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+# Multi-Rig Support
+
+This document specifies the requirements for running N simultaneous rig backends in one `trx-server` process and the protocol/config changes required to support them.
+
+---
+
+## Progress
+
+> **For AI agents:** This section is the single source of truth for implementation status.
+> Each task has a unique ID (e.g. `MR-01`), a status badge, a description, the files it touches, and any blocking dependencies.
+>
+> Status legend: `[ ]` not started · `[~]` in progress · `[x]` done · `[!]` blocked
+
+### Foundational (parallel)
+
+| ID | Status | Task | Files | Needs |
+|----|--------|------|-------|-------|
+| MR-01 | `[x]` | Add `rig_id: Option<String>` to `ClientEnvelope`; add `rig_id: Option<String>` to `ClientResponse`; add `ClientCommand::GetRigs`; add `GetRigsResponseBody` + `RigEntry`; add sentinel arm in `mapping.rs` | `src/trx-protocol/src/types.rs`, `mapping.rs`, `lib.rs` | — |
+| MR-02 | `[x]` | Add `RigInstanceConfig`; add `rigs: Vec<RigInstanceConfig>` to `ServerConfig`; implement `resolved_rigs()`; extend `validate()` for unique IDs + unique audio ports | `src/trx-server/src/config.rs` | — |
+| MR-03 | `[x]` | Remove four `OnceLock` statics from `audio.rs`; add `DecoderHistories { aprs, ft8, wspr }` struct + `new()`; convert history free-fns to take `&DecoderHistories`; update decoder task signatures + `run_audio_listener` | `src/trx-server/src/audio.rs` | — |
+| MR-04 | `[x]` | Create `src/trx-server/src/rig_handle.rs` with `RigHandle { rig_id, rig_tx, state_rx }`; declare mod in `main.rs` | `src/trx-server/src/rig_handle.rs`, `main.rs` | — |
+
+### Sequential
+
+| ID | Status | Task | Files | Needs |
+|----|--------|------|-------|-------|
+| MR-05 | `[x]` | Add `rig_id: String` + `histories: Arc<DecoderHistories>` to `RigTaskConfig`; fix `clear_*_history` calls in `process_command` | `src/trx-server/src/rig_task.rs` | MR-03 |
+| MR-06 | `[x]` | Rewrite `run_listener` to take `Arc<HashMap<String, RigHandle>>` + `default_rig_id`; route by `envelope.rig_id`; add `GetRigs` fast path; populate `rig_id` in every `ClientResponse` | `src/trx-server/src/listener.rs` | MR-01, MR-04 |
+| MR-07 | `[x]` | Rewrite `main.rs` spawn loop over `resolved_rigs()`; extract `spawn_rig_audio_stack()`; per-rig pskreporter + aprsfi; build `HashMap<String, RigHandle>`; pass to `run_listener` | `src/trx-server/src/main.rs` | MR-02–06 |
+
+### Tests
+
+| ID | Status | Task | Files | Needs |
+|----|--------|------|-------|-------|
+| MR-08 | `[x]` | Config tests: `resolved_rigs()` with multi-rig TOML and legacy TOML; duplicate ID/port rejection | `src/trx-server/src/config.rs` | MR-02 |
+| MR-09 | `[x]` | Protocol tests: `ClientEnvelope` absent `rig_id` parses; `rig_id` in responses; `GetRigs` round-trip; existing tests still pass | `src/trx-protocol/src/codec.rs` | MR-01 |
+
+---
+
+## Goals
+
+- Run N simultaneous rig backends (SDR, transceivers, or any mix) in one server process
+- Route control commands to the correct rig via `rig_id` in the JSON protocol
+- Backward compatibility: single-rig configs (`[rig]`/`[audio]` at top level) continue to work unchanged
+- Per-rig audio streaming on separate TCP ports
+- New `GetRigs` command to enumerate all connected rigs and their states
+
+---
+
+## Non-Goals
+
+- Load-balancing or failover between rigs
+- Sharing a single audio port across multiple rigs (each rig keeps its own port)
+
+---
+
+## Architecture
+
+```
+Single [listen] port (4530)
+  └─ listener.rs: Arc<HashMap<rig_id, RigHandle>>
+       ├─ route by envelope.rig_id  (absent → first rig, backward compat)
+       └─ GetRigs → aggregate all states
+
+Per-rig:
+  rig_task ←→ RigHandle (rig_tx + state_rx)
+  audio capture → pcm_tx → decoder tasks → decode_tx
+  run_audio_listener (own TCP port per rig)
+  pskreporter + aprsfi tasks
+```
+
+---
+
+## TOML Format
+
+### Multi-rig (`[[rigs]]` array)
+
+```toml
+[general]
+callsign = "W1AW"
+
+[listen]
+port = 4530
+
+[[rigs]]
+id = "hf"
+[rigs.rig]
+model = "ft450d"
+initial_freq_hz = 14074000
+[rigs.rig.access]
+type = "serial"
+port = "/dev/ttyUSB0"
+baud = 9600
+[rigs.audio]
+port = 4531
+
+[[rigs]]
+id = "sdr"
+[rigs.rig]
+model = "soapysdr"
+[rigs.rig.access]
+type = "sdr"
+args = "driver=rtlsdr"
+[rigs.audio]
+port = 4532
+[rigs.sdr]
+sample_rate = 1920000
+```
+
+### Legacy (flat `[rig]` + `[audio]`) — continues to work unchanged
+
+```toml
+[rig]
+model = "ft817"
+[rig.access]
+type = "serial"
+port = "/dev/ttyUSB0"
+baud = 9600
+[audio]
+port = 4531
+```
+
+Legacy configs are synthesised into a single-element `[[rigs]]` list with `id = "default"` via `resolved_rigs()`.
+
+---
+
+## Protocol Wire Format
+
+Request (`rig_id` optional; absent = first rig):
+```json
+{"rig_id": "hf", "cmd": "set_freq", "freq_hz": 14074000}
+{"cmd": "get_state"}
+```
+
+Response (`rig_id` always present):
+```json
+{"success": true, "rig_id": "hf", "state": {...}}
+{"success": false, "rig_id": "default", "error": "Unknown rig_id: xyz"}
+```
+
+`GetRigs` response:
+```json
+{"success": true, "rig_id": "server", "rigs": [
+  {"rig_id": "hf",  "state": {...}},
+  {"rig_id": "sdr", "state": {...}}
+]}
+```
+
+---
+
+## Validation Rules (startup)
+
+- When `[[rigs]]` is non-empty: each `id` must be unique (case-sensitive).
+- When `[[rigs]]` is non-empty: each `audio.port` must be unique.
+- When `[[rigs]]` is empty: legacy flat fields are used with `id = "default"`.
+- Mixing `[[rigs]]` and legacy flat `[rig]`/`[audio]` is undefined; `[[rigs]]` takes precedence.