Secondary SDR priority: every spare SDR runs the next decoder in an ordered list

Replaces the single secondary_sdr_mode with secondary_sdr_priority, e.g.
["adsb", "ais"]. OP25 always keeps its own dongle; the secondary-sdr
container starts decoders top-down until it runs out of free SDRs, so a
3-SDR node runs ADS-B and AIS at once and a 2-SDR node runs the top pick.

- secondary-sdr: one decoder per mode, POST /secondary/apply(priority)
  (no-op when the right prefix is already running), orphaned decoders
  from a uvicorn reload are reaped on start, /status reports sdr_count
  via lsusb (op25's :stable image has none).
- edge-node: one apply path (set_secondary_priority) for the local
  dashboard, a new C2 'set_secondary_priority' MQTT command, and config
  pushes; it never restarts op25. Legacy mode migrates on load. Checkin
  reports priority, what's running, and sdr_count. Uplink forwards
  aircraft and vessels whenever either is present.
- Local dashboard: 'Secondary SDRs' card to enable/reorder/save.

Verified: edge-node pytest 190 passed, flake8 clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.env.example

@@ -111,6 +111,13 @@ OP25_TERMINAL_URL=http://localhost:8081
 # for local development off a real node; leave false everywhere else.
 OP25_DEBUG_EXPOSE=false
 
+# Secondary SDR container (node-26#9) — only matters if a second physical SDR
+# is present and secondary_sdr_mode is set to adsb|ais via the edge dashboard
+# or C2. Usually no need to change.
+SECONDARY_SDR_API_URL=http://localhost:8002
+# Same caveat as OP25_DEBUG_EXPOSE — debugging aid only, leave false.
+SECONDARY_SDR_DEBUG_EXPOSE=false
+
 # --- Local dashboard / API login ---------------------------------------------
 # Protects the node's local dashboard (port 80) and JSON API. The node is
 # reachable by anyone on whatever site's LAN it's deployed to, so this MUST be

.gitea/workflows/build-secondary-sdr.yml

@@ -0,0 +1,52 @@
+name: Build secondary-sdr
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [main, master]
+    paths:
+      - "secondary-sdr-container/**"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    env:
+      CONTAINER_NAME: secondary-sdr
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: docker/setup-qemu-action@v3
+
+      - uses: docker/setup-buildx-action@v3
+        with:
+          config-inline: |
+            [registry."git.vpn.cusano.net"]
+              http = false
+              insecure = false
+
+      - uses: docker/login-action@v3
+        with:
+          registry: git.vpn.cusano.net
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.BUILD_TOKEN }}
+
+      - name: Get version
+        id: meta
+        run: |
+          echo "REPO_NAME=$(echo ${GITHUB_REPOSITORY} | awk -F'/' '{print $2}')" >> $GITHUB_OUTPUT
+          echo "VERSION=$(git describe --tags --always | sed 's/^v//')" >> $GITHUB_OUTPUT
+
+      - uses: docker/build-push-action@v6
+        with:
+          context: ./secondary-sdr-container
+          file: ./secondary-sdr-container/Dockerfile
+          platforms: linux/arm64
+          push: true
+          tags: |
+            git.vpn.cusano.net/${{ vars.DOCKER_ORG }}/${{ steps.meta.outputs.REPO_NAME }}/${{ env.CONTAINER_NAME }}:${{ steps.meta.outputs.VERSION }}
+            git.vpn.cusano.net/${{ vars.DOCKER_ORG }}/${{ steps.meta.outputs.REPO_NAME }}/${{ env.CONTAINER_NAME }}:latest
+          cache-from: type=registry,ref=git.vpn.cusano.net/${{ vars.DOCKER_ORG }}/${{ steps.meta.outputs.REPO_NAME }}/${{ env.CONTAINER_NAME }}:buildcache
+          cache-to: type=registry,ref=git.vpn.cusano.net/${{ vars.DOCKER_ORG }}/${{ steps.meta.outputs.REPO_NAME }}/${{ env.CONTAINER_NAME }}:buildcache,mode=max

.gitea/workflows/publish-public.yml

@@ -0,0 +1,103 @@
+name: Publish public images
+
+# Push the three node images to a PUBLIC registry on a version tag, so a fresh
+# Pi can `docker pull` them without a Gitea login (git.vpn.cusano.net is now
+# behind REQUIRE_SIGNIN_VIEW — see INCIDENT-2026-09-06). Source + the private
+# registry stay walled; only the built node images go public.
+#
+# ── DISABLED ────────────────────────────────────────────────────────────────
+# The job is gated on `vars.NODE_PUBLIC_PUBLISH == 'true'`. Until that repo
+# variable is set the workflow triggers on tags but the job is skipped, so
+# this file is wired and inert. We're still building the core; flip it on when
+# self-serve node install is actually needed.
+#
+# To enable:
+#   1. Repo → Settings → Actions → Variables:
+#        NODE_PUBLIC_PUBLISH = true
+#        PUBLIC_REGISTRY     = ghcr.io            (or docker.io)
+#        PUBLIC_NAMESPACE    = <org-or-user>      (images land at <ns>/drb-<name>)
+#   2. Repo → Settings → Actions → Secrets:
+#        PUBLIC_REGISTRY_USER   = <push user>
+#        PUBLIC_REGISTRY_TOKEN  = <push token / PAT with write:packages>
+#   3. Re-push a tag (or run this workflow via workflow_dispatch).
+# ---------------------------------------------------------------------------
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - "v*"
+
+concurrency:
+  group: publish-public-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  publish:
+    # Inert until the repo variable is set. Do NOT convert this to `if: false`
+    # — the variable is the switch, no code change needed to go live.
+    if: ${{ vars.NODE_PUBLIC_PUBLISH == 'true' }}
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: edge-node
+            context: ./drb-edge-node
+            file: ./drb-edge-node/Dockerfile
+            cache_name: edge-node
+          - name: icecast
+            context: ./icecast
+            file: ./icecast/Dockerfile
+            cache_name: icecast
+          - name: op25-client
+            context: ./op25-container
+            file: ./op25-container/Dockerfile
+            cache_name: op25-client
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0   # need tags for `git describe`
+
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+        with:
+          config-inline: |
+            [registry."git.vpn.cusano.net"]
+              http = false
+              insecure = false
+
+      # Private Gitea registry — read only, to reuse the existing build cache
+      # (keeps the op25 image off a ~1h from-scratch compile).
+      - uses: docker/login-action@v3
+        with:
+          registry: git.vpn.cusano.net
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.BUILD_TOKEN }}
+
+      # Public registry — where the images are pushed.
+      - uses: docker/login-action@v3
+        with:
+          registry: ${{ vars.PUBLIC_REGISTRY }}
+          username: ${{ secrets.PUBLIC_REGISTRY_USER }}
+          password: ${{ secrets.PUBLIC_REGISTRY_TOKEN }}
+
+      - name: Version
+        id: meta
+        run: |
+          echo "REPO_NAME=$(echo ${GITHUB_REPOSITORY} | awk -F'/' '{print $2}')" >> $GITHUB_OUTPUT
+          echo "VERSION=$(git describe --tags --always | sed 's/^v//')" >> $GITHUB_OUTPUT
+
+      - uses: docker/build-push-action@v6
+        with:
+          context: ${{ matrix.context }}
+          file: ${{ matrix.file }}
+          platforms: linux/arm64
+          push: true
+          tags: |
+            ${{ vars.PUBLIC_REGISTRY }}/${{ vars.PUBLIC_NAMESPACE }}/drb-${{ matrix.name }}:${{ steps.meta.outputs.VERSION }}
+            ${{ vars.PUBLIC_REGISTRY }}/${{ vars.PUBLIC_NAMESPACE }}/drb-${{ matrix.name }}:latest
+          cache-from: type=registry,ref=git.vpn.cusano.net/${{ vars.DOCKER_ORG }}/${{ steps.meta.outputs.REPO_NAME }}/${{ matrix.cache_name }}:buildcache

docker-compose.yml

@@ -32,6 +32,21 @@ services:
     depends_on:
       - icecast
 
+  # Claims the node's SECOND physical SDR (op25 always claims the first).
+  # Only useful if secondary_sdr_mode is set to adsb|ais via the edge-node
+  # config; otherwise it just sits idle answering /secondary/status. See
+  # node-26#9. Same network/device access as op25 for the same reason: it
+  # needs the raw USB device, not a virtualized one.
+  secondary-sdr:
+    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/secondary-sdr:latest
+    build: ./secondary-sdr-container
+    restart: unless-stopped
+    privileged: true
+    network_mode: host
+    env_file: .env
+    volumes:
+      - /dev:/dev
+
   edge-node:
     image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/edge-node:latest
     build: ./drb-edge-node

drb-edge-node/app/config.py

@@ -136,6 +136,9 @@ class Settings(BaseSettings):
     op25_api_url: str = "http://localhost:8001"
     op25_terminal_url: str = "http://localhost:8081"
 
+    # Secondary SDR container (node-26#9) — ADS-B / AIS on a second SDR
+    secondary_sdr_api_url: str = "http://localhost:8002"
+
     # Paths (volume mounts)
     config_path: str = "/configs"
     recordings_path: str = "/recordings"

drb-edge-node/app/internal/mqtt_manager.py

@@ -210,10 +210,16 @@ class MQTTManager:
             logger.info("No API key on disk — requesting re-delivery from C2 server.")
             self._publish(self._t_key_request, {}, qos=1)
 
+    async def publish_checkin(self):
+        await self._publish_checkin()
+
     async def _publish_checkin(self):
         from app.internal.discord_radio import radio_bot
         from app.internal.config_manager import load_node_config
+        from app.internal.op25_client import op25_client
+        from app.internal.secondary_sdr_client import secondary_sdr_client
         config = load_node_config()
+        devices = await op25_client.devices()
         payload = {
             "node_id": settings.node_id,
             "name": settings.node_name,
@@ -225,7 +231,19 @@ class MQTTManager:
             "is_overridden": config.override_system_id is not None and config.node_type != "portable",
             "override_system_id": config.override_system_id,
             "enforce_override_timeout": config.enforce_override_timeout,
+            "secondary_sdr_mode": config.secondary_sdr_mode,
+            "secondary_sdr_priority": config.secondary_sdr_priority,
         }
+        secondary = await secondary_sdr_client.status()
+        if secondary is not None:
+            payload["secondary_sdr_running"] = [r["mode"] for r in secondary.get("running", [])]
+        # Best-effort hardware report — omit rather than guess. op25's :stable
+        # image has no lsusb, so fall back to the secondary-sdr container's count.
+        count = devices.get("count") if devices else None
+        if count is None and secondary is not None:
+            count = secondary.get("sdr_count")
+        if count is not None:
+            payload["sdr_count"] = count
         self._publish(self._t_checkin, payload, qos=1)
 
     def _publish(self, topic: str, payload: dict, qos: int = 0, retain: bool = False):

drb-edge-node/app/internal/op25_client.py

@@ -65,6 +65,16 @@ class OP25Client:
             logger.error(f"OP25 status failed: {e}")
             return None
 
+    async def devices(self) -> Optional[Dict[str, Any]]:
+        try:
+            async with httpx.AsyncClient(timeout=5) as client:
+                r = await client.get(f"{self.api_url}/op25/devices")
+                r.raise_for_status()
+                return r.json()
+        except Exception as e:
+            logger.error(f"OP25 device enumeration failed: {e}")
+            return None
+
     async def generate_config(self, config: Dict[str, Any]) -> bool:
         try:
             async with httpx.AsyncClient(timeout=10) as client:

drb-edge-node/app/internal/secondary_priority.py

@@ -0,0 +1,29 @@
+import asyncio
+from typing import Iterable, List, Optional
+
+from app.internal.config_manager import load_node_config, save_node_config
+from app.internal.logger import logger
+from app.internal.secondary_sdr_client import secondary_sdr_client
+from app.models import normalize_secondary_priority
+
+
+async def set_secondary_priority(priority: Iterable[str]) -> Optional[List[str]]:
+    """Persist and apply the node's secondary SDR priority — one path for the
+    local dashboard, a C2 command and a config push alike. Never touches op25:
+    changing what the spare dongles do must not interrupt P25 recording.
+
+    Returns the decoders now running (None if the container is unreachable).
+    """
+    ordered = normalize_secondary_priority(priority)
+    cfg = load_node_config()
+    cfg.secondary_sdr_priority = ordered
+    cfg.secondary_sdr_mode = ordered[0] if ordered else "none"
+    save_node_config(cfg)
+
+    running = await secondary_sdr_client.apply(ordered)
+    logger.info(f"Secondary SDR priority set to {ordered!r}; running {running!r}")
+
+    # Report straight away so C2's view doesn't wait for the next heartbeat.
+    from app.internal.mqtt_manager import mqtt_manager
+    asyncio.create_task(mqtt_manager.publish_checkin())
+    return running

drb-edge-node/app/internal/secondary_sdr_client.py

@@ -0,0 +1,71 @@
+import httpx
+from typing import Any, Dict, List, Optional
+from app.config import settings
+from app.internal.logger import logger
+
+
+class SecondarySdrClient:
+    """Talks to the secondary-sdr-container (node-26#9) over its control API.
+
+    Mirrors op25_client.py's shape on purpose — same failure handling (log
+    and return None/False rather than raise), since this container is
+    optional and its absence must never break the primary op25 radio path.
+    """
+
+    def __init__(self):
+        self.api_url = settings.secondary_sdr_api_url
+
+    async def apply(self, priority: List[str]) -> Optional[List[str]]:
+        """Run decoders down the priority list until SDRs run out. Returns the
+        modes actually running, or None if the container is unreachable."""
+        try:
+            async with httpx.AsyncClient(timeout=30) as client:
+                r = await client.post(f"{self.api_url}/secondary/apply", json={"priority": priority})
+                r.raise_for_status()
+                return r.json().get("running", [])
+        except Exception as e:
+            logger.error(f"Secondary SDR apply (priority={priority!r}) failed: {e}")
+            return None
+
+    async def start(self, mode: str) -> bool:
+        try:
+            async with httpx.AsyncClient(timeout=10) as client:
+                r = await client.post(f"{self.api_url}/secondary/start", json={"mode": mode})
+                r.raise_for_status()
+                return True
+        except Exception as e:
+            logger.error(f"Secondary SDR start (mode={mode!r}) failed: {e}")
+            return False
+
+    async def stop(self) -> bool:
+        try:
+            async with httpx.AsyncClient(timeout=10) as client:
+                r = await client.post(f"{self.api_url}/secondary/stop")
+                r.raise_for_status()
+                return True
+        except Exception as e:
+            logger.error(f"Secondary SDR stop failed: {e}")
+            return False
+
+    async def status(self) -> Optional[Dict[str, Any]]:
+        try:
+            async with httpx.AsyncClient(timeout=5) as client:
+                r = await client.get(f"{self.api_url}/secondary/status")
+                r.raise_for_status()
+                return r.json()
+        except Exception as e:
+            logger.error(f"Secondary SDR status failed: {e}")
+            return None
+
+    async def data(self) -> Optional[Dict[str, Any]]:
+        try:
+            async with httpx.AsyncClient(timeout=5) as client:
+                r = await client.get(f"{self.api_url}/secondary/data")
+                r.raise_for_status()
+                return r.json()
+        except Exception as e:
+            logger.error(f"Secondary SDR data fetch failed: {e}")
+            return None
+
+
+secondary_sdr_client = SecondarySdrClient()

drb-edge-node/app/internal/telemetry_uplink.py

@@ -0,0 +1,45 @@
+import asyncio
+
+import httpx
+
+from app.config import settings
+from app.internal import credentials
+from app.internal.config_manager import load_node_config
+from app.internal.logger import logger
+from app.internal.secondary_sdr_client import secondary_sdr_client
+
+# How often the second-SDR decoder's current snapshot is forwarded to C2
+# (node-26#9). This is a live-map overlay, not a flight/vessel history, so
+# there is no backlog/retry on a missed tick — the next one supersedes it.
+UPLINK_INTERVAL_SECONDS = 10
+
+
+async def _post_snapshot(path: str, body: dict) -> None:
+    if not settings.c2_url:
+        return
+    api_key = credentials.get_api_key()
+    if not api_key:
+        return
+    headers = {"Authorization": f"Bearer {api_key}"}
+    try:
+        async with httpx.AsyncClient(timeout=10) as client:
+            r = await client.post(f"{settings.c2_url}{path}", json=body, headers=headers)
+            r.raise_for_status()
+    except Exception as e:
+        logger.debug(f"Telemetry uplink to {path} failed: {e}")
+
+
+async def telemetry_uplink_loop():
+    while True:
+        await asyncio.sleep(UPLINK_INTERVAL_SECONDS)
+        if not load_node_config().secondary_sdr_priority:
+            continue
+        snapshot = await secondary_sdr_client.data()
+        if not snapshot:
+            continue
+        # Several decoders can run at once (one per spare SDR), so forward
+        # whatever each produced rather than keying off a single mode.
+        if snapshot.get("aircraft"):
+            await _post_snapshot("/telemetry/adsb", {"aircraft": snapshot["aircraft"]})
+        if snapshot.get("vessels"):
+            await _post_snapshot("/telemetry/ais", {"vessels": snapshot["vessels"]})

drb-edge-node/app/main.py

@@ -158,6 +158,9 @@ async def on_command(payload: dict):
         )
     elif action == "discord_leave":
         await radio_bot.leave()
+    elif action == "set_secondary_priority":
+        from app.internal.secondary_priority import set_secondary_priority
+        await set_secondary_priority(payload.get("priority") or [])
     elif action == "op25_restart":
         from app.internal.op25_client import op25_client
         await op25_client.stop()
@@ -224,6 +227,8 @@ async def on_config_push(payload: dict):
     hardware_preset = payload.pop("hardware_preset", None)
     ppm_override = payload.pop("ppm_override", None)
     node_type = payload.pop("node_type", None)
+    secondary_sdr_priority = payload.pop("secondary_sdr_priority", None)
+    secondary_sdr_mode = payload.pop("secondary_sdr_mode", None)  # legacy single-mode C2
     enforce_override_timeout = payload.pop("enforce_override_timeout", None)
     try:
         config = SystemConfig(**payload)
@@ -257,6 +262,12 @@ async def on_config_push(payload: dict):
     await op25_client.start()
     logger.info(f"Config push applied: {config.name}")
 
+    if secondary_sdr_priority is None and secondary_sdr_mode is not None:
+        secondary_sdr_priority = [secondary_sdr_mode]
+    if secondary_sdr_priority is not None:
+        from app.internal.secondary_priority import set_secondary_priority
+        await set_secondary_priority(secondary_sdr_priority)
+
 
 # ---------------------------------------------------------------------------
 # App lifecycle
@@ -312,12 +323,21 @@ async def lifespan(app: FastAPI):
             logger.warning(f"OP25 not ready yet (attempt {attempt + 1}/10), retrying in 3s…")
             await asyncio.sleep(3)
 
+    # After op25 has claimed its dongle, so the decoders only get the spares.
+    if node_cfg.secondary_sdr_priority:
+        from app.internal.secondary_sdr_client import secondary_sdr_client
+        logger.info(f"Resuming secondary SDRs (priority={node_cfg.secondary_sdr_priority!r}) after restart.")
+        await secondary_sdr_client.apply(node_cfg.secondary_sdr_priority)
+
     heartbeat_task = asyncio.create_task(mqtt_manager.heartbeat_loop())
+    from app.internal.telemetry_uplink import telemetry_uplink_loop
+    telemetry_task = asyncio.create_task(telemetry_uplink_loop())
 
     yield  # --- app running ---
 
     logger.info("Edge node shutting down.")
     heartbeat_task.cancel()
+    telemetry_task.cancel()
     await metadata_watcher.stop()
     await call_recorder.stop()
     await radio_bot.stop()

drb-edge-node/app/models.py

@@ -1,5 +1,5 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, model_validator
-from typing import Optional, Dict, Any
+from typing import Optional, Dict, Any, Iterable, List
 from enum import Enum
 from datetime import datetime
 
@@ -23,6 +23,21 @@ class SystemConfig(BaseModel):
     config: Dict[str, Any]  # OP25-compatible config blob passed through to op25-container
 
 
+# Decoders a node can run on the SDRs beyond op25's (node-26#9). op25 always
+# keeps its own dongle; each further dongle runs the next entry of the node's
+# secondary_sdr_priority, so a 3-SDR node with ["adsb", "ais"] runs both.
+SECONDARY_SDR_MODES = ("adsb", "ais")
+
+
+def normalize_secondary_priority(items: Iterable[str]) -> List[str]:
+    """Known modes only, first occurrence wins, order preserved."""
+    out: List[str] = []
+    for m in items or []:
+        if m in SECONDARY_SDR_MODES and m not in out:
+            out.append(m)
+    return out
+
+
 class NodeConfig(BaseModel):
     node_id: str
     node_name: str
@@ -34,11 +49,22 @@ class NodeConfig(BaseModel):
     hardware_preset: str = "rtl-sdr-v3"
     ppm_override: Optional[float] = None
     node_type: str = "fixed"  # fixed or portable
+    secondary_sdr_priority: List[str] = []  # ordered; SDRs beyond op25's run these top-down
+    # Legacy single-mode field (pre-priority). Still written as priority[0] so
+    # an older C2 reading checkins sees something sensible; read only to
+    # migrate a node_config.json saved before priority existed.
+    secondary_sdr_mode: str = "none"
     enforce_override_timeout: bool = True
     override_system_id: Optional[str] = None
     override_config: Optional[SystemConfig] = None
     offline_call_buffer_size: int = 35  # max call_end events to buffer while MQTT is offline
 
+    @model_validator(mode="after")
+    def _migrate_secondary_mode(self) -> "NodeConfig":
+        if not self.secondary_sdr_priority and self.secondary_sdr_mode in SECONDARY_SDR_MODES:
+            self.secondary_sdr_priority = [self.secondary_sdr_mode]
+        return self
+
 
 class CallEvent(BaseModel):
     call_id: str

drb-edge-node/app/routers/api.py

@@ -1,9 +1,9 @@
 from fastapi import APIRouter, Depends, HTTPException, Body
-from typing import Optional
+from typing import List, Optional
 import asyncio
 import httpx
 from app.config import settings
-from app.models import SystemConfig
+from app.models import SystemConfig, SECONDARY_SDR_MODES
 from app.internal.op25_client import op25_client
 from app.internal.config_manager import load_node_config, save_node_config, apply_system_config
 from app.internal.call_recorder import call_recorder
@@ -204,6 +204,30 @@ async def ack_override(timeout_minutes: int = Body(1440)):
         raise HTTPException(500, f"Failed to contact C2: {e}")
 
 
+@router.get("/secondary")
+async def get_secondary():
+    """Secondary SDR priority plus what's actually running (node-26#9)."""
+    from app.internal.secondary_sdr_client import secondary_sdr_client
+    status = await secondary_sdr_client.status()
+    return {
+        "priority": load_node_config().secondary_sdr_priority,
+        "modes": list(SECONDARY_SDR_MODES),
+        "running": [r["mode"] for r in status.get("running", [])] if status else None,
+        "sdr_count": status.get("sdr_count") if status else None,
+    }
+
+
+@router.post("/secondary/priority")
+async def set_secondary_priority(priority: List[str] = Body(..., embed=True)):
+    """Set the ordered list the spare SDRs work through. Never restarts op25."""
+    from app.internal.secondary_priority import set_secondary_priority as apply_priority
+    unknown = [m for m in priority if m not in SECONDARY_SDR_MODES]
+    if unknown:
+        raise HTTPException(400, f"Unknown secondary SDR mode(s): {unknown}")
+    running = await apply_priority(priority)
+    return {"ok": True, "priority": load_node_config().secondary_sdr_priority, "running": running}
+
+
 @router.post("/discord/join")
 async def discord_join(guild_id: int, channel_id: int):
     ok = await radio_bot.join(guild_id, channel_id)

drb-edge-node/app/templates/index.html

@@ -105,6 +105,30 @@
       background: rgba(255, 255, 255, 0.1);
     }
 
+    .sdr-row {
+      display: flex;
+      align-items: center;
+      gap: 0.6rem;
+      padding: 0.55rem 0;
+      border-bottom: 1px solid var(--glass-border);
+    }
+    .sdr-row:last-child { border-bottom: none; }
+    .sdr-rank { width: 1.2rem; color: var(--text-muted); font-size: 0.8rem; text-align: right; }
+    .sdr-name { flex: 1; }
+    .sdr-name small { display: block; color: var(--text-muted); font-size: 0.75rem; }
+    .sdr-move {
+      background: rgba(255, 255, 255, 0.05);
+      border: 1px solid var(--glass-border);
+      color: var(--text-main);
+      border-radius: 6px;
+      width: 1.9rem;
+      height: 1.9rem;
+      cursor: pointer;
+    }
+    .sdr-move:disabled { opacity: 0.3; cursor: default; }
+    .sdr-state { font-size: 0.75rem; min-width: 6.5rem; text-align: right; color: var(--text-muted); }
+    .sdr-state.on { color: var(--success); }
+
     .grid {
       display: grid;
       grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
@@ -360,6 +384,22 @@
         </div>
       </div>
 
+      <!-- Secondary SDRs Card (node-26#9) -->
+      <div class="glass-card">
+        <div class="card-header">
+          <div class="card-title">Secondary SDRs</div>
+        </div>
+        <p style="color: var(--text-muted); font-size: 0.8rem; margin: 0 0 0.5rem;">
+          OP25 always keeps its own SDR. Every other SDR runs the next enabled item below, top first.
+          <span id="sdr-summary"></span>
+        </p>
+        <div id="sdr-list"></div>
+        <div style="display:flex; gap:0.75rem; align-items:center; margin-top:0.75rem;">
+          <button id="sdr-save" class="btn btn-primary" style="padding:0.5rem 1rem;" onclick="saveSdrPriority()" disabled>Save priority</button>
+          <span id="sdr-msg" style="color: var(--text-muted); font-size: 0.8rem;"></span>
+        </div>
+      </div>
+
       <!-- Local Listening Card -->
       <div class="glass-card player-card">
         <div class="card-header" style="margin-bottom:0.5rem; border:none;">
@@ -492,6 +532,99 @@
       }
     }
 
+    // ── Secondary SDR priority ────────────────────────────────────────────
+    const SDR_LABELS = {
+      adsb: ['ADS-B', 'Aircraft · 1090 MHz'],
+      ais: ['AIS', 'Vessels · 162 MHz'],
+    };
+    let sdrRows = [];      // [{mode, enabled}] in display order
+    let sdrRunning = [];
+    let sdrDirty = false;
+
+    function renderSdr() {
+      const list = document.getElementById('sdr-list');
+      list.innerHTML = '';
+      let rank = 0;
+      sdrRows.forEach((row, i) => {
+        const [name, hint] = SDR_LABELS[row.mode] || [row.mode, ''];
+        const running = sdrRunning.includes(row.mode);
+        const state = !row.enabled ? 'Off' : running ? 'Running' : (sdrDirty ? 'Unsaved' : 'Waiting for SDR');
+        const el = document.createElement('div');
+        el.className = 'sdr-row';
+        el.innerHTML = `
+          <span class="sdr-rank">${row.enabled ? ++rank : ''}</span>
+          <input type="checkbox" ${row.enabled ? 'checked' : ''} aria-label="Enable ${name}">
+          <span class="sdr-name">${name}<small>${hint}</small></span>
+          <button class="sdr-move" aria-label="Move ${name} up" ${i === 0 ? 'disabled' : ''}>▲</button>
+          <button class="sdr-move" aria-label="Move ${name} down" ${i === sdrRows.length - 1 ? 'disabled' : ''}>▼</button>
+          <span class="sdr-state ${running && row.enabled ? 'on' : ''}">${state}</span>`;
+        const [box] = el.getElementsByTagName('input');
+        const [up, down] = el.getElementsByTagName('button');
+        box.onchange = () => { row.enabled = box.checked; markSdrDirty(); };
+        up.onclick = () => { [sdrRows[i - 1], sdrRows[i]] = [sdrRows[i], sdrRows[i - 1]]; markSdrDirty(); };
+        down.onclick = () => { [sdrRows[i + 1], sdrRows[i]] = [sdrRows[i], sdrRows[i + 1]]; markSdrDirty(); };
+        list.appendChild(el);
+      });
+      document.getElementById('sdr-save').disabled = !sdrDirty;
+    }
+
+    function markSdrDirty() {
+      sdrDirty = true;
+      document.getElementById('sdr-msg').textContent = '';
+      renderSdr();
+    }
+
+    async function loadSdr() {
+      if (sdrDirty) return;  // never clobber unsaved edits with a poll
+      try {
+        const r = await fetch('/api/secondary');
+        if (!r.ok) return;
+        const d = await r.json();
+        sdrRunning = d.running || [];
+        sdrRows = [
+          ...d.priority.map(mode => ({ mode, enabled: true })),
+          ...d.modes.filter(m => !d.priority.includes(m)).map(mode => ({ mode, enabled: false })),
+        ];
+        const summary = document.getElementById('sdr-summary');
+        if (d.running === null) {
+          summary.textContent = 'Secondary SDR service is not responding.';
+        } else if (d.sdr_count != null) {
+          const spare = Math.max(d.sdr_count - 1, 0);
+          summary.textContent = `This node has ${d.sdr_count} SDR${d.sdr_count === 1 ? '' : 's'}, so ${spare} spare.`;
+        }
+        renderSdr();
+      } catch (e) {
+        console.error('Secondary SDR load failed:', e);
+      }
+    }
+
+    async function saveSdrPriority() {
+      const priority = sdrRows.filter(r => r.enabled).map(r => r.mode);
+      const btn = document.getElementById('sdr-save');
+      const msg = document.getElementById('sdr-msg');
+      btn.disabled = true;
+      msg.textContent = 'Applying…';
+      try {
+        const r = await fetch('/api/secondary/priority', {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({ priority }),
+        });
+        if (!r.ok) throw new Error(await r.text());
+        const d = await r.json();
+        sdrDirty = false;
+        msg.textContent = d.running === null ? 'Saved, but the secondary SDR service did not respond.' : 'Saved.';
+        await loadSdr();
+      } catch (e) {
+        console.error('Secondary SDR save failed:', e);
+        msg.textContent = 'Save failed.';
+        btn.disabled = false;
+      }
+    }
+
+    loadSdr();
+    setInterval(loadSdr, 10000);
+
     refresh();
     setInterval(refresh, 2000); // Polling every 2 seconds
   </script>

drb-edge-node/tests/test_secondary_priority.py

@@ -0,0 +1,58 @@
+"""
+node-26#9 — secondary SDR priority: an ordered list the SDRs beyond op25's work
+through. Normalisation, migration from the legacy single-mode field, and the one
+apply path shared by the dashboard, C2 commands and config pushes.
+"""
+import asyncio
+from unittest.mock import AsyncMock, patch
+
+from app.models import NodeConfig, normalize_secondary_priority
+
+
+def _cfg(**kw) -> NodeConfig:
+    return NodeConfig(node_id="n1", node_name="N1", lat=0.0, lon=0.0, **kw)
+
+
+def test_normalize_keeps_order_drops_unknown_and_duplicates():
+    assert normalize_secondary_priority(["ais", "bogus", "adsb", "ais"]) == ["ais", "adsb"]
+    assert normalize_secondary_priority([]) == []
+
+
+def test_legacy_single_mode_migrates_to_priority():
+    assert _cfg(secondary_sdr_mode="adsb").secondary_sdr_priority == ["adsb"]
+    assert _cfg(secondary_sdr_mode="none").secondary_sdr_priority == []
+
+
+def test_explicit_priority_wins_over_legacy_mode():
+    assert _cfg(secondary_sdr_mode="adsb", secondary_sdr_priority=["ais"]).secondary_sdr_priority == ["ais"]
+
+
+def test_set_priority_persists_applies_and_never_touches_op25(tmp_path):
+    config_file = tmp_path / "node_config.json"
+    import app.internal.config_manager as cm
+    with patch.object(cm, "_CONFIG_FILE", config_file):
+        cm.save_node_config(_cfg(secondary_sdr_mode="adsb"))
+        from app.internal import secondary_priority as sp
+        with patch.object(sp.secondary_sdr_client, "apply", AsyncMock(return_value=["ais"])) as apply, \
+             patch("app.internal.mqtt_manager.mqtt_manager.publish_checkin", AsyncMock()), \
+             patch("app.internal.op25_client.op25_client.stop", AsyncMock()) as op25_stop:
+            running = asyncio.run(sp.set_secondary_priority(["ais", "adsb", "ais"]))
+        saved = cm.load_node_config()
+
+    assert running == ["ais"]
+    apply.assert_awaited_once_with(["ais", "adsb"])
+    op25_stop.assert_not_awaited()
+    assert saved.secondary_sdr_priority == ["ais", "adsb"]
+    assert saved.secondary_sdr_mode == "ais"
+
+
+def test_clearing_priority_is_not_undone_by_legacy_migration(tmp_path):
+    config_file = tmp_path / "node_config.json"
+    import app.internal.config_manager as cm
+    with patch.object(cm, "_CONFIG_FILE", config_file):
+        cm.save_node_config(_cfg(secondary_sdr_mode="adsb"))
+        from app.internal import secondary_priority as sp
+        with patch.object(sp.secondary_sdr_client, "apply", AsyncMock(return_value=[])), \
+             patch("app.internal.mqtt_manager.mqtt_manager.publish_checkin", AsyncMock()):
+            asyncio.run(sp.set_secondary_priority([]))
+        assert cm.load_node_config().secondary_sdr_priority == []

install.sh

@@ -181,6 +181,13 @@ else
   warn "no RTL-SDR dongle detected on USB — plug one in before expecting audio"
 fi
 
+# The kernel's DVB-TV driver auto-binds RTL2838 dongles. op25 detaches it from
+# the one it opens, but any other dongle stays claimed and the secondary-sdr
+# decoder fails with "usb_claim_interface error -6" (node-26#9).
+echo "blacklist dvb_usb_rtl28xxu" > /etc/modprobe.d/blacklist-rtl-sdr.conf
+modprobe -r rtl2832_sdr dvb_usb_rtl28xxu 2>/dev/null || true
+ok "DVB-TV kernel driver blacklisted for RTL-SDR"
+
 # ── 2. Dependencies ─────────────────────────────────────────────────────────
 say "Installing dependencies"
 export DEBIAN_FRONTEND=noninteractive

op25-container/Dockerfile

@@ -12,7 +12,7 @@ ENV DEBIAN_FRONTEND=noninteractive
 # Install system dependencies
 RUN apt-get update && \
     apt-get upgrade -y && \
-    apt-get install git pulseaudio pulseaudio-utils liquidsoap -y
+    apt-get install git pulseaudio pulseaudio-utils liquidsoap usbutils -y
 
 # Install custom PulseAudio system config (enables anonymous access for edge-node)
 COPY system.pa /etc/pulse/system.pa

op25-container/app/routers/op25_controller.py

@@ -1,6 +1,7 @@
 from fastapi import HTTPException, APIRouter
 import subprocess
 import os
+import re
 import signal
 import json
 from models import ConfigGenerator, DecodeMode, ChannelConfig, DeviceConfig, TrunkingConfig, TrunkingChannelConfig, TerminalConfig, MetadataConfig, MetadataStreamConfig, HARDWARE_PRESETS
@@ -69,6 +70,24 @@ def create_op25_router():
     async def get_status():
         return {"status": "running" if _is_running() else "stopped"}
 
+    @router.get("/devices")
+    async def list_sdr_devices():
+        """Enumerate connected SDR-looking USB devices via lsusb.
+
+        Same match heuristic as install.sh's one-shot host check — good enough
+        to answer "is a second SDR plugged in", not a serial-level device
+        binding (op25's DeviceConfig.args has no serial concept yet either).
+        """
+        devices = []
+        try:
+            out = subprocess.run(["lsusb"], capture_output=True, text=True, timeout=5).stdout
+            for line in out.splitlines():
+                if re.search(r"rtl2838|realtek.*283[28]|sdr", line, re.IGNORECASE):
+                    devices.append(line.strip())
+        except Exception as e:
+            LOGGER.warning(f"SDR device enumeration failed: {e}")
+        return {"count": len(devices), "devices": devices}
+
     @router.post("/generate-config")
     async def generate_config(generator: ConfigGenerator):
         try:

secondary-sdr-container/Dockerfile

@@ -0,0 +1,54 @@
+# Secondary-SDR Container — node-26#9
+#
+# Claims the node's SECOND physical SDR (the first is always op25's). Mode is
+# chosen at runtime via the control API, not baked in: dump1090 for ADS-B,
+# AIS-catcher for AIS (op25_2 mode is not handled here yet — see node-26#9).
+#
+# Device claiming is by RTL-SDR index, not serial (op25's DeviceConfig.args
+# has no serial concept either — see op25-container/app/models.py). Index 0
+# is reserved for op25; this container always addresses index 1. That's a
+# real limitation once serial-stable device binding matters (hot-unplug /
+# replug can swap indices) — tracked in node-26#9, not fixed here.
+#
+# UNVERIFIED: this image has not been built or run against real hardware in
+# this session (sandboxed authoring machine, no docker). dump1090 and
+# AIS-catcher's exact CLI flags below are believed correct from their
+# published docs but not confirmed against a real capture — the CTO/QA
+# review before this ships to a real node should build and smoke-test it.
+FROM python:3.14-slim
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && \
+    apt-get upgrade -y && \
+    apt-get install -y --no-install-recommends \
+        git build-essential cmake pkg-config \
+        librtlsdr-dev libusb-1.0-0-dev libssl-dev zlib1g-dev libzstd-dev libncurses-dev usbutils
+
+# readsb (wiedehopf) — ADS-B decoder. antirez/dump1090 was used here first but
+# has no --write-json at all (it only serves /data.json over --net), so the
+# decoder exited on an unknown flag. readsb writes the dump1090-fa style
+# aircraft.json that _read_adsb_snapshot() parses.
+RUN git clone --depth 1 https://github.com/wiedehopf/readsb /opt/readsb && \
+    cd /opt/readsb && make RTLSDR=yes
+
+# AIS-catcher — AIS decoder.
+RUN git clone https://github.com/jvde-github/AIS-catcher /opt/AIS-catcher && \
+    cd /opt/AIS-catcher && mkdir build && cd build && cmake .. && make
+
+EXPOSE 8002
+
+VOLUME ["/configs"]
+
+WORKDIR /app
+COPY ./app /app
+
+COPY docker-entrypoint.sh /usr/local/bin/
+RUN sed -i 's/\r$//' /usr/local/bin/docker-entrypoint.sh && \
+    chmod +x /usr/local/bin/docker-entrypoint.sh
+
+COPY requirements.txt /tmp/requirements.txt
+RUN pip3 install --no-cache-dir -r /tmp/requirements.txt
+
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
+CMD ["python", "main.py"]

secondary-sdr-container/app/config.py

@@ -0,0 +1,20 @@
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    # Same rationale as op25-container's OP25_DEBUG_EXPOSE: both containers
+    # share the host network namespace (network_mode: host), so edge-node
+    # reaches this control API over localhost regardless of this flag. False
+    # (default) binds 127.0.0.1; true exposes unauthenticated start/stop to
+    # the node's LAN and should only ever be set for local development.
+    secondary_sdr_debug_expose: bool = False
+
+    class Config:
+        env_file = ".env"
+
+
+settings = Settings()
+
+
+def bind_host() -> str:
+    return "0.0.0.0" if settings.secondary_sdr_debug_expose else "127.0.0.1"

secondary-sdr-container/app/internal/decoder_control.py

@@ -0,0 +1,302 @@
+import json
+import os
+import signal
+import subprocess
+import threading
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+from internal.logger import create_logger
+
+LOGGER = create_logger(__name__)
+
+# One decoder per mode, each on its own SDR (node-26#9). The node's secondary
+# SDR *priority* (e.g. ["adsb", "ais"]) is applied by apply(): decoders start
+# down the list until no free dongle is left, so every SDR the node has gets
+# used and the ones beyond the list's reach simply aren't started. OP25 always
+# keeps its own dongle — it is started first and never part of this list.
+MODES = ("adsb", "ais")
+
+# Which RTL-SDR index op25 holds is NOT fixed — on radio-box op25 had index 1
+# and index 0 was free, so "op25 is always 0" was wrong. rtlsdr can't open a
+# dongle another process has claimed, and the decoders exit within ~50ms when
+# that happens, so _start_one() tries each index and keeps the first that
+# stays up. op25 is never disturbed: a failed claim doesn't touch its dongle.
+MAX_SDR_INDEX = 4
+_STARTUP_GRACE_S = 2.0
+
+_STATE_DIR = Path("/tmp/secondary_sdr")
+ADSB_JSON_DIR = Path("/tmp/adsb")
+
+# Live decoder handles. poll() is the only reliable liveness check: a decoder
+# that dies on startup stays an unreaped zombie, and killpg(pgid, 0) still
+# succeeds on a zombie.
+_procs: Dict[str, subprocess.Popen] = {}
+_indices: Dict[str, int] = {}
+_lock = threading.Lock()
+
+# AIS-catcher streams one JSON object per received message on stdout rather
+# than writing a periodic snapshot file (readsb's approach) — so the
+# current-vessel snapshot lives in memory, keyed by mmsi, kept warm by a
+# background reader thread for as long as the decoder is alive.
+_ais_vessels: Dict[str, Dict[str, Any]] = {}
+_ais_lock = threading.Lock()
+
+
+def _pgid_file(mode: str) -> Path:
+    return _STATE_DIR / f"{mode}.pgid"
+
+
+def _reap_orphans() -> None:
+    """Kill decoders left behind by a previous API process (uvicorn --reload
+    restarts this process, but decoders run in their own session and would
+    otherwise keep holding their SDRs)."""
+    if not _STATE_DIR.exists():
+        return
+    for f in _STATE_DIR.glob("*.pgid"):
+        try:
+            os.killpg(int(f.read_text().strip()), signal.SIGTERM)
+            LOGGER.info(f"Stopped orphaned secondary decoder from {f.name}")
+        except Exception:
+            pass
+        f.unlink(missing_ok=True)
+
+
+_reap_orphans()
+
+
+def _adsb_command(index: int) -> List[str]:
+    ADSB_JSON_DIR.mkdir(parents=True, exist_ok=True)
+    return [
+        "/opt/readsb/readsb",
+        "--net",
+        "--device-type", "rtlsdr",
+        "--device", str(index),
+        "--write-json", str(ADSB_JSON_DIR),
+        "--write-json-every", "1",
+    ]
+
+
+def _ais_command(index: int) -> List[str]:
+    return [
+        "/opt/AIS-catcher/build/AIS-catcher",
+        f"-d:{index}",  # "-d <x>" would select by serial, not index
+        "-o", "5",  # JSON Full: decoded fields (4 = sparse, "JSON" is rejected)
+    ]
+
+
+_COMMANDS = {"adsb": _adsb_command, "ais": _ais_command}
+
+
+def _ais_reader(proc: subprocess.Popen) -> None:
+    """
+    Consume AIS-catcher's stdout, one JSON message per line, and keep the
+    latest report per mmsi. Field names (mmsi/lat/lon/speed/course or
+    heading/shipname or name) are believed correct from AIS-catcher's
+    published JSON output docs but UNVERIFIED against a real capture in
+    this session — same caveat as dump1090's aircraft.json mapping.
+    Malformed/partial lines (e.g. static-data-only messages with no
+    position) are skipped rather than raising, since dropping one line must
+    never kill the reader thread.
+    """
+    if not proc.stdout:
+        return
+    for line in proc.stdout:
+        try:
+            msg = json.loads(line)
+        except Exception:
+            continue
+        mmsi = msg.get("mmsi")
+        if not mmsi:
+            continue
+        # AIS-catcher emits separate message TYPES per mmsi — static data
+        # (name, no position) and position reports (lat/lon, no name) arrive
+        # as distinct lines. Merge onto the existing entry, only overwriting
+        # a field the new message actually carries, so a position-only
+        # report doesn't blank out a name learned from an earlier message.
+        name = (msg.get("shipname") or msg.get("name") or "").strip() or None
+        heading = msg.get("heading") if msg.get("heading") is not None else msg.get("course")
+        updates = {
+            "mmsi": str(mmsi),
+            "name": name,
+            "lat": msg.get("lat"),
+            "lon": msg.get("lon"),
+            "speed_kt": msg.get("speed"),
+            "heading_deg": heading,
+        }
+        with _ais_lock:
+            existing = _ais_vessels.get(str(mmsi), {})
+            for key, value in updates.items():
+                if value is not None:
+                    existing[key] = value
+            _ais_vessels[str(mmsi)] = existing
+
+
+def is_running(mode: str) -> bool:
+    proc = _procs.get(mode)
+    return proc is not None and proc.poll() is None
+
+
+def running() -> List[str]:
+    return [m for m in MODES if is_running(m)]
+
+
+def _start_one(mode: str) -> bool:
+    """Start one decoder on the first free SDR. False when none is free."""
+    if mode not in _COMMANDS:
+        raise ValueError(f"Unknown secondary SDR mode: {mode!r}")
+    if is_running(mode):
+        return True
+    if mode == "ais":
+        with _ais_lock:
+            _ais_vessels.clear()
+
+    needs_stdout = mode == "ais"
+    for index in range(MAX_SDR_INDEX):
+        if index in {_indices[m] for m in running() if m in _indices}:
+            continue
+        try:
+            proc = subprocess.Popen(
+                _COMMANDS[mode](index),
+                preexec_fn=os.setsid,
+                stdout=subprocess.PIPE if needs_stdout else None,
+                text=True if needs_stdout else None,
+                bufsize=1 if needs_stdout else -1,
+            )
+        except Exception as e:
+            LOGGER.error(f"Failed to start secondary SDR decoder mode={mode!r}: {e}")
+            return False
+        try:
+            proc.wait(timeout=_STARTUP_GRACE_S)
+            LOGGER.info(f"Secondary SDR decoder mode={mode!r} could not use SDR index {index}, trying next")
+            continue
+        except subprocess.TimeoutExpired:
+            pass
+        if needs_stdout:
+            threading.Thread(target=_ais_reader, args=(proc,), daemon=True).start()
+        _procs[mode] = proc
+        _indices[mode] = index
+        _STATE_DIR.mkdir(parents=True, exist_ok=True)
+        _pgid_file(mode).write_text(str(proc.pid))
+        LOGGER.info(f"Started secondary SDR decoder mode={mode!r} on SDR index {index} pid={proc.pid}")
+        return True
+
+    LOGGER.info(f"Secondary SDR decoder mode={mode!r}: no free SDR left")
+    return False
+
+
+def _stop_one(mode: str) -> None:
+    proc = _procs.pop(mode, None)
+    _indices.pop(mode, None)
+    if proc is not None:
+        try:
+            os.killpg(proc.pid, signal.SIGTERM)
+        except OSError:
+            pass
+        try:
+            proc.wait(timeout=5)
+        except subprocess.TimeoutExpired:
+            pass
+    _pgid_file(mode).unlink(missing_ok=True)
+
+
+def start(mode: str) -> bool:
+    with _lock:
+        return _start_one(mode)
+
+
+def stop(mode: Optional[str] = None) -> None:
+    with _lock:
+        for m in [mode] if mode else list(_procs):
+            _stop_one(m)
+
+
+def apply(priority: List[str]) -> List[str]:
+    """Run decoders in priority order until SDRs run out; stop everything else.
+
+    Unchanged when the running set is already the right prefix of the list, so
+    re-applying the same priority (every restart/config push) is a no-op
+    rather than a decoder restart.
+    """
+    for m in priority:
+        if m not in _COMMANDS:
+            raise ValueError(f"Unknown secondary SDR mode: {m!r}")
+    with _lock:
+        live = set(running())
+        if live and live == set(priority[:len(live)]):
+            # Already running the head of the list; only try to extend it.
+            for m in priority[len(live):]:
+                if not _start_one(m):
+                    break
+            return running()
+        for m in list(_procs):
+            _stop_one(m)
+        for m in priority:
+            if not _start_one(m):
+                break
+        return running()
+
+
+def sdr_count() -> Optional[int]:
+    """RTL-SDR dongles on USB, same heuristic as install.sh. This container has
+    usbutils; op25's :stable image doesn't, so its /op25/devices can't answer."""
+    try:
+        out = subprocess.run(["lsusb"], capture_output=True, text=True, timeout=5).stdout
+    except Exception:
+        return None
+    return sum(1 for line in out.splitlines() if "0bda:2838" in line or "0bda:2832" in line)
+
+
+def status() -> Dict[str, Any]:
+    live = running()
+    return {
+        "running": [{"mode": m, "sdr_index": _indices.get(m)} for m in live],
+        "sdr_count": sdr_count(),
+    }
+
+
+def _altitude(a: Dict[str, Any]) -> Optional[int]:
+    alt = a.get("alt_baro", a.get("altitude"))
+    if alt == "ground":
+        return 0
+    return alt if isinstance(alt, (int, float)) else None
+
+
+def _read_adsb_snapshot() -> List[Dict[str, Any]]:
+    """
+    Map readsb's aircraft.json (--write-json output) to the server's
+    telemetry schema. readsb uses the dump1090-fa field names: alt_baro (int,
+    or the string "ground"), gs, track. Older dump1090 forks used
+    altitude/speed, kept as a fallback.
+    """
+    path = ADSB_JSON_DIR / "aircraft.json"
+    try:
+        raw = json.loads(path.read_text())
+    except Exception:
+        return []
+
+    out = []
+    for a in raw.get("aircraft", []):
+        icao = a.get("hex")
+        if not icao:
+            continue
+        out.append({
+            "icao": icao.upper(),
+            "callsign": (a.get("flight") or "").strip() or None,
+            "lat": a.get("lat"),
+            "lon": a.get("lon"),
+            "altitude_ft": _altitude(a),
+            "ground_speed_kt": a.get("gs", a.get("speed")),
+            "track_deg": a.get("track"),
+        })
+    return out
+
+
+def data() -> Dict[str, Any]:
+    with _ais_lock:
+        vessels = list(_ais_vessels.values()) if is_running("ais") else []
+    return {
+        "running": running(),
+        "aircraft": _read_adsb_snapshot() if is_running("adsb") else [],
+        "vessels": vessels,
+    }

secondary-sdr-container/app/internal/logger.py

@@ -0,0 +1,31 @@
+import logging
+from logging.handlers import RotatingFileHandler
+
+
+def create_logger(name, level=logging.DEBUG, max_bytes=10485760, backup_count=2):
+    debug_log_file = "./secondary-sdr.debug.log"
+    info_log_file = "./secondary-sdr.log"
+
+    logger = logging.getLogger(name)
+    logger.setLevel(level)
+
+    if not logger.hasHandlers():
+        console_handler = logging.StreamHandler()
+        console_handler.setLevel(level)
+
+        debug_file_handler = RotatingFileHandler(debug_log_file, maxBytes=max_bytes, backupCount=backup_count)
+        debug_file_handler.setLevel(logging.DEBUG)
+
+        info_file_handler = RotatingFileHandler(info_log_file, maxBytes=max_bytes, backupCount=backup_count)
+        info_file_handler.setLevel(logging.INFO)
+
+        formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+        console_handler.setFormatter(formatter)
+        debug_file_handler.setFormatter(formatter)
+        info_file_handler.setFormatter(formatter)
+
+        logger.addHandler(console_handler)
+        logger.addHandler(debug_file_handler)
+        logger.addHandler(info_file_handler)
+
+    return logger

secondary-sdr-container/app/main.py

@@ -0,0 +1,13 @@
+from fastapi import FastAPI
+import routers.secondary_controller as secondary_controller
+from config import bind_host
+
+app = FastAPI()
+
+app.include_router(secondary_controller.create_secondary_router(), prefix="/secondary")
+
+
+if __name__ == "__main__":
+    import uvicorn
+
+    uvicorn.run("main:app", host=bind_host(), port=8002, reload=True)

secondary-sdr-container/app/routers/secondary_controller.py

@@ -0,0 +1,58 @@
+from typing import List, Optional
+
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+
+from internal import decoder_control
+from internal.logger import create_logger
+
+LOGGER = create_logger(__name__)
+
+
+class StartBody(BaseModel):
+    mode: str  # adsb | ais
+
+
+class StopBody(BaseModel):
+    mode: Optional[str] = None  # omit to stop every decoder
+
+
+class ApplyBody(BaseModel):
+    priority: List[str]  # ordered, e.g. ["adsb", "ais"]
+
+
+def create_secondary_router():
+    router = APIRouter()
+
+    @router.post("/apply")
+    async def apply(body: ApplyBody):
+        try:
+            live = decoder_control.apply(body.priority)
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=str(e))
+        return {"running": live}
+
+    @router.post("/start")
+    async def start(body: StartBody):
+        try:
+            ok = decoder_control.start(body.mode)
+        except ValueError as e:
+            raise HTTPException(status_code=400, detail=str(e))
+        if not ok:
+            raise HTTPException(status_code=409, detail="No free SDR for this decoder")
+        return {"status": f"secondary SDR started ({body.mode})"}
+
+    @router.post("/stop")
+    async def stop(body: Optional[StopBody] = None):
+        decoder_control.stop(body.mode if body else None)
+        return {"status": "secondary SDR stopped"}
+
+    @router.get("/status")
+    async def get_status():
+        return decoder_control.status()
+
+    @router.get("/data")
+    async def get_data():
+        return decoder_control.data()
+
+    return router

secondary-sdr-container/docker-entrypoint.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+mkdir -p /tmp/adsb
+exec "$@"

secondary-sdr-container/requirements.txt

@@ -0,0 +1,3 @@
+uvicorn
+fastapi
+pydantic-settings