw_screen(max25_ui_t *ui, const max25_status_t *status,
+                          const char *input_line);
+void max25_ui_show_menu(max25_ui_t *ui, const max25_status_t *status);
+void max25_ui_hide_menu(max25_ui_t *ui);
+int max25_ui_menu_visible(const max25_ui_t *ui);
+
+max25_menu_action_t max25_ui_menu_pick(max25_ui_t *ui, int ch);
+int max25_ui_prompt(max25_ui_t *ui, const char *label, char *buf, size_t buf_sz);
+
+#endif /* MAX25_UI_H */
diff --git a/stacks/terminal/test-terminal.sh b/stacks/terminal/test-terminal.sh
new file mode 100755
index 0000000..6a510f3
--- /dev/null
+++ b/stacks/terminal/test-terminal.sh
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# max25-terminal offline probe — binary + TCP connect test.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+REPO="$(cd "${ROOT}/../.." && pwd)"
+TERM="${MAX25_TERMINAL:-${REPO}/build/bin/max25-terminal}"
+
+[[ -x "${TERM}" ]] || { echo "FAIL: ${TERM} missing" >&2; exit 1; }
+
+CLIENT="${REPO}/build/bin/max25-client"
+if [[ -L "${CLIENT}" ]] || [[ -x "${CLIENT}" ]]; then
+  :
+else
+  echo "WARN: max25-client symlink missing until cmake --install" >&2
+fi
+
+"${TERM}" --help >/dev/null
+
+# Unit: EVENT connected/disconnected updates status (header bug regression)
+UNIT="${ROOT}/.test_apply_event"
+gcc -std=c11 -Wall -Wextra -O2 -I"${ROOT}" \
+    -o "${UNIT}" "${ROOT}/test_apply_event.c" "${ROOT}/max25_proto.c"
+"${UNIT}"
+rm -f "${UNIT}"
+
+MAX25_TERMINAL="${TERM}" python3 "${ROOT}/test_connect.py"
+echo "OK: max25-terminal"
diff --git a/stacks/terminal/test_apply_event.c b/stacks/terminal/test_apply_event.c
new file mode 100644
index 0000000..36e10f0
--- /dev/null
+++ b/stacks/terminal/test_apply_event.c
@@ -0,0 +1,30 @@
+/* Offline unit test: EVENT connected/disconnected → status.connected */
+#include "max25_proto.h"
+
+#include <stdio.h>
+#include <string.h>
+
+int main(void)
+{
+    max25_status_t st;
+
+    memset(&st, 0, sizeof(st));
+    if (max25_client_apply_event("EVENT connected", &st) != 1 || !st.connected) {
+        fprintf(stderr, "FAIL: EVENT connected\n");
+        return 1;
+    }
+    if (max25_client_apply_event("EVENT disconnected", &st) != 1 || st.connected) {
+        fprintf(stderr, "FAIL: EVENT disconnected\n");
+        return 1;
+    }
+    if (max25_client_apply_event("EVENT device=max25e0 serial=ready", &st) != 0) {
+        fprintf(stderr, "FAIL: unrelated EVENT should be ignored\n");
+        return 1;
+    }
+    if (max25_client_apply_event("OK", &st) != 0) {
+        fprintf(stderr, "FAIL: non-EVENT\n");
+        return 1;
+    }
+    puts("OK: apply_event");
+    return 0;
+}
diff --git a/stacks/terminal/test_connect.py b/stacks/terminal/test_connect.py
new file mode 100644
index 0000000..6496b69
--- /dev/null
+++ b/stacks/terminal/test_connect.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""TCP connect smoke test for max25-terminal --probe."""
+import socket
+import subprocess
+import sys
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+DAEMON = ROOT / "stacks/daemon/max25d"
+INI = ROOT / "share/max25/max25d.ini.example"
+
+
+def terminal_binary() -> Path:
+    import os
+
+    env = os.environ.get("MAX25_TERMINAL")
+    if env:
+        return Path(env)
+    for candidate in (
+        ROOT / "build/bin/max25-terminal",
+        ROOT / "stacks/terminal/max25-terminal",
+    ):
+        if candidate.is_file():
+            return candidate
+    return ROOT / "build/bin/max25-terminal"
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def main() -> int:
+    terminal = terminal_binary()
+    if not terminal.is_file():
+        print(
+            f"FAIL: max25-terminal missing — run cmake --build build --target max25-terminal "
+            f"(looked for {terminal})",
+            file=sys.stderr,
+        )
+        return 1
+
+    port = free_port()
+    proc = subprocess.Popen(
+        [str(DAEMON), "--no-stack", "-c", str(INI), "--tcp-port", str(port)],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.DEVNULL,
+    )
+    time.sleep(0.6)
+    try:
+        out = subprocess.check_output(
+            [str(terminal), "-T", "-H", "127.0.0.1", "-p", str(port), "--probe"],
+            text=True,
+            timeout=10,
+        )
+    except (subprocess.CalledProcessError, subprocess.TimeoutExpired) as exc:
+        proc.terminate()
+        proc.wait(timeout=5)
+        print(f"FAIL: terminal probe: {exc}", file=sys.stderr)
+        return 1
+    finally:
+        proc.terminate()
+        proc.wait(timeout=5)
+
+    if "STATUS hardware=" not in out or "callerid=" not in out:
+        print(f"FAIL: unexpected probe output: {out!r}", file=sys.stderr)
+        return 1
+
+    print("OK: max25-terminal TCP probe")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/CMakeLists.txt b/stacks/tncs/CMakeLists.txt
new file mode 100644
index 0000000..3bc43ce
--- /dev/null
+++ b/stacks/tncs/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_executable(tnc2c-probe tnc2c-probe.c)
+target_compile_options(tnc2c-probe PRIVATE -std=c99 -Wall -Wextra -O2)
+
+add_executable(tnc2c-find tnc2c-find.c)
+target_compile_options(tnc2c-find PRIVATE -std=c99 -Wall -Wextra -O2)
+
+install(TARGETS tnc2c-probe tnc2c-find RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
diff --git a/stacks/tncs/README.md b/stacks/tncs/README.md
new file mode 100644
index 0000000..e07a9ac
--- /dev/null
+++ b/stacks/tncs/README.md
@@ -0,0 +1,40 @@
+# stacks/tncs — Serial TNC tools
+
+Operator tools and docs for **Landolt TNC2C** and **PK-TNC2** (TheFirmware TNC-2 class). HyBBX attaches via `packet_radio` after MAX25 prep.
+
+**Recovery:** software-first (no power cycle in normal ops). Power-cycle boot-wait is rescue only. See [docs/TNC-RECOVERY.md](docs/TNC-RECOVERY.md).
+
+## Quick start
+
+```bash
+./scripts/build.sh
+./scripts/max25-ctl start --hardware tncs --device tnc2c
+```
+
+Adjust serial port in `tnc2c-serial.env` before first use.
+
+## Documentation
+
+| Doc | Content |
+|-----|---------|
+| [docs/TNC-RECOVERY.md](docs/TNC-RECOVERY.md) | Software ladder, rescue power-cycle |
+| [docs/TNC2C-OPERATIONS.md](docs/TNC2C-OPERATIONS.md) | Boot-wait, health, HyBBX handoff |
+| [docs/TNC2C-REFERENCE.md](docs/TNC2C-REFERENCE.md) | Parameters, tools, example profile |
+| [docs/HYBBX-TNC2C.md](docs/HYBBX-TNC2C.md) | HyBBX Secondary attach |
+
+HyBBX INI: [`hybbx-tnc2c.ini`](hybbx-tnc2c.ini) (onboard ttyS4 example) · shipped copy: `../../share/hybbx/tnc2c-host.ini.example` · dual TNC: [`hybbx-dual.ini`](hybbx-dual.ini)
+
+## Tools
+
+| Tool | Purpose |
+|------|---------|
+| `tnc2c-host-reset.sh` | Software recovery (no power cycle) |
+| `tnc2c-boot-wait.sh` | DTR during power-on — **rescue**; `--recover-only` for ladder only |
+| `pktnc2-boot-wait.sh` | PK-TNC2 wrapper (9600 8N1); supports `--recover-only` |
+| `tnc2c-integration-test.sh` | HyBBX-ready check |
+| `tnc2c-health.sh` | Serial/TNC check (no TX) |
+| `tnc2c-probe` | Scan serial ports for TNC response |
+
+## Safety
+
+KISS and TX tests can key the radio. Use a dummy load for transmit tests.
diff --git a/stacks/tncs/RS232A259.jpg b/stacks/tncs/RS232A259.jpg
new file mode 100644
index 0000000..c1dfe04
--- /dev/null
+++ b/stacks/tncs/RS232A259.jpg
diff --git a/stacks/tncs/TNC2C.pdf b/stacks/tncs/TNC2C.pdf
new file mode 100644
index 0000000..d9f7b9d
--- /dev/null
+++ b/stacks/tncs/TNC2C.pdf
diff --git a/stacks/tncs/docs/HYBBX-TNC2C.md b/stacks/tncs/docs/HYBBX-TNC2C.md
new file mode 100644
index 0000000..8d2207f
--- /dev/null
+++ b/stacks/tncs/docs/HYBBX-TNC2C.md
@@ -0,0 +1,54 @@
+# HyBBX + TNC2C
+
+MAX25 prepares the TNC (recovery + KISS entry); HyBBX attaches with **`kiss_entry = none`**.
+
+## Flow
+
+```
+max25d auto_start / max25-ctl start --hardware tncs --device tnc2c
+        ↓  (software recovery + kiss on)
+HyBBX Secondary starts packet_radio plugin (attach-only)
+        ↓
+KISS on serial → AX.25 sessions
+```
+
+Software recovery without power cycle: [TNC-RECOVERY.md](TNC-RECOVERY.md).
+
+## Preparation (MAX25)
+
+```bash
+./scripts/max25-ctl start --hardware tncs --device tnc2c
+# Production: max25d with [stack] auto_start = yes
+```
+
+One process per serial port — stop other userspace serial owners before HyBBX starts.
+
+## HyBBX INI
+
+Merge `share/hybbx/tnc2c-host.ini.example` or `stacks/tncs/hybbx-tnc2c.ini` into Secondary `hybbx.ini`:
+
+```ini
+[transport.packet_radio1]
+tnc = tnc2c
+device = /dev/ttyUSB0
+baud = 19200
+serial_line = 8n1
+rts_dtr = yes
+kiss_entry = none
+persist = 255
+
+[max25]
+check = yes
+```
+
+Set `device`, callsign, and frequency for your station.
+
+For HyBBX **without** max25d (standalone), use `kiss_entry = kiss_on` or `auto` instead — HyBBX runs its own recovery before KISS entry.
+
+## Checks
+
+- MAX25 prep returned host/KISS ready (boot-wait OK or max25d `ready`)
+- `fuser` on device is empty before HyBBX start (max25d holds port in production)
+- Log shows KISS active on the expected port
+
+Full contract: [docs/HYBBX.md](../../docs/HYBBX.md)
diff --git a/stacks/tncs/docs/TNC-RECOVERY.md b/stacks/tncs/docs/TNC-RECOVERY.md
new file mode 100644
index 0000000..2e36357
--- /dev/null
+++ b/stacks/tncs/docs/TNC-RECOVERY.md
@@ -0,0 +1,108 @@
+# TNC recovery (software-first)
+
+TheFirmware / TNC-2 class devices (Landolt TNC2C, PK-TNC2, TAPR TNC-2) can usually return to **host command mode** and **KISS** without a power cycle. Power-cycle with DTR held high is a **rescue fallback** only.
+
+Shared implementation: `stacks/tncs/tnc_serial_recovery.py` (used by `tnc2c-host-reset`, `tnc2c-boot-wait`, and `max25d` `kiss_bridge`).
+
+## When to use what
+
+| Situation | First action | Rescue (if software fails) |
+|-----------|--------------|----------------------------|
+| Echo-only (`INFO` → `INFO`, no banner) | `max25d` serial watch / `./tnc2c-host-reset.sh` | `./tnc2c-boot-wait.sh` only if cold-boot without DTR |
+| After `max25d` prep `error-host` | Auto boot-wait escalate (power OFF 10s → ON) | `./tnc2c-boot-wait.sh` if escalate disabled |
+| PK-TNC2 (9600 8N1) | `./pktnc2-boot-wait.sh --recover-only` | `./pktnc2-boot-wait.sh` + power cycle |
+| Cold boot, never saw `cmd:` | `./tnc2c-boot-wait.sh` (DTR before power-on) | Fix wiring (DTR/RTS, CTS bridge) |
+
+## Software recovery ladder (TheFirmware TF 2.7 native)
+
+Run with **DTR+RTS high** and the port open:
+
+1. Passive listen (~1.5 s) + **DTR settle 2 s** after open (max25d)
+2. KISS return `0xC0 0xFF 0xC0` (firmware reset → banner)
+3. Buffer flush `^Q^X` + JHOST 0 (leave host mode)
+4. **ESC V** — version / terminal probe
+5. **ESC QRES** — software cold boot (no mains power cycle; DTR must stay high)
+6. ESC E 0 + second ESC QRES
+7. Legacy TAPR `kiss off` + `INFO` (last resort only)
+
+Success markers: `TheFirmware`, `NORD`, `Version 2.7`, `Checksum`, `cmd:`.
+
+Then enter KISS: **ESC `@K`** (`0x1B 40 4B`). MYCALL: **ESC I** `<call>`.
+
+Native TF sequence: see [Software recovery ladder](#software-recovery-ladder-thefirmware-tf-27-native) above.
+
+## Operator commands
+
+```bash
+cd stacks/tncs
+
+# Software recovery (no power cycle)
+./tnc2c-host-reset.sh              # terminal mode
+./tnc2c-host-reset.sh --kiss       # terminal + KISS
+./tnc2c-boot-wait.sh --recover-only
+
+# PK-TNC2
+./pktnc2-boot-wait.sh --recover-only
+
+# Rescue: power cycle with DTR held (Landolt TNC2C cold-boot requirement)
+./tnc2c-boot-wait.sh               # power OFF → ON while script runs
+```
+
+## MAX25 + HyBBX contract
+
+| Layer | Responsibility |
+|-------|----------------|
+| `max25d` / boot-wait | DTR sequencing, software recovery, `kiss on` / `auto` |
+| HyBBX `packet_radio` | Attach only — `kiss_entry = none` |
+| Power cycle | Rescue when DTR was low at cold boot or hardware hang |
+
+HyBBX INI (production): `kiss_entry = none`, `persist = 255` (CB CSMA), optional `[max25] check = yes`.
+
+max25d runs `recover_terminal()` in `kiss_bridge.stabilize_session()` before `MYCALL` and KISS entry. The KISS RX thread starts **only after** successful stabilization (avoids a race where RX consumes recovery replies).
+
+### max25d serial watch (automatic)
+
+When `[stack] serial_watch = yes` and `stack_recover_only = yes` (default), max25d **opens the TNC serial port itself** — no `boot-wait` subprocess (avoids port conflict). Recovery runs inline via `stabilize_session`.
+
+| INI key | Default | Role |
+|---------|---------|------|
+| `serial_watch` | yes | Enable periodic probe + auto-repair |
+| `serial_watch_interval` | 60 | Seconds between health probes |
+| `serial_repair_cooldown` | 20 | Minimum gap between repair attempts |
+| `stack_recover_only` | yes | Daemon start uses `--recover-only` (no power cycle) |
+| `stack_retry_interval` | 120 | Retry failed stack prep with recover-only |
+| `serial_bootwait_escalate` | yes | Escalate to boot-wait after repeated inline failures |
+| `serial_bootwait_escalate_after` | 3 | Inline `error-host` failures before boot-wait |
+| `serial_bootwait_escalate_cooldown` | 300 | Minimum seconds between boot-wait escalations |
+
+Triggers: initial prep `error-host` (immediate boot-wait escalate), `error-host` / `error-kiss` / `error-tx` / `error-io`, failed TX (one auto-retry). Serial watch still escalates after `serial_bootwait_escalate_after` consecutive inline failures if prep did not already escalate.
+
+**Healthy KISS:** when the backend is `ready`, serial watch does **not** tear down KISS on the periodic interval — repair runs only when status is in the error set above (not a periodic `kiss off` / probe on a working session).
+
+## Firmware RX diagnostics (max25d / boot-wait)
+
+On each recovery step, logs include byte count, matched firmware markers (`TheFirmware`, `cmd:`, …), and a printable preview. On failure:
+
+- `recovery: firmware assessment — …` — classified state (silent, echo-only, binary/KISS, non-banner text)
+- `recovery: RX capture — …` — full accumulated RX summary with hex snippet
+
+Use these lines to distinguish **DTR/cold-boot** (echo-only, 0 B passive) from **wrong baud/line** (garbage/binary) from **stuck KISS** (binary frames, no `cmd:`).
+
+Use when:
+
+- Software ladder ends in echo-only or silence
+- TNC was powered on **without** DTR high (Landolt TNC2C terminal detection)
+- Suspected hardware hang
+
+```bash
+./tnc2c-boot-wait.sh
+# While script listens: power OFF 10 s, power ON — keep script running (DTR stays high)
+```
+
+Do **not** close the serial port between boot-wait and HyBBX/max25d attach — DTR drop can return the TNC to echo mode.
+
+## See also
+
+- [TNC2C-OPERATIONS.md](TNC2C-OPERATIONS.md) — daily ops
+- [HYBBX-TNC2C.md](HYBBX-TNC2C.md) — HyBBX attach
+- [../../docs/PACKET-RADIO.md](../../docs/PACKET-RADIO.md) — serial profiles, CSMA
diff --git a/stacks/tncs/docs/TNC2C-OPERATIONS.md b/stacks/tncs/docs/TNC2C-OPERATIONS.md
new file mode 100644
index 0000000..aa9b8ef
--- /dev/null
+++ b/stacks/tncs/docs/TNC2C-OPERATIONS.md
@@ -0,0 +1,66 @@
+# TNC2C operations
+
+Landolt TNC2C on a serial port — software recovery, boot-wait rescue, verify, HyBBX attach.
+
+## Prerequisites
+
+- Port free: no HyBBX or other userspace serial owner on the TNC serial device
+- `tnc2c-serial.env` matches your wiring (device, baud, line format)
+- DTR+RTS asserted while talking to the TNC (boot-wait and host-reset do this)
+
+## Normal prep (max25d / HyBBX)
+
+Production path: `max25d` with `auto_start` runs boot-wait and software recovery before KISS attach.
+
+```bash
+./scripts/max25-ctl start --hardware tncs --device tnc2c
+# or: sudo max25d -c /etc/max25/max25d.ini
+```
+
+Manual recovery without power cycle:
+
+```bash
+cd stacks/tncs
+./tnc2c-host-reset.sh --kiss
+# or: ./tnc2c-boot-wait.sh --recover-only
+```
+
+Full ladder and rescue rules: [TNC-RECOVERY.md](TNC-RECOVERY.md).
+
+## Boot-wait (rescue — power cycle)
+
+Use when software recovery fails or the TNC was cold-started without DTR high:
+
+```bash
+cd stacks/tncs
+./tnc2c-boot-wait.sh
+```
+
+Power cycle the TNC while the script holds DTR+RTS. Expect `OK: HOST` when successful.
+
+## Verify
+
+```bash
+./tnc2c-integration-test.sh
+./tnc2c-health.sh
+```
+
+Integration test runs boot-wait + verify in one process so DTR does not drop between steps.
+
+## HyBBX
+
+1. MAX25 prep complete (boot-wait or `max25d` auto_start with recovery).
+2. Merge `share/hybbx/tnc2c-host.ini.example` into Secondary `hybbx.ini` — **`kiss_entry = none`** (MAX25 owns KISS entry).
+3. Do not run another userspace serial client on the same device while HyBBX is active.
+
+See [HYBBX-TNC2C.md](HYBBX-TNC2C.md) and [../../docs/HYBBX.md](../../docs/HYBBX.md).
+
+## Recovery
+
+| Symptom | Action |
+|---------|--------|
+| Echo only, no `cmd:` | `./tnc2c-host-reset.sh` then `./tnc2c-boot-wait.sh --recover-only` |
+| Still echo-only / silent | **Rescue:** `./tnc2c-boot-wait.sh` + power cycle (DTR high) |
+| `max25d` reports `error-host` | Stop other serial owners; run `--recover-only`; restart max25d |
+| Port busy | Stop HyBBX or other serial owner; check `fuser` on device |
+| Wrong baud | Fix `tnc2c-serial.env` and retry |
diff --git a/stacks/tncs/docs/TNC2C-REFERENCE.md b/stacks/tncs/docs/TNC2C-REFERENCE.md
new file mode 100644
index 0000000..774248c
--- /dev/null
+++ b/stacks/tncs/docs/TNC2C-REFERENCE.md
@@ -0,0 +1,43 @@
+# TNC2C reference (example profile)
+
+Example profile for a Landolt TNC2C with **19200 8N1** host link and **2400** radio AFSK. Adjust for your hardware.
+
+## Serial (host)
+
+| Parameter | Example |
+|-----------|---------|
+| Device | `/dev/ttyUSB0` |
+| Baud | 19200 |
+| Format | 8N1 |
+| RTS/DTR | Required for boot-wait |
+
+## Radio (typical CB packet)
+
+| Parameter | Example |
+|-----------|---------|
+| Modem | TCM3105 |
+| Radio baud | 2400 |
+| Band | CB |
+| Duplex | Half |
+
+## Config file
+
+`stacks/tncs/tnc2c-serial.env` — copy and edit device/baud for your station.
+
+## Tool matrix
+
+| Tool | Use |
+|------|-----|
+| `tnc2c-boot-wait.sh` | Host mode after power-on (rescue) |
+| `tnc2c-host-reset.sh` | Software recovery without power cycle |
+| `tnc2c-autotest.sh` | Quick 19200-8N1 probe |
+| `tnc2c-health.sh` | Full check, no TX |
+| `tnc2c-integration-test.sh` | Post boot-wait HyBBX gate |
+| `tnc2c-listen.sh` | Passive monitor |
+| `tnc2c-probe` | Port scan utility |
+
+## HyBBX INI snippet
+
+Use `share/hybbx/tnc2c-host.ini.example` — set `device`, `mycall`, and RF fields for your station.
+
+HyBBX TNC profiles: [hyBBX docs/TNCS.md](https://github.com/ngteq/hyBBX/blob/main/docs/TNCS.md)
diff --git a/stacks/tncs/hybbx-ax25-beacon-once.py b/stacks/tncs/hybbx-ax25-beacon-once.py
new file mode 100755
index 0000000..192d986
--- /dev/null
+++ b/stacks/tncs/hybbx-ax25-beacon-once.py
@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+"""One-shot AX.25 UI beacon matching HyBBX [broadcast] INI (HyBBX must stay running).
+
+Connects to the internal circuit hub and sends an HBX AX25_UI frame with TX flag
+the same way hybbx_broadcast_ax25() does. Requires packet_radio1 linked with
+link_password on the Main.
+"""
+import argparse
+import socket
+import struct
+import sys
+import time
+
+MAGIC = b"HBX"
+VERSION = 0x01
+HEADER_SIZE = 12
+PROTO_LINK_AUTH = 0x03
+PROTO_LINK_AUTH_ACK = 0x04
+PROTO_AX25_UI = 0x02
+FLAG_TX = 0x0002
+FLAG_PATH = 0x0004
+ADDR_LEN = 7
+
+
+def be16(v):
+    return struct.pack(">H", v)
+
+
+def be32(v):
+    return struct.pack(">I", v)
+
+
+def encode_frame(proto, flags, payload):
+    return bytes([ord("H"), ord("B"), ord("X"), VERSION, proto]) + be16(flags) + be32(len(payload)) + payload
+
+
+def encode_addr(call, ssid=0, last=False):
+    call = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in call)
+    ssid_b = ((ssid & 0x0F) << 1) | (0x60 if not last else 0x61)
+    return raw + bytes([ssid_b])
+
+
+def pack_ax25_ui(dest, src, message):
+    body = bytes([0])  # digi count
+    body += encode_addr(dest, last=False)
+    body += encode_addr(src, last=True)
+    body += message.encode("ascii", errors="replace")
+    return encode_frame(PROTO_AX25_UI, FLAG_TX | FLAG_PATH, body)
+
+
+def link_auth_payload(password, link_id, role, baud=2400, duplex="half", bandwidth="low", mhz="27.235"):
+    lines = [
+        f"password={password}",
+        f"role={role}",
+        f"id={link_id}",
+        f"baud={baud}",
+        f"duplex={duplex}",
+        f"bandwidth={bandwidth}",
+        f"frequency_mhz={mhz}",
+    ]
+    return "\n".join(lines).encode("ascii")
+
+
+def recv_frames(sock, timeout=5.0):
+    sock.settimeout(timeout)
+    buf = b""
+    try:
+        while True:
+            chunk = sock.recv(4096)
+            if not chunk:
+                break
+            buf += chunk
+    except socket.timeout:
+        pass
+    return buf
+
+
+def main():
+    ap = argparse.ArgumentParser(description="HyBBX one-shot AX.25 RF beacon via circuit hub")
+    ap.add_argument("--host", default="127.0.0.1")
+    ap.add_argument("--port", type=int, default=7323)
+    ap.add_argument("--password", default="changeme")
+    ap.add_argument("--link-id", default="beacon-once")
+    ap.add_argument("--mycall", default="CB-0")
+    ap.add_argument("--dest", default="*")
+    ap.add_argument("--message", default="Broadcast: CB-0 online")
+    args = ap.parse_args()
+
+    sock = socket.create_connection((args.host, args.port), timeout=5)
+    auth = link_auth_payload(args.password, args.link_id, "gateway")
+    sock.sendall(encode_frame(PROTO_LINK_AUTH, 0, auth))
+    ack = recv_frames(sock, 3.0)
+    if b"ok=yes" not in ack:
+        print("LINK_AUTH failed:", ack[:200], file=sys.stderr)
+        sys.exit(1)
+    print(f"LINK_AUTH ok — TX {args.mycall} -> {args.dest}: {args.message!r}")
+    sock.sendall(pack_ax25_ui(args.dest, args.mycall, args.message))
+    time.sleep(2)
+    sock.close()
+    print("Beacon frame sent to circuit hub.")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/stacks/tncs/hybbx-dual.ini b/stacks/tncs/hybbx-dual.ini
new file mode 100644
index 0000000..5e7e753
--- /dev/null
+++ b/stacks/tncs/hybbx-dual.ini
@@ -0,0 +1,62 @@
+; TNCs-Stack — HyBBX service mode dual TNC (packet_radio)
+; For two serial TNCs on unique UARTs. Do not use when BayCom already owns ttyS0.
+; Prerequisite: max25d [devices] with tnc2c + pktnc2, boot-wait / recovery per port.
+; BayCom dual-radio HyBBX: share/hybbx/service-dual.ini.example instead.
+;
+; Example (both TNCs active, no BayCom on ttyS0):
+;   tnc2c  → /dev/ttyS4
+;   pktnc2 → /dev/ttyS5
+;
+; MAX25 owns KISS entry on both ports — kiss_entry = none on each transport.
+
+[networks]
+ax25 = yes
+
+[transport.packet_radio1]
+enabled = yes
+tnc = tnc2c
+protocol = kiss
+device_type = serial
+device = /dev/ttyS4
+baud = 19200
+serial_line = 8n1
+rts_dtr = yes
+kiss_entry = none
+modem = tcm3105
+radio_baud = 2400
+radio_band = cb
+frequency_mhz = 27.235
+txdelay = 50
+persist = 255
+slot = 10
+circuit_host = main.example.com
+circuit_port = 7323
+link_id = max25-tnc2c
+link_password = changeme
+mycall = CB-0
+
+[transport.packet_radio2]
+enabled = yes
+tnc = pktnc2
+protocol = kiss
+device_type = serial
+device = /dev/ttyS5
+baud = 9600
+serial_line = 8n1
+rts_dtr = no
+kiss_entry = none
+modem = tcm3105
+radio_baud = 1200
+radio_band = cb
+frequency_mhz = 27.205
+txdelay = 50
+persist = 255
+slot = 10
+circuit_host = main.example.com
+circuit_port = 7323
+link_id = max25-pktnc2
+link_password = changeme
+mycall = CB-1
+
+[max25]
+check = yes
diff --git a/stacks/tncs/hybbx-tnc2c.ini b/stacks/tncs/hybbx-tnc2c.ini
new file mode 100644
index 0000000..e1d0faa
--- /dev/null
+++ b/stacks/tncs/hybbx-tnc2c.ini
@@ -0,0 +1,38 @@
+; TNCs-Stack — HyBBX Secondary host (TNC2C / packet_radio)
+; Canonical shipped copy: share/hybbx/tnc2c-host.ini.example
+; Merge into HyBBX hybbx.ini on Secondary node.
+; Prerequisite: max25d auto_start or ./scripts/max25-ctl start --hardware tncs --device tnc2c
+;
+; Example onboard layout: TNC2C on /dev/ttyS4 (ttyS0 = BayCom, ttyS5 = PK-TNC2).
+; USB Linux hosts: set device = /dev/ttyUSB0 or /dev/serial/by-id/...
+
+[networks]
+ax25 = yes
+
+[transport.packet_radio1]
+enabled = yes
+tnc = tnc2c
+protocol = kiss
+device_type = serial
+device = /dev/ttyS4
+baud = 19200
+serial_line = 8n1
+rts_dtr = yes
+kiss_entry = none
+modem = tcm3105
+radio_baud = 2400
+clock_mhz = 4.9
+radio_band = cb
+radio_duplex = half
+frequency_mhz = 27.235
+txdelay = 50
+persist = 255
+slot = 10
+circuit_host = main.example.com
+circuit_port = 7323
+link_id = max25-tnc2c
+link_password = changeme
+mycall = CB-0
+
+[max25]
+check = yes
diff --git a/stacks/tncs/load-serial-env.sh b/stacks/tncs/load-serial-env.sh
new file mode 100755
index 0000000..a7f0e76
--- /dev/null
+++ b/stacks/tncs/load-serial-env.sh
@@ -0,0 +1,71 @@
+# shellcheck shell=bash
+# Load station serial env for TNC boot-wait (tnc2c | pktnc2).
+# Sourced by tnc2c-boot-wait.sh / pktnc2-boot-wait.sh — do not execute directly.
+#
+# Search order (first match wins):
+#   /etc/max25/<id>-serial.env
+#   $MAX25_ROOT/local/<id>-serial.env
+#   $PWD/local/<id>-serial.env          (cwd when start script runs)
+#   <checkout>/local/<id>-serial.env    (walk up from script dir)
+#   $PREFIX/share/max25/stacks/tncs/<id>-serial.env
+
+load_serial_env() {
+  local device_id="${1:?device_id required}"
+  local script_dir="${2:?script_dir required}"
+  local env_name="${device_id}-serial.env"
+  local candidates=()
+  local p dir
+
+  candidates+=("/etc/max25/${env_name}")
+
+  if [[ -n "${MAX25_ROOT:-}" ]]; then
+    candidates+=("${MAX25_ROOT}/local/${env_name}")
+    candidates+=("${MAX25_ROOT}/stacks/tncs/${env_name}")
+  fi
+
+  if [[ -n "${PWD:-}" ]]; then
+    candidates+=("${PWD}/local/${env_name}")
+    candidates+=("${PWD}/stacks/tncs/${env_name}")
+  fi
+
+  dir="${script_dir}"
+  while [[ "${dir}" != "/" ]]; do
+    candidates+=("${dir}/local/${env_name}")
+    candidates+=("${dir}/stacks/tncs/${env_name}")
+    local parent
+    parent="$(dirname "${dir}")"
+    [[ "${parent}" == "${dir}" ]] && break
+    dir="${parent}"
+  done
+
+  candidates+=("${script_dir}/${env_name}")
+
+  local prefix="${script_dir}"
+  for _ in 1 2 3 4; do
+    prefix="$(dirname "${prefix}")"
+    candidates+=("${prefix}/share/max25/stacks/tncs/${env_name}")
+  done
+
+  for p in "${candidates[@]}"; do
+    if [[ -f "${p}" ]]; then
+      # shellcheck source=/dev/null
+      source "${p}"
+      SERIAL_ENV_FILE="${p}"
+      return 0
+    fi
+  done
+  SERIAL_ENV_FILE=""
+  return 1
+}
+
+apply_tnc2c_env() {
+  export TNC_DEV="${TNC2C_DEV:-${TNC_DEV:-/dev/ttyS4}}"
+  export TNC_BAUD="${TNC2C_BAUD:-${TNC_BAUD:-19200}}"
+  export TNC_LINE="${TNC2C_LINE:-${TNC_LINE:-8n1}}"
+}
+
+apply_pktnc2_env() {
+  export TNC_DEV="${PKTNC2_DEV:-${TNC_DEV:-/dev/ttyS5}}"
+  export TNC_BAUD="${PKTNC2_BAUD:-${TNC_BAUD:-9600}}"
+  export TNC_LINE="${PKTNC2_LINE:-${TNC_LINE:-8n1}}"
+}
diff --git a/stacks/tncs/pktnc2-boot-wait.sh b/stacks/tncs/pktnc2-boot-wait.sh
new file mode 100755
index 0000000..965fac8
--- /dev/null
+++ b/stacks/tncs/pktnc2-boot-wait.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+# PK-TNC2 boot-wait — TheFirmware TNC-2 class, typically 9600 8N1
+#
+# Software recovery (no power cycle):
+#   ./pktnc2-boot-wait.sh --recover-only
+# Rescue (DTR + power cycle while script runs):
+#   ./pktnc2-boot-wait.sh
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=load-serial-env.sh
+source "${ROOT}/load-serial-env.sh"
+load_serial_env pktnc2 "${ROOT}" || true
+apply_pktnc2_env
+if [[ -n "${SERIAL_ENV_FILE:-}" ]]; then
+  echo "Using serial env: ${SERIAL_ENV_FILE}" >&2
+else
+  echo "WARN: no pktnc2-serial.env found — using ${TNC_DEV} ${TNC_BAUD} ${TNC_LINE}" >&2
+fi
+exec python3 "${ROOT}/tnc2c-boot-wait.py" "${TNC_DEV}" --baud "${TNC_BAUD}" --line "${TNC_LINE}" "$@"
diff --git a/stacks/tncs/pktnc2-serial.env b/stacks/tncs/pktnc2-serial.env
new file mode 100644
index 0000000..046e6d0
--- /dev/null
+++ b/stacks/tncs/pktnc2-serial.env
@@ -0,0 +1,4 @@
+# PK-TNC2 serial — planned; probe port after hardware delivery
+PKTNC2_DEV=/dev/ttyUSB1
+PKTNC2_BAUD=9600
+PKTNC2_LINE=8n1
diff --git a/stacks/tncs/pktnc2-to-hybbx.sh b/stacks/tncs/pktnc2-to-hybbx.sh
new file mode 100755
index 0000000..0444b5f
--- /dev/null
+++ b/stacks/tncs/pktnc2-to-hybbx.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+# AX.25 UI frame PK-TNC2 -> HyBBX/TNC2C over the air.
+# HyBBX must be running on Unit A (ttyS4). PK-TNC2: boot-wait first.
+#
+# Usage: ./pktnc2-to-hybbx.sh [message] [src] [dst]
+# Default: "CONNECT" CB-0-2 CB-0
+
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=/dev/null
+source "$ROOT/pktnc2-serial.env"
+
+MSG="${1:-CONNECT}"
+SRC="${2:-CB-0-2}"
+DST="${3:-CB-0}"
+
+if pgrep -x hybbx >/dev/null && fuser -s "$TNC_DEV" 2>/dev/null; then
+    echo "WARN: HyBBX may hold ttyS5 - only ttyS4 should be active" >&2
+fi
+
+echo "ON-AIR TX: $SRC -> $DST: $MSG"
+echo "Radio: both on same MHz (e.g. 27.235 K24), SQ closed before TX"
+export TNC2C_DEV="$TNC_DEV" TNC2C_BAUD="$TNC_BAUD" TNC2C_LINE="$TNC_LINE"
+exec "$ROOT/tnc2c-send-test.sh" "$MSG" "$SRC" "$DST"
diff --git a/stacks/tncs/test_tnc_serial_recovery.py b/stacks/tncs/test_tnc_serial_recovery.py
new file mode 100644
index 0000000..99c9476
--- /dev/null
+++ b/stacks/tncs/test_tnc_serial_recovery.py
@@ -0,0 +1,128 @@
+#!/usr/bin/env python3
+"""Offline unit tests for tnc_serial_recovery (no serial hardware)."""
+from __future__ import annotations
+
+import importlib.util
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent
+spec = importlib.util.spec_from_file_location(
+    "tnc_serial_recovery", ROOT / "tnc_serial_recovery.py"
+)
+assert spec and spec.loader
+mod = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(mod)
+
+
+class MockPort:
+    def __init__(self) -> None:
+        self.written: list[bytes] = []
+        self.responses: list[bytes] = []
+        self._read_idx = 0
+
+    def write_flush(self, data: bytes) -> None:
+        self.written.append(data)
+
+    def read_for(self, seconds: float) -> bytes:
+        del seconds
+        if self._read_idx < len(self.responses):
+            chunk = self.responses[self._read_idx]
+            self._read_idx += 1
+            return chunk
+        return b""
+
+
+def test_has_banner() -> None:
+    assert mod.has_banner(b"NORD><LINK TheFirmware Version 2.7")
+    assert mod.has_banner(b"cmd: ")
+    assert not mod.has_banner(b"INFO\r\nINFO")
+
+
+def test_format_rx_brief_and_classify() -> None:
+    assert mod.format_rx_brief(b"") == "0 B silent"
+    brief = mod.format_rx_brief(b"kiss off\rINFO\r")
+    assert "14 B" in brief
+    assert "markers=none" in brief
+    assert "echo-only" in mod.classify_recovery_failure(b"kiss off\rINFO\r")
+    assert "silent" in mod.classify_recovery_failure(b"")
+    diag = mod.classify_recovery_failure(b"TheFirmware cmd:")
+    assert "banner" in diag
+
+
+def test_probe_tf_terminal() -> None:
+    port = MockPort()
+    port.responses = [b"TheFirmware Version 2.7 DAMA\r\nChecksum"]
+    ok, combined, only_echo = mod.probe_tf_terminal(port.write_flush, port.read_for)
+    assert ok
+    assert not only_echo
+    assert port.written[0] == mod.TF_ESC_V
+
+
+def test_tf_mycall_frame() -> None:
+    assert mod.tf_mycall_frame("cb-0") == b"\x1bI CB-0\r"
+
+
+def test_recover_terminal_ok_on_passive_banner() -> None:
+    port = MockPort()
+    port.responses = [b"NORD TheFirmware Version 2.7\r\n"]
+    ok, rx = mod.recover_terminal(
+        port.write_flush, port.read_for, skip_kiss_frame=True, log=lambda _m: None
+    )
+    assert ok
+    assert b"TheFirmware" in rx
+    assert b"\xc0\xff\xc0" not in port.written
+
+
+def test_recover_terminal_ok_after_kiss_return() -> None:
+    port = MockPort()
+    port.responses = [
+        b"",
+        b"TheFirmware Version 2.7\r\nChecksum (0000) = DC0A\r\n",
+    ]
+    ok, rx = mod.recover_terminal(
+        port.write_flush, port.read_for, skip_kiss_frame=False, log=lambda _m: None
+    )
+    assert ok
+    assert b"TheFirmware" in rx
+    assert port.written[0] == b"\xc0\xff\xc0"
+
+
+def test_recover_terminal_sends_qres_on_failure() -> None:
+    port = MockPort()
+    port.responses = [b""] * 40
+    ok, _ = mod.recover_terminal(
+        port.write_flush, port.read_for, skip_kiss_frame=True, log=lambda _m: None
+    )
+    assert not ok
+    assert mod.TF_ESC_QRES in port.written
+    assert b"RESTART\r" not in port.written
+
+
+def test_enter_kiss_native() -> None:
+    port = MockPort()
+    port.responses = [b""]
+    mod.enter_kiss(port.write_flush, port.read_for, entry="kiss_on")
+    assert port.written[0] == mod.TF_ESC_AT_K
+
+
+def main() -> int:
+    tests = [
+        test_has_banner,
+        test_format_rx_brief_and_classify,
+        test_probe_tf_terminal,
+        test_tf_mycall_frame,
+        test_recover_terminal_ok_on_passive_banner,
+        test_recover_terminal_ok_after_kiss_return,
+        test_recover_terminal_sends_qres_on_failure,
+        test_enter_kiss_native,
+    ]
+    for fn in tests:
+        fn()
+        print(f"OK {fn.__name__}")
+    print(f"All {len(tests)} tests passed")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-2.jpg b/stacks/tncs/tnc2c-2.jpg
new file mode 100644
index 0000000..29c70c4
--- /dev/null
+++ b/stacks/tncs/tnc2c-2.jpg
diff --git a/stacks/tncs/tnc2c-autotest.py b/stacks/tncs/tnc2c-autotest.py
new file mode 100755
index 0000000..4470695
--- /dev/null
+++ b/stacks/tncs/tnc2c-autotest.py
@@ -0,0 +1,925 @@
+#!/usr/bin/env python3
+"""
+tnc2c-autotest - safe, exhaustive Landolt TNC2C serial discovery.
+
+Tests baud/parity combinations, modem lines, host vs echo vs garbage,
+firmware banner, and (optionally) KISS without RF frames.
+
+Does NOT send KISS UI frames or key PTT unless --tx is passed.
+
+Usage:
+  ./tnc2c-autotest.sh
+  ./tnc2c-autotest.sh /dev/ttyS4
+  ./tnc2c-autotest.sh --quick          # likely bauds only (~45s)
+  ./tnc2c-autotest.sh --write-env      # update tnc2c-serial.env if confident
+  ./tnc2c-autotest.sh --json out.json
+  ./tnc2c-autotest.sh --host-check    # after power reset: 19200 8N1 only (~6s)
+  ./tnc2c-autotest.sh --host-check --write-env
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import struct
+import subprocess
+import sys
+import time
+import termios
+import fcntl
+from dataclasses import asdict, dataclass, field
+from typing import Optional
+
+BAUD_MAP: dict[int, int] = {
+    300: termios.B300,
+    600: termios.B600,
+    1200: termios.B1200,
+    2400: termios.B2400,
+    4800: termios.B4800,
+    9600: termios.B9600,
+    19200: termios.B19200,
+}
+
+BAUDS_FULL = (300, 600, 1200, 2400, 4800, 9600, 19200)
+BAUDS_QUICK = (19200, 2400, 4800, 9600)
+HOST_CHECK_LINES = ("8N1",)
+
+LINE_FORMATS = (
+    ("8N1", 8, "none", 1),
+    ("7E1", 7, "even", 1),
+    ("8E1", 8, "even", 1),
+)
+
+LINE_PREFERENCE = {"8N1": 3, "7E1": 2, "8E1": 1}
+
+FIRMWARE_MARKERS = (
+    b"TheFirmware",
+    b"NORD",
+    b"Version 2.7",
+    b"Checksum",
+    b"Copyright",
+    b"DAMA",
+    b"SMACK",
+)
+
+HOST_MARKERS = (
+    b"cmd:",
+    b"CMD:",
+    b"help",
+    b"HELP",
+    b"MYCALL",
+    b"KISS was",
+    b"KISS is",
+    b"KISS now",
+    b"Invalid",
+    b"Unknown",
+)
+
+
+@dataclass
+class ProfileResult:
+    name: str
+    baud: int
+    line: str
+    rts: bool = False
+    cts: bool = False
+    dsr: bool = False
+    dcd: bool = False
+    passive_bytes: int = 0
+    boot_bytes: int = 0
+    info_reply: bytes = b""
+    help_reply: bytes = b""
+    kiss_reply: bytes = b""
+    combined_reply: bytes = b""
+    printable_ratio: float = 0.0
+    host_score: int = 0
+    echo_only: bool = False
+    garbage: bool = False
+    has_cmd: bool = False
+    has_firmware: bool = False
+    notes: list[str] = field(default_factory=list)
+
+    def classify(self) -> str:
+        if (
+            self.has_firmware
+            or self.has_cmd
+            or has_firmware_banner(self.info_reply)
+        ):
+            return "HOST"
+        if self.garbage:
+            return "GARBAGE"
+        if self.echo_only or (
+            is_echo(b"INFO\r", self.info_reply) and is_echo(b"HELP\r", self.help_reply)
+        ):
+            return "ECHO"
+        if self.combined_reply:
+            return "PARTIAL"
+        return "SILENT"
+
+
+def has_firmware_banner(data: bytes) -> bool:
+    if not data:
+        return False
+    lower = data.lower()
+    return any(m.lower() in lower for m in FIRMWARE_MARKERS)
+
+
+def order_bauds(bauds: tuple[int, ...]) -> tuple[int, ...]:
+    """Test 19200 first so wrong bauds don't disturb a working host session."""
+    rest = tuple(b for b in bauds if b != 19200)
+    return (19200, *rest) if 19200 in bauds else bauds
+
+
+def line_format(line: str) -> tuple[int, str, int]:
+    for name, data_bits, parity, stop_bits in LINE_FORMATS:
+        if name == line:
+            return data_bits, parity, stop_bits
+    raise ValueError(f"unknown line format {line}")
+
+
+def timings_for(baud: int, gentle: bool) -> tuple[float, float, float]:
+    """Returns listen_s, cmd_wait, info_read."""
+    if gentle or baud == 19200:
+        return (2.0 if gentle else 1.5, 0.9 if gentle else 0.7, 3.0 if gentle else 3.0)
+    return (1.2, 0.55, 1.6)
+
+
+def finalize_profile(
+    res: ProfileResult,
+    info_cmd: bytes,
+    info: bytes,
+    help_cmd: bytes,
+    help: bytes,
+    kiss_on: bytes,
+    combined: bytes,
+) -> None:
+    res.info_reply = info
+    res.help_reply = help
+    res.kiss_reply = kiss_on
+    res.combined_reply = combined
+    res.printable_ratio = printable_ratio(combined)
+
+    s1, e1, c1, f1 = score_replies(info_cmd, info)
+    s2, e2, c2, f2 = score_replies(help_cmd, help)
+    s3, _, c3, f3 = score_replies(b"kiss on\r", kiss_on)
+    res.host_score = max(s1, s2, s3)
+    res.has_cmd = c1 or c2 or c3
+    res.has_firmware = (
+        f1 or f2 or f3
+        or has_firmware_banner(info)
+        or has_firmware_banner(help)
+    )
+    if res.has_firmware:
+        res.host_score = max(res.host_score, 55)
+        res.echo_only = False
+    elif is_echo(info_cmd, info) and (not help or is_echo(help_cmd, help)):
+        res.echo_only = True
+    else:
+        res.echo_only = (e1 and e2) and res.host_score < 15
+    res.garbage = (
+        bool(combined)
+        and res.printable_ratio < 0.55
+        and not res.has_firmware
+        and res.host_score < 20
+    )
+    if res.passive_bytes and res.has_firmware:
+        res.notes.append("boot_banner")
+    if kiss_on and not is_echo(b"kiss on\r", kiss_on):
+        res.notes.append("kiss_ack")
+
+
+def rank_key(res: ProfileResult) -> tuple:
+    """Higher is better. Prefer real host, then 8N1/7E1 over 8E1."""
+    return (
+        int(res.has_firmware),
+        int(res.has_cmd),
+        int(not res.echo_only),
+        res.host_score,
+        res.printable_ratio,
+        LINE_PREFERENCE.get(res.line, 0),
+        len(res.combined_reply),
+    )
+
+
+def load_env(path: str) -> dict[str, str]:
+    env: dict[str, str] = {}
+    if not os.path.isfile(path):
+        return env
+    with open(path, encoding="utf-8") as f:
+        for raw in f:
+            line = raw.strip()
+            if not line or line.startswith("#") or "=" not in line:
+                continue
+            k, v = line.split("=", 1)
+            env[k.strip()] = v.strip()
+    return env
+
+
+def printable_ratio(data: bytes) -> float:
+    if not data:
+        return 0.0
+    good = sum(1 for b in data if b in (9, 10, 13) or 32 <= b < 127)
+    return good / len(data)
+
+
+def open_serial(
+    dev: str,
+    baud: int,
+    data_bits: int,
+    parity: str,
+    stop_bits: int,
+    rts: bool = True,
+    dtr: bool = True,
+) -> int:
+    if baud not in BAUD_MAP:
+        raise ValueError(f"unsupported baud {baud}")
+    fd = os.open(dev, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+    t = termios.tcgetattr(fd)
+    t[0] = t[1] = 0
+    cflag = termios.CLOCAL | termios.CREAD
+    if data_bits == 7:
+        cflag |= termios.CS7
+    else:
+        cflag |= termios.CS8
+    if parity == "even":
+        cflag |= termios.PARENB
+    elif parity == "odd":
+        cflag |= termios.PARENB | termios.PARODD
+    t[2] = cflag
+    speed = BAUD_MAP[baud]
+    t[3] = t[4] = t[5] = speed
+    t[6][termios.VMIN] = 0
+    t[6][termios.VTIME] = 5
+    termios.tcsetattr(fd, termios.TCSANOW, t)
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    if rts:
+        flags |= 0x004
+    else:
+        flags &= ~0x004
+    if dtr:
+        flags |= 0x002
+    else:
+        flags &= ~0x002
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    return fd
+
+
+def modem_lines(fd: int) -> tuple[bool, bool, bool, bool]:
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    return (
+        bool(flags & 0x004),
+        bool(flags & 0x008),
+        bool(flags & 0x100),
+        bool(flags & 0x080),
+    )
+
+
+def read_for(fd: int, seconds: float) -> bytes:
+    end = time.time() + seconds
+    chunks: list[bytes] = []
+    while time.time() < end:
+        try:
+            b = os.read(fd, 4096)
+            if b:
+                chunks.append(b)
+        except BlockingIOError:
+            time.sleep(0.02)
+    return b"".join(chunks)
+
+
+def write_flush(fd: int, data: bytes) -> None:
+    os.write(fd, data)
+    termios.tcdrain(fd)
+
+
+def is_echo(cmd: bytes, reply: bytes) -> bool:
+    if not reply:
+        return False
+    c = cmd.strip(b"\r\n")
+    r = reply.strip()
+    return r in (c, c + b"\r", c + b"\n", c + b"\r\n")
+
+
+def score_replies(cmd: bytes, *chunks: bytes) -> tuple[int, bool, bool, bool]:
+    reply = b"".join(chunks)
+    if not reply:
+        return 0, False, False, False
+
+    score = 0
+    lower = reply.lower()
+    has_cmd = b"cmd:" in lower
+    has_fw = any(m.lower() in lower for m in FIRMWARE_MARKERS)
+
+    if has_cmd:
+        score += 60
+    if has_fw:
+        score += 50
+    for m in HOST_MARKERS:
+        if m.lower() in lower:
+            score += 8
+    if len(reply) > len(cmd) + 8 and not is_echo(cmd, reply):
+        score += 10
+    if b"\n" in reply and len(reply) > 30:
+        score += 5
+
+    echo = is_echo(cmd, reply) and score < 20
+    garbage = printable_ratio(reply) < 0.55 and len(reply) >= 4
+    return score, echo, has_cmd, has_fw
+
+
+def profile_name(baud: int, line: str) -> str:
+    return f"{baud}-{line}"
+
+
+def test_profile(
+    dev: str,
+    baud: int,
+    line: str,
+    data_bits: int,
+    parity: str,
+    stop_bits: int,
+    gentle: bool = False,
+) -> ProfileResult:
+    listen_s, cmd_wait, info_read = timings_for(baud, gentle)
+    res = ProfileResult(name=profile_name(baud, line), baud=baud, line=line)
+    fd = open_serial(dev, baud, data_bits, parity, stop_bits)
+    res.rts, res.cts, res.dsr, res.dcd = modem_lines(fd)
+
+    passive = read_for(fd, listen_s)
+    res.passive_bytes = len(passive)
+
+    if not gentle:
+        write_flush(fd, b"\x03\x1a")
+        time.sleep(0.15)
+        read_for(fd, 0.2)
+
+    write_flush(fd, b"\r\r")
+    time.sleep(cmd_wait)
+    wake = read_for(fd, listen_s)
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(cmd_wait)
+    kiss_off = read_for(fd, listen_s)
+
+    info_cmd = b"INFO\r"
+    write_flush(fd, info_cmd)
+    time.sleep(cmd_wait)
+    info = read_for(fd, info_read)
+
+    help_cmd = b"HELP\r"
+    write_flush(fd, help_cmd)
+    time.sleep(cmd_wait)
+    help = read_for(fd, listen_s + 0.3)
+
+    write_flush(fd, b"kiss on\r")
+    time.sleep(cmd_wait)
+    kiss_on = read_for(fd, listen_s)
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.2)
+    read_for(fd, 0.2)
+
+    finalize_profile(
+        res, info_cmd, info, help_cmd, help, kiss_on,
+        passive + wake + kiss_off + info + help + kiss_on,
+    )
+    os.close(fd)
+    return res
+
+
+def test_host_check(
+    dev: str,
+    baud: int,
+    line: str,
+    dtr_cycle: bool = False,
+    no_kiss: bool = False,
+) -> ProfileResult:
+    """Gentle single-profile check - DTR high, optional KISS-reset, kiss off, INFO."""
+    data_bits, parity, stop_bits = line_format(line)
+    res = ProfileResult(name=profile_name(baud, line), baud=baud, line=line)
+
+    prelude = b""
+    if dtr_cycle:
+        boot = boot_listen(dev, baud, line, data_bits, parity, stop_bits)
+        res.boot_bytes = len(boot)
+        prelude = boot
+        if has_firmware_banner(boot):
+            res.has_firmware = True
+            res.notes.append("dtr_boot_banner")
+
+    fd = open_serial(dev, baud, data_bits, parity, stop_bits)
+    res.rts, res.cts, res.dsr, res.dcd = modem_lines(fd)
+
+    passive = read_for(fd, 1.0)
+    res.passive_bytes = len(passive)
+    prelude += passive
+    if has_firmware_banner(passive):
+        res.has_firmware = True
+        res.notes.append("passive_boot_banner")
+
+    if not no_kiss:
+        write_flush(fd, b"\xc0\xff\xc0")
+        time.sleep(0.8)
+        prelude += read_for(fd, 0.8)
+        res.notes.append("kiss_reset")
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.4)
+    kiss_off = read_for(fd, 0.8)
+
+    info_cmd = b"INFO\r"
+    write_flush(fd, info_cmd)
+    time.sleep(0.3)
+    info = read_for(fd, 3.5)
+
+    finalize_profile(res, info_cmd, info, b"HELP\r", b"", b"", prelude + kiss_off + info)
+    os.close(fd)
+    return res
+
+
+def boot_listen(dev: str, baud: int, line: str, data_bits: int, parity: str, stop_bits: int) -> bytes:
+    fd = open_serial(dev, baud, data_bits, parity, stop_bits)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    flags &= ~0x002
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    time.sleep(0.8)
+    flags |= 0x002 | 0x004
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    data = read_for(fd, 4.0)
+    os.close(fd)
+    return data
+
+
+def deep_test(dev: str, res: ProfileResult) -> ProfileResult:
+    line = res.line
+    data_bits, parity, stop_bits = line_format(line)
+    gentle = res.baud == 19200
+
+    fd = open_serial(dev, res.baud, data_bits, parity, stop_bits)
+    res.rts, res.cts, res.dsr, res.dcd = modem_lines(fd)
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.6 if gentle else 0.4)
+    read_for(fd, 0.3)
+
+    for _ in range(4):
+        write_flush(fd, b"\r")
+        time.sleep(0.35)
+    enters = read_for(fd, 1.5)
+    if b"cmd:" in enters.lower():
+        res.has_cmd = True
+        res.host_score += 20
+        res.notes.append("cmd_after_enter")
+
+    write_flush(fd, b"MYCALL TEST-0\r")
+    time.sleep(0.6)
+    mycall = read_for(fd, 1.0)
+    if mycall and not is_echo(b"MYCALL TEST-0\r", mycall):
+        lower = mycall.lower()
+        if b"cmd:" in lower or has_firmware_banner(mycall):
+            res.host_score += 15
+            res.notes.append("mycall_ack")
+
+    if not res.has_firmware:
+        boot = boot_listen(dev, res.baud, line, data_bits, parity, stop_bits)
+        res.boot_bytes = len(boot)
+        if has_firmware_banner(boot):
+            res.has_firmware = True
+            res.host_score = max(res.host_score, 55)
+            res.echo_only = False
+            res.notes.append("dtr_boot_banner")
+
+    os.close(fd)
+    return res
+
+
+def port_holders(dev: str) -> list[str]:
+    holders: list[str] = []
+    try:
+        out = subprocess.run(
+            ["fuser", "-v", dev],
+            capture_output=True,
+            text=True,
+            timeout=3,
+        )
+        if out.returncode == 0 and out.stderr:
+            for line in out.stderr.splitlines():
+                line = line.strip()
+                if line and not line.startswith("USER"):
+                    holders.append(line)
+    except (FileNotFoundError, subprocess.TimeoutExpired):
+        pass
+    return holders
+
+
+def preflight(dev: str) -> list[str]:
+    issues: list[str] = []
+    if os.system("pgrep -x hybbx >/dev/null 2>&1") == 0:
+        issues.append("hybbx is running - stop it first")
+    if not os.path.exists(dev):
+        issues.append(f"{dev} does not exist")
+    elif not os.access(dev, os.R_OK | os.W_OK):
+        issues.append(f"no access to {dev} (dialout group?)")
+    holders = port_holders(dev)
+    if holders:
+        issues.append(f"port in use: {', '.join(holders[:3])}")
+    return issues
+
+
+def quartz_hint(baud: int) -> str:
+    hints = []
+    term_98304 = {9600: "TERM Pos.1", 4800: "TERM Pos.2", 2400: "TERM Pos.3", 1200: "TERM Pos.4"}
+    term_49152 = {4800: "TERM Pos.1", 2400: "TERM Pos.2", 1200: "TERM Pos.3", 600: "TERM Pos.4"}
+    if baud in term_98304:
+        hints.append(f"with 9.8304 MHz crystal: {term_98304[baud]}")
+    if baud in term_49152:
+        hints.append(f"with 4.9152 MHz crystal: {term_49152[baud]}")
+    if baud == 19200:
+        hints.append("19200 is in the manual only with RADIO bridge (2.4576 MHz Pos.5), not TERM")
+        hints.append("-> possible mod, extended firmware, or different crystal")
+    return "; ".join(hints) if hints else "-"
+
+
+def suggest_env(best: ProfileResult) -> dict[str, str]:
+    line = best.line.lower()
+    return {
+        "TNC2C_DEV": "",  # filled by caller
+        "TNC2C_BAUD": str(best.baud),
+        "TNC2C_LINE": line,
+        "TNC2C_RADIO_BAUD": "2400",
+        "TNC2C_MODEM": "tcm3105",
+        "HYBBX_SERIAL_LINE": line,
+    }
+
+
+def write_env_file(path: str, dev: str, best: ProfileResult) -> None:
+    vals = suggest_env(best)
+    vals["TNC2C_DEV"] = dev
+    lines = [
+        f"# Auto-generated by tnc2c-autotest {time.strftime('%Y-%m-%d %H:%M:%S')}",
+        f"# Best profile: {best.name} ({best.classify()}, score={best.host_score})",
+    ]
+    for k, v in vals.items():
+        lines.append(f"{k}={v}")
+    lines.append("")
+    with open(path, "w", encoding="utf-8") as f:
+        f.write("\n".join(lines))
+
+
+# --- optional TX (from health check) ---
+
+def kiss_escape(data: bytes) -> bytes:
+    out = bytearray()
+    for b in data:
+        if b == 0xC0:
+            out.extend((0xDB, 0xDC))
+        elif b == 0xDB:
+            out.extend((0xDB, 0xDD))
+        else:
+            out.append(b)
+    return bytes(out)
+
+
+def ax25_addr(call: str, ssid: int, last: bool) -> bytes:
+    call = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in call)
+    ssid_b = ((ssid & 0x0F) << 1) | (0x01 if last else 0x00)
+    return raw + bytes([ssid_b])
+
+
+def ax25_crc(data: bytes) -> int:
+    crc = 0xFFFF
+    for b in data:
+        crc ^= b
+        for _ in range(8):
+            crc = (crc >> 1) ^ 0x8408 if crc & 1 else crc >> 1
+    return crc ^ 0xFFFF
+
+
+def ax25_ui(src: str, dst: str, info: bytes) -> bytes:
+    body = ax25_addr(dst, 0, False) + ax25_addr(src, 0, True) + b"\x03\xF0" + info
+    crc = ax25_crc(body)
+    return body + bytes((crc & 0xFF, crc >> 8))
+
+
+def run_tx_test(dev: str, best: ProfileResult) -> dict:
+    fmt = next(f for f in LINE_FORMATS if f[0] == best.line)
+    _, data_bits, parity, stop_bits = fmt
+    fd = open_serial(dev, best.baud, data_bits, parity, stop_bits)
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.4)
+    read_for(fd, 0.3)
+    write_flush(fd, b"kiss on\r")
+    time.sleep(0.5)
+    read_for(fd, 0.3)
+    payload = ax25_ui("TEST-0", "CQ", b"AUTOTEST")
+    pkt = b"\xC0" + bytes([0]) + kiss_escape(payload) + b"\xC0"
+    write_flush(fd, pkt)
+    time.sleep(3.0)
+    rx = read_for(fd, 1.0)
+    write_flush(fd, b"kiss off\r")
+    os.close(fd)
+    return {
+        "sent": len(pkt),
+        "rx_len": len(rx),
+        "echoed": pkt in rx or payload in rx,
+    }
+
+
+def preview(data: bytes, limit: int = 72) -> str:
+    if not data:
+        return "(empty)"
+    s = data[:limit].decode("ascii", errors="replace")
+    s = s.replace("\r", "\\r").replace("\n", "\\n")
+    if len(data) > limit:
+        s += "..."
+    return s
+
+
+def print_header(title: str) -> None:
+    print(f"\n{'=' * 64}")
+    print(title)
+    print("=" * 64)
+
+
+def print_result_summary(
+    best: ProfileResult,
+    dev: str,
+    ranked: list[ProfileResult],
+    root: str,
+    args: argparse.Namespace,
+    suggested: dict[str, str],
+    tx_result: Optional[dict],
+    t0: float,
+) -> int:
+    host_profiles = [r for r in ranked if r.classify() == "HOST"]
+    echo_profiles = [r for r in ranked if r.classify() == "ECHO"]
+    garbage_profiles = [r for r in ranked if r.classify() == "GARBAGE"]
+
+    print_header("Result")
+    print(f"  Best profile:   {best.name}")
+    print(f"  Class:          {best.classify()}")
+    print(f"  Host score:     {best.host_score}")
+    print(f"  Modem:          RTS={int(best.rts)} CTS={int(best.cts)} DSR={int(best.dsr)}")
+    print(f"  INFO:           {preview(best.info_reply, 120)}")
+    if best.has_firmware or has_firmware_banner(best.info_reply):
+        print("  Firmware banner: YES")
+    if best.has_cmd:
+        print("  cmd: prompt:     YES")
+    print(f"  Crystal/bridge: {quartz_hint(best.baud)}")
+
+    if host_profiles:
+        print(f"\n  HOST profiles ({len(host_profiles)}): {', '.join(r.name for r in host_profiles[:5])}")
+    if echo_profiles and not host_profiles:
+        print(f"\n  ECHO only ({len(echo_profiles)}) - TNC mirrors commands, does not process them.")
+        print("  -> Power-reset the TNC, then: ./tnc2c-autotest.sh --host-check --write-env")
+    if garbage_profiles:
+        top_g = sorted(garbage_profiles, key=lambda r: r.printable_ratio, reverse=True)[:3]
+        print(f"  GARBAGE profiles: {', '.join(r.name for r in top_g)} (wrong baud/parity)")
+
+    print("\n  Recommended settings:")
+    print(f"    max25-terminal or tnc2c-host-reset @ {dev} -b {best.baud}   (# {best.line})")
+    for k in ("TNC2C_BAUD", "TNC2C_LINE", "HYBBX_SERIAL_LINE"):
+        print(f"    {k}={suggested[k]}")
+
+    if args.write_env and best.classify() == "HOST":
+        env_path = os.path.join(root, "tnc2c-serial.env")
+        write_env_file(env_path, dev, best)
+        print(f"\n  Written: {env_path}")
+    elif args.write_env:
+        print("\n  --write-env skipped (no reliable HOST profile)")
+
+    print_header("KISS-TX")
+    if not args.tx:
+        print("  Skipped (safe). Optional: --tx (PTT may key!)")
+    else:
+        print("  WARNING: sends AX.25 UI frame - check PTT LED!")
+        tx_result = run_tx_test(dev, best)
+        print(f"  Sent {tx_result['sent']} B, RX {tx_result['rx_len']} B, Echo={tx_result['echoed']}")
+
+    elapsed = time.time() - t0
+    status = "OK" if best.classify() == "HOST" else (
+        "DEGRADED" if best.classify() in ("ECHO", "PARTIAL") else "FAIL"
+    )
+
+    print_header("SUMMARY")
+    print(f"  Status:   {status}")
+    print(f"  Device:   {dev}")
+    print(f"  Profile:  {best.name} ({best.classify()})")
+    print(f"  Duration: {elapsed:.0f}s")
+
+    if args.json:
+        report = {
+            "device": dev,
+            "status": status,
+            "elapsed_s": round(elapsed, 1),
+            "best": asdict(best),
+            "ranking": [asdict(r) for r in ranked[:12]],
+            "suggested_env": suggested,
+            "tx": tx_result,
+        }
+
+        def fix(obj):
+            if isinstance(obj, dict):
+                return {k: fix(v) for k, v in obj.items()}
+            if isinstance(obj, list):
+                return [fix(v) for v in obj]
+            if isinstance(obj, bytes):
+                return obj.decode("ascii", errors="replace")
+            return obj
+
+        with open(args.json, "w", encoding="utf-8") as f:
+            json.dump(fix(report), f, indent=2, ensure_ascii=False)
+        print(f"  JSON:     {args.json}")
+
+    return 0 if status == "OK" else (1 if status == "DEGRADED" else 2)
+
+
+def run_host_check(
+    dev: str,
+    root: str,
+    env: dict[str, str],
+    args: argparse.Namespace,
+) -> int:
+    t0 = time.time()
+    print_header("TNC2C HOST-CHECK (DTR high - no DTR drop, no baud sweep)")
+    print(f"Device:  {dev}")
+    print(f"Started: {time.strftime('%Y-%m-%d %H:%M:%S')}")
+    if args.dtr_cycle:
+        print("Note: --dtr-cycle active (DTR drop - may trigger echo mode)")
+
+    print_header("1) Preflight")
+    issues = preflight(dev)
+    if issues:
+        for i in issues:
+            print(f"  FAIL: {i}")
+        print("\nAbort - clear port/background services and retry.")
+        return 2
+    print("  OK: port free, hybbx inactive, access OK")
+
+    kiss_step = "kiss off -> INFO" if args.no_kiss else "KISS-reset -> kiss off -> INFO"
+    print_header(f"2) Host-Check 19200-8N1 (passive -> {kiss_step})")
+    results: list[ProfileResult] = []
+    for line in HOST_CHECK_LINES:
+        name = profile_name(19200, line)
+        if not args.quiet:
+            print(f"  {name:12} ...", end="", flush=True)
+        try:
+            r = test_host_check(
+                dev, 19200, line, dtr_cycle=args.dtr_cycle, no_kiss=args.no_kiss
+            )
+            results.append(r)
+            if not args.quiet:
+                print(
+                    f" {r.classify():7} score={r.host_score:3} fw={int(r.has_firmware)} "
+                    f"INFO={preview(r.info_reply, 50)!r}"
+                )
+        except OSError as e:
+            if not args.quiet:
+                print(f" ERROR: {e}")
+
+    if not results:
+        print("  No profiles tested.")
+        return 2
+
+    ranked = sorted(results, key=rank_key, reverse=True)
+    best = ranked[0]
+    suggested = suggest_env(best)
+    suggested["TNC2C_DEV"] = dev
+    return print_result_summary(best, dev, ranked, root, args, suggested, None, t0)
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="TNC2C safe exhaustive autotest")
+    parser.add_argument("device", nargs="?", default=None)
+    parser.add_argument(
+        "--host-check",
+        action="store_true",
+        help="gentle 19200-8N1 only - after power reset (~10s)",
+    )
+    parser.add_argument(
+        "--dtr-cycle",
+        action="store_true",
+        help="brief DTR drop (legacy; may trigger echo mode - not for host-check)",
+    )
+    parser.add_argument(
+        "--no-kiss",
+        action="store_true",
+        help="host-check: skip KISS-reset frame",
+    )
+    parser.add_argument("--quick", action="store_true", help="19200 first, then 2400/4800/9600")
+    parser.add_argument("--write-env", action="store_true", help="write tnc2c-serial.env if HOST found")
+    parser.add_argument("--json", metavar="FILE", help="write JSON report")
+    parser.add_argument("--tx", action="store_true", help="KISS TX test - keys PTT!")
+    parser.add_argument("-q", "--quiet", action="store_true")
+    args = parser.parse_args()
+
+    root = os.path.dirname(os.path.abspath(__file__))
+    env = load_env(os.path.join(root, "tnc2c-serial.env"))
+    dev = args.device or env.get("TNC2C_DEV", "/dev/ttyS4")
+
+    if args.host_check:
+        return run_host_check(dev, root, env, args)
+
+    bauds = order_bauds(BAUDS_QUICK if args.quick else BAUDS_FULL)
+    total = len(bauds) * len(LINE_FORMATS)
+
+    t0 = time.time()
+    print_header("TNC2C AUTOTEST (safe - no PTT unless --tx)")
+    print(f"Device:  {dev}")
+    print(f"Mode:    {'quick' if args.quick else 'full'} ({total} profiles, 19200 first)")
+    print(f"Started: {time.strftime('%Y-%m-%d %H:%M:%S')}")
+
+    print_header("1) Preflight")
+    issues = preflight(dev)
+    if issues:
+        for i in issues:
+            print(f"  FAIL: {i}")
+        print("\nAbort - clear port/background services and retry.")
+        return 2
+    print("  OK: port free, hybbx inactive, access OK")
+
+    print_header("2) Host precheck 19200-8N1")
+    precheck = test_host_check(dev, 19200, "8N1", dtr_cycle=args.dtr_cycle)
+    print(
+        f"  {precheck.name:12} {precheck.classify():7} fw={int(precheck.has_firmware)} "
+        f"INFO={preview(precheck.info_reply, 60)!r}"
+    )
+
+    print_header("3) Profile sweep (19200 first, no Ctrl+C at 19200)")
+    results: list[ProfileResult] = [precheck]
+    seen = {precheck.name}
+    n = 0
+    for baud in bauds:
+        for line, data_bits, parity, stop_bits in LINE_FORMATS:
+            name = profile_name(baud, line)
+            if name in seen:
+                continue
+            n += 1
+            if not args.quiet:
+                print(f"  [{n:2}/{total - 1}] {name:12} ...", end="", flush=True)
+            try:
+                gentle = baud == 19200
+                r = test_profile(dev, baud, line, data_bits, parity, stop_bits, gentle=gentle)
+                results.append(r)
+                seen.add(name)
+                if not args.quiet:
+                    print(
+                        f" {r.classify():7} score={r.host_score:3} "
+                        f"CTS={int(r.cts)} pr={r.printable_ratio:.0%} "
+                        f"INFO={preview(r.info_reply, 40)!r}"
+                    )
+            except OSError as e:
+                if not args.quiet:
+                    print(f" ERROR: {e}")
+
+    ranked = sorted(results, key=rank_key, reverse=True)
+    best = ranked[0] if ranked else None
+
+    print_header("4) Ranking (Top 8)")
+    for r in ranked[:8]:
+        print(
+            f"  {r.name:12} {r.classify():7} score={r.host_score:3} "
+            f"cmd={int(r.has_cmd)} fw={int(r.has_firmware)} echo={int(r.echo_only)} "
+            f"CTS={int(r.cts)}"
+        )
+
+    print_header("5) Deep test (Top 3)")
+    deep_targets = [r for r in ranked[:3] if r.host_score > 0 or r.combined_reply]
+    if not deep_targets and ranked:
+        deep_targets = ranked[:1]
+    for r in deep_targets:
+        if r.name == precheck.name and precheck.classify() == "HOST":
+            continue
+        print(f"  -> {r.name} ...", flush=True)
+        deep_test(dev, r)
+
+    ranked = sorted(results, key=rank_key, reverse=True)
+    best = ranked[0]
+
+    if best and best.classify() in ("ECHO", "PARTIAL") and env.get("TNC2C_BAUD"):
+        saved_line = env.get("TNC2C_LINE", "8n1").upper()
+        if "7" in saved_line and "E" in saved_line:
+            saved_line = "7E1"
+        elif saved_line.startswith("8") and "E" in saved_line:
+            saved_line = "8E1"
+        else:
+            saved_line = "8N1"
+        saved_name = profile_name(int(env["TNC2C_BAUD"]), saved_line)
+        saved = next((r for r in results if r.name == saved_name), None)
+        if saved and saved.classify() != "HOST":
+            print(f"  (Note: saved profile {saved_name} - use --host-check after power reset)")
+
+    if best is None:
+        print("  No response on any profile.")
+        return 2
+
+    suggested = suggest_env(best)
+    suggested["TNC2C_DEV"] = dev
+    return print_result_summary(best, dev, ranked, root, args, suggested, None, t0)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-autotest.sh b/stacks/tncs/tnc2c-autotest.sh
new file mode 100755
index 0000000..d0f119d
--- /dev/null
+++ b/stacks/tncs/tnc2c-autotest.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+# Exhaustive safe TNC2C autotest — no PTT unless --tx.
+# Usage:
+#   ./tnc2c-autotest.sh --host-check          # after power reset (~6s, DTR stays high)
+#   ./tnc2c-autotest.sh --host-check --write-env
+#   ./tnc2c-autotest.sh --quick               # full sweep, 19200 first (~2 min)
+#   ./tnc2c-autotest.sh --write-env
+
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+exec python3 "$ROOT/tnc2c-autotest.py" "$@"
diff --git a/stacks/tncs/tnc2c-boot-wait.py b/stacks/tncs/tnc2c-boot-wait.py
new file mode 100644
index 0000000..ba24e26
--- /dev/null
+++ b/stacks/tncs/tnc2c-boot-wait.py
@@ -0,0 +1,326 @@
+#!/usr/bin/env python3
+"""
+Hold /dev/ttyS4 open with DTR+RTS during TNC power-on, then native TF probe (ESC V).
+
+Usage:
+  1. Run this FIRST (waits for port):
+     ./tnc2c-boot-wait.sh
+  2. While it says "waiting", power-cycle the TNC (off 10s, on).
+  3. Script detects banner or runs KISS return + ESC V automatically.
+"""
+
+from __future__ import annotations
+
+import argparse
+import importlib.util
+import fcntl
+import os
+import struct
+import sys
+import time
+import termios
+
+def load_recovery():
+    root = os.path.dirname(os.path.abspath(__file__))
+    path = os.path.join(root, "tnc_serial_recovery.py")
+    spec = importlib.util.spec_from_file_location("tnc_serial_recovery", path)
+    if spec is None or spec.loader is None:
+        return None
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+FIRMWARE_MARKERS = (
+    b"TheFirmware",
+    b"NORD",
+    b"Version 2.7",
+    b"Checksum",
+    b"Copyright",
+)
+
+
+def has_banner(data: bytes) -> bool:
+    lower = data.lower()
+    return any(m.lower() in lower for m in FIRMWARE_MARKERS)
+
+
+def parse_line(line: str) -> tuple[int, int]:
+    line = line.lower()
+    if line == "7e1":
+        return termios.CS7, termios.PARENB
+    if line == "8n1":
+        return termios.CS8, 0
+    raise ValueError(f"unsupported serial line: {line}")
+
+
+def parse_baud(baud: int) -> int:
+    table = {
+        1200: termios.B1200,
+        2400: termios.B2400,
+        4800: termios.B4800,
+        9600: termios.B9600,
+        19200: termios.B19200,
+    }
+    if baud not in table:
+        raise ValueError(f"unsupported baud: {baud}")
+    return table[baud]
+
+
+def open_serial(dev: str, baud: int, line: str) -> int:
+    speed = parse_baud(baud)
+    databits, parity = parse_line(line)
+    fd = os.open(dev, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+    t = termios.tcgetattr(fd)
+    t[0] = t[1] = 0
+    t[2] = termios.CLOCAL | termios.CREAD | databits | parity
+    t[3] = t[4] = t[5] = speed
+    t[6][termios.VMIN] = 0
+    t[6][termios.VTIME] = 5
+    termios.tcsetattr(fd, termios.TCSANOW, t)
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    flags |= 0x004 | 0x002
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    return fd
+
+
+def read_for(fd: int, seconds: float) -> bytes:
+    end = time.time() + seconds
+    chunks: list[bytes] = []
+    while time.time() < end:
+        try:
+            b = os.read(fd, 4096)
+            if b:
+                chunks.append(b)
+        except BlockingIOError:
+            time.sleep(0.02)
+    return b"".join(chunks)
+
+
+def write_flush(fd: int, data: bytes) -> None:
+    os.write(fd, data)
+    termios.tcdrain(fd)
+
+
+def show(data: bytes) -> None:
+    if data:
+        print(data.decode("ascii", errors="replace"))
+
+
+def is_cmd_echo(cmd: bytes, reply: bytes) -> bool:
+    c = cmd.strip(b"\r\n")
+    r = reply.strip()
+    return r in (c, c + b"\r", c + b"\n", c + b"\r\n")
+
+
+def run_tx_rx(fd: int) -> None:
+    """TX KISS frame + passive RX on same open fd (before port close)."""
+    print("\n--- TX (KISS TEST-0 -> CQ, TXRX) ---")
+    write_flush(fd, b"\x1b@K")
+    time.sleep(0.5)
+    read_for(fd, 0.3)
+
+    def kiss_escape(data: bytes) -> bytes:
+        out = bytearray()
+        for b in data:
+            if b == 0xC0:
+                out.extend((0xDB, 0xDC))
+            elif b == 0xDB:
+                out.extend((0xDB, 0xDD))
+            else:
+                out.append(b)
+        return bytes(out)
+
+    def ax25_addr(call: str, last: bool) -> bytes:
+        call = call.upper().ljust(6)[:6]
+        raw = bytes((ord(c) << 1) for c in call)
+        ssid = ((0 & 0x0F) << 1) | (0x01 if last else 0x00)
+        return raw + bytes([ssid])
+
+    def ax25_crc(data: bytes) -> int:
+        crc = 0xFFFF
+        for b in data:
+            crc ^= b
+            for _ in range(8):
+                crc = (crc >> 1) ^ 0x8408 if crc & 1 else crc >> 1
+        return crc ^ 0xFFFF
+
+    body = ax25_addr("CQ", False) + ax25_addr("TEST-0", True) + b"\x03\xF0TXRX"
+    crc = ax25_crc(body)
+    payload = body + bytes((crc & 0xFF, crc >> 8))
+    pkt = b"\xC0\x00" + kiss_escape(payload) + b"\xC0"
+    write_flush(fd, pkt)
+    time.sleep(3.0)
+    tx_rx = read_for(fd, 1.0)
+    print(f"  Sent {len(pkt)} B, serial RX {len(tx_rx)} B")
+    print("  -> CHECK: LED2 PTT + modem tone on 2m CB")
+
+    write_flush(fd, b"\xc0\xff\xc0")
+    time.sleep(1.0)
+    read_for(fd, 0.5)
+
+    print("\n--- RX (passive 10s) ---")
+    print("  Listening ... (empty band = 0 bytes OK; LED3 CD with noise?)")
+    rx = read_for(fd, 10.0)
+    print(f"  Passive RX: {len(rx)} bytes")
+    if rx and b"\xc0" in rx:
+        print("  OK: KISS frame received")
+
+
+def verify_hybbx_ready(fd: int) -> tuple[bool, bytes, bool]:
+    """ESC V on open fd. Returns (banner_in_reply, data, only_echo)."""
+    write_flush(fd, b"\x1bV\r")
+    time.sleep(0.4)
+    info = read_for(fd, 5.0)
+    only_echo = is_cmd_echo(b"\x1bV\r", info)
+    return has_banner(info), info, only_echo
+
+
+def finish_host(fd: int, hybbx_ready: bool, do_tx_rx: bool) -> int:
+    if hybbx_ready:
+        print("\n--- HyBBX-Verify (ESC V) ---")
+        ok, verify, only_echo = verify_hybbx_ready(fd)
+        show(verify)
+        host_ok = ok or only_echo
+        if not host_ok:
+            if do_tx_rx:
+                run_tx_rx(fd)
+            os.close(fd)
+            print("\nWARN: unexpected ESC V response")
+            return 1
+    else:
+        host_ok = True
+
+    if do_tx_rx:
+        run_tx_rx(fd)
+
+    os.close(fd)
+    if host_ok:
+        print("\nOK: HOST - HyBBX-ready" + (" + TX/RX tested" if do_tx_rx else ""))
+        return 0
+    return 1
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Hold DTR during TNC boot")
+    default_dev = (
+        os.environ.get("TNC_DEV")
+        or os.environ.get("TNC2C_DEV")
+        or os.environ.get("PKTNC2_DEV")
+        or "/dev/ttyS4"
+    )
+    default_baud = int(
+        os.environ.get("TNC_BAUD")
+        or os.environ.get("TNC2C_BAUD")
+        or os.environ.get("PKTNC2_BAUD")
+        or "19200"
+    )
+    default_line = (
+        os.environ.get("TNC_LINE")
+        or os.environ.get("TNC2C_LINE")
+        or os.environ.get("PKTNC2_LINE")
+        or "8n1"
+    )
+
+    parser.add_argument("device", nargs="?", default=default_dev)
+    parser.add_argument("--baud", type=int, default=default_baud)
+    parser.add_argument("--line", default=default_line, choices=("8n1", "7e1"))
+    parser.add_argument("--wait", type=int, default=45, help="seconds to listen for boot")
+    parser.add_argument(
+        "--no-hybbx-ready",
+        action="store_true",
+        help="only detect boot banner, skip ESC V verify",
+    )
+    parser.add_argument(
+        "--tx-rx",
+        action="store_true",
+        help="TX KISS + passive RX on same port before close (with power cycle)",
+    )
+    parser.add_argument(
+        "--recover-only",
+        action="store_true",
+        help="skip boot listen; run software recovery ladder only (no power cycle)",
+    )
+    args = parser.parse_args()
+    hybbx_ready = not args.no_hybbx_ready
+    do_tx_rx = args.tx_rx
+
+    if not os.access(args.device, os.R_OK | os.W_OK):
+        print(f"FAIL: no access to {args.device}", file=sys.stderr)
+        return 2
+
+    fd = open_serial(args.device, args.baud, args.line)
+
+    if args.recover_only:
+        print(f"=== TNC recover-only @ {args.device} {args.baud} {args.line.upper()} ===")
+        rec = load_recovery()
+        if rec is None:
+            print("FAIL: tnc_serial_recovery.py not found", file=sys.stderr)
+            os.close(fd)
+            return 2
+
+        def wf(data: bytes) -> None:
+            write_flush(fd, data)
+
+        def rf(seconds: float) -> bytes:
+            return read_for(fd, seconds)
+
+        ok, rx = rec.recover_terminal(wf, rf, log=lambda m: print(f"  {m}"))
+        if ok:
+            show(rx[-800:] if len(rx) > 800 else rx)
+            return finish_host(fd, hybbx_ready, do_tx_rx)
+        os.close(fd)
+        print("\nFAIL: software recovery — try power-cycle with DTR high (re-run without --recover-only)")
+        return 1
+
+    print(f"=== TNC boot-wait @ {args.device} {args.baud} {args.line.upper()} ===")
+    print("DTR+RTS HIGH - power OFF the TNC now (10s), then power ON.")
+    print("CB: squelch CLOSED (CD off) - otherwise TX/boot may be disturbed.")
+    print(f"Listening {args.wait}s for boot banner ...\n")
+
+    buf = read_for(fd, args.wait)
+
+    if has_banner(buf):
+        print("--- Boot banner (passive) ---")
+        show(buf)
+        return finish_host(fd, hybbx_ready, do_tx_rx)
+
+    print(f"(no banner in {args.wait}s - trying KISS return + ESC V)\n")
+    write_flush(fd, b"\xc0\xff\xc0")
+    time.sleep(1.0)
+    buf += read_for(fd, 2.5)
+    write_flush(fd, b"\x1bV\r")
+    time.sleep(0.4)
+    info = read_for(fd, 4.0)
+    buf += info
+
+    print("--- KISS return + ESC V ---")
+    show(info if info else buf[-500:])
+
+    if has_banner(buf):
+        return finish_host(fd, hybbx_ready, do_tx_rx)
+
+    rec = load_recovery()
+    if rec is not None:
+        print("\n--- software recovery ladder ---")
+
+        def wf(data: bytes) -> None:
+            write_flush(fd, data)
+
+        def rf(seconds: float) -> bytes:
+            return read_for(fd, seconds)
+
+        ok, rx = rec.recover_terminal(wf, rf, log=lambda m: print(f"  {m}"))
+        buf += rx
+        if ok:
+            show(rx[-800:] if len(rx) > 800 else rx)
+            return finish_host(fd, hybbx_ready, do_tx_rx)
+
+    os.close(fd)
+    print("\nDEGRADED: try ./tnc2c-host-reset.sh or power-cycle with this script running")
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-boot-wait.sh b/stacks/tncs/tnc2c-boot-wait.sh
new file mode 100755
index 0000000..ac101c1
--- /dev/null
+++ b/stacks/tncs/tnc2c-boot-wait.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+# TNC2C boot-wait — Landolt TNC2C, typically 19200 8N1, DTR during power-on
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=load-serial-env.sh
+source "${ROOT}/load-serial-env.sh"
+load_serial_env tnc2c "${ROOT}" || true
+apply_tnc2c_env
+if [[ -n "${SERIAL_ENV_FILE:-}" ]]; then
+  echo "Using serial env: ${SERIAL_ENV_FILE}" >&2
+else
+  echo "WARN: no tnc2c-serial.env found — using ${TNC_DEV} ${TNC_BAUD} ${TNC_LINE}" >&2
+fi
+exec python3 "${ROOT}/tnc2c-boot-wait.py" "${TNC_DEV}" --baud "${TNC_BAUD}" --line "${TNC_LINE}" "$@"
diff --git a/stacks/tncs/tnc2c-chat.sh b/stacks/tncs/tnc2c-chat.sh
new file mode 100755
index 0000000..9323b5e
--- /dev/null
+++ b/stacks/tncs/tnc2c-chat.sh
@@ -0,0 +1,52 @@
+#!/bin/bash
+# Quick TNC2C terminal check on /dev/ttyS4 (no RF required).
+# WARNING: kiss on / MONitor can KEY PTT and transmit on the radio!
+# For passive RX only use: ./tnc2c-listen.sh
+# Usage: ./tnc2c-chat.sh [baud] [line]
+#   line: 7e1 | 8n1   (default from $TNC2C_LINE or 9600/7e1)
+
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=/dev/null
+[[ -f "$ROOT/tnc2c-serial.env" ]] && source "$ROOT/tnc2c-serial.env"
+
+DEV="${TNC2C_DEV:-/dev/ttyS4}"
+BAUD="${1:-${TNC2C_BAUD:-19200}}"
+LINE="${2:-${TNC2C_LINE:-7e1}}"
+
+case "$LINE" in
+7e1|7E1) STTY="cs7 parenb -cstopb" ;;
+8n1|8N1) STTY="cs8 -parenb -cstopb" ;;
+*) echo "Unknown line format: $LINE (use 7e1 or 8n1)" >&2; exit 1 ;;
+esac
+
+if [[ ! -r "$DEV" || ! -w "$DEV" ]]; then
+    echo "Cannot access $DEV (dialout group?)" >&2
+    exit 1
+fi
+
+echo "TNC2C chat: $DEV @ ${BAUD} ${LINE}"
+stty -F "$DEV" "$BAUD" $STTY raw -echo -icanon min 0 time 10
+
+exec 3<>"$DEV"
+
+printf '\r' >&3
+sleep 0.5
+timeout 2 cat <&3 | xxd -g1 | head -8 || true
+
+# Do NOT send kiss on — keys PTT. Only safe host echo probes:
+for cmd in '' INFO HELP; do
+    echo "--- $cmd ---"
+    if [[ -n "$cmd" ]]; then
+        printf '%s\r' "$cmd" >&3
+    else
+        printf '\r' >&3
+    fi
+    sleep 1
+    timeout 4 cat <&3 | tee /tmp/tnc2c-last.bin | xxd -g1 | head -12
+    strings -n 3 /tmp/tnc2c-last.bin || true
+done
+
+exec 3<&-
+exec 3>&-
diff --git a/stacks/tncs/tnc2c-check.sh b/stacks/tncs/tnc2c-check.sh
new file mode 100755
index 0000000..c0ab705
--- /dev/null
+++ b/stacks/tncs/tnc2c-check.sh
@@ -0,0 +1,62 @@
+#!/bin/bash
+# Preflight: HyBBX off? handshake OK? quick echo on TNC2C.
+# Usage: ./tnc2c-check.sh [device]
+
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=/dev/null
+[[ -f "$ROOT/tnc2c-serial.env" ]] && source "$ROOT/tnc2c-serial.env"
+
+DEV="${1:-${TNC2C_DEV:-/dev/ttyS4}}"
+BAUD="${TNC2C_BAUD:-19200}"
+LINE="${TNC2C_LINE:-7e1}"
+
+echo "=== TNC2C check: $DEV (${BAUD} ${LINE}) ==="
+
+if pgrep -x hybbx >/dev/null 2>&1; then
+    echo "WARN: hybbx is running ($(pgrep -x hybbx | tr '\n' ' ')) - port may be in use"
+fi
+
+if fuser -s "$DEV" 2>/dev/null; then
+    echo "WARN: $DEV in use:"
+    fuser -v "$DEV" 2>&1 || true
+else
+    echo "OK: $DEV not in use"
+fi
+
+if [[ ! -r "$DEV" || ! -w "$DEV" ]]; then
+    echo "FAIL: no access to $DEV (dialout group?)" >&2
+    exit 1
+fi
+
+case "$LINE" in
+7e1|7E1) STTY="cs7 parenb -cstopb" ;;
+8n1|8N1) STTY="cs8 -parenb -cstopb" ;;
+*) echo "Unknown line: $LINE" >&2; exit 1 ;;
+esac
+
+stty -F "$DEV" "$BAUD" $STTY raw -echo min 0 time 5
+
+python3 <<PY
+import fcntl, os, struct, time
+
+TIOCMGET = 0x5415
+fd = os.open("$DEV", os.O_RDWR | os.O_NOCTTY)
+flags = struct.unpack("I", fcntl.ioctl(fd, TIOCMGET, struct.pack("I", 0)))[0]
+names = [(0x004, "RTS"), (0x008, "CTS"), (0x002, "DTR"), (0x100, "DSR")]
+for bit, name in names:
+    print(f"  {name}={'1' if flags & bit else '0'}")
+os.write(fd, b"INFO\r")
+time.sleep(0.8)
+data = os.read(fd, 512)
+os.close(fd)
+print(f"  RX {len(data)} bytes:", data[:80])
+PY
+
+if [[ -x "$ROOT/tnc2c-probe" ]]; then
+    echo "--- tnc2c-probe (single port) ---"
+    "$ROOT/tnc2c-probe" "$DEV" 2>&1 | tail -20
+fi
+
+echo "=== done ==="
diff --git a/stacks/tncs/tnc2c-expect.exp b/stacks/tncs/tnc2c-expect.exp
new file mode 100755
index 0000000..eaef9c0
--- /dev/null
+++ b/stacks/tncs/tnc2c-expect.exp
@@ -0,0 +1,80 @@
+#!/usr/bin/expect -f
+# Auto-detect TNC2C host line on a serial device.
+# Usage: ./tnc2c-expect.exp /dev/ttyS4
+
+set timeout 6
+if {[llength $argv] < 1} {
+    puts "Usage: $argv0 <device>"
+    exit 1
+}
+set dev [lindex $argv 0]
+
+proc try_line {dev baud parity} {
+    global timeout
+    if {$parity eq "7E1"} {
+        spawn stty -F $dev $baud cs7 parenb -cstopb raw -echo min 0 time 10
+        expect eof
+    } else {
+        spawn stty -F $dev $baud cs8 -parenb -cstopb raw -echo min 0 time 10
+        expect eof
+    }
+
+    spawn cu -l $dev -s $baud
+    if {[catch {expect {
+        -re "." { }
+        timeout { }
+    }}]} {
+        catch {close}
+        return 0
+    }
+
+    set score 0
+    set sample ""
+
+    send "\r\r"
+    sleep 1
+    send "INFO\r"
+    sleep 3
+
+    if {[catch {set sample $expect_out(buffer)}]} {
+        set sample ""
+    }
+
+    if {[string match -nocase *cmd:* $sample]} { incr score 300 }
+    if {[string match -nocase *MYCALL* $sample]} { incr score 150 }
+    if {[string match -nocase *TXDELAY* $sample]} { incr score 100 }
+    if {[string match -nocase *INFO* $sample]} { incr score 20 }
+    incr score [string length $sample]
+
+    puts "  $baud $parity score=$score"
+    if {$sample ne ""} {
+        set short [string range $sample 0 180]
+        regsub -all {\r} $short {\\r} short
+        regsub -all {\n} $short {\\n} short
+        puts "    $short"
+    }
+
+    send "~.\r"
+    catch {close}
+    return $score
+}
+
+puts "TNC2C expect scan on $dev"
+set best 0
+set bestcfg ""
+
+foreach baud {9600 2400 4800 1200 19200 600 300} {
+    foreach parity {7E1 8N1} {
+        set s [try_line $dev $baud $parity]
+        if {$s > $best} {
+            set best $s
+            set bestcfg "$baud $parity"
+        }
+    }
+}
+
+puts "\nBest: $bestcfg (score=$best)"
+if {$best >= 200} {
+    exit 0
+}
+exit 2
diff --git a/stacks/tncs/tnc2c-find.c b/stacks/tncs/tnc2c-find.c
new file mode 100644
index 0000000..fe26a1b
--- /dev/null
+++ b/stacks/tncs/tnc2c-find.c
@@ -0,0 +1,306 @@
+/*
+ * tnc2c-find — detect host baud/format for Landolt TNC2C on a serial port.
+ * Tries TERM jumper speeds (300..9600) with 7E1 and 8N1, scores cmd:/INFO replies.
+ *
+ * Build: make find
+ * Run:   ./tnc2c-find /dev/ttyS4
+ */
+
+#if defined(__linux__) || defined(__GLIBC__)
+#define _DEFAULT_SOURCE 1
+#define _GNU_SOURCE 1
+#endif
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <time.h>
+#include <unistd.h>
+
+typedef struct line_profile {
+    const char *label;
+    speed_t speed;
+    unsigned int baud;
+    tcflag_t databits;
+    tcflag_t parity;
+} line_profile_t;
+
+static const line_profile_t PROFILES[] = {
+    { "19200-8N1", B19200, 19200, CS8, 0 },
+    { "19200-7E1", B19200, 19200, CS7, PARENB },
+    { "9600-7E1",  B9600,  9600,  CS7, PARENB },
+    { "2400-7E1",  B2400,  2400,  CS7, PARENB },
+    { "4800-7E1",  B4800,  4800,  CS7, PARENB },
+    { "1200-7E1",  B1200,  1200,  CS7, PARENB },
+    { "9600-8N1",  B9600,  9600,  CS8, 0 },
+    { "2400-8N1",  B2400,  2400,  CS8, 0 },
+    { "4800-8N1",  B4800,  4800,  CS8, 0 },
+    { "1200-8N1",  B1200,  1200,  CS8, 0 },
+    { "600-7E1",   B600,   600,   CS7, PARENB },
+    { "300-7E1",   B300,   300,   CS7, PARENB },
+    { "600-8N1",   B600,   600,   CS8, 0 },
+    { "300-8N1",   B300,   300,   CS8, 0 },
+};
+
+static int sleep_ms(unsigned ms)
+{
+    struct timespec ts;
+
+    ts.tv_sec = (time_t)(ms / 1000u);
+    ts.tv_nsec = (long)(ms % 1000u) * 1000000L;
+    return nanosleep(&ts, NULL);
+}
+
+static int set_modem_lines(int fd)
+{
+#ifdef TIOCMGET
+    int flags;
+
+    if (ioctl(fd, TIOCMGET, &flags) != 0) {
+        return -1;
+    }
+    flags |= TIOCM_RTS | TIOCM_DTR;
+    return ioctl(fd, TIOCMSET, &flags);
+#else
+    (void)fd;
+    return 0;
+#endif
+}
+
+static int open_line(const char *device, const line_profile_t *profile)
+{
+    struct termios tty;
+    int fd;
+
+    fd = open(device, O_RDWR | O_NOCTTY | O_NONBLOCK);
+    if (fd < 0) {
+        return -1;
+    }
+
+    if (tcgetattr(fd, &tty) != 0) {
+        close(fd);
+        return -1;
+    }
+
+    cfmakeraw(&tty);
+    tty.c_cflag |= (CLOCAL | CREAD);
+    tty.c_cflag &= ~(CSIZE | PARENB | PARODD | CSTOPB);
+    tty.c_cflag |= profile->databits;
+    if (profile->parity != 0) {
+        tty.c_cflag |= profile->parity;
+    }
+    tty.c_cc[VMIN] = 0;
+    tty.c_cc[VTIME] = 10;
+
+#if defined(__linux__) || defined(__GLIBC__)
+    if (cfsetspeed(&tty, profile->speed) != 0) {
+        cfsetispeed(&tty, profile->speed);
+        cfsetospeed(&tty, profile->speed);
+    }
+#else
+    cfsetispeed(&tty, profile->speed);
+    cfsetospeed(&tty, profile->speed);
+#endif
+
+    if (tcsetattr(fd, TCSANOW, &tty) != 0) {
+        close(fd);
+        return -1;
+    }
+
+    tcflush(fd, TCIOFLUSH);
+    (void)set_modem_lines(fd);
+    return fd;
+}
+
+static size_t read_for(int fd, unsigned char *buf, size_t cap, unsigned ms)
+{
+    size_t total = 0;
+    unsigned elapsed = 0;
+
+    while (elapsed < ms && total < cap) {
+        ssize_t n = read(fd, buf + total, cap - total);
+
+        if (n > 0) {
+            total += (size_t)n;
+            elapsed = 0;
+            continue;
+        }
+        if (n < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+            break;
+        }
+        sleep_ms(40);
+        elapsed += 40;
+    }
+
+    return total;
+}
+
+static int score_reply(const unsigned char *buf, size_t len)
+{
+    size_t i;
+    int score = 0;
+    int printable = 0;
+
+    if (len == 0) {
+        return 0;
+    }
+
+    for (i = 0; i < len; i++) {
+        unsigned char c = buf[i];
+
+        if (c >= 0x20 && c < 0x7f) {
+            printable++;
+        }
+    }
+
+    score += printable;
+    if (memmem(buf, len, "cmd:", 4) != NULL ||
+        memmem(buf, len, "CMD:", 4) != NULL) {
+        score += 200;
+    }
+    if (memmem(buf, len, "MYCALL", 6) != NULL ||
+        memmem(buf, len, "mycall", 6) != NULL) {
+        score += 120;
+    }
+    if (memmem(buf, len, "TXDELAY", 7) != NULL) {
+        score += 80;
+    }
+    if (memmem(buf, len, "KISS", 4) != NULL) {
+        score += 40;
+    }
+    if (len > 40) {
+        score += 60;
+    } else if (len > 15) {
+        score += 20;
+    }
+
+    /* Pure echo of a short command is weak. */
+    if (len <= 12 && printable > 0 && printable == (int)len) {
+        score -= 10;
+    }
+
+    return score;
+}
+
+static void dump_ascii(const unsigned char *buf, size_t len)
+{
+    size_t i;
+
+    for (i = 0; i < len; i++) {
+        unsigned char c = buf[i];
+
+        if (c == '\r') {
+            fputs("\\r", stdout);
+        } else if (c == '\n') {
+            fputs("\\n", stdout);
+        } else if (c >= 0x20 && c < 0x7f) {
+            putchar((int)c);
+        } else {
+            printf("\\x%02x", c);
+        }
+    }
+}
+
+static int try_profile(const char *device, const line_profile_t *profile,
+                       int *best_score, char *best_label, size_t label_cap,
+                       unsigned char *best_buf, size_t *best_len,
+                       size_t best_cap)
+{
+    int fd;
+    unsigned char buf[4096];
+    size_t len;
+    int score;
+    const char *seq[] = { "\r\r\r", "INFO\r" };
+    size_t s;
+
+    fd = open_line(device, profile);
+    if (fd < 0) {
+        return -1;
+    }
+
+    sleep_ms(200);
+    len = 0;
+    for (s = 0; s < sizeof(seq) / sizeof(seq[0]); s++) {
+        (void)write(fd, seq[s], strlen(seq[s]));
+        sleep_ms(400);
+        len += read_for(fd, buf + len, sizeof(buf) - len, 3500);
+    }
+
+    close(fd);
+    score = score_reply(buf, len);
+
+    if (score > *best_score) {
+        *best_score = score;
+        snprintf(best_label, label_cap, "%s", profile->label);
+        if (len > best_cap) {
+            len = best_cap;
+        }
+        memcpy(best_buf, buf, len);
+        *best_len = len;
+    }
+
+    if (score >= 30) {
+        printf("  %-12s score=%4d len=%4zu  ",
+               profile->label, score, len);
+        dump_ascii(buf, len < 120 ? len : 120);
+        putchar('\n');
+    }
+
+    return score;
+}
+
+int main(int argc, char **argv)
+{
+    const char *device;
+    size_t i;
+    int best_score = -1;
+    char best_label[32] = "";
+    unsigned char best_buf[4096];
+    size_t best_len = 0;
+
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <serial-device>\n", argv[0]);
+        return 1;
+    }
+
+    device = argv[1];
+    printf("TNC2C auto-detect on %s\n", device);
+    printf("(RTS/DTR on, probe cmd:/INFO; best TERM jumper speeds)\n\n");
+
+    for (i = 0; i < sizeof(PROFILES) / sizeof(PROFILES[0]); i++) {
+        (void)try_profile(device, &PROFILES[i], &best_score, best_label,
+                          sizeof(best_label), best_buf, &best_len,
+                          sizeof(best_buf));
+    }
+
+    printf("\n");
+    if (best_score < 0) {
+        printf("No profile could open %s\n", device);
+        return 2;
+    }
+
+    printf("Best profile: %s (score=%d, %zu bytes)\n",
+           best_label[0] ? best_label : "?", best_score, best_len);
+    if (best_len > 0) {
+        printf("Sample: ");
+        dump_ascii(best_buf, best_len < 200 ? best_len : 200);
+        printf("\n");
+    }
+
+    if (best_score >= 200) {
+        printf("\nHost mode OK — use baud/serial_line from profile above in HyBBX.\n");
+        return 0;
+    }
+
+    if (best_score >= 30) {
+        printf("\nPartial link — check TERM jumper; try: tnc2c-host-reset %s\n", device);
+        return 3;
+    }
+
+    printf("\nNo usable TNC dialog detected.\n");
+    return 4;
+}
diff --git a/stacks/tncs/tnc2c-health.py b/stacks/tncs/tnc2c-health.py
new file mode 100644
index 0000000..642b6cf
--- /dev/null
+++ b/stacks/tncs/tnc2c-health.py
@@ -0,0 +1,445 @@
+#!/usr/bin/env python3
+"""
+tnc2c-health - full Landolt TNC2C health check (serial, host, KISS, optional TX).
+
+Does NOT replace visual LED checks (Power/PTT/CD/Connected/Status).
+
+Usage:
+  ./tnc2c-health.sh
+  ./tnc2c-health.sh /dev/ttyS4
+  ./tnc2c-health.sh --tx          # include KISS TX attempt (keys PTT!)
+  ./tnc2c-health.sh --tx --quiet
+"""
+
+from __future__ import annotations
+
+import argparse
+import fcntl
+import os
+import struct
+import sys
+import time
+import termios
+from dataclasses import dataclass, field
+from typing import Optional
+
+BAUD_MAP = {
+    300: termios.B300,
+    600: termios.B600,
+    1200: termios.B1200,
+    2400: termios.B2400,
+    4800: termios.B4800,
+    9600: termios.B9600,
+    19200: termios.B19200,
+}
+
+PROFILES = [
+    ("19200-8N1", 19200, False),
+    ("19200-7E1", 19200, True),
+    ("9600-7E1", 9600, True),
+    ("9600-8N1", 9600, False),
+    ("2400-7E1", 2400, True),
+    ("4800-7E1", 4800, True),
+]
+
+HOST_MARKERS = (
+    b"cmd:",
+    b"CMD:",
+    b"TNC",
+    b"***",
+    b"help",
+    b"HELP",
+    b"version",
+    b"Version",
+    b"MYCALL",
+    b"KISS was",
+    b"KISS is",
+)
+
+ECHO_ONLY_MARKERS = (
+    b"kiss off",
+    b"kiss on",
+    b"INFO",
+    b"HELP",
+    b"RESTART",
+)
+
+
+@dataclass
+class ProfileResult:
+    name: str
+    rts: bool
+    cts: bool
+    dsr: bool
+    info_reply: bytes = b""
+    host_score: int = 0
+    echo_only: bool = False
+    has_cmd_prompt: bool = False
+    kiss_ack: bool = False
+    kiss_echo_only: bool = False
+    notes: list[str] = field(default_factory=list)
+
+
+def load_env(path: str) -> dict[str, str]:
+    env: dict[str, str] = {}
+    if not os.path.isfile(path):
+        return env
+    with open(path, encoding="utf-8") as f:
+        for line in f:
+            line = line.strip()
+            if not line or line.startswith("#"):
+                continue
+            if "=" in line:
+                k, v = line.split("=", 1)
+                env[k.strip()] = v.strip()
+    return env
+
+
+def open_serial(dev: str, baud: int, seven_e1: bool) -> int:
+    fd = os.open(dev, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+    if baud not in BAUD_MAP:
+        raise ValueError(f"unsupported baud {baud}")
+    t = termios.tcgetattr(fd)
+    t[0] = t[1] = 0
+    t[2] = termios.CLOCAL | termios.CREAD | (termios.CS7 if seven_e1 else termios.CS8)
+    if seven_e1:
+        t[2] |= termios.PARENB
+    speed = BAUD_MAP[baud]
+    t[3] = t[4] = t[5] = speed
+    t[6][termios.VMIN] = 0
+    t[6][termios.VTIME] = 5
+    termios.tcsetattr(fd, termios.TCSANOW, t)
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    flags |= 0x004 | 0x002  # RTS DTR
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    return fd
+
+
+def modem_lines(fd: int) -> tuple[bool, bool, bool]:
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    return bool(flags & 0x004), bool(flags & 0x008), bool(flags & 0x100)
+
+
+def read_for(fd: int, seconds: float) -> bytes:
+    end = time.time() + seconds
+    chunks: list[bytes] = []
+    while time.time() < end:
+        try:
+            b = os.read(fd, 4096)
+            if b:
+                chunks.append(b)
+        except BlockingIOError:
+            time.sleep(0.03)
+    return b"".join(chunks)
+
+
+def write_flush(fd: int, data: bytes) -> None:
+    os.write(fd, data)
+    termios.tcdrain(fd)
+
+
+def score_host_reply(cmd: bytes, reply: bytes) -> tuple[int, bool, bool]:
+    if not reply:
+        return 0, False, False
+
+    stripped_cmd = cmd.strip(b"\r\n")
+    echo_only = reply.strip() == stripped_cmd or reply.strip() in (
+        stripped_cmd,
+        stripped_cmd + b"\r",
+        stripped_cmd + b"\n",
+        stripped_cmd + b"\r\n",
+    )
+
+    score = 0
+    if b"cmd:" in reply.lower() or b"cmd>" in reply.lower():
+        score += 50
+    for m in HOST_MARKERS:
+        if m.lower() in reply.lower():
+            score += 10
+    if len(reply) > len(cmd) + 4 and not echo_only:
+        score += 5
+    if b"\n" in reply and len(reply) > 20:
+        score += 5
+
+    has_cmd = b"cmd:" in reply.lower()
+    return score, echo_only, has_cmd
+
+
+def kiss_escape(data: bytes) -> bytes:
+    out = bytearray()
+    for b in data:
+        if b == 0xC0:
+            out.extend((0xDB, 0xDC))
+        elif b == 0xDB:
+            out.extend((0xDB, 0xDD))
+        else:
+            out.append(b)
+    return bytes(out)
+
+
+def ax25_addr(call: str, ssid: int, last: bool) -> bytes:
+    call = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in call)
+    ssid_b = ((ssid & 0x0F) << 1) | (0x01 if last else 0x00)
+    return raw + bytes([ssid_b])
+
+
+def ax25_crc(data: bytes) -> int:
+    crc = 0xFFFF
+    for b in data:
+        crc ^= b
+        for _ in range(8):
+            crc = (crc >> 1) ^ 0x8408 if crc & 1 else crc >> 1
+    return crc ^ 0xFFFF
+
+
+def ax25_ui(src: str, dst: str, info: bytes) -> bytes:
+    body = ax25_addr(dst, 0, False) + ax25_addr(src, 0, True)
+    body += b"\x03\xF0" + info
+    crc = ax25_crc(body)
+    return body + bytes((crc & 0xFF, crc >> 8))
+
+
+def kiss_frame(port: int, payload: bytes) -> bytes:
+    return b"\xC0" + bytes([port & 0x0F]) + kiss_escape(payload) + b"\xC0"
+
+
+def test_profile(dev: str, name: str, baud: int, seven_e1: bool) -> ProfileResult:
+    res = ProfileResult(name=name, rts=False, cts=False, dsr=False)
+    fd = open_serial(dev, baud, seven_e1)
+    res.rts, res.cts, res.dsr = modem_lines(fd)
+
+    # break out of possible modes
+    write_flush(fd, b"\x03\x1a")  # Ctrl+C, Ctrl+Z
+    time.sleep(0.2)
+    read_for(fd, 0.3)
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.4)
+    read_for(fd, 0.4)
+
+    write_flush(fd, b"\r")
+    time.sleep(0.2)
+    read_for(fd, 0.3)
+
+    cmd = b"INFO\r"
+    write_flush(fd, cmd)
+    time.sleep(0.6)
+    info = read_for(fd, 1.0)
+    res.info_reply = info
+    score, echo, has_cmd = score_host_reply(cmd, info)
+    res.host_score = score
+    res.echo_only = echo and score < 15
+    res.has_cmd_prompt = has_cmd
+
+    write_flush(fd, b"HELP\r")
+    time.sleep(0.5)
+    help_r = read_for(fd, 0.8)
+    hs, echo2, hc = score_host_reply(b"HELP\r", help_r)
+    res.host_score = max(res.host_score, hs)
+    if hc:
+        res.has_cmd_prompt = True
+    if echo2 and hs < 10:
+        res.echo_only = res.echo_only or True
+
+    write_flush(fd, b"kiss on\r")
+    time.sleep(0.5)
+    kiss_r = read_for(fd, 0.6)
+    if b"kiss" in kiss_r.lower() and len(kiss_r) < 32:
+        res.kiss_echo_only = True
+    if b"on" in kiss_r.lower() and len(kiss_r) > 8 and not res.kiss_echo_only:
+        res.kiss_ack = True
+
+    passive = read_for(fd, 1.0)
+    if passive:
+        res.notes.append(f"passive_after_kiss={len(passive)}B")
+
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.2)
+    os.close(fd)
+    return res
+
+
+def run_tx_test(dev: str, profile_name: str, baud: int, seven_e1: bool) -> dict:
+    fd = open_serial(dev, baud, seven_e1)
+    write_flush(fd, b"kiss off\r")
+    time.sleep(0.4)
+    read_for(fd, 0.3)
+    write_flush(fd, b"kiss on\r")
+    time.sleep(0.5)
+    read_for(fd, 0.3)
+
+    payload = ax25_ui("TEST-0", "CQ", b"HEALTH")
+    pkt = kiss_frame(0, payload)
+    write_flush(fd, pkt)
+    time.sleep(3.0)
+    rx = read_for(fd, 1.0)
+    write_flush(fd, b"kiss off\r")
+    os.close(fd)
+
+    echoed = pkt in rx or payload in rx
+    return {
+        "sent": len(pkt),
+        "rx_len": len(rx),
+        "frame_echoed_back": echoed,
+        "rx_sample": rx[:96],
+    }
+
+
+def print_header(title: str) -> None:
+    print(f"\n{'=' * 60}")
+    print(title)
+    print("=" * 60)
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="TNC2C full health check")
+    parser.add_argument("device", nargs="?", default=None)
+    parser.add_argument("--tx", action="store_true", help="attempt KISS TX (keys PTT)")
+    parser.add_argument("--quiet", action="store_true")
+    args = parser.parse_args()
+
+    root = os.path.dirname(os.path.abspath(__file__))
+    env = load_env(os.path.join(root, "tnc2c-serial.env"))
+    dev = args.device or env.get("TNC2C_DEV", "/dev/ttyS4")
+
+    print_header("TNC2C HEALTH CHECK")
+    print(f"Device: {dev}")
+    print(f"Time:   {time.strftime('%Y-%m-%d %H:%M:%S')}")
+
+    # --- preflight ---
+    print_header("1) Preflight")
+    if os.system("pgrep -x hybbx >/dev/null 2>&1") == 0:
+        print("FAIL: hybbx is running - stop it first")
+        return 2
+    print("OK: hybbx not active")
+
+    if not os.access(dev, os.R_OK | os.W_OK):
+        print(f"FAIL: no access to {dev} (dialout group?)")
+        return 2
+    print(f"OK: access to {dev}")
+
+    # --- profile sweep ---
+    print_header("2) Serial profiles (host detection)")
+    results: list[ProfileResult] = []
+    for name, baud, seven in PROFILES:
+        try:
+            r = test_profile(dev, name, baud, seven)
+            results.append(r)
+            info_preview = r.info_reply[:40].replace(b"\r", b"\\r").replace(b"\n", b"\\n")
+            print(
+                f"  {name:12} RTS={int(r.rts)} CTS={int(r.cts)} DSR={int(r.dsr)} "
+                f"score={r.host_score:2} cmd={int(r.has_cmd_prompt)} "
+                f"echo_only={int(r.echo_only)} INFO={info_preview!r}"
+            )
+        except OSError as e:
+            print(f"  {name:12} ERROR: {e}")
+
+    best = max(results, key=lambda x: x.host_score, default=None)
+    if best is None:
+        print("FAIL: no profiles tested")
+        return 2
+
+    # pick working line: prefer env, else best score, else 19200-8N1 clean echo
+    preferred = env.get("TNC2C_LINE", "8n1").lower()
+    work_name = best.name
+    work_baud = 19200
+    work_7e1 = preferred.startswith("7e")
+    for name, baud, seven in PROFILES:
+        if name == best.name:
+            work_baud, work_7e1 = baud, seven
+            break
+    if best.host_score < 15:
+        for r in results:
+            if r.name == "19200-8N1" and r.info_reply.strip() in (
+                b"INFO\r\n",
+                b"INFO\r",
+                b"INFO",
+            ):
+                work_name = r.name
+                work_baud, work_7e1 = 19200, False
+                break
+
+    print(f"\nBest profile (host score): {best.name} (score={best.host_score})")
+    print(f"Working profile for tests: {work_name}")
+
+    # --- diagnosis ---
+    print_header("3) Serial / host mode diagnosis")
+    any_cmd = any(r.has_cmd_prompt for r in results)
+    mostly_echo = all(r.echo_only or r.host_score < 15 for r in results)
+
+    if any_cmd:
+        print("OK: real host mode (cmd: prompt) detected")
+    elif mostly_echo:
+        print("WARN: command echo only - no cmd: prompt, no INFO listing")
+        print("      -> TNC probably does NOT process commands")
+        print("      -> KISS/PTT via software probably ineffective")
+        print("      -> LEDs do not change (matches this picture)")
+    else:
+        print("PARTIAL: replies present but no clear host dialog")
+
+    if all(not r.cts for r in results):
+        print("WARN: CTS=0 on all profiles - handshake problem")
+        print("      -> bridge DB25 pins 4 and 5 in cable if needed (manual)")
+
+    # --- RF / LED manual ---
+    print_header("4) TNC LEDs (no radio / with radio)")
+    print("No radio (audio off): Pin4 open -> LED3 (CD) often ON continuously (normal)")
+    print("With radio: LED3 should be ON with noise, OFF with squelch closed")
+    print("LED 1 Power | LED 2 PTT | LED 3 CD | LED 4 Connected | LED 5 Status")
+
+    # --- optional TX ---
+    print_header("5) KISS send test")
+    if not args.tx:
+        print("Skipped (without --tx). To test: ./tnc2c-health.sh --tx")
+    else:
+        print("WARNING: sends KISS frame - PTT may key!")
+        tx = run_tx_test(dev, work_name, work_baud, work_7e1)
+        print(f"  Profile: {work_name}")
+        print(f"  Sent: {tx['sent']} bytes KISS")
+        print(f"  RX: {tx['rx_len']} bytes")
+        print(f"  Frame echoed back directly: {tx['frame_echoed_back']}")
+        if tx["frame_echoed_back"]:
+            print("  WARN: frame returns unchanged -> possible serial loopback,")
+            print("        not sent over radio")
+        print("  -> CHECK NOW: LED2 (PTT) and S-meter on radio")
+
+    # --- hardware checklist ---
+    print_header("6) Hardware checklist (if not transmitting)")
+    print("  [ ] PTT  radio red      -> TNC DIN Pin 3")
+    print("  [ ] GND  radio black    -> TNC DIN Pin 2")
+    print("  [ ] TX   radio white    -> TNC DIN Pin 1")
+    print("  [ ] RX   3.5mm tip      -> TNC DIN Pin 4 (left center)")
+    print("  [ ] VOX  on AE6110      -> OFF")
+    print("  [ ] Mike gain on TNC    -> increase slowly (pot on modem)")
+    print("  [ ] RADIO bridge TNC    -> 2400 baud (Pos. 2)")
+    print("  [ ] TERM bridge TNC     -> 19200")
+
+    # --- software checklist ---
+    print_header("7) Software / next steps")
+    if mostly_echo and not any_cmd:
+        print("  1. Software recovery (no power cycle):")
+        print("       ./tnc2c-host-reset.sh --kiss")
+        print("       ./tnc2c-boot-wait.sh --recover-only")
+        print("  2. Expect cmd: or TheFirmware banner after recovery")
+        print("  3. Rescue only if still echo-only: ./tnc2c-boot-wait.sh + power cycle (DTR high)")
+        print("  4. When cmd: appears -> ./tnc2c-health.sh --tx")
+        print("  5. HyBBX: kiss_entry=none when max25d owns KISS (see docs/TNC-RECOVERY.md)")
+    else:
+        print(f"  Serial OK with {work_name}")
+        print("  ./tnc2c-send-test.sh for single send test")
+        print("  HyBBX: baud=19200 serial_line=8n1 (this device)")
+
+    print_header("SUMMARY")
+    status = "DEGRADED" if mostly_echo and not any_cmd else "OK"
+    print(f"Overall: {status}")
+    print(f"Device: {dev}")
+    print(f"Best host profile: {best.name} (score={best.host_score})")
+    print(f"CTS on best: {int(best.cts)}  echo_only: {int(best.echo_only)}  cmd: {int(best.has_cmd_prompt)}")
+
+    return 1 if status == "DEGRADED" else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-health.sh b/stacks/tncs/tnc2c-health.sh
new file mode 100755
index 0000000..9d9ee10
--- /dev/null
+++ b/stacks/tncs/tnc2c-health.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+# Full TNC2C health check — serial, host mode, KISS, optional TX.
+# Usage:
+#   ./tnc2c-health.sh              # safe, no transmit
+#   ./tnc2c-health.sh --tx         # includes KISS send (PTT!)
+
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+exec python3 "$ROOT/tnc2c-health.py" "$@"
diff --git a/stacks/tncs/tnc2c-host-reset.py b/stacks/tncs/tnc2c-host-reset.py
new file mode 100755
index 0000000..340642f
--- /dev/null
+++ b/stacks/tncs/tnc2c-host-reset.py
@@ -0,0 +1,229 @@
+#!/usr/bin/env python3
+"""
+tnc2c-host-reset - recover TNC-2 class terminal/host mode over serial.
+
+Uses full software recovery ladder (KISS-return, JHOST0, RESTART) — no power
+cycle required unless DTR was low at cold boot.
+
+Usage:
+  ./tnc2c-host-reset.sh
+  ./tnc2c-host-reset.sh /dev/ttyS4
+  ./tnc2c-host-reset.sh --kiss          # recover + enter KISS
+  ./tnc2c-host-reset.sh --power-hint    # remind to cycle TNC power first
+  ./tnc2c-host-reset.sh --no-kiss       # skip KISS reset frame (step 2 only)
+"""
+
+from __future__ import annotations
+
+import argparse
+import importlib.util
+import os
+import sys
+import time
+
+BAUD_DEFAULT = 19200
+LINE_DEFAULT = "8n1"
+
+FIRMWARE_MARKERS = (
+    b"TheFirmware",
+    b"NORD",
+    b"Version 2.7",
+    b"Checksum",
+    b"Copyright",
+    b"DAMA",
+    b"SMACK",
+)
+
+
+def load_recovery():
+    root = os.path.dirname(os.path.abspath(__file__))
+    path = os.path.join(root, "tnc_serial_recovery.py")
+    spec = importlib.util.spec_from_file_location("tnc_serial_recovery", path)
+    if spec is None or spec.loader is None:
+        raise RuntimeError(f"cannot load {path}")
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+def load_env(path: str) -> dict[str, str]:
+    out: dict[str, str] = {}
+    if not os.path.isfile(path):
+        return out
+    with open(path, encoding="utf-8") as f:
+        for line in f:
+            line = line.strip()
+            if not line or line.startswith("#") or "=" not in line:
+                continue
+            k, v = line.split("=", 1)
+            out[k.strip()] = v.strip()
+    return out
+
+
+def parse_line(line: str) -> tuple[int, int]:
+    import termios
+
+    line = line.lower()
+    if line == "7e1":
+        return termios.CS7, termios.PARENB
+    if line == "8n1":
+        return termios.CS8, 0
+    raise ValueError(f"unsupported serial line: {line}")
+
+
+def parse_baud(baud: int) -> int:
+    import termios
+
+    table = {
+        1200: termios.B1200,
+        2400: termios.B2400,
+        4800: termios.B4800,
+        9600: termios.B9600,
+        19200: termios.B19200,
+    }
+    if baud not in table:
+        raise ValueError(f"unsupported baud: {baud}")
+    return table[baud]
+
+
+def open_serial(dev: str, baud: int, line: str) -> int:
+    import fcntl
+    import struct
+    import termios
+
+    speed = parse_baud(baud)
+    databits, parity = parse_line(line)
+    fd = os.open(dev, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+    t = termios.tcgetattr(fd)
+    t[0] = t[1] = 0
+    t[2] = termios.CLOCAL | termios.CREAD | databits | parity
+    t[3] = t[4] = t[5] = speed
+    t[6][termios.VMIN] = 0
+    t[6][termios.VTIME] = 5
+    termios.tcsetattr(fd, termios.TCSANOW, t)
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    flags |= 0x004 | 0x002
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    return fd
+
+
+def read_for(fd: int, seconds: float) -> bytes:
+    end = time.time() + seconds
+    chunks: list[bytes] = []
+    while time.time() < end:
+        try:
+            b = os.read(fd, 4096)
+            if b:
+                chunks.append(b)
+        except BlockingIOError:
+            time.sleep(0.02)
+    return b"".join(chunks)
+
+
+def write_flush(fd: int, data: bytes) -> None:
+    import termios
+
+    os.write(fd, data)
+    termios.tcdrain(fd)
+
+
+POWER_HINT = """\
+Note: If recovery fails (echo only), disconnect TNC power (10-15 s), reconnect
+while DTR+RTS stay high — run tnc2c-boot-wait.sh or this script immediately.
+"""
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(
+        description="TNC host-mode recovery with DTR+RTS (TheFirmware ladder)"
+    )
+    parser.add_argument("device", nargs="?", default=None)
+    parser.add_argument("--baud", type=int, default=None)
+    parser.add_argument("--line", default=None, choices=("8n1", "7e1"))
+    parser.add_argument("--kiss", action="store_true", help="enter KISS after recover")
+    parser.add_argument(
+        "--kiss-entry",
+        default="kiss_on",
+        choices=("kiss_on", "auto"),
+        help="KISS entry method with --kiss",
+    )
+    parser.add_argument("--power-hint", action="store_true")
+    parser.add_argument(
+        "--no-kiss",
+        action="store_true",
+        help="skip KISS return frame in recovery ladder",
+    )
+    args = parser.parse_args()
+
+    root = os.path.dirname(os.path.abspath(__file__))
+    env = load_env(os.path.join(root, "tnc2c-serial.env"))
+    dev = (
+        args.device
+        or env.get("TNC_DEV")
+        or env.get("TNC2C_DEV")
+        or env.get("PKTNC2_DEV")
+        or "/dev/ttyS4"
+    )
+    baud = args.baud or int(
+        env.get("TNC_BAUD") or env.get("TNC2C_BAUD") or env.get("PKTNC2_BAUD") or BAUD_DEFAULT
+    )
+    line = args.line or env.get("TNC_LINE") or env.get("TNC2C_LINE") or LINE_DEFAULT
+
+    if args.power_hint:
+        print(POWER_HINT)
+
+    if not os.path.exists(dev):
+        print(f"FAIL: {dev} does not exist", file=sys.stderr)
+        return 2
+    if not os.access(dev, os.R_OK | os.W_OK):
+        print(f"FAIL: no access to {dev}", file=sys.stderr)
+        return 2
+
+    recovery = load_recovery()
+
+    print(f"TNC host-reset @ {dev} {baud} {line.upper()} (DTR+RTS high)")
+    try:
+        fd = open_serial(dev, baud, line)
+    except OSError as e:
+        print(f"FAIL: {dev}: {e}", file=sys.stderr)
+        return 2
+
+    def wf(data: bytes) -> None:
+        write_flush(fd, data)
+
+    def rf(seconds: float) -> bytes:
+        return read_for(fd, seconds)
+
+    def log(msg: str) -> None:
+        print(f"  {msg}")
+
+    ok, received = recovery.recover_terminal(
+        wf, rf, skip_kiss_frame=args.no_kiss, log=log
+    )
+
+    if ok and args.kiss:
+        recovery.enter_kiss(wf, rf, args.kiss_entry)
+        print("  KISS entry sent")
+
+    os.close(fd)
+
+    print()
+    if ok:
+        label = "HOST+KISS" if args.kiss else "HOST"
+        print(f"OK: {label} - terminal mode active (software recovery)")
+        if received:
+            text = received.decode("ascii", errors="replace")
+            if "NORD" in text or "TheFirmware" in text:
+                for line_out in text.splitlines():
+                    if any(m.decode() in line_out for m in FIRMWARE_MARKERS[:5]):
+                        print(f"  | {line_out.strip()}")
+        return 0
+
+    print("FAIL: software recovery exhausted")
+    print("  -> Power-cycle with DTR high: ./tnc2c-boot-wait.sh")
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-host-reset.sh b/stacks/tncs/tnc2c-host-reset.sh
new file mode 100755
index 0000000..d0d1499
--- /dev/null
+++ b/stacks/tncs/tnc2c-host-reset.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+# TNC2C host-mode recovery — DTR+RTS high, software ladder (no power cycle usually).
+#
+# Usage:
+#   ./tnc2c-host-reset.sh
+#   ./tnc2c-host-reset.sh --kiss       # recover + enter KISS
+#   ./tnc2c-host-reset.sh --power-hint # if recovery fails: cycle power + boot-wait
+#   ./tnc2c-host-reset.sh --no-kiss    # skip KISS return frame in ladder
+
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=load-serial-env.sh
+source "${ROOT}/load-serial-env.sh"
+load_serial_env tnc2c "${ROOT}" || true
+apply_tnc2c_env
+if [[ -n "${SERIAL_ENV_FILE:-}" ]]; then
+  echo "Using serial env: ${SERIAL_ENV_FILE}" >&2
+else
+  echo "WARN: no tnc2c-serial.env found — using ${TNC_DEV} ${TNC_BAUD} ${TNC_LINE}" >&2
+fi
+exec python3 "${ROOT}/tnc2c-host-reset.py" "${TNC_DEV}" --baud "${TNC_BAUD}" --line "${TNC_LINE}" "$@"
diff --git a/stacks/tncs/tnc2c-hybbx-beacon-once.sh b/stacks/tncs/tnc2c-hybbx-beacon-once.sh
new file mode 100755
index 0000000..7249191
--- /dev/null
+++ b/stacks/tncs/tnc2c-hybbx-beacon-once.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+# One-shot AX.25 beacon like INI [broadcast] - stop HyBBX briefly, then restart.
+# Auto-beacon (300s) runs from new HyBBX start.
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+MSG="${1:-Broadcast: CB-0 online}"
+SRC="${2:-CB-0}"
+DST="${3:-*}"
+
+echo "Manual beacon: ${SRC} -> ${DST}: ${MSG}"
+if pgrep -x hybbx >/dev/null; then
+    echo "Stopping HyBBX ..."
+    pkill -x hybbx || sudo -u hybbx pkill -x hybbx
+    sleep 2
+fi
+"$ROOT/tnc2c-send-test.sh" "$MSG" "$SRC" "$DST"
+echo "Starting HyBBX ... (auto-beacon in ~300s)"
+sudo -u hybbx /etc/hybbx/hybbx-start &
+sleep 3
+pgrep -a hybbx || echo "WARN: hybbx not started - try boot-wait + hybbx-start"
+echo "Log: tail -f /etc/hybbx/logs/*.log  - expect: [broadcast] ax25"
diff --git a/stacks/tncs/tnc2c-integration-test.py b/stacks/tncs/tnc2c-integration-test.py
new file mode 100644
index 0000000..930e0a6
--- /dev/null
+++ b/stacks/tncs/tnc2c-integration-test.py
@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+"""
+HyBBX-ready check - must use same open port as boot-wait (DTR must stay high).
+
+After boot-wait closes the port, DTR drops and the TNC often returns to echo mode.
+Use:  ./tnc2c-boot-wait.sh   (includes HyBBX verify by default)
+Or:   ./tnc2c-integration-test.sh --boot   (boot-wait + verify in one process)
+"""
+
+from __future__ import annotations
+
+import argparse
+import importlib.util
+import os
+import subprocess
+import sys
+import time
+
+ROOT = os.path.dirname(os.path.abspath(__file__))
+
+
+def load_module(name: str, filename: str):
+    path = os.path.join(ROOT, filename)
+    spec = importlib.util.spec_from_file_location(name, path)
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+def preflight() -> int | None:
+    if os.system("pgrep -x hybbx >/dev/null 2>&1") == 0:
+        print("FAIL: hybbx is running")
+        return 2
+    return None
+
+
+def run_quick_check(dev: str) -> int:
+    hr = load_module("host_reset", "tnc2c-host-reset.py")
+
+    print(f"TNC2C integration-test @ {dev}")
+    print("(Port was closed - DTR was low; echo is likely)\n")
+
+    try:
+        fd = hr.open_serial(dev)
+    except OSError as e:
+        print(f"FAIL: {e}")
+        return 2
+
+    received = b""
+    received += hr.read_for(fd, 1.0)
+    hr.write_flush(fd, b"kiss off\r")
+    time.sleep(0.6)
+    received += hr.read_for(fd, 1.0)
+    hr.write_flush(fd, b"INFO\r")
+    time.sleep(0.3)
+    received += hr.read_for(fd, 5.0)
+    os.close(fd)
+
+    if hr.has_banner(received):
+        print("OK: HOST - HyBBX may start")
+        print(received.decode("ascii", errors="replace")[:500])
+        return 0
+
+    print("FAIL: ECHO or no banner")
+    print("  -> Closing the port after boot-wait drops DTR.")
+    print("  -> Use ONE command:")
+    print("       ./tnc2c-boot-wait.sh")
+    print("     (power off/on while script runs - checks HyBBX-ready before close)")
+    print("  or:")
+    print("       ./tnc2c-integration-test.sh --boot")
+    return 1
+
+
+def run_with_boot(dev: str) -> int:
+    print("Starting boot-wait + HyBBX verify in one process ...\n")
+    script = os.path.join(ROOT, "tnc2c-boot-wait.sh")
+    return subprocess.call([script, dev])
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="TNC2C HyBBX-ready check")
+    parser.add_argument("device", nargs="?", default=None)
+    parser.add_argument(
+        "--boot",
+        action="store_true",
+        help="run boot-wait (power-cycle TNC while script runs)",
+    )
+    args = parser.parse_args()
+
+    fail = preflight()
+    if fail is not None:
+        return fail
+
+    hr = load_module("host_reset", "tnc2c-host-reset.py")
+    dev = args.device or hr.load_env(os.path.join(ROOT, "tnc2c-serial.env")) or "/dev/ttyS4"
+
+    if args.boot:
+        return run_with_boot(dev)
+    return run_quick_check(dev)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c-integration-test.sh b/stacks/tncs/tnc2c-integration-test.sh
new file mode 100755
index 0000000..e0523e4
--- /dev/null
+++ b/stacks/tncs/tnc2c-integration-test.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+set -euo pipefail
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+exec python3 "$ROOT/tnc2c-integration-test.py" "$@"
diff --git a/stacks/tncs/tnc2c-listen.sh b/stacks/tncs/tnc2c-listen.sh
new file mode 100755
index 0000000..7020e17
--- /dev/null
+++ b/stacks/tncs/tnc2c-listen.sh
@@ -0,0 +1,56 @@
+#!/bin/bash
+# Passive listen on TNC2C - NO commands that can key PTT (no kiss on, no MONitor).
+# Usage: ./tnc2c-listen.sh [seconds] [device]
+
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=/dev/null
+[[ -f "$ROOT/tnc2c-serial.env" ]] && source "$ROOT/tnc2c-serial.env"
+
+DEV="${2:-${TNC2C_DEV:-/dev/ttyS4}}"
+SECS="${1:-5}"
+BAUD="${TNC2C_BAUD:-19200}"
+LINE="${TNC2C_LINE:-7e1}"
+
+case "$LINE" in
+7e1|7E1) STTY="cs7 parenb -cstopb" ;;
+8n1|8N1) STTY="cs8 -parenb -cstopb" ;;
+*) echo "Unknown line: $LINE" >&2; exit 1 ;;
+esac
+
+if pgrep -x hybbx >/dev/null 2>&1; then
+    echo "WARN: hybbx is running - port may be in use" >&2
+fi
+
+echo "Passive listen: $DEV @ ${BAUD} ${LINE} for ${SECS}s (no TX commands)"
+stty -F "$DEV" "$BAUD" $STTY raw -echo min 0 time 5
+
+python3 <<PY
+import fcntl, os, struct, time, termios
+
+fd = os.open("$DEV", os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+TIOCM_RTS, TIOCM_DTR = 0x004, 0x002
+TIOCMGET, TIOCMSET = 0x5415, 0x5416
+flags = struct.unpack("I", fcntl.ioctl(fd, TIOCMGET, struct.pack("I", 0)))[0]
+flags |= TIOCM_RTS | TIOCM_DTR
+fcntl.ioctl(fd, TIOCMSET, struct.pack("I", flags))
+termios.tcflush(fd, termios.TCIOFLUSH)
+
+end = time.time() + float("$SECS")
+chunks = []
+while time.time() < end:
+    try:
+        b = os.read(fd, 4096)
+        if b:
+            chunks.append(b)
+            print(f"+{len(b)} bytes")
+    except BlockingIOError:
+        time.sleep(0.05)
+
+data = b"".join(chunks)
+os.close(fd)
+print(f"Total: {len(data)} bytes")
+if data:
+    print(data[:256].hex(" "))
+PY
diff --git a/stacks/tncs/tnc2c-probe.c b/stacks/tncs/tnc2c-probe.c
new file mode 100644
index 0000000..8770409
--- /dev/null
+++ b/stacks/tncs/tnc2c-probe.c
@@ -0,0 +1,535 @@
+/*
+ * tnc2c-probe — scan /dev/ttyS* and /dev/ttyUSB* for a Landolt TNC2C.
+ *
+ * TNC2C host port (per manual): 7-bit, even parity, 1 stop bit.
+ * Terminal speed set by TERM jumper (this unit: 19200; manual default often 9600).
+ * RTS/CTS handshake; DTR asserted to wake some adapters.
+ *
+ * Build: make
+ * Run:   ./tnc2c-probe
+ *        ./tnc2c-probe /dev/ttyS4
+ */
+
+#if defined(__linux__) || defined(__GLIBC__)
+#define _DEFAULT_SOURCE 1
+#endif
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <glob.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <time.h>
+#include <unistd.h>
+
+#define PROBE_READ_MS   900
+#define PROBE_GAP_MS    120
+#define RX_BUF_SIZE     4096
+#define MAX_DEVICES     64
+
+typedef struct serial_profile {
+    const char *label;
+    speed_t speed;
+    unsigned int baud_num;
+    tcflag_t databits;
+    tcflag_t parity;
+} serial_profile_t;
+
+typedef struct probe_result {
+    char device[64];
+    char profile[32];
+    char command[32];
+    int got_data;
+    size_t len;
+    char text[RX_BUF_SIZE];
+    unsigned char raw[RX_BUF_SIZE];
+} probe_result_t;
+
+static const serial_profile_t PROFILES[] = {
+    { "19200-7E1", B19200, 19200, CS7, PARENB },
+    { "19200-8N1", B19200, 19200, CS8, 0 },
+    { "9600-7E1", B9600, 9600, CS7, PARENB },
+    { "9600-8N1", B9600, 9600, CS8, 0 },
+    { "4800-7E1", B4800, 4800, CS7, PARENB },
+    { "2400-7E1", B2400, 2400, CS7, PARENB },
+    { "1200-7E1", B1200, 1200, CS7, PARENB },
+};
+
+static const char *PROBE_COMMANDS[] = {
+    "\r",
+    "INFO\r",
+    "HELP\r",
+    "?\r",
+};
+
+static int verbose = 0;
+
+static int sleep_ms(unsigned ms)
+{
+    struct timespec ts;
+
+    ts.tv_sec = (time_t)(ms / 1000u);
+    ts.tv_nsec = (long)(ms % 1000u) * 1000000L;
+    return nanosleep(&ts, NULL);
+}
+
+static int set_modem_lines(int fd, int rts_on, int dtr_on)
+{
+#ifdef TIOCMGET
+    int flags;
+
+    if (ioctl(fd, TIOCMGET, &flags) != 0) {
+        return -1;
+    }
+    if (rts_on) {
+        flags |= TIOCM_RTS;
+    } else {
+        flags &= ~TIOCM_RTS;
+    }
+    if (dtr_on) {
+        flags |= TIOCM_DTR;
+    } else {
+        flags &= ~TIOCM_DTR;
+    }
+    return ioctl(fd, TIOCMSET, &flags);
+#else
+    (void)fd;
+    (void)rts_on;
+    (void)dtr_on;
+    return 0;
+#endif
+}
+
+static int read_modem_lines(int fd, int *rts, int *cts, int *dtr, int *dsr)
+{
+#ifdef TIOCMGET
+    int flags;
+
+    if (ioctl(fd, TIOCMGET, &flags) != 0) {
+        return -1;
+    }
+    if (rts != NULL) {
+        *rts = (flags & TIOCM_RTS) != 0;
+    }
+    if (cts != NULL) {
+        *cts = (flags & TIOCM_CTS) != 0;
+    }
+    if (dtr != NULL) {
+        *dtr = (flags & TIOCM_DTR) != 0;
+    }
+    if (dsr != NULL) {
+        *dsr = (flags & TIOCM_DSR) != 0;
+    }
+    return 0;
+#else
+    (void)fd;
+    if (rts) {
+        *rts = -1;
+    }
+    if (cts) {
+        *cts = -1;
+    }
+    if (dtr) {
+        *dtr = -1;
+    }
+    if (dsr) {
+        *dsr = -1;
+    }
+    return 0;
+#endif
+}
+
+static int configure_port(int fd, const serial_profile_t *profile)
+{
+    struct termios tty;
+
+    if (tcgetattr(fd, &tty) != 0) {
+        return -1;
+    }
+
+    cfmakeraw(&tty);
+    tty.c_cflag |= (CLOCAL | CREAD);
+    tty.c_cflag &= ~(CSIZE | PARENB | PARODD | CSTOPB);
+    tty.c_cflag |= profile->databits;
+    if (profile->parity != 0) {
+        tty.c_cflag |= profile->parity;
+    }
+    tty.c_cc[VMIN] = 0;
+    tty.c_cc[VTIME] = 1;
+
+#if defined(__linux__) || defined(__GLIBC__)
+    if (cfsetspeed(&tty, profile->speed) != 0) {
+        cfsetispeed(&tty, profile->speed);
+        cfsetospeed(&tty, profile->speed);
+    }
+#else
+    cfsetispeed(&tty, profile->speed);
+    cfsetospeed(&tty, profile->speed);
+#endif
+
+    if (tcsetattr(fd, TCSANOW, &tty) != 0) {
+        return -1;
+    }
+
+    tcflush(fd, TCIOFLUSH);
+    return 0;
+}
+
+static int is_printable_ascii(unsigned char c)
+{
+    return c == '\r' || c == '\n' || c == '\t' || (c >= 0x20 && c <= 0x7e);
+}
+
+static void sanitize_text(const unsigned char *raw, size_t len, char *out, size_t out_cap)
+{
+    size_t i;
+    size_t o = 0;
+
+    if (out_cap == 0) {
+        return;
+    }
+
+    for (i = 0; i < len && o + 1 < out_cap; i++) {
+        unsigned char c = raw[i];
+
+        if (c == '\r') {
+            if (o + 2 < out_cap) {
+                out[o++] = '\\';
+                out[o++] = 'r';
+            }
+        } else if (c == '\n') {
+            if (o + 2 < out_cap) {
+                out[o++] = '\\';
+                out[o++] = 'n';
+            }
+        } else if (is_printable_ascii(c)) {
+            out[o++] = (char)c;
+        } else {
+            int n = snprintf(out + o, out_cap - o, "\\x%02x", c);
+            if (n <= 0 || (size_t)n >= out_cap - o) {
+                break;
+            }
+            o += (size_t)n;
+        }
+    }
+    out[o] = '\0';
+}
+
+static int looks_like_tnc(const unsigned char *raw, size_t len)
+{
+    static const char *needles[] = {
+        "cmd:", "CMD:", "TNC", "tnc", "INFO", "help", "HELP",
+        "***", "connected", "DISCONNECTED", "kiss", "KISS",
+        "MYCALL", "WA8DED", "NOCALL", "?"
+    };
+    char buf[RX_BUF_SIZE];
+    size_t i;
+
+    if (len == 0) {
+        return 0;
+    }
+
+    sanitize_text(raw, len, buf, sizeof(buf));
+    for (i = 0; i < sizeof(needles) / sizeof(needles[0]); i++) {
+        if (strstr(buf, needles[i]) != NULL) {
+            return 1;
+        }
+    }
+    return len >= 3;
+}
+
+static size_t read_for_ms(int fd, unsigned char *buf, size_t cap, unsigned ms)
+{
+    size_t total = 0;
+    unsigned elapsed = 0;
+
+    while (elapsed < ms && total < cap) {
+        ssize_t n = read(fd, buf + total, cap - total);
+
+        if (n > 0) {
+            total += (size_t)n;
+            elapsed = 0;
+            continue;
+        }
+        if (n < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+            break;
+        }
+        sleep_ms(40);
+        elapsed += 40;
+    }
+
+    return total;
+}
+
+static int probe_once(const char *device, const serial_profile_t *profile,
+                      const char *command, probe_result_t *result)
+{
+    int fd;
+    ssize_t wlen;
+
+    memset(result, 0, sizeof(*result));
+    snprintf(result->device, sizeof(result->device), "%s", device);
+    snprintf(result->profile, sizeof(result->profile), "%s", profile->label);
+    snprintf(result->command, sizeof(result->command), "%s",
+             command[0] == '\r' ? "<CR>" : command);
+
+    fd = open(device, O_RDWR | O_NOCTTY | O_NONBLOCK);
+    if (fd < 0) {
+        return -1;
+    }
+
+    if (configure_port(fd, profile) != 0) {
+        close(fd);
+        return -1;
+    }
+
+    (void)set_modem_lines(fd, 1, 1);
+    sleep_ms(80);
+    (void)read_for_ms(fd, result->raw, sizeof(result->raw), 150);
+
+    wlen = write(fd, command, strlen(command));
+    if (wlen < 0) {
+        close(fd);
+        return -1;
+    }
+
+    sleep_ms(PROBE_GAP_MS);
+    result->len = read_for_ms(fd, result->raw, sizeof(result->raw), PROBE_READ_MS);
+    close(fd);
+
+    result->got_data = result->len > 0;
+    sanitize_text(result->raw, result->len, result->text, sizeof(result->text));
+    return 0;
+}
+
+static int device_accessible(const char *path)
+{
+    return access(path, R_OK | W_OK) == 0;
+}
+
+static int collect_devices(char devices[][64], int max_devices)
+{
+    glob_t g;
+    size_t i;
+    int count = 0;
+    static const char *patterns[] = {
+        "/dev/ttyUSB[0-9]*",
+        "/dev/ttyS[0-9]*",
+        NULL
+    };
+    int p;
+
+    for (p = 0; patterns[p] != NULL; p++) {
+        if (glob(patterns[p], 0, NULL, &g) != 0) {
+            continue;
+        }
+        for (i = 0; i < g.gl_pathc && count < max_devices; i++) {
+            const char *path = g.gl_pathv[i];
+            int j;
+            int dup = 0;
+
+            for (j = 0; j < count; j++) {
+                if (strcmp(devices[j], path) == 0) {
+                    dup = 1;
+                    break;
+                }
+            }
+            if (!dup) {
+                snprintf(devices[count], 64, "%s", path);
+                count++;
+            }
+        }
+        globfree(&g);
+    }
+
+    return count;
+}
+
+static void print_device_header(const char *device)
+{
+    int fd;
+    int rts = -1, cts = -1, dtr = -1, dsr = -1;
+
+    printf("\n============================================================\n");
+    printf("Device: %s\n", device);
+    if (!device_accessible(device)) {
+        printf("Access: NO (need dialout group or root)\n");
+        return;
+    }
+    printf("Access: yes\n");
+
+    fd = open(device, O_RDWR | O_NOCTTY | O_NONBLOCK);
+    if (fd >= 0) {
+        if (read_modem_lines(fd, &rts, &cts, &dtr, &dsr) == 0) {
+            printf("Lines (before probe): RTS=%d CTS=%d DTR=%d DSR=%d\n",
+                   rts, cts, dtr, dsr);
+        }
+        close(fd);
+    }
+}
+
+static void listen_quiet(const char *device, const serial_profile_t *profile)
+{
+    int fd;
+    unsigned char buf[512];
+    size_t n;
+
+    fd = open(device, O_RDWR | O_NOCTTY | O_NONBLOCK);
+    if (fd < 0) {
+        return;
+    }
+    if (configure_port(fd, profile) != 0) {
+        close(fd);
+        return;
+    }
+    (void)set_modem_lines(fd, 1, 1);
+    n = read_for_ms(fd, buf, sizeof(buf), 1200);
+    close(fd);
+
+    if (n > 0) {
+        char text[512];
+        sanitize_text(buf, n, text, sizeof(text));
+        printf("  Spontaneous traffic @ %s: %s\n", profile->label, text);
+    } else if (verbose) {
+        printf("  Spontaneous traffic @ %s: (none)\n", profile->label);
+    }
+}
+
+static int run_device_scan(const char *device)
+{
+    size_t pi;
+    size_t ci;
+    int hits = 0;
+    int best_score = 0;
+    char best_profile[32] = "";
+    char best_text[512] = "";
+
+    print_device_header(device);
+    if (!device_accessible(device)) {
+        return 0;
+    }
+
+    listen_quiet(device, &PROFILES[0]);
+    listen_quiet(device, &PROFILES[1]);
+
+    for (pi = 0; pi < sizeof(PROFILES) / sizeof(PROFILES[0]); pi++) {
+        for (ci = 0; ci < sizeof(PROBE_COMMANDS) / sizeof(PROBE_COMMANDS[0]); ci++) {
+            probe_result_t result;
+            int score;
+
+            if (probe_once(device, &PROFILES[pi], PROBE_COMMANDS[ci], &result) != 0) {
+                continue;
+            }
+            if (!result.got_data) {
+                if (verbose) {
+                    printf("  %s + %s -> (no data)\n",
+                           result.profile, result.command);
+                }
+                continue;
+            }
+
+            score = looks_like_tnc(result.raw, result.len) ? 2 : 1;
+            hits++;
+            printf("  HIT  %s + %s (%zu bytes, score=%d)\n",
+                   result.profile, result.command, result.len, score);
+            printf("       %s\n", result.text);
+
+            if (score > best_score) {
+                best_score = score;
+                snprintf(best_profile, sizeof(best_profile), "%s", result.profile);
+                strncpy(best_text, result.text, sizeof(best_text) - 1);
+                best_text[sizeof(best_text) - 1] = '\0';
+            }
+        }
+    }
+
+    if (hits == 0) {
+        printf("  Result: no response on any profile/command.\n");
+        printf("  Hint:   check power, cable (DTE<->DCE modem cable), baud jumper.\n");
+    } else {
+        printf("  Result: %d response(s); best profile=%s (score=%d)\n",
+               hits, best_profile[0] ? best_profile : "?", best_score);
+        if (best_text[0] != '\0') {
+            printf("  Best:   %s\n", best_text);
+        }
+    }
+
+    return hits;
+}
+
+static void usage(const char *argv0)
+{
+    fprintf(stderr,
+            "Usage: %s [-v] [device ...]\n"
+            "\n"
+            "Scan serial ports for a Landolt TNC2C.\n"
+            "Without device arguments, probes all /dev/ttyUSB* and /dev/ttyS*.\n"
+            "\n"
+            "Options:\n"
+            "  -v   verbose (show silent probes too)\n"
+            "  -h   this help\n",
+            argv0);
+}
+
+int main(int argc, char **argv)
+{
+    char devices[MAX_DEVICES][64];
+    int device_count = 0;
+    int argi;
+    int total_hits = 0;
+    int scanned = 0;
+
+    for (argi = 1; argi < argc; argi++) {
+        if (strcmp(argv[argi], "-h") == 0 || strcmp(argv[argi], "--help") == 0) {
+            usage(argv[0]);
+            return 0;
+        }
+        if (strcmp(argv[argi], "-v") == 0 || strcmp(argv[argi], "--verbose") == 0) {
+            verbose = 1;
+            continue;
+        }
+        if (device_count < MAX_DEVICES) {
+            snprintf(devices[device_count], 64, "%s", argv[argi]);
+            device_count++;
+        }
+    }
+
+    if (device_count == 0) {
+        device_count = collect_devices(devices, MAX_DEVICES);
+    }
+
+    printf("TNC2C serial probe\n");
+    printf("Profiles: 7E1 (manual) and 8N1 (HyBBX default) at common baud rates.\n");
+    printf("Found %d serial device(s).\n", device_count);
+
+    if (device_count == 0) {
+        fprintf(stderr, "No /dev/ttyUSB* or /dev/ttyS* devices found.\n");
+        return 1;
+    }
+
+    for (argi = 0; argi < device_count; argi++) {
+        total_hits += run_device_scan(devices[argi]);
+        scanned++;
+    }
+
+    printf("\n============================================================\n");
+    printf("Summary: scanned %d port(s), %d response(s) total.\n",
+           scanned, total_hits);
+
+    if (total_hits == 0) {
+        printf("\nCable note (TNC2C manual):\n");
+        printf("  - TNC2C DB25 is wired like a modem (DCE).\n");
+        printf("  - PC/USB-serial is DTE -> use a straight modem cable,\n");
+        printf("    not a null-modem crossover cable.\n");
+        printf("  - Some PCs need RTS-CTS bridged on the host side (pins 4+5).\n");
+        printf("  - Host settings: 7-bit, even parity (7E1), baud per TERM jumper.\n");
+        printf("  - LEDs after power-on: Power on; Status+Connected off after ~3 s.\n");
+        return 2;
+    }
+
+    return 0;
+}
diff --git a/stacks/tncs/tnc2c-rf-tx-test.sh b/stacks/tncs/tnc2c-rf-tx-test.sh
new file mode 100755
index 0000000..fc23eff
--- /dev/null
+++ b/stacks/tncs/tnc2c-rf-tx-test.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+# Send N AX.25 UI frames via KISS (HyBBX must be stopped).
+# Usage: ./tnc2c-rf-tx-test.sh [count] [message-prefix] [src] [dst]
+# Example (root): pkill hybbx; ./tnc2c-rf-tx-test.sh 3 "TX test" CB-0 QST
+
+set -euo pipefail
+
+COUNT="${1:-3}"
+PREFIX="${2:-TX test}"
+SRC="${3:-CB-0}"
+DST="${4:-QST}"
+GAP="${TNC2C_TX_GAP:-8}"
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+
+if pgrep -x hybbx >/dev/null 2>&1; then
+    echo "ERROR: hybbx is running - as root: pkill hybbx" >&2
+    exit 1
+fi
+
+echo "RF TX: ${COUNT}x ${SRC} -> ${DST}, ${GAP}s gap (SQ closed, CD off)"
+for i in $(seq 1 "$COUNT"); do
+    echo "=== SEND ${i}/${COUNT} $(date +%H:%M:%S) ==="
+    "$ROOT/tnc2c-send-test.sh" "${PREFIX} ${i}/${COUNT}" "$SRC" "$DST"
+    if [[ "$i" -lt "$COUNT" ]]; then
+        sleep "$GAP"
+    fi
+done
+echo "Done - check PTT LED / modem tone on radio."
diff --git a/stacks/tncs/tnc2c-send-test.sh b/stacks/tncs/tnc2c-send-test.sh
new file mode 100755
index 0000000..4ac1b52
--- /dev/null
+++ b/stacks/tncs/tnc2c-send-test.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+# Send one AX.25 UI frame via KISS on TNC2C - keys PTT / transmits on radio.
+# Requires: antenna or dummyload, VOX off, HyBBX stopped.
+# Usage: ./tnc2c-send-test.sh [message] [src] [dst]
+
+set -euo pipefail
+
+MSG="${1:-HI}"
+SRC="${2:-TEST-0}"
+DST="${3:-CQ}"
+
+ROOT="$(cd "$(dirname "$0")" && pwd)"
+# shellcheck source=/dev/null
+[[ -f "$ROOT/tnc2c-serial.env" ]] && source "$ROOT/tnc2c-serial.env"
+
+if pgrep -x hybbx >/dev/null 2>&1; then
+    echo "ERROR: hybbx is running - stop it first" >&2
+    exit 1
+fi
+
+export TNC2C_DEV TNC2C_LINE
+python3 - "$MSG" "$SRC" "$DST" <<'PY'
+import fcntl, os, struct, sys, time, termios
+
+msg, src, dst = sys.argv[1:4]
+dev = os.environ.get("TNC2C_DEV", "/dev/ttyS4")
+line = os.environ.get("TNC2C_LINE", "8n1").lower()
+seven_e1 = line.startswith("7e")
+
+def kiss_escape(data: bytes) -> bytes:
+    out = bytearray()
+    for b in data:
+        if b == 0xC0:
+            out.extend((0xDB, 0xDC))
+        elif b == 0xDB:
+            out.extend((0xDB, 0xDD))
+        else:
+            out.append(b)
+    return bytes(out)
+
+def ax25_addr(call: str, ssid: int, last: bool) -> bytes:
+    call = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in call)
+    ssid_b = ((ssid & 0x0F) << 1) | (0x01 if last else 0x00)
+    return raw + bytes([ssid_b])
+
+def ax25_crc(data: bytes) -> int:
+    crc = 0xFFFF
+    for b in data:
+        crc ^= b
+        for _ in range(8):
+            crc = (crc >> 1) ^ 0x8408 if crc & 1 else crc >> 1
+    return crc ^ 0xFFFF
+
+def ax25_ui(src, dst, info: bytes) -> bytes:
+    body = ax25_addr(dst, 0, False) + ax25_addr(src, 0, True)
+    body += b"\x03\xF0" + info
+    crc = ax25_crc(body)
+    return body + bytes((crc & 0xFF, crc >> 8))
+
+def kiss_frame(port: int, payload: bytes) -> bytes:
+    return b"\xC0" + bytes([port & 0x0F]) + kiss_escape(payload) + b"\xC0"
+
+print(f"Serial: {dev} 19200 {line}")
+
+fd = os.open(dev, os.O_RDWR | os.O_NOCTTY)
+t = termios.tcgetattr(fd)
+t[0] = t[1] = 0
+t[2] = termios.CLOCAL | termios.CREAD | (termios.CS7 if seven_e1 else termios.CS8)
+if seven_e1:
+    t[2] |= termios.PARENB
+t[3] = t[4] = t[5] = termios.B19200
+t[6][termios.VMIN] = 0
+t[6][termios.VTIME] = 5
+termios.tcsetattr(fd, termios.TCSANOW, t)
+termios.tcflush(fd, termios.TCIOFLUSH)
+flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0] | 0x006
+fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+
+for cmd in (b"kiss off\r", b"kiss on\r"):
+    os.write(fd, cmd)
+    termios.tcdrain(fd)
+    time.sleep(0.5)
+
+pkt = kiss_frame(0, ax25_ui(src, dst, msg.encode("ascii", errors="replace")))
+print(f"TX {src} -> {dst}: {msg!r} ({len(pkt)} bytes KISS)")
+os.write(fd, pkt)
+termios.tcdrain(fd)
+time.sleep(3.0)
+try:
+    rx = os.read(fd, 4096)
+    if rx:
+        print(f"RX {len(rx)} bytes: {rx[:80]!r}")
+except BlockingIOError:
+    pass
+os.write(fd, b"kiss off\r")
+termios.tcdrain(fd)
+os.close(fd)
+print("Check LED 2 (PTT) on TNC and S-meter on radio.")
+PY
diff --git a/stacks/tncs/tnc2c-serial.env b/stacks/tncs/tnc2c-serial.env
new file mode 100644
index 0000000..89f111a
--- /dev/null
+++ b/stacks/tncs/tnc2c-serial.env
@@ -0,0 +1,8 @@
+# TNC2C serial — edit for your station
+# Example: USB-serial adapter; onboard UART is often /dev/ttyS0
+TNC2C_DEV=/dev/ttyUSB0
+TNC2C_BAUD=19200
+TNC2C_LINE=8n1
+TNC2C_RADIO_BAUD=2400
+TNC2C_MODEM=tcm3105
+HYBBX_SERIAL_LINE=8n1
diff --git a/stacks/tncs/tnc2c-tx-rx-test.py b/stacks/tncs/tnc2c-tx-rx-test.py
new file mode 100644
index 0000000..76e639d
--- /dev/null
+++ b/stacks/tncs/tnc2c-tx-rx-test.py
@@ -0,0 +1,184 @@
+#!/usr/bin/env python3
+"""TX then RX diagnostic for TNC2C + CB - no HyBBX."""
+
+from __future__ import annotations
+
+import fcntl
+import os
+import struct
+import sys
+import time
+import termios
+
+DEV = "/dev/ttyS4"
+BAUD = termios.B19200
+
+FIRMWARE = (b"TheFirmware", b"NORD", b"Version 2.7", b"Checksum")
+
+
+def open_port() -> int:
+    fd = os.open(DEV, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK)
+    t = termios.tcgetattr(fd)
+    t[0] = t[1] = 0
+    t[2] = termios.CLOCAL | termios.CREAD | termios.CS8
+    t[3] = t[4] = t[5] = BAUD
+    t[6][termios.VMIN] = 0
+    t[6][termios.VTIME] = 5
+    termios.tcsetattr(fd, termios.TCSANOW, t)
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    flags = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    flags |= 0x006
+    fcntl.ioctl(fd, 0x5416, struct.pack("I", flags))
+    return fd
+
+
+def modem(fd: int) -> str:
+    f = struct.unpack("I", fcntl.ioctl(fd, 0x5415, struct.pack("I", 0)))[0]
+    return f"RTS={int(bool(f&4))} CTS={int(bool(f&8))} DSR={int(bool(f&0x100))} DCD={int(bool(f&0x80))}"
+
+
+def read_sec(fd: int, sec: float) -> bytes:
+    end = time.time() + sec
+    chunks: list[bytes] = []
+    while time.time() < end:
+        try:
+            b = os.read(fd, 4096)
+            if b:
+                chunks.append(b)
+        except BlockingIOError:
+            time.sleep(0.02)
+    return b"".join(chunks)
+
+
+def write(fd: int, data: bytes) -> None:
+    os.write(fd, data)
+    termios.tcdrain(fd)
+
+
+def has_fw(data: bytes) -> bool:
+    lo = data.lower()
+    return any(m.lower() in lo for m in FIRMWARE)
+
+
+def kiss_escape(data: bytes) -> bytes:
+    out = bytearray()
+    for b in data:
+        if b == 0xC0:
+            out.extend((0xDB, 0xDC))
+        elif b == 0xDB:
+            out.extend((0xDB, 0xDD))
+        else:
+            out.append(b)
+    return bytes(out)
+
+
+def ax25_addr(call: str, last: bool) -> bytes:
+    call = call.upper().ljust(6)[:6]
+    raw = bytes((ord(c) << 1) for c in call)
+    return raw + bytes([((0 & 0x0F) << 1) | (0x01 if last else 0x00)])
+
+
+def ax25_crc(data: bytes) -> int:
+    crc = 0xFFFF
+    for b in data:
+        crc ^= b
+        for _ in range(8):
+            crc = (crc >> 1) ^ 0x8408 if crc & 1 else crc >> 1
+    return crc ^ 0xFFFF
+
+
+def ax25_ui(src: str, dst: str, info: bytes) -> bytes:
+    body = ax25_addr(dst, False) + ax25_addr(src, True) + b"\x03\xF0" + info
+    crc = ax25_crc(body)
+    return body + bytes((crc & 0xFF, crc >> 8))
+
+
+def kiss_frame(payload: bytes) -> bytes:
+    return b"\xC0\x00" + kiss_escape(payload) + b"\xC0"
+
+
+def main() -> int:
+    print("=" * 60)
+    print("TNC2C TX/RX Test")
+    print("=" * 60)
+
+    if os.system("pgrep -x hybbx >/dev/null 2>&1") == 0:
+        print("FAIL: hybbx is running - stop it first")
+        return 2
+
+    fd = open_port()
+    print(f"Device: {DEV} 19200 8N1  {modem(fd)}")
+
+    # --- Host check ---
+    print("\n[1] Host check")
+    passive = read_sec(fd, 2.0)
+    write(fd, b"kiss off\r")
+    time.sleep(0.5)
+    pre = read_sec(fd, 1.0)
+    write(fd, b"INFO\r")
+    time.sleep(0.3)
+    info = read_sec(fd, 4.0)
+    all_host = passive + pre + info
+    if has_fw(all_host):
+        print("  OK: firmware/host detected")
+    elif info.strip() in (b"INFO", b"INFO\r", b"INFO\r\n"):
+        print("  WARN: echo only - try ./tnc2c-host-reset.sh --kiss or ./tnc2c-boot-wait.sh --recover-only")
+    else:
+        print(f"  INFO reply: {info[:120]!r}")
+
+    # --- TX ---
+    print("\n[2] TX (KISS UI TEST-0 -> CQ, Msg=TXRX)")
+    write(fd, b"kiss on\r")
+    time.sleep(0.5)
+    read_sec(fd, 0.3)
+    pkt = kiss_frame(ax25_ui("TEST-0", "CQ", b"TXRX"))
+    t0 = time.time()
+    write(fd, pkt)
+    time.sleep(3.0)
+    tx_rx = read_sec(fd, 1.0)
+    write(fd, b"kiss off\r")
+    time.sleep(0.3)
+
+    kiss_back = b"\xc0" in tx_rx or b"TXRX" in tx_rx
+    print(f"  Sent: {len(pkt)} bytes KISS")
+    print(f"  Serial RX: {len(tx_rx)} bytes")
+    if kiss_back:
+        print("  OK: KISS frame seen on serial")
+    else:
+        print("  WARN: no KISS echo on serial")
+    print("  -> CHECK NOW: LED2 PTT + modem tone on 2m CB radio")
+
+    # --- RX (passive, no TX) ---
+    print("\n[3] RX (passive 12s, kiss off - listening on radio/monitor)")
+    termios.tcflush(fd, termios.TCIOFLUSH)
+    write(fd, b"kiss off\r")
+    time.sleep(0.5)
+    read_sec(fd, 0.5)
+    print("  Listening 12s ... (RF noise/CD should keep LED3 on)")
+    rx_data = read_sec(fd, 12.0)
+    os.close(fd)
+
+    print(f"  Passive RX: {len(rx_data)} bytes")
+    if rx_data:
+        printable = sum(1 for b in rx_data if 32 <= b < 127 or b in (9, 10, 13))
+        ratio = printable / len(rx_data)
+        print(f"  Printable ratio: {ratio:.0%}")
+        if b"\xc0" in rx_data:
+            print("  OK: KISS frame(s) received (RF traffic or monitor)")
+        else:
+            print(f"  Sample: {rx_data[:80]!r}")
+    else:
+        print("  (no serial traffic - normal on empty band)")
+        print("  -> Hardware RX: LED3 CD with noise/SQ open?")
+
+    print("\n" + "=" * 60)
+    print("Hardware checklist:")
+    print("  TX: LED2 (PTT) blinked? 2m CB heard modem tone?")
+    print("  RX: LED3 (CD) on with noise? SQ closed -> CD off?")
+    print("  DIN: Pin1=TX(white) Pin2=GND Pin3=PTT(red) Pin4=RX(tip)")
+    print("=" * 60)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/tncs/tnc2c.jpg b/stacks/tncs/tnc2c.jpg
new file mode 100644
index 0000000..91a3116
--- /dev/null
+++ b/stacks/tncs/tnc2c.jpg
diff --git a/stacks/tncs/tnc_serial_recovery.py b/stacks/tncs/tnc_serial_recovery.py
new file mode 100644
index 0000000..f7b1370
--- /dev/null
+++ b/stacks/tncs/tnc_serial_recovery.py
@@ -0,0 +1,359 @@
+"""
+TheFirmware TF 2.7 — terminal recovery without power cycle.
+
+Native command set (NORD><LINK source / ALAS — see stacks/tncs/docs/TNC-RECOVERY.md).
+TAPR strings (kiss off, INFO, RESTART) are not primary; kept as last-resort legacy.
+
+Recovery ladder (stop on first banner):
+  0. DTR+RTS high + settle (caller)
+  1. Passive listen
+  2. KISS return 0xC0 0xFF 0xC0  (tfkiss.mac cmd 0xFF → firmware reset + banner)
+  3. Buffer flush ^Q^X + JHOST 0
+  4. ESC V  (version / terminal probe)
+  5. ESC QRES  (cold boot from EPROM — no mains power cycle)
+  6. ESC E 0 + ESC V
+  7. Legacy TAPR kiss off + INFO (optional last resort)
+"""
+
+from __future__ import annotations
+
+import time
+from typing import Callable
+
+FIRMWARE_MARKERS = (
+    b"TheFirmware",
+    b"NORD",
+    b"Version 2.7",
+    b"Checksum",
+    b"Copyright",
+    b"DAMA",
+    b"SMACK",
+    b"cmd:",
+    b"CMD:",
+)
+
+TF_ESC_V = b"\x1bV\r"
+TF_ESC_QRES = b"\x1bQRES\r"
+TF_ESC_AT_K = b"\x1b@K"
+TF_ESC_E0 = b"\x1bE0\r"
+
+LogFn = Callable[[str], None]
+
+
+def matched_markers(data: bytes) -> list[str]:
+    return [m.decode("ascii", errors="replace") for m in FIRMWARE_MARKERS if m.lower() in data.lower()]
+
+
+def escape_bytes(data: bytes, max_len: int = 96) -> str:
+    out: list[str] = []
+    for byte in data[:max_len]:
+        if 32 <= byte < 127:
+            out.append(chr(byte))
+        elif byte == 0x0D:
+            out.append("\\r")
+        elif byte == 0x0A:
+            out.append("\\n")
+        else:
+            out.append(f"\\x{byte:02x}")
+    if len(data) > max_len:
+        out.append("…")
+    return "".join(out)
+
+
+def format_rx_brief(data: bytes) -> str:
+    if not data:
+        return "0 B silent"
+    markers = matched_markers(data)
+    marker_txt = ",".join(markers) if markers else "none"
+    return f"{len(data)} B, markers={marker_txt}, text={escape_bytes(data)!r}"
+
+
+def format_rx_diag(data: bytes) -> str:
+    """One-line firmware/RX summary for operator logs."""
+    if not data:
+        return "silent (0 bytes) — check power, baud, CTS/DTR wiring"
+    markers = matched_markers(data)
+    hex_snip = data[:48].hex(" ")
+    if len(data) > 48:
+        hex_snip += " …"
+    parts = [
+        f"{len(data)} bytes",
+        f"markers={markers or 'none'}",
+        f"text={escape_bytes(data, 120)!r}",
+        f"hex={hex_snip}",
+    ]
+    return "; ".join(parts)
+
+
+def classify_recovery_failure(received: bytes) -> str:
+    if not received:
+        return (
+            "silent — TNC sent nothing (power, baud/line, DE-9 wiring, or boot without DTR)"
+        )
+    if has_banner(received):
+        return "banner seen in RX but terminal probe failed — check host mode or double-echo"
+    lower = received.lower()
+    if b"\x1bv" in lower or b"* " in received:
+        if not has_banner(received):
+            return (
+                "TF terminal alive (ESC V prompt) but no firmware banner — try ESC QRES with DTR high"
+            )
+    echo_hits = sum(
+        1
+        for token in (
+            b"kiss off",
+            b"info\r",
+            b"info\n",
+            b"restart\r",
+            b"jhost 0",
+        )
+        if token in lower
+    )
+    if echo_hits >= 2 or (
+        b"kiss off" in lower and (b"info" in lower or b"info\r" in lower)
+    ):
+        return (
+            "echo-only — TAPR-style or transparent echo, no TheFirmware banner "
+            "(Landolt: DTR high at power-on; try boot-wait or ESC QRES)"
+        )
+    if any(b < 0x20 and b not in (0x0D, 0x0A, 0x09) for b in received[:64]):
+        return (
+            f"binary/non-text ({len(received)} B) — likely KISS/stream mode, not terminal"
+        )
+    return f"non-banner text ({len(received)} B) — firmware state unclear, capture full RX"
+
+
+def has_banner(data: bytes) -> bool:
+    lower = data.lower()
+    return any(m.lower() in lower for m in FIRMWARE_MARKERS)
+
+
+def is_echo_only(cmd: bytes, reply: bytes) -> bool:
+    c = cmd.strip(b"\r\n")
+    r = reply.strip()
+    return r in (c, c + b"\r", c + b"\n", c + b"\r\n")
+
+
+def probe_tf_terminal(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    pause: float = 0.4,
+) -> tuple[bool, bytes, bool]:
+    """ESC V — native TheFirmware version / terminal probe."""
+    write_flush(TF_ESC_V)
+    time.sleep(pause)
+    reply = read_for(4.0)
+    only_echo = is_echo_only(TF_ESC_V, reply)
+    return has_banner(reply), reply, only_echo
+
+
+def probe_info(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    pause: float = 0.4,
+) -> tuple[bool, bytes, bool]:
+    """Alias: native TF probe (was TAPR kiss off + INFO)."""
+    return probe_tf_terminal(write_flush, read_for, pause=pause)
+
+
+def probe_combined(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+) -> tuple[bool, bytes, bool]:
+    """Legacy TAPR kiss off + INFO — last resort only."""
+    write_flush(b"kiss off\rINFO\r")
+    time.sleep(0.8)
+    reply = read_for(5.0)
+    only_echo = is_echo_only(b"kiss off\rINFO\r", reply) or (
+        is_echo_only(b"kiss off\r", reply[:20]) and is_echo_only(b"INFO\r", reply[-20:])
+    )
+    return has_banner(reply), reply, only_echo
+
+
+def send_jhost0(write_flush: Callable[[bytes], None]) -> None:
+    """Leave WA8DED host mode → terminal (gettoweb / WA8DED guide)."""
+    send_buffer_flush(write_flush)
+    write_flush(b"\x00" * 300)
+    time.sleep(0.15)
+    write_flush(b"\x00\x01\x06JHOST 0\r")
+    time.sleep(0.8)
+
+
+def send_kiss_return(write_flush: Callable[[bytes], None]) -> None:
+    write_flush(b"\xc0\xff\xc0")
+    time.sleep(1.0)
+
+
+def send_esc_at_k(write_flush: Callable[[bytes], None]) -> None:
+    """Enter KISS from terminal (tfb.c @K) — not an exit path."""
+    write_flush(TF_ESC_AT_K)
+    time.sleep(0.8)
+
+
+def send_echo_off(write_flush: Callable[[bytes], None]) -> None:
+    """TheFirmware ESC E 0 — disable terminal echo."""
+    write_flush(TF_ESC_E0)
+    time.sleep(0.3)
+
+
+def send_qres(write_flush: Callable[[bytes], None]) -> None:
+    """Software cold boot from EPROM (tfd.c Qcmd) — DTR must stay high."""
+    write_flush(TF_ESC_QRES)
+    time.sleep(2.5)
+
+
+def send_buffer_flush(write_flush: Callable[[bytes], None]) -> None:
+    """WA8DED host guide: ^Q^X before commands if junk in buffer."""
+    write_flush(b"\x11\x18")
+    time.sleep(0.2)
+
+
+def tf_mycall_frame(call: str) -> bytes:
+    """ESC I — set own callsign (tfb.c Icmd)."""
+    return f"\x1bI {call.upper()}\r".encode("ascii", errors="replace")
+
+
+def _try_probe(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    out: LogFn,
+    label: str,
+) -> tuple[bool, bytes]:
+    ok, probe, only_echo = probe_tf_terminal(write_flush, read_for)
+    if ok:
+        out(f"recovery: OK after {label}")
+        return True, probe
+    out(
+        f"recovery: probe after {label} — {format_rx_brief(probe)}, "
+        f"echo_only={only_echo}, banner={has_banner(probe)}"
+    )
+    if not only_echo and probe:
+        out(f"recovery: partial reply after {label}")
+    return False, probe
+
+
+def recover_terminal(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    *,
+    skip_kiss_frame: bool = False,
+    log: LogFn | None = None,
+) -> tuple[bool, bytes]:
+    """Run full software recovery ladder. Returns (host_ok, all_rx_bytes)."""
+    out = log or (lambda _msg: None)
+    received = b""
+
+    chunk = read_for(1.5)
+    received += chunk
+    out(f"recovery: passive listen — {format_rx_brief(chunk)}")
+    if has_banner(chunk):
+        out("recovery: OK — banner on passive listen")
+        return True, received
+
+    if not skip_kiss_frame:
+        send_kiss_return(write_flush)
+        chunk = read_for(2.5)
+        received += chunk
+        out(f"recovery: KISS return frame — {format_rx_brief(chunk)}")
+        if has_banner(chunk):
+            out("recovery: OK after KISS return (firmware reset)")
+            return True, received
+
+    send_jhost0(write_flush)
+    chunk = read_for(1.0)
+    received += chunk
+    out(f"recovery: JHOST 0 — {format_rx_brief(chunk)}")
+    if has_banner(chunk):
+        out("recovery: OK after JHOST 0")
+        return True, received
+
+    ok, probe = _try_probe(write_flush, read_for, out, "ESC V")
+    received += probe
+    if ok:
+        return True, received
+
+    send_qres(write_flush)
+    chunk = read_for(3.0)
+    received += chunk
+    out(f"recovery: ESC QRES — {format_rx_brief(chunk)}")
+    if has_banner(chunk):
+        out("recovery: OK after ESC QRES")
+        return True, received
+
+    ok, probe = _try_probe(write_flush, read_for, out, "post-QRES ESC V")
+    received += probe
+    if ok:
+        return True, received
+
+    send_echo_off(write_flush)
+    received += read_for(0.3)
+    ok, probe = _try_probe(write_flush, read_for, out, "ESC E 0")
+    received += probe
+    if ok:
+        return True, received
+
+    send_qres(write_flush)
+    received += read_for(3.0)
+    out("recovery: second ESC QRES")
+    ok, probe = _try_probe(write_flush, read_for, out, "second QRES")
+    received += probe
+    if ok:
+        return True, received
+
+    ok, probe, _ = probe_combined(write_flush, read_for)
+    received += probe
+    if ok:
+        out("recovery: OK after legacy TAPR kiss off + INFO")
+        return True, received
+    if probe:
+        out(f"recovery: legacy TAPR probe — {format_rx_brief(probe)}")
+
+    out(
+        "recovery: FAILED — echo only or silent "
+        "(retry with DTR high; cold-boot without DTR may need boot-wait + power cycle)"
+    )
+    out(f"recovery: firmware assessment — {classify_recovery_failure(received)}")
+    out(f"recovery: RX capture — {format_rx_diag(received)}")
+    return False, received
+
+
+def enter_kiss(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    entry: str = "kiss_on",
+) -> None:
+    """Enter KISS after terminal recovery (native TF: ESC @K)."""
+    if entry == "tapr":
+        write_flush(b"kiss on\r")
+        time.sleep(0.5)
+        read_for(0.5)
+        return
+    if entry == "auto":
+        write_flush(TF_ESC_AT_K)
+        time.sleep(0.5)
+        reply = read_for(0.5)
+        if reply.strip() in (b"kiss on", b"kiss on\r", b"kiss on\n"):
+            write_flush(TF_ESC_AT_K)
+            time.sleep(0.5)
+            read_for(0.5)
+        return
+    write_flush(TF_ESC_AT_K)
+    time.sleep(0.5)
+    read_for(0.3)
+
+
+def recover_and_enter_kiss(
+    write_flush: Callable[[bytes], None],
+    read_for: Callable[[float], bytes],
+    *,
+    kiss_entry: str = "kiss_on",
+    skip_kiss_frame: bool = False,
+    log: LogFn | None = None,
+) -> bool:
+    ok, _ = recover_terminal(
+        write_flush, read_for, skip_kiss_frame=skip_kiss_frame, log=log
+    )
+    if not ok:
+        return False
+    enter_kiss(write_flush, read_for, kiss_entry)
+    return True
diff --git a/stacks/web/CMakeLists.txt b/stacks/web/CMakeLists.txt
new file mode 100644
index 0000000..e24e4a5
--- /dev/null
+++ b/stacks/web/CMakeLists.txt
@@ -0,0 +1,42 @@
+cmake_minimum_required(VERSION 3.16)
+
+if(NOT MAX25_BUILD_WEB)
+    return()
+endif()
+
+set(_MAX25_WEB_SRC "${CMAKE_SOURCE_DIR}/stacks/web")
+
+execute_process(
+    COMMAND "${CMAKE_COMMAND}" -E chmod u+x
+            "${_MAX25_WEB_SRC}/proxy/max25-ws-proxy.py"
+            "${_MAX25_WEB_SRC}/scripts/dev-server.sh"
+    ERROR_QUIET
+)
+
+install(PROGRAMS "${_MAX25_WEB_SRC}/proxy/max25-ws-proxy.py"
+        DESTINATION "${CMAKE_INSTALL_BINDIR}"
+        RENAME max25-ws-proxy)
+
+install(FILES "${_MAX25_WEB_SRC}/share/web-proxy.ini.example"
+        "${_MAX25_WEB_SRC}/share/web-terminal.ini.example"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25")
+
+install(FILES "${_MAX25_WEB_SRC}/share/web-terminal.ini.example"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25")
+
+install(FILES "${CMAKE_SOURCE_DIR}/share/max25/max25-ws-proxy.service.example"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25")
+
+install(DIRECTORY "${_MAX25_WEB_SRC}/share/reverse-proxy/"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25/reverse-proxy")
+
+install(PROGRAMS "${_MAX25_WEB_SRC}/scripts/dev-server.sh"
+        DESTINATION "${CMAKE_INSTALL_DATADIR}/max25/web"
+        RENAME max25-web-dev)
+
+add_custom_target(max25_web_smoke
+    COMMAND "${CMAKE_COMMAND}" -E env PYTHONPATH=
+            python3 "${_MAX25_WEB_SRC}/proxy/test_ws_proxy.py"
+    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+    COMMENT "MAX25 web proxy smoke test"
+)
diff --git a/stacks/web/README.md b/stacks/web/README.md
new file mode 100644
index 0000000..18cc291
--- /dev/null
+++ b/stacks/web/README.md
@@ -0,0 +1,112 @@
+# MAX25 Web UI — browser remote terminal
+
+> **Status: available** — full remote terminal (M25/1 via WebSocket proxy). Same session model as `max25-terminal`. Not a replacement for the CLI client.
+
+**Operator guide:** [docs/WEBSOCKET.md](../../docs/WEBSOCKET.md) · **Roadmap:** [docs/V2.0.0-SCOPE.md](../../docs/V2.0.0-SCOPE.md#dev-levels-roadmap-stack-wide)
+
+Browser terminal for **max25d** M25/1 — hyBBX-style httpd + reverse-proxy pattern, MAX25-correct separate loopback proxy.
+
+| Layer | Component | Role |
+|-------|-----------|------|
+| Browser UI | PHP + JS (`docroot/max25-websocket/`) | Remote terminal; `/` commands + menu |
+| Session defaults | `web-terminal.ini` | CALLERID, CALLID, device, ax25_ui per session |
+| HTTP reverse-proxy | nginx / Apache / lighttpd examples | `WS /max25-websocket/ws` → loopback proxy |
+| WebSocket proxy | `max25-ws-proxy.py` | RFC6455 ↔ M25/1 TCP forward (no translation) |
+| Daemon | `max25d` | M25/1 on TCP `7325` |
+
+CLI operator client remains **max25-terminal** — see [docs/MAX25-TERMINAL.md](../../docs/MAX25-TERMINAL.md).
+
+## Implementation status
+
+| Item | State |
+|------|--------|
+| PHP + JS UI (`docroot/max25-websocket/`) | **Available** — header, dropdown menu, device select |
+| `max25-terminal.js` | **Available** — F10-equivalent `/` commands, bootstrap from INI |
+| `web-terminal.ini.example` | **Available** — session defaults from max25d logic |
+| `max25-ws-proxy.py` | **Available** — CI smoke test passes |
+| httpd examples | Draft configs (nginx, Apache, lighttpd) |
+| systemd unit example | Shipped — `share/max25/max25-ws-proxy.service.example` |
+| Admin dashboard | Later |
+
+## Browser commands (F10 equivalent)
+
+| `/command` | M25/1 |
+|------------|-------|
+| `/callerid` `/callid` | `SET CALLERID` / `SET CALLID` |
+| `/status` | `GET STATUS` |
+| `/send <text>` | `SEND` |
+| `/monitor` | `MONITOR on\|off` |
+| `/connect` `/disconnect` | `CONNECT` / `DISCONNECT` |
+| `/devices` | `GET DEVICES` |
+| `/device <id>` | `SET DEVICE` (max25d ids only) |
+| `/ax25_ui on\|off` | `SET AX25_UI` |
+| `/help` | Command list |
+
+Plain text without `/` → `SEND` (same as max25-terminal Enter). **Menu ▾** dropdown mirrors these actions.
+
+One **device per session**; change via dropdown or `/device`. Device list always from **GET DEVICES** — unknown ids rejected.
+
+## Quick start (local dev)
+
+```bash
+# Terminal 1: max25d
+python3 stacks/daemon/max25d.py --tcp-port 7325
+
+# Terminal 2: dev stack (proxy + PHP)
+./stacks/web/scripts/dev-server.sh
+```
+
+Browser: `http://127.0.0.1:8080/`
+
+Copy `share/web-terminal.ini.example` → `/etc/max25/web-terminal.ini` for session defaults (CALLERID, CALLID, device from max25d.ini logic).
+
+## Configuration
+
+### WebSocket proxy (`web-proxy.ini`)
+
+Copy `share/web-proxy.ini.example` to `/etc/max25/web-proxy.ini` (or `MAX25_WEB_PROXY_INI`).
+
+| Section | Key | Default | Meaning |
+|---------|-----|---------|---------|
+| `[proxy]` | `bind` | `127.0.0.1` | Loopback only |
+| `[proxy]` | `port` | `7326` | WebSocket listen port |
+| `[proxy]` | `path` | `/max25` | Upgrade path |
+| `[upstream]` | `host` / `port` | `127.0.0.1` / `7325` | max25d M25/1 |
+| `[upstream]` | `tcp_password` | *(empty)* | Proxy-side AUTH |
+
+### Browser session (`web-terminal.ini`)
+
+Copy `share/web-terminal.ini.example` to `/etc/max25/web-terminal.ini` (or `MAX25_WEB_TERMINAL_INI`).
+
+Merges with max25d `[modem]` and `[devices] default` when keys omitted — see [docs/WEBSOCKET.md](../../docs/WEBSOCKET.md).
+
+## Production deploy
+
+```bash
+cmake --install $BUILD --prefix $PREFIX
+```
+
+Installs: `max25-ws-proxy`, `web-proxy.ini.example`, `web-terminal.ini.example`, `reverse-proxy/` tree.
+
+1. Copy `docroot/max25-websocket/` to httpd docroot
+2. Add httpd WS snippet → `127.0.0.1:7326/max25`
+3. Configure `web-proxy.ini` + `web-terminal.ini`
+4. Run `max25-ws-proxy` (systemd example shipped)
+
+## Architecture
+
+```
+Browser → httpd (wss) → max25-ws-proxy :7326 → max25d M25/1 :7325
+```
+
+M25/1 uses `\n` line endings. Proxy forwards bytes after connect handshake (`OK` + `STATUS`).
+
+## CI
+
+Target `max25_web_smoke` — PING through max25d + proxy + WebSocket (offline, no UART).
+
+## Related
+
+- [docs/WEBSOCKET.md](../../docs/WEBSOCKET.md) — operator guide
+- [include/max25/protocol.md](../../include/max25/protocol.md) — M25/1 spec
+- [docs/MAX25-CLIENT.md](../../docs/MAX25-CLIENT.md) — client contract
diff --git a/stacks/web/proxy/max25-ws-proxy.py b/stacks/web/proxy/max25-ws-proxy.py
new file mode 100755
index 0000000..fe593e8
--- /dev/null
+++ b/stacks/web/proxy/max25-ws-proxy.py
@@ -0,0 +1,399 @@
+#!/usr/bin/env python3
+"""
+max25-ws-proxy — WebSocket forward-proxy to max25d M25/1 TCP (loopback only).
+
+Accepts RFC6455 text frames and forwards bytes to max25d without protocol
+translation. Optional upstream AUTH uses [upstream] tcp_password from config.
+
+Intended behind a TLS reverse proxy; see stacks/web/share/reverse-proxy/.
+"""
+from __future__ import annotations
+
+import argparse
+import asyncio
+import base64
+import configparser
+import hashlib
+import logging
+import os
+import signal
+import struct
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Optional
+
+WS_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
+LOG = logging.getLogger("max25-ws-proxy")
+
+
+@dataclass
+class ProxyConfig:
+    bind: str = "127.0.0.1"
+    port: int = 7326
+    path: str = "/max25"
+    upstream_host: str = "127.0.0.1"
+    upstream_port: int = 7325
+    tcp_password: str = ""
+    max_connections: int = 10
+
+
+def load_config(path: Optional[str]) -> ProxyConfig:
+    cfg = ProxyConfig()
+    if not path:
+        return cfg
+
+    ini = configparser.ConfigParser()
+    ini.read(path)
+    if ini.has_section("proxy"):
+        sec = ini["proxy"]
+        cfg.bind = sec.get("bind", cfg.bind)
+        cfg.port = sec.getint("port", fallback=cfg.port)
+        cfg.path = sec.get("path", cfg.path)
+        cfg.max_connections = sec.getint("max_connections", fallback=cfg.max_connections)
+    if ini.has_section("upstream"):
+        sec = ini["upstream"]
+        cfg.upstream_host = sec.get("host", cfg.upstream_host)
+        cfg.upstream_port = sec.getint("port", fallback=cfg.upstream_port)
+        cfg.tcp_password = sec.get("tcp_password", cfg.tcp_password)
+    return cfg
+
+
+def resolve_config_path(explicit: Optional[str]) -> Optional[str]:
+    if explicit:
+        return explicit
+    env = os.environ.get("MAX25_WEB_PROXY_INI")
+    if env:
+        return env
+    for candidate in (
+        "/etc/max25/web-proxy.ini",
+    ):
+        if Path(candidate).is_file():
+            return candidate
+    return None
+
+
+async def read_http_request(reader: asyncio.StreamReader) -> tuple[str, dict[str, str]]:
+    request_line = (await reader.readline()).decode("ascii", errors="replace").strip()
+    if not request_line:
+        raise ConnectionError("empty request")
+    headers: dict[str, str] = {}
+    while True:
+        line = (await reader.readline()).decode("ascii", errors="replace").strip()
+        if line == "":
+            break
+        if ":" not in line:
+            continue
+        key, value = line.split(":", 1)
+        headers[key.strip().lower()] = value.strip()
+    return request_line, headers
+
+
+def ws_accept_key(sec_key: str) -> str:
+    digest = hashlib.sha1((sec_key + WS_GUID).encode("ascii")).digest()
+    return base64.b64encode(digest).decode("ascii")
+
+
+async def ws_handshake(
+    reader: asyncio.StreamReader,
+    writer: asyncio.StreamWriter,
+    expected_path: str,
+) -> None:
+    request_line, headers = await read_http_request(reader)
+    parts = request_line.split()
+    if len(parts) < 2:
+        raise ConnectionError("bad request line")
+    path = parts[1].split("?", 1)[0]
+    if path != expected_path:
+        raise ConnectionError(f"path mismatch: {path!r}")
+
+    upgrade = headers.get("upgrade", "").lower()
+    connection = headers.get("connection", "").lower()
+    sec_key = headers.get("sec-websocket-key", "")
+    if upgrade != "websocket" or "upgrade" not in connection or not sec_key:
+        raise ConnectionError("not a websocket upgrade")
+
+    accept = ws_accept_key(sec_key)
+    response = (
+        "HTTP/1.1 101 Switching Protocols\r\n"
+        "Upgrade: websocket\r\n"
+        "Connection: Upgrade\r\n"
+        f"Sec-WebSocket-Accept: {accept}\r\n"
+        "\r\n"
+    )
+    writer.write(response.encode("ascii"))
+    await writer.drain()
+
+
+async def ws_read_frame(reader: asyncio.StreamReader) -> tuple[int, bytes]:
+    header = await reader.readexactly(2)
+    b1, b2 = header[0], header[1]
+    opcode = b1 & 0x0F
+    masked = bool(b2 & 0x80)
+    length = b2 & 0x7F
+    if length == 126:
+        length = struct.unpack("!H", await reader.readexactly(2))[0]
+    elif length == 127:
+        length = struct.unpack("!Q", await reader.readexactly(8))[0]
+    mask = await reader.readexactly(4) if masked else b""
+    payload = await reader.readexactly(length) if length else b""
+    if masked:
+        payload = bytes(b ^ mask[i % 4] for i, b in enumerate(payload))
+    return opcode, payload
+
+
+async def ws_write_text(writer: asyncio.StreamWriter, text: bytes) -> None:
+    length = len(text)
+    header = bytearray([0x81])  # FIN + text frame
+    if length < 126:
+        header.append(length)
+    elif length < 65536:
+        header.append(126)
+        header.extend(struct.pack("!H", length))
+    else:
+        header.append(127)
+        header.extend(struct.pack("!Q", length))
+    writer.write(bytes(header) + text)
+    await writer.drain()
+
+
+async def ws_write_pong(writer: asyncio.StreamWriter, payload: bytes) -> None:
+    length = len(payload)
+    header = bytearray([0x8A])  # FIN + pong
+    if length < 126:
+        header.append(length)
+    else:
+        header.append(126)
+        header.extend(struct.pack("!H", length))
+    writer.write(bytes(header) + payload)
+    await writer.drain()
+
+
+async def read_line(reader: asyncio.StreamReader) -> Optional[str]:
+    line = await reader.readline()
+    if not line:
+        return None
+    text = line.decode("utf-8", errors="replace")
+    if text.endswith("\n"):
+        text = text[:-1]
+    if text.endswith("\r"):
+        text = text[:-1]
+    return text
+
+
+async def upstream_handshake(
+    reader: asyncio.StreamReader,
+    writer: asyncio.StreamWriter,
+    tcp_password: str,
+) -> list[str]:
+    """Complete max25d connect handshake; return lines to forward to the client."""
+    first = await read_line(reader)
+    if first is None:
+        raise ConnectionError("upstream closed during handshake")
+
+    forwarded: list[str] = []
+    if first == "AUTH required":
+        if not tcp_password:
+            forwarded.append(first)
+            return forwarded
+        writer.write(f"AUTH {tcp_password}\n".encode("utf-8"))
+        await writer.drain()
+        reply = await read_line(reader)
+        if reply != "OK":
+            raise ConnectionError(f"upstream auth failed: {reply!r}")
+        forwarded.append("OK")
+        status = await read_line(reader)
+        if status is None:
+            raise ConnectionError("upstream closed after auth")
+        forwarded.append(status)
+        return forwarded
+
+    if first != "OK":
+        raise ConnectionError(f"unexpected upstream greeting: {first!r}")
+    forwarded.append(first)
+    status = await read_line(reader)
+    if status is None:
+        raise ConnectionError("upstream closed after OK")
+    forwarded.append(status)
+    return forwarded
+
+
+async def pipe_tcp_to_ws(
+    tcp_reader: asyncio.StreamReader,
+    ws_writer: asyncio.StreamWriter,
+) -> None:
+    while True:
+        chunk = await tcp_reader.read(4096)
+        if not chunk:
+            break
+        await ws_write_text(ws_writer, chunk)
+
+
+async def pipe_ws_to_tcp(
+    ws_reader: asyncio.StreamReader,
+    ws_writer: asyncio.StreamWriter,
+    tcp_writer: asyncio.StreamWriter,
+) -> None:
+    while True:
+        opcode, payload = await ws_read_frame(ws_reader)
+        if opcode == 0x8:
+            break
+        if opcode == 0x9:
+            await ws_write_pong(ws_writer, payload)
+            continue
+        if opcode == 0xA:
+            continue
+        if opcode != 0x1:
+            LOG.warning("ignoring non-text websocket frame opcode=%s", opcode)
+            continue
+        tcp_writer.write(payload)
+        await tcp_writer.drain()
+
+
+class ConnectionLimiter:
+    def __init__(self, limit: int) -> None:
+        self.limit = limit
+        self.active = 0
+
+    def try_acquire(self) -> bool:
+        if self.active >= self.limit:
+            return False
+        self.active += 1
+        return True
+
+    def release(self) -> None:
+        if self.active > 0:
+            self.active -= 1
+
+
+async def handle_client(
+    ws_reader: asyncio.StreamReader,
+    ws_writer: asyncio.StreamWriter,
+    cfg: ProxyConfig,
+    limiter: ConnectionLimiter,
+) -> None:
+    peer = ws_writer.get_extra_info("peername")
+    if not limiter.try_acquire():
+        LOG.warning("connection limit reached; rejecting %s", peer)
+        ws_writer.close()
+        await ws_writer.wait_closed()
+        return
+
+    try:
+        await ws_handshake(ws_reader, ws_writer, cfg.path)
+    except Exception as exc:
+        LOG.warning("handshake failed from %s: %s", peer, exc)
+        limiter.release()
+        ws_writer.close()
+        await ws_writer.wait_closed()
+        return
+
+    LOG.info("websocket accepted from %s", peer)
+    tcp_reader: Optional[asyncio.StreamReader] = None
+    tcp_writer: Optional[asyncio.StreamWriter] = None
+    try:
+        tcp_reader, tcp_writer = await asyncio.open_connection(
+            cfg.upstream_host, cfg.upstream_port
+        )
+        lines = await upstream_handshake(tcp_reader, tcp_writer, cfg.tcp_password)
+        for line in lines:
+            await ws_write_text(ws_writer, (line + "\n").encode("utf-8"))
+
+        tcp_task = asyncio.create_task(pipe_tcp_to_ws(tcp_reader, ws_writer))
+        ws_task = asyncio.create_task(pipe_ws_to_tcp(ws_reader, ws_writer, tcp_writer))
+        done, pending = await asyncio.wait(
+            {tcp_task, ws_task}, return_when=asyncio.FIRST_COMPLETED
+        )
+        for task in pending:
+            task.cancel()
+        await asyncio.gather(*pending, return_exceptions=True)
+    except Exception as exc:
+        LOG.warning("session ended for %s: %s", peer, exc)
+        try:
+            await ws_write_text(ws_writer, f"\n[proxy error: {exc}]\n".encode("utf-8"))
+        except Exception:
+            pass
+    finally:
+        if tcp_writer is not None:
+            tcp_writer.close()
+            try:
+                await tcp_writer.wait_closed()
+            except Exception:
+                pass
+        ws_writer.close()
+        try:
+            await ws_writer.wait_closed()
+        except Exception:
+            pass
+        limiter.release()
+        LOG.info("websocket closed for %s", peer)
+
+
+async def run_server(cfg: ProxyConfig) -> None:
+    limiter = ConnectionLimiter(cfg.max_connections)
+    server = await asyncio.start_server(
+        lambda r, w: handle_client(r, w, cfg, limiter),
+        host=cfg.bind,
+        port=cfg.port,
+    )
+    addrs = ", ".join(str(sock.getsockname()) for sock in server.sockets or [])
+    LOG.info(
+        "listening on %s path=%s -> %s:%s",
+        addrs,
+        cfg.path,
+        cfg.upstream_host,
+        cfg.upstream_port,
+    )
+    async with server:
+        await server.serve_forever()
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="MAX25 WebSocket forward-proxy to max25d TCP")
+    parser.add_argument("-c", "--config", help="web-proxy.ini path")
+    parser.add_argument("--bind", help="override [proxy] bind")
+    parser.add_argument("--port", type=int, help="override [proxy] port")
+    parser.add_argument("--path", help="override [proxy] path")
+    parser.add_argument("--upstream-host", help="override [upstream] host")
+    parser.add_argument("--upstream-port", type=int, help="override [upstream] port")
+    parser.add_argument("-v", "--verbose", action="store_true")
+    args = parser.parse_args()
+
+    logging.basicConfig(
+        level=logging.DEBUG if args.verbose else logging.INFO,
+        format="%(asctime)s %(levelname)s %(message)s",
+    )
+
+    config_path = resolve_config_path(args.config)
+    cfg = load_config(config_path)
+    if args.bind:
+        cfg.bind = args.bind
+    if args.port:
+        cfg.port = args.port
+    if args.path:
+        cfg.path = args.path
+    if args.upstream_host:
+        cfg.upstream_host = args.upstream_host
+    if args.upstream_port:
+        cfg.upstream_port = args.upstream_port
+
+    if config_path:
+        LOG.info("config: %s", config_path)
+
+    loop = asyncio.new_event_loop()
+    asyncio.set_event_loop(loop)
+
+    for sig in (signal.SIGINT, signal.SIGTERM):
+        loop.add_signal_handler(sig, loop.stop)
+
+    try:
+        loop.run_until_complete(run_server(cfg))
+    except KeyboardInterrupt:
+        pass
+    finally:
+        loop.close()
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/web/proxy/test_ws_proxy.py b/stacks/web/proxy/test_ws_proxy.py
new file mode 100755
index 0000000..fccba84
--- /dev/null
+++ b/stacks/web/proxy/test_ws_proxy.py
@@ -0,0 +1,237 @@
+#!/usr/bin/env python3
+"""CI-safe smoke: max25-ws-proxy forwards M25/1 PING (no UART / no stack)."""
+from __future__ import annotations
+
+import asyncio
+import base64
+import hashlib
+import os
+import signal
+import socket
+import struct
+import subprocess
+import sys
+import tempfile
+import time
+from pathlib import Path
+
+WS_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
+ROOT = Path(__file__).resolve().parents[3]
+PROXY = ROOT / "stacks/web/proxy/max25-ws-proxy.py"
+DAEMON = ROOT / "stacks/daemon/max25d"
+
+
+def ws_accept(sec_key: str) -> str:
+    digest = hashlib.sha1((sec_key + WS_GUID).encode()).digest()
+    return base64.b64encode(digest).decode()
+
+
+def free_port() -> int:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+    return port
+
+
+def wait_for_unix(path: str, proc: subprocess.Popen[str], timeout: float = 8.0) -> bool:
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+        if proc.poll() is not None:
+            return False
+        if Path(path).exists():
+            try:
+                probe = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+                probe.settimeout(0.25)
+                probe.connect(path)
+                probe.close()
+                return True
+            except OSError:
+                pass
+        time.sleep(0.05)
+    return False
+
+
+def wait_for_port(port: int, proc: subprocess.Popen[str], timeout: float = 8.0) -> bool:
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+        if proc.poll() is not None:
+            return False
+        try:
+            probe = socket.create_connection(("127.0.0.1", port), timeout=0.25)
+            probe.close()
+            return True
+        except OSError:
+            time.sleep(0.05)
+    return False
+
+
+def drain_stderr(proc: subprocess.Popen[str]) -> str:
+    if not proc.stderr:
+        return ""
+    try:
+        return proc.stderr.read() or ""
+    except OSError:
+        return ""
+
+
+async def ws_exchange(host: str, port: int, path: str, send: str) -> str:
+    reader, writer = await asyncio.open_connection(host, port)
+    key = base64.b64encode(os.urandom(16)).decode()
+    req = (
+        f"GET {path} HTTP/1.1\r\n"
+        f"Host: {host}:{port}\r\n"
+        "Upgrade: websocket\r\n"
+        "Connection: Upgrade\r\n"
+        f"Sec-WebSocket-Key: {key}\r\n"
+        "Sec-WebSocket-Version: 13\r\n"
+        "\r\n"
+    )
+    writer.write(req.encode())
+    await writer.drain()
+    status = await reader.readline()
+    if b"101" not in status:
+        raise RuntimeError(f"upgrade failed: {status!r}")
+    while True:
+        line = await reader.readline()
+        if line in (b"\r\n", b"\n", b""):
+            break
+
+    payload = send.encode()
+    header = bytes([0x81, len(payload)])
+    writer.write(header + payload)
+    await writer.drain()
+
+    hdr = await reader.readexactly(2)
+    length = hdr[1] & 0x7F
+    if length == 126:
+        length = struct.unpack("!H", await reader.readexactly(2))[0]
+    data = await reader.readexactly(length)
+    writer.close()
+    await writer.wait_closed()
+    return data.decode()
+
+
+def stop(proc: subprocess.Popen[str]) -> None:
+    if proc.poll() is not None:
+        return
+    proc.send_signal(signal.SIGTERM)
+    try:
+        proc.wait(timeout=3)
+    except subprocess.TimeoutExpired:
+        proc.kill()
+        proc.wait(timeout=2)
+
+
+def main() -> int:
+    if not DAEMON.is_file():
+        print(f"max25_web_smoke: missing daemon launcher {DAEMON}", file=sys.stderr)
+        return 1
+    if not PROXY.is_file():
+        print(f"max25_web_smoke: missing proxy {PROXY}", file=sys.stderr)
+        return 1
+
+    with tempfile.TemporaryDirectory(prefix="max25-web-smoke-") as tmp:
+        sock = str(Path(tmp) / "modem.sock")
+        tcp_port = free_port()
+        proxy_port = free_port()
+        ini = Path(tmp) / "max25d.ini"
+        proxy_ini = Path(tmp) / "web-proxy.ini"
+        # /dev/null: CI must not open a real UART (ttyS0 is flaky / absent).
+        ini.write_text(
+            "[daemon]\nmode=standalone\nhardware=tncs\ndevice=tnc2c\n"
+            "[network]\ntcp_host=127.0.0.1\n"
+            f"tcp_port={tcp_port}\nunix_socket={sock}\ntcp_password=\n"
+            "[devices]\ntnc2c=/dev/null\n",
+            encoding="utf-8",
+        )
+        proxy_ini.write_text(
+            f"[proxy]\nbind=127.0.0.1\nport={proxy_port}\npath=/max25\n"
+            f"[upstream]\nhost=127.0.0.1\nport={tcp_port}\ntcp_password=\n",
+            encoding="utf-8",
+        )
+
+        daemon = subprocess.Popen(
+            [
+                str(DAEMON),
+                "--no-stack",
+                "--no-serial",
+                "-c",
+                str(ini),
+                "--tcp-port",
+                str(tcp_port),
+            ],
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.PIPE,
+            text=True,
+        )
+        proxy: subprocess.Popen[str] | None = None
+        try:
+            if not wait_for_unix(sock, daemon):
+                err = drain_stderr(daemon)
+                print(
+                    f"max25_web_smoke: max25d unix sock not ready: {err.strip()}",
+                    file=sys.stderr,
+                )
+                return 1
+            if not wait_for_port(tcp_port, daemon):
+                err = drain_stderr(daemon)
+                print(
+                    f"max25_web_smoke: max25d TCP not listening: {err.strip()}",
+                    file=sys.stderr,
+                )
+                return 1
+
+            proxy = subprocess.Popen(
+                [sys.executable, str(PROXY), "-c", str(proxy_ini)],
+                stdout=subprocess.DEVNULL,
+                stderr=subprocess.PIPE,
+                text=True,
+            )
+            if not wait_for_port(proxy_port, proxy):
+                err = drain_stderr(proxy)
+                print(
+                    f"max25_web_smoke: proxy not listening: {err.strip()}",
+                    file=sys.stderr,
+                )
+                return 1
+
+            deadline = time.time() + 8
+            last_exc: Exception | None = None
+            while time.time() < deadline:
+                if daemon.poll() is not None or proxy.poll() is not None:
+                    break
+                try:
+                    out = asyncio.run(
+                        ws_exchange("127.0.0.1", proxy_port, "/max25", "PING\n")
+                    )
+                    if "OK" in out or "PONG" in out or "STATUS" in out:
+                        print("max25_web_smoke: ok")
+                        return 0
+                    last_exc = RuntimeError(f"unexpected reply: {out!r}")
+                except (
+                    ConnectionRefusedError,
+                    OSError,
+                    RuntimeError,
+                    asyncio.IncompleteReadError,
+                ) as exc:
+                    last_exc = exc
+                    time.sleep(0.15)
+
+            d_err = drain_stderr(daemon)
+            p_err = drain_stderr(proxy) if proxy else ""
+            detail = f"last={last_exc!r}" if last_exc else "no M25/1 response"
+            print(f"max25_web_smoke: failed — {detail}", file=sys.stderr)
+            if d_err.strip():
+                print(f"max25d stderr:\n{d_err.rstrip()}", file=sys.stderr)
+            if p_err.strip():
+                print(f"proxy stderr:\n{p_err.rstrip()}", file=sys.stderr)
+            return 1
+        finally:
+            if proxy is not None:
+                stop(proxy)
+            stop(daemon)
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/stacks/web/scripts/dev-router.php b/stacks/web/scripts/dev-router.php
new file mode 100644
index 0000000..fd44559
--- /dev/null
+++ b/stacks/web/scripts/dev-router.php
@@ -0,0 +1,21 @@
+<?php
+/**
+ * PHP built-in server router for local dev (direct loopback WebSocket URL).
+ */
+$uri = parse_url($_SERVER['REQUEST_URI'] ?? '/', PHP_URL_PATH) ?: '/';
+$root = __DIR__ . '/../share/reverse-proxy/docroot/max25-websocket';
+
+if ($uri === '/' || $uri === '/index.php') {
+    $ws_url = getenv('MAX25_DEV_WS_URL') ?: 'ws://127.0.0.1:7326/max25';
+    require $root . '/index.php';
+    return true;
+}
+
+$file = $root . $uri;
+if (is_file($file)) {
+    return false;
+}
+
+http_response_code(404);
+echo "not found\n";
+return true;
diff --git a/stacks/web/scripts/dev-server.sh b/stacks/web/scripts/dev-server.sh
new file mode 100755
index 0000000..00b9f0c
--- /dev/null
+++ b/stacks/web/scripts/dev-server.sh
@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# Local dev: max25-ws-proxy + PHP built-in server (direct WebSocket to loopback proxy).
+set -euo pipefail
+
+SRC="$(cd "$(dirname "$0")/../../.." && pwd)"
+WEB="$SRC/stacks/web"
+DOCROOT="$WEB/share/reverse-proxy/docroot/max25-websocket"
+PROXY_INI="${MAX25_WEB_PROXY_INI:-$WEB/share/web-proxy.ini.example}"
+PHP_HOST="${MAX25_WEB_PHP_HOST:-127.0.0.1}"
+PHP_PORT="${MAX25_WEB_PHP_PORT:-8080}"
+PROXY_PORT="${MAX25_WEB_PROXY_PORT:-7326}"
+
+cleanup() {
+  if [[ -n "${PROXY_PID:-}" ]]; then
+    kill "$PROXY_PID" 2>/dev/null || true
+  fi
+}
+trap cleanup EXIT
+
+echo "MAX25 web dev"
+echo "  max25d expected on 127.0.0.1:7325 (start separately)"
+echo "  proxy ini: $PROXY_INI"
+echo "  WebSocket: ws://127.0.0.1:$PROXY_PORT/max25"
+echo "  PHP UI:    http://$PHP_HOST:$PHP_PORT/"
+echo ""
+
+python3 "$WEB/proxy/max25-ws-proxy.py" -c "$PROXY_INI" --port "$PROXY_PORT" &
+PROXY_PID=$!
+sleep 0.3
+
+export MAX25_DEV_WS_URL="ws://127.0.0.1:${PROXY_PORT}/max25"
+php -S "$PHP_HOST:$PHP_PORT" -t "$DOCROOT" "$WEB/scripts/dev-router.php"
diff --git a/stacks/web/share/reverse-proxy/README.txt b/stacks/web/share/reverse-proxy/README.txt
new file mode 100644
index 0000000..43d2748
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/README.txt
@@ -0,0 +1,10 @@
+MAX25 reverse-proxy examples. WebSocket proxy = M25/1 data on loopback only.
+
+1. HTTPD_DOCROOT=/srv/www   # your httpd document root
+2. cp -r docroot/max25-websocket $HTTPD_DOCROOT/
+3. Add nginx/apache/lighttpd snippet (adjust paths) — see docs/WEBSOCKET.md
+4. web-proxy.ini — copy share/web-proxy.ini.example to /etc/max25/web-proxy.ini
+5. web-terminal.ini — copy share/web-terminal.ini.example to /etc/max25/web-terminal.ini
+6. max25-ws-proxy -c /etc/max25/web-proxy.ini  (systemd example in share/max25/)
+
+Match URL paths in web-proxy.ini and the httpd snippets in docs/WEBSOCKET.md.
diff --git a/stacks/web/share/reverse-proxy/apache2.conf.example b/stacks/web/share/reverse-proxy/apache2.conf.example
new file mode 100644
index 0000000..f702fe0
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/apache2.conf.example
@@ -0,0 +1,21 @@
+# MAX25 — Apache httpd 2.4. HTTPD_DOCROOT example: /srv/www
+
+<IfModule mod_proxy.c>
+    ProxyPreserveHost On
+    ProxyTimeout 3600
+
+    ProxyPass "/max25-websocket/ws" "ws://127.0.0.1:7326/max25" timeout=3600 keepalive=On
+    ProxyPassReverse "/max25-websocket/ws" "ws://127.0.0.1:7326/max25"
+</IfModule>
+
+Alias /max25-websocket /srv/www/max25-websocket
+<Directory /srv/www/max25-websocket>
+    DirectoryIndex index.php
+    Require all granted
+    <FilesMatch \.php$>
+        SetHandler application/x-httpd-php
+    </FilesMatch>
+</Directory>
+
+# UI: cp -r reverse-proxy/docroot/max25-websocket $HTTPD_DOCROOT/
+# Proxy: max25-ws-proxy -c /etc/max25/web-proxy.ini
diff --git a/stacks/web/share/reverse-proxy/docroot/README.txt b/stacks/web/share/reverse-proxy/docroot/README.txt
new file mode 100644
index 0000000..a23c84b
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/docroot/README.txt
@@ -0,0 +1,7 @@
+Copy docroot/max25-websocket/ to HTTPD_DOCROOT (not $PREFIX).
+max25-ws-proxy serves M25/1 on loopback only (default 127.0.0.1:7326).
+
+  HTTPD_DOCROOT=/srv/www
+  cp -r docroot/max25-websocket $HTTPD_DOCROOT/
+
+Match URL paths in web-proxy.ini and the httpd snippets in docs/WEBSOCKET.md.
diff --git a/stacks/web/share/reverse-proxy/docroot/max25-websocket/config.php b/stacks/web/share/reverse-proxy/docroot/max25-websocket/config.php
new file mode 100644
index 0000000..7a7f8cf
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/docroot/max25-websocket/config.php
@@ -0,0 +1,98 @@
+<?php
+/**
+ * Browser terminal defaults — merged from web-terminal.ini and max25d.ini.
+ */
+declare(strict_types=1);
+
+function max25_web_ini_path(): string
+{
+    $p = getenv('MAX25_WEB_TERMINAL_INI');
+    if ($p !== false && $p !== '') {
+        return $p;
+    }
+    if (is_readable('/etc/max25/web-terminal.ini')) {
+        return '/etc/max25/web-terminal.ini';
+    }
+    return __DIR__ . '/../../../web-terminal.ini.example';
+}
+
+function max25_web_parse_bool(string $v, bool $default): bool
+{
+    $v = strtolower(trim($v));
+    if ($v === '') {
+        return $default;
+    }
+    return in_array($v, ['1', 'yes', 'true', 'on'], true);
+}
+
+/** @return array{device:string,callerid:string,callid:string,ax25_ui:bool,connect_on_start:bool} */
+function max25_web_session_defaults(): array
+{
+    $defaults = [
+        'device' => '',
+        'callerid' => '',
+        'callid' => '',
+        'ax25_ui' => true,
+        'connect_on_start' => true,
+    ];
+
+    $web_ini = max25_web_ini_path();
+    $web = @parse_ini_file($web_ini, true, INI_SCANNER_RAW);
+    $sec = [];
+    if (is_array($web)) {
+        $sec = $web['session'] ?? [];
+        if (isset($sec['device'])) {
+            $defaults['device'] = trim((string)$sec['device']);
+        }
+        if (isset($sec['callerid']) && trim((string)$sec['callerid']) !== '') {
+            $defaults['callerid'] = strtoupper(trim((string)$sec['callerid']));
+        }
+        if (isset($sec['callid']) && trim((string)$sec['callid']) !== '') {
+            $defaults['callid'] = strtoupper(trim((string)$sec['callid']));
+        }
+        if (isset($sec['ax25_ui'])) {
+            $defaults['ax25_ui'] = max25_web_parse_bool((string)$sec['ax25_ui'], true);
+        }
+        if (isset($sec['connect_on_start'])) {
+            $defaults['connect_on_start'] = max25_web_parse_bool((string)$sec['connect_on_start'], true);
+        }
+        $max25d_ini = trim((string)($web['max25-web-terminal']['max25d_ini'] ?? ''));
+    } else {
+        $max25d_ini = '';
+    }
+
+    if ($max25d_ini === '') {
+        $env = getenv('MAX25D_INI');
+        $max25d_ini = ($env !== false && $env !== '') ? $env : '/etc/max25/max25d.ini';
+    }
+    if (!is_readable($max25d_ini)) {
+        return $defaults;
+    }
+
+    $md = @parse_ini_file($max25d_ini, true, INI_SCANNER_RAW);
+    if (!is_array($md)) {
+        return $defaults;
+    }
+
+    $modem = $md['modem'] ?? [];
+    $devices = $md['devices'] ?? [];
+
+    if ($defaults['device'] === '') {
+        if (isset($devices['default'])) {
+            $defaults['device'] = trim((string)$devices['default']);
+        } elseif (isset($md['daemon']['device'])) {
+            $defaults['device'] = trim((string)$md['daemon']['device']);
+        }
+    }
+    if ($defaults['callerid'] === '' && isset($modem['callerid'])) {
+        $defaults['callerid'] = strtoupper(trim((string)$modem['callerid']));
+    }
+    if ($defaults['callid'] === '' && isset($modem['callid'])) {
+        $defaults['callid'] = strtoupper(trim((string)$modem['callid']));
+    }
+    if (!isset($sec['ax25_ui']) && isset($modem['ax25_ui'])) {
+        $defaults['ax25_ui'] = max25_web_parse_bool((string)$modem['ax25_ui'], true);
+    }
+
+    return $defaults;
+}
diff --git a/stacks/web/share/reverse-proxy/docroot/max25-websocket/index.php b/stacks/web/share/reverse-proxy/docroot/max25-websocket/index.php
new file mode 100644
index 0000000..9876c61
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/docroot/max25-websocket/index.php
@@ -0,0 +1,180 @@
+<?php
+/**
+ * MAX25 browser terminal — remote operator UI (M25/1 via WebSocket proxy).
+ */
+require_once __DIR__ . '/config.php';
+
+$base = rtrim(dirname($_SERVER['SCRIPT_NAME'] ?? ''), '/');
+$ws_path = ($base !== '' ? $base : '/max25-websocket') . '/ws';
+$scheme = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off') ? 'wss' : 'ws';
+$host = $_SERVER['HTTP_HOST'] ?? 'localhost';
+$dev_ws = getenv('MAX25_DEV_WS_URL');
+$ws_url = ($dev_ws !== false && $dev_ws !== '') ? $dev_ws : ($scheme . '://' . $host . $ws_path);
+$session_defaults = max25_web_session_defaults();
+?><!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>MAX25 Terminal</title>
+  <style>
+    html, body { height: 100%; margin: 0; }
+    body {
+      display: flex;
+      flex-direction: column;
+      background: #0a0a12;
+      color: #c8d0d8;
+      font-family: ui-monospace, "Cascadia Mono", "Consolas", monospace;
+      font-size: 14px;
+    }
+    #topbar {
+      flex: none;
+      display: flex;
+      flex-wrap: wrap;
+      align-items: center;
+      gap: .5rem 1rem;
+      padding: .45rem .75rem;
+      background: #12121c;
+      border-bottom: 1px solid #2a2a38;
+      z-index: 2;
+    }
+    #topbar .brand { font-weight: 600; color: #e8ecf0; margin-right: .25rem; }
+    #topbar .field { color: #9aa4b2; font-size: .85rem; }
+    #topbar .field b { color: #dce2ea; font-weight: 500; }
+    #conn-status { margin-left: auto; font-size: .8rem; color: #8a94a4; }
+    #menu-wrap { position: relative; }
+    #menu-btn {
+      background: #1e1e2e;
+      border: 1px solid #3a3a4a;
+      color: #c8d0d8;
+      font: inherit;
+      font-size: .85rem;
+      padding: .25rem .65rem;
+      border-radius: 4px;
+      cursor: pointer;
+    }
+    #menu-btn:hover, #menu-btn[aria-expanded="true"] { background: #262638; }
+    #menu-panel {
+      display: none;
+      position: absolute;
+      top: calc(100% + 4px);
+      left: 0;
+      min-width: 15rem;
+      background: #161622;
+      border: 1px solid #3a3a4a;
+      border-radius: 4px;
+      box-shadow: 0 8px 24px rgba(0,0,0,.45);
+      z-index: 10;
+      padding: .35rem 0;
+    }
+    #menu-panel.open { display: block; }
+    #menu-panel button {
+      display: block;
+      width: 100%;
+      text-align: left;
+      background: none;
+      border: none;
+      color: #c8d0d8;
+      font: inherit;
+      font-size: .85rem;
+      padding: .4rem .85rem;
+      cursor: pointer;
+    }
+    #menu-panel button:hover { background: #222230; }
+    #menu-panel hr { border: none; border-top: 1px solid #2a2a38; margin: .25rem 0; }
+    #device-select {
+      background: #1e1e2e;
+      border: 1px solid #3a3a4a;
+      color: #dce2ea;
+      font: inherit;
+      font-size: .85rem;
+      padding: .2rem .45rem;
+      border-radius: 4px;
+      max-width: 11rem;
+    }
+    #term {
+      flex: 1;
+      min-height: 0;
+      box-sizing: border-box;
+      width: 100%;
+      margin: 0;
+      padding: .75rem 1rem;
+      white-space: pre-wrap;
+      overflow-y: auto;
+      overflow-x: hidden;
+    }
+    #input-bar {
+      flex: none;
+      display: flex;
+      width: 100%;
+      box-sizing: border-box;
+      border-top: 1px solid #2a2a38;
+      background: #12121c;
+    }
+    #cmd {
+      flex: 1;
+      width: 100%;
+      min-width: 0;
+      box-sizing: border-box;
+      border: none;
+      border-radius: 0;
+      background: #12121c;
+      color: #e0e4e8;
+      font: inherit;
+      font-size: 1rem;
+      line-height: 1.4;
+      padding: .75rem 1rem;
+      outline: none;
+    }
+    #cmd::placeholder { color: #6a7280; }
+    #cmd:focus { background: #161622; }
+    #cmd:disabled { opacity: .55; cursor: not-allowed; }
+    .hint { font-size: .75rem; color: #6a7280; padding: 0 .75rem .35rem; }
+  </style>
+</head>
+<body>
+  <header id="topbar">
+    <span class="brand">MAX25</span>
+    <div id="menu-wrap">
+      <button type="button" id="menu-btn" aria-expanded="false" aria-haspopup="true">Menu ▾</button>
+      <div id="menu-panel" role="menu">
+        <button type="button" data-action="callerid">/callerid — Change CALLERID</button>
+        <button type="button" data-action="callid">/callid — Change CALLID</button>
+        <button type="button" data-action="status">/status — GET STATUS</button>
+        <button type="button" data-action="send">/send — Send line</button>
+        <button type="button" data-action="monitor">/monitor — Toggle MONITOR</button>
+        <button type="button" data-action="connect">/connect — Connection on/off</button>
+        <hr>
+        <button type="button" data-action="devices">/devices — List devices</button>
+        <button type="button" data-action="ax25_ui">/ax25_ui — Toggle AX.25 UI</button>
+        <hr>
+        <button type="button" data-action="help">/help — Commands</button>
+      </div>
+    </div>
+    <span class="field">DEVICE: <b id="hdr-device">-</b></span>
+    <label class="field" for="device-select">select
+      <select id="device-select" disabled title="max25d registered devices only">
+        <option value="">—</option>
+      </select>
+    </label>
+    <span class="field">CALLERID: <b id="hdr-callerid">-</b></span>
+    <span class="field">CALLID: <b id="hdr-callid">-</b></span>
+    <span class="field">ax25-ui: <b id="hdr-ax25">-</b></span>
+    <span class="field">connected: <b id="hdr-connected">-</b></span>
+    <span id="conn-status">disconnected</span>
+  </header>
+  <pre id="term"></pre>
+  <form id="input-bar" autocomplete="off">
+    <input type="text" id="cmd" disabled
+           autocomplete="off" autocapitalize="off" autocorrect="off" spellcheck="false"
+           enterkeyhint="send"
+           placeholder="Type to SEND — or /help for commands">
+  </form>
+  <div class="hint">One device per session · /device &lt;id&gt; · plain text = SEND · only max25d devices</div>
+  <script>
+    window.MAX25_WS_URL = <?php echo json_encode($ws_url, JSON_UNESCAPED_SLASHES); ?>;
+    window.MAX25_SESSION_DEFAULTS = <?php echo json_encode($session_defaults, JSON_UNESCAPED_SLASHES); ?>;
+  </script>
+  <script src="max25-terminal.js"></script>
+</body>
+</html>
diff --git a/stacks/web/share/reverse-proxy/docroot/max25-websocket/max25-terminal.js b/stacks/web/share/reverse-proxy/docroot/max25-websocket/max25-terminal.js
new file mode 100644
index 0000000..9988a77
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/docroot/max25-websocket/max25-terminal.js
@@ -0,0 +1,609 @@
+(function () {
+  'use strict';
+
+  var term = document.getElementById('term');
+  var connStatus = document.getElementById('conn-status');
+  var form = document.getElementById('input-bar');
+  var input = document.getElementById('cmd');
+  var menuBtn = document.getElementById('menu-btn');
+  var menuPanel = document.getElementById('menu-panel');
+  var deviceSelect = document.getElementById('device-select');
+  var hdrDevice = document.getElementById('hdr-device');
+  var hdrCallerid = document.getElementById('hdr-callerid');
+  var hdrCallid = document.getElementById('hdr-callid');
+  var hdrAx25 = document.getElementById('hdr-ax25');
+  var hdrConnected = document.getElementById('hdr-connected');
+
+  var wsUrl = window.MAX25_WS_URL;
+  var defaults = window.MAX25_SESSION_DEFAULTS || {};
+  var ws = null;
+  var reconnectTimer = null;
+  var reconnectDelayMs = 2000;
+  var reconnectAttempt = 0;
+  var lineBuf = '';
+  var rxLines = [];
+  var RX_MAX = 200;
+  var waitingReply = false;
+  var pendingCmd = null;
+  var devices = [];
+  var sessionReady = false;
+  var bootstrapQueue = [];
+
+  var status = {
+    device: '',
+    callerid: '',
+    callid: '',
+    ax25_ui: true,
+    connected: false,
+    monitor: false,
+    stack: ''
+  };
+
+  function classifyLine(line) {
+    if (!line) {
+      return 'ignore';
+    }
+    if (line === 'OK') {
+      return 'ok';
+    }
+    if (line.indexOf('ERR ') === 0) {
+      return 'err';
+    }
+    if (line.indexOf('STATUS ') === 0) {
+      return 'status';
+    }
+    if (line.indexOf('RX ') === 0) {
+      return 'rx';
+    }
+    if (line.indexOf('EVENT ') === 0) {
+      return 'event';
+    }
+    if (line.indexOf('DEVICE ') === 0) {
+      return 'device';
+    }
+    return 'other';
+  }
+
+  function parseKvLine(payload) {
+    var out = {};
+    var parts = payload.split(' ');
+    var i;
+    for (i = 0; i < parts.length; i++) {
+      var eq = parts[i].indexOf('=');
+      if (eq > 0) {
+        out[parts[i].slice(0, eq)] = parts[i].slice(eq + 1);
+      }
+    }
+    return out;
+  }
+
+  function parseStatus(line) {
+    var kv = parseKvLine(line.slice(7));
+    if (kv.device !== undefined) {
+      status.device = kv.device;
+    }
+    if (kv.callerid !== undefined) {
+      status.callerid = kv.callerid;
+    }
+    if (kv.callid !== undefined) {
+      status.callid = kv.callid;
+    }
+    if (kv.ax25_ui !== undefined) {
+      status.ax25_ui = kv.ax25_ui === 'on';
+    }
+    if (kv.connected !== undefined) {
+      status.connected = kv.connected === 'yes';
+    }
+    if (kv.stack !== undefined) {
+      status.stack = kv.stack;
+    }
+    updateHeader();
+  }
+
+  function parseDeviceLine(line) {
+    var kv = parseKvLine(line.slice(7));
+    if (!kv.id) {
+      return null;
+    }
+    return {
+      id: kv.id,
+      hardware: kv.hardware || '',
+      serial: kv.serial || '',
+      stack: kv.stack || '',
+      enabled: kv.enabled || 'yes',
+      error: kv.error || '',
+      voice: kv.voice || ''
+    };
+  }
+
+  function validCallsign(value) {
+    if (!value) {
+      return false;
+    }
+    var m = /^([A-Z0-9]{1,6})(?:-([0-9]{1,2}))?$/i.exec(value.trim());
+    if (!m) {
+      return false;
+    }
+    if (m[2] !== undefined && parseInt(m[2], 10) > 15) {
+      return false;
+    }
+    return true;
+  }
+
+  function updateHeader() {
+    hdrDevice.textContent = status.device || '-';
+    hdrCallerid.textContent = status.callerid || '-';
+    hdrCallid.textContent = status.callid || '-';
+    hdrAx25.textContent = status.ax25_ui ? 'on' : 'off';
+    hdrConnected.textContent = status.connected ? 'yes' : 'no';
+  }
+
+  function refreshDeviceSelect() {
+    var html = '';
+    var i;
+    if (devices.length === 0) {
+      deviceSelect.innerHTML = '<option value="">—</option>';
+      deviceSelect.disabled = true;
+      return;
+    }
+    for (i = 0; i < devices.length; i++) {
+      var d = devices[i];
+      var sel = d.id === status.device ? ' selected' : '';
+      html += '<option value="' + escapeAttr(d.id) + '"' + sel + '>' +
+        escapeHtml(d.id) + '</option>';
+    }
+    deviceSelect.innerHTML = html;
+    deviceSelect.disabled = !sessionReady;
+  }
+
+  function escapeHtml(s) {
+    return String(s)
+      .replace(/&/g, '&amp;')
+      .replace(/</g, '&lt;')
+      .replace(/>/g, '&gt;');
+  }
+
+  function escapeAttr(s) {
+    return escapeHtml(s).replace(/"/g, '&quot;');
+  }
+
+  function appendRx(text) {
+    var lines = String(text).split('\n');
+    var i;
+    for (i = 0; i < lines.length; i++) {
+      if (lines[i] === '' && i === lines.length - 1) {
+        continue;
+      }
+      rxLines.push(lines[i]);
+      if (rxLines.length > RX_MAX) {
+        rxLines.shift();
+      }
+    }
+    term.textContent = rxLines.join('\n') + (rxLines.length ? '\n' : '');
+    term.scrollTop = term.scrollHeight;
+  }
+
+  function setConnStatus(s) {
+    connStatus.textContent = s;
+  }
+
+  function setInputEnabled(enabled) {
+    input.disabled = !enabled;
+    if (enabled) {
+      input.focus();
+    }
+  }
+
+  function sendRaw(cmd) {
+    if (!ws || ws.readyState !== WebSocket.OPEN) {
+      return false;
+    }
+    ws.send(cmd + '\n');
+    return true;
+  }
+
+  function sendCmd(cmd, label) {
+    pendingCmd = label || cmd;
+    waitingReply = true;
+    return sendRaw(cmd);
+  }
+
+  function applyEvent(line) {
+    if (line === 'EVENT connected') {
+      status.connected = true;
+      updateHeader();
+      return true;
+    }
+    if (line === 'EVENT disconnected') {
+      status.connected = false;
+      updateHeader();
+      return true;
+    }
+    return false;
+  }
+
+  var bootstrapped = false;
+
+  function handleLine(line) {
+    var kind = classifyLine(line);
+
+    if (kind === 'rx') {
+      appendRx(line.slice(3));
+      return;
+    }
+
+    if (kind === 'event') {
+      if (applyEvent(line)) {
+        appendRx(line);
+      }
+      return;
+    }
+
+    if (waitingReply) {
+      if (kind === 'status') {
+        parseStatus(line);
+        appendRx('STATUS device=' + (status.device || '-') +
+          ' stack=' + (status.stack || '-') +
+          ' connected=' + (status.connected ? 'yes' : 'no') +
+          ' callerid=' + (status.callerid || '-') +
+          ' callid=' + (status.callid || '-'));
+        return;
+      }
+      if (kind === 'device') {
+        var dev = parseDeviceLine(line);
+        if (dev) {
+          devices.push(dev);
+        }
+        if (pendingCmd === 'GET DEVICES') {
+          appendRx(line);
+        }
+        return;
+      }
+      if (kind === 'ok') {
+        waitingReply = false;
+        if (pendingCmd === 'GET DEVICES') {
+          refreshDeviceSelect();
+        }
+        pendingCmd = null;
+        if (bootstrapQueue.length > 0) {
+          window.setTimeout(runBootstrapStep, 0);
+        }
+        return;
+      }
+      if (kind === 'err') {
+        waitingReply = false;
+        appendRx(line);
+        pendingCmd = null;
+        if (bootstrapQueue.length > 0) {
+          bootstrapQueue = [];
+        }
+        return;
+      }
+      return;
+    }
+
+    if (kind === 'status') {
+      parseStatus(line);
+      if (!bootstrapped) {
+        bootstrapped = true;
+        startBootstrap();
+      }
+      return;
+    }
+    if (kind === 'err') {
+      appendRx(line);
+    }
+  }
+
+  function feedText(chunk) {
+    lineBuf += chunk;
+    var idx;
+    while ((idx = lineBuf.indexOf('\n')) >= 0) {
+      var line = lineBuf.slice(0, idx);
+      lineBuf = lineBuf.slice(idx + 1);
+      if (line.endsWith('\r')) {
+        line = line.slice(0, -1);
+      }
+      handleLine(line);
+    }
+  }
+
+  function queueBootstrap(cmd, label) {
+    bootstrapQueue.push({ cmd: cmd, label: label || cmd });
+  }
+
+  function runBootstrapStep() {
+    if (!sessionReady || waitingReply || bootstrapQueue.length === 0) {
+      return;
+    }
+    var step = bootstrapQueue.shift();
+    sendCmd(step.cmd, step.label);
+  }
+
+  function startBootstrap() {
+    bootstrapQueue = [];
+    devices = [];
+    refreshDeviceSelect();
+    sessionReady = true;
+
+    if (defaults.callerid && defaults.callerid !== status.callerid) {
+      queueBootstrap('SET CALLERID ' + defaults.callerid.toUpperCase());
+    }
+    if (defaults.callid && defaults.callid !== status.callid) {
+      queueBootstrap('SET CALLID ' + defaults.callid.toUpperCase());
+    }
+    queueBootstrap('SET AX25_UI ' + (defaults.ax25_ui !== false ? 'on' : 'off'));
+    if (defaults.device) {
+      queueBootstrap('SET DEVICE ' + defaults.device);
+    }
+    queueBootstrap('GET DEVICES', 'GET DEVICES');
+    if (defaults.connect_on_start !== false) {
+      queueBootstrap('CONNECT');
+    }
+    queueBootstrap('GET STATUS');
+
+    sessionReady = true;
+    runBootstrapStep();
+  }
+
+  function fetchDevices() {
+    devices = [];
+    sendCmd('GET DEVICES', 'GET DEVICES');
+  }
+
+  function setDevice(id) {
+    if (!id) {
+      return;
+    }
+    var known = false;
+    var i;
+    for (i = 0; i < devices.length; i++) {
+      if (devices[i].id === id) {
+        known = true;
+        break;
+      }
+    }
+    if (devices.length === 0) {
+      appendRx('ERR device list empty — run /devices first');
+      return;
+    }
+    if (!known) {
+      appendRx('ERR unknown device (not in max25d): ' + id);
+      return;
+    }
+    sendCmd('SET DEVICE ' + id);
+    window.setTimeout(function () {
+      sendCmd('GET STATUS');
+    }, 50);
+  }
+
+  function slashHelp() {
+    appendRx(
+      '-- MAX25 browser commands (F10 menu equivalent) --\n' +
+      '/callerid [id]   /callid [id]   /status\n' +
+      '/send <text>     /monitor [on|off|toggle]\n' +
+      '/connect         /disconnect\n' +
+      '/device <id>     /devices\n' +
+      '/ax25_ui on|off  /help\n' +
+      'Plain text (no /) is sent as SEND (like max25-terminal Enter).'
+    );
+  }
+
+  function handleSlash(line) {
+    var parts = line.slice(1).trim().split(/\s+/);
+    var cmd = (parts[0] || '').toLowerCase();
+    var arg = parts.slice(1).join(' ');
+
+    menuPanel.classList.remove('open');
+    menuBtn.setAttribute('aria-expanded', 'false');
+
+    if (cmd === 'help' || cmd === 'menu') {
+      slashHelp();
+      return;
+    }
+    if (cmd === 'callerid' || cmd === 'caller') {
+      if (arg) {
+        if (!validCallsign(arg)) {
+          appendRx('ERR invalid CALLERID');
+          return;
+        }
+        sendCmd('SET CALLERID ' + arg.toUpperCase());
+      } else {
+        var v = window.prompt('CALLERID', status.callerid || defaults.callerid || '');
+        if (v && validCallsign(v)) {
+          sendCmd('SET CALLERID ' + v.toUpperCase());
+        }
+      }
+      return;
+    }
+    if (cmd === 'callid' || cmd === 'call') {
+      if (arg) {
+        if (!validCallsign(arg)) {
+          appendRx('ERR invalid CALLID');
+          return;
+        }
+        sendCmd('SET CALLID ' + arg.toUpperCase());
+      } else {
+        var w = window.prompt('CALLID', status.callid || defaults.callid || '');
+        if (w && validCallsign(w)) {
+          sendCmd('SET CALLID ' + w.toUpperCase());
+        }
+      }
+      return;
+    }
+    if (cmd === 'status') {
+      sendCmd('GET STATUS');
+      return;
+    }
+    if (cmd === 'send') {
+      if (!arg) {
+        arg = window.prompt('Send line', '');
+      }
+      if (arg) {
+        sendCmd('SEND ' + arg);
+      }
+      return;
+    }
+    if (cmd === 'monitor') {
+      var on;
+      if (arg === 'on' || arg === 'yes' || arg === '1') {
+        on = true;
+      } else if (arg === 'off' || arg === 'no' || arg === '0') {
+        on = false;
+      } else {
+        on = !status.monitor;
+      }
+      status.monitor = on;
+      sendCmd('MONITOR ' + (on ? 'on' : 'off'));
+      appendRx(on ? 'MONITOR on' : 'MONITOR off');
+      return;
+    }
+    if (cmd === 'connect') {
+      sendCmd(status.connected ? 'DISCONNECT' : 'CONNECT');
+      return;
+    }
+    if (cmd === 'disconnect') {
+      sendCmd('DISCONNECT');
+      return;
+    }
+    if (cmd === 'devices') {
+      fetchDevices();
+      return;
+    }
+    if (cmd === 'device') {
+      if (!arg) {
+        fetchDevices();
+        appendRx('Pick device from dropdown or: /device <id>');
+        return;
+      }
+      setDevice(arg);
+      return;
+    }
+    if (cmd === 'ax25_ui' || cmd === 'ax25-ui') {
+      var flag = (arg || '').toLowerCase();
+      if (flag !== 'on' && flag !== 'off') {
+        flag = status.ax25_ui ? 'off' : 'on';
+      }
+      sendCmd('SET AX25_UI ' + flag);
+      return;
+    }
+    if (cmd === 'quit' || cmd === 'exit') {
+      if (ws) {
+        ws.close();
+      }
+      return;
+    }
+    appendRx('ERR unknown /command — try /help');
+  }
+
+  function scheduleReconnect() {
+    if (reconnectTimer) {
+      return;
+    }
+    reconnectAttempt += 1;
+    setConnStatus('reconnecting in ' + (reconnectDelayMs / 1000) + 's');
+    reconnectTimer = window.setTimeout(function () {
+      reconnectTimer = null;
+      connect();
+    }, reconnectDelayMs);
+  }
+
+  function connect() {
+    setConnStatus('connecting');
+    setInputEnabled(false);
+    sessionReady = false;
+    lineBuf = '';
+    ws = new WebSocket(wsUrl);
+
+    ws.onopen = function () {
+      reconnectAttempt = 0;
+      setConnStatus('connected');
+      setInputEnabled(true);
+    };
+
+    ws.onmessage = function (ev) {
+      feedText(ev.data);
+    };
+
+    ws.onclose = function (ev) {
+      var reason = ev.reason ? ' (' + ev.reason + ')' : '';
+      appendRx('\n[websocket disconnected: code ' + ev.code + reason + ']\n');
+      setConnStatus('disconnected: ' + ev.code);
+      ws = null;
+      sessionReady = false;
+      setInputEnabled(false);
+      deviceSelect.disabled = true;
+      scheduleReconnect();
+    };
+
+    ws.onerror = function () {
+      setConnStatus('error');
+      setInputEnabled(false);
+    };
+  }
+
+  form.addEventListener('submit', function (ev) {
+    ev.preventDefault();
+    if (!ws || ws.readyState !== WebSocket.OPEN || waitingReply) {
+      return;
+    }
+    var text = input.value;
+    input.value = '';
+    if (!text) {
+      return;
+    }
+    if (text.charAt(0) === '/') {
+      handleSlash(text);
+      return;
+    }
+    sendCmd('SEND ' + text);
+  });
+
+  menuBtn.addEventListener('click', function (ev) {
+    ev.stopPropagation();
+    var open = menuPanel.classList.toggle('open');
+    menuBtn.setAttribute('aria-expanded', open ? 'true' : 'false');
+  });
+
+  document.addEventListener('click', function () {
+    menuPanel.classList.remove('open');
+    menuBtn.setAttribute('aria-expanded', 'false');
+  });
+
+  menuPanel.addEventListener('click', function (ev) {
+    ev.stopPropagation();
+    var btn = ev.target.closest('button[data-action]');
+    if (!btn) {
+      return;
+    }
+    var action = btn.getAttribute('data-action');
+    if (action === 'callerid') {
+      handleSlash('/callerid');
+    } else if (action === 'callid') {
+      handleSlash('/callid');
+    } else if (action === 'status') {
+      handleSlash('/status');
+    } else if (action === 'send') {
+      handleSlash('/send');
+    } else if (action === 'monitor') {
+      handleSlash('/monitor toggle');
+    } else if (action === 'connect') {
+      handleSlash('/connect');
+    } else if (action === 'devices') {
+      handleSlash('/devices');
+    } else if (action === 'ax25_ui') {
+      handleSlash('/ax25_ui');
+    } else if (action === 'help') {
+      handleSlash('/help');
+    }
+  });
+
+  deviceSelect.addEventListener('change', function () {
+    if (deviceSelect.value) {
+      setDevice(deviceSelect.value);
+    }
+  });
+
+  updateHeader();
+  connect();
+})();
diff --git a/stacks/web/share/reverse-proxy/lighttpd.conf.example b/stacks/web/share/reverse-proxy/lighttpd.conf.example
new file mode 100644
index 0000000..d1e2c15
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/lighttpd.conf.example
@@ -0,0 +1,27 @@
+# MAX25 — lighttpd 1.4. HTTPD_DOCROOT example: /srv/www
+
+# Raise idle limits for upgraded WebSocket connections.
+server.max-read-idle = 3600
+server.max-write-idle = 3600
+
+$HTTP["url"] == "/max25-websocket/ws" {
+    proxy.server = ( "" => (
+        "max25" => (
+            "proxy"   => "http://127.0.0.1:7326/max25",
+            "upgrade" => "enable"
+        )
+    ))
+    proxy.header = ( "upgrade" => "enable" )
+}
+
+alias.url += ( "/max25-websocket/" => "/srv/www/max25-websocket/" )
+index-file.names += ( "index.php" )
+
+fastcgi.server += ( ".php" =>
+    ( "localhost" =>
+        ( "socket" => "/run/php-fpm/www.sock" )
+    )
+)
+
+# UI: cp -r reverse-proxy/docroot/max25-websocket $HTTPD_DOCROOT/
+# Proxy: max25-ws-proxy -c /etc/max25/web-proxy.ini
diff --git a/stacks/web/share/reverse-proxy/nginx.conf.example b/stacks/web/share/reverse-proxy/nginx.conf.example
new file mode 100644
index 0000000..ef49632
--- /dev/null
+++ b/stacks/web/share/reverse-proxy/nginx.conf.example
@@ -0,0 +1,27 @@
+# MAX25 — nginx. Set HTTPD_DOCROOT (example: /srv/www).
+
+location = /max25-websocket/ws {
+    proxy_pass http://127.0.0.1:7326/max25;
+    proxy_http_version 1.1;
+    proxy_socket_keepalive on;
+    proxy_set_header Upgrade $http_upgrade;
+    proxy_set_header Connection "upgrade";
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_read_timeout 3600s;
+    proxy_send_timeout 3600s;
+}
+
+location /max25-websocket/ {
+    root /srv/www;
+    index index.php;
+    location ~ \.php$ {
+        include fastcgi_params;
+        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
+        fastcgi_pass unix:/run/php-fpm/www.sock;
+    }
+}
+
+# UI: cp -r reverse-proxy/docroot/max25-websocket $HTTPD_DOCROOT/
+# Proxy: max25-ws-proxy -c /etc/max25/web-proxy.ini
diff --git a/stacks/web/share/web-proxy.ini.example b/stacks/web/share/web-proxy.ini.example
new file mode 100644
index 0000000..89a755f
--- /dev/null
+++ b/stacks/web/share/web-proxy.ini.example
@@ -0,0 +1,15 @@
+; MAX25 WebSocket forward-proxy (loopback only)
+; Copy to /etc/max25/web-proxy.ini or pass -c / MAX25_WEB_PROXY_INI=
+
+[proxy]
+bind = 127.0.0.1
+port = 7326
+path = /max25
+max_connections = 10
+
+[upstream]
+; max25d M25/1 TCP endpoint
+host = 127.0.0.1
+port = 7325
+; Match max25d.ini [network] tcp_password when set (proxy performs AUTH once)
+tcp_password =
diff --git a/stacks/web/share/web-terminal.ini.example b/stacks/web/share/web-terminal.ini.example
new file mode 100644
index 0000000..d259b66
--- /dev/null
+++ b/stacks/web/share/web-terminal.ini.example
@@ -0,0 +1,18 @@
+; MAX25 browser terminal — session defaults (per WebSocket connection).
+; Copy to /etc/max25/web-terminal.ini or set MAX25_WEB_TERMINAL_INI.
+;
+; Values mirror max25d [modem] + [devices] default. Omitted keys are read from
+; max25d_ini when set. Device list at runtime always comes from GET DEVICES.
+
+[max25-web-terminal]
+max25d_ini = /etc/max25/max25d.ini
+
+[session]
+; One device per session — must be an id registered in max25d [devices].
+; Empty = use [devices] default from max25d.ini.
+device =
+callerid = CB-0
+callid = QST
+ax25_ui = yes
+; CONNECT after session setup (same as max25-terminal)
+connect_on_start = yes
author	info@mode42.com <info@mode42.com>	2026-08-07 18:25:13 +0000
committer	info@mode42.com <info@mode42.com>	2026-08-07 18:25:13 +0000
commit	04d965d67a7264a1c7c211494aebda1953df7603 (patch)
tree	0ebd700a6e219f84a26a656f4bee8778bc75da7b /stacks