feat(companion): add reconnect resilience

docs/api/PROTOCOL.md

@@ -1067,6 +1067,9 @@ Flynn now propagates a run-level abort signal into model/tool execution, so prov
 
 Register node role/capabilities for the current WebSocket connection.
 
+Registration is scoped to the connection. If a companion reconnects it must call `node.register` again
+to restore node identity, capabilities, and access to `node.*` methods.
+
 **Request:**
 ```json
 {
@@ -1840,5 +1843,5 @@ For more implementation details, see:
 - Protocol types: `src/gateway/protocol.ts`
 - Handlers: `src/gateway/handlers/`
 - Gateway server: `src/gateway/server.ts`
-- Companion runtime client helper: `src/companion/runtimeClient.ts` (node + system + `canvas.*` typed RPC wrappers, optional `autoConnect`)
+- Companion runtime client helper: `src/companion/runtimeClient.ts` (node + system + `canvas.*` typed RPC wrappers, optional `autoConnect`/`autoReconnect`, connection event subscriptions)
 - Platform companion wrappers: `src/companion/platformClients.ts`

docs/architecture/AGENT_DIAGRAM.md

@@ -143,6 +143,7 @@ Gateway streaming UX signals:
 
 - WebSocket `agent.send` emits `run_state` lifecycle events (`start`, `cancel_requested`, `cancelled`, `complete`, `error`) for UI/state rendering.
 - Routing applies reaction rules with deterministic priority/cooldown (and recursion guard) before intent routing.
+- Companion nodes re-register `node.*` capabilities after reconnect; runtime clients can auto-reconnect and surface connection events.
 
 Key files:
 

docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md

@@ -16,6 +16,7 @@ If you only want the protocol surface, see `docs/api/PROTOCOL.md`.
 - Backend routing outcomes are auditable via `backend.route` / `backend.success` / `backend.fallback`, which enables offline canary evaluation without changing gateway protocol methods.
 - Run lifecycle/cancel intent and reaction decisions are emitted to audit logs, and aggregated into `system.metrics` counters (runStates, cancelLatencyMs, reactions) for dashboards.
 - Reaction matching is deterministic (priority + cooldown + recursion guard) before intent/agent routing.
+- Companion `node.*` registration is per WebSocket connection; reconnects must re-register capabilities before invoking node RPC methods.
 
 ## Component Map
 

docs/plans/state.json

@@ -6699,10 +6699,28 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/automation/reactions.test.ts src/config/schema.test.ts src/daemon/routing.test.ts passing"
+    },
+    "deeper-surfaces-phase3-companion-reconnect": {
+      "status": "completed",
+      "date": "2026-02-25",
+      "updated": "2026-02-25",
+      "summary": "Hardened companion runtime connectivity with auto-reconnect support, connection event subscriptions, CLI re-registration/heartbeat resilience, and updated protocol/architecture notes plus targeted tests.",
+      "files_modified": [
+        "src/companion/runtimeClient.ts",
+        "src/companion/runtimeClient.test.ts",
+        "src/companion/index.ts",
+        "src/cli/companion.ts",
+        "src/cli/companion.test.ts",
+        "docs/api/PROTOCOL.md",
+        "docs/architecture/AGENT_DIAGRAM.md",
+        "docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/cli/companion.test.ts passing"
     }
   },
   "overall_progress": {
-    "total_test_count": 2018,
+    "total_test_count": 2020,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",