README: document Plan 2 device-hub surface area

README.md

@@ -4,8 +4,12 @@ Voice assistant on a Raspberry Pi talking to the OpenAI Realtime API via an
 ASP.NET backend deployed on Coolify.
 
 See `docs/superpowers/specs/2026-06-11-smart-assistant-design.md` for the full
-design and `docs/superpowers/plans/2026-06-11-smart-assistant-backend-foundation.md`
-for the Plan 1 implementation steps that produced this code.
+design. Implementation plans:
+
+- Plan 1 — `docs/superpowers/plans/2026-06-11-smart-assistant-backend-foundation.md`
+  (Identity, devices, pairing, install endpoints).
+- Plan 2 — `docs/superpowers/plans/2026-06-11-smart-assistant-device-hub-realtime-tools.md`
+  (device WebSocket hub, OpenAI Realtime relay, tools registry).
 
 ## Repo layout
 
@@ -84,11 +88,59 @@ curl -sf -X POST "$COOLIFY_URL/api/v1/deploy?uuid=$APP" \
 Fire-and-forget; the API returns a `deployment_uuid` immediately. Don't poll
 (per the global Coolify rule in `CLAUDE.md`).
 
+## Plan 2: device hub + Realtime relay
+
+- `wss://<domain>/device` — bearer-token WebSocket. Pair a device first to get a token.
+- Handshake: client sends `{type:"hello", device_id, client_version}`, backend
+  replies `hello_ack` with per-device config (voice, model, system prompt, idle
+  timeout, enabled tools).
+- Heartbeat: client sends `{type:"ping"}` every 15 s, backend replies `pong`
+  and updates `Devices.LastSeenAt`.
+- Wake: `{type:"wake"}` opens a Realtime session against OpenAI; backend emits
+  `session_started` (with `conversation_id`), forwards `response.audio.delta`
+  as binary frames to the device, persists `response.audio_transcript.done` as
+  an assistant turn, persists `conversation.item.input_audio_transcription.completed`
+  as a user turn, and emits `assistant_done` after each `response.done`.
+- Tools shipped (per-device toggle via `DeviceConfig.EnabledToolsJson`):
+  - `get_current_time` (server-side, returns `{"now":"<ISO-UTC>"}`),
+  - `end_session` (closes the session after the current `response.done`
+    completes; emits `session_ended(reason="tool")`),
+  - `set_volume` (round-trips a `tool_call`/`tool_result` envelope to the Pi;
+    the Pi side will run `amixer` in Plan 3).
+- Idle timeout: server-side. With no `input_audio_buffer.speech_started` upstream
+  event for `IdleTimeoutSeconds`, the relay emits `session_ended(reason="idle")`.
+
+The Python Pi client (Plan 3) is the production consumer of this surface. A
+quick handshake-only smoke against the live deploy:
+
+```sh
+DOMAIN="https://assistant.volcanic.tes.gd"
+# Reuse the curl recipe above to log in, generate a pair-code, and pair
+# a "smoke" device — capture $TOKEN from the /api/pair response.
+python3 - <<PY
+import asyncio, json, websockets
+URL, TOKEN = "wss://assistant.volcanic.tes.gd/device", "$TOKEN"
+async def main():
+    async with websockets.connect(
+        URL, additional_headers={"Authorization": f"Bearer {TOKEN}"}
+    ) as ws:
+        await ws.send(json.dumps({
+            "type":"hello","device_id":"00000000-0000-0000-0000-000000000000",
+            "client_version":"0.1"}))
+        print("ack:", json.loads(await ws.recv())["type"])
+        await ws.send(json.dumps({"type":"ping"}))
+        print("pong:", json.loads(await ws.recv())["type"])
+asyncio.run(main())
+PY
+```
+
+Don't send `wake` from the smoke — it would open a real OpenAI session and
+burn budget. Plan 3 exercises that end-to-end.
+
 ## What's next
 
-- **Plan 2** — backend device hub + OpenAI Realtime relay + tools registry
-  (the `end_session`, `get_current_time`, `set_volume` tools the spec describes).
 - **Plan 3** — full Python client on the Pi (wakeword, VAD, audio plumbing,
-  state machine, install + pair CLIs).
-- **Plan 4** — React management UI for the admin dashboard and conversation
-  history viewer.
+  state machine, install + pair CLIs). This is the production caller of
+  `/device` and the integration test for everything above.
+- **Plan 4** — React management UI for the admin dashboard, per-device
+  config editor, and conversation history viewer.