test(voice): cover tts fallback

docs/api/PROTOCOL.md

@@ -1539,6 +1539,8 @@ Outbound attachment (image, audio, file).
 }
 ```
 
+Audio attachments (TTS responses) are best-effort: if synthesis fails, the gateway still returns the text reply without any audio attachment.
+
 #### `context_warning`
 
 Proactive context pressure signal emitted by `agent.send` before `done`.

docs/architecture/AGENT_DIAGRAM.md

@@ -145,6 +145,7 @@ Gateway streaming UX signals:
 - 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.
 - Canvas artifacts are persisted by the gateway so session UI surfaces can recover after daemon restarts.
+- TTS synthesis failures degrade to text-only replies without dropping the response.
 
 Key files:
 

docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md

@@ -18,6 +18,7 @@ If you only want the protocol surface, see `docs/api/PROTOCOL.md`.
 - 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.
 - Canvas artifacts are persisted per session under the gateway data directory for UI recovery across restarts.
+- TTS output is best-effort; synthesis failures fall back to text-only responses.
 
 ## Component Map
 

docs/plans/state.json

@@ -6737,10 +6737,24 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/gateway/canvas-store.test.ts src/gateway/ui/pages/chat.test.ts passing"
+    },
+    "deeper-surfaces-phase3-voice-continuity": {
+      "status": "completed",
+      "date": "2026-02-25",
+      "updated": "2026-02-25",
+      "summary": "Verified voice continuity by adding explicit test coverage for TTS synthesis failure fallbacks and documenting the text-only degradation behavior in protocol/architecture notes.",
+      "files_modified": [
+        "src/daemon/routing.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/daemon/routing.test.ts passing"
     }
   },
   "overall_progress": {
-    "total_test_count": 2021,
+    "total_test_count": 2022,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",