feat(canvas): persist artifacts and surface UI

docs/api/PROTOCOL.md

@@ -1229,6 +1229,8 @@ Push tokens are returned as masked previews (`tokenPreview`) and never exposed i
 
 ### Canvas Methods
 
+Canvas artifacts are stored per session and persisted to the gateway data directory so they survive daemon restarts.
+
 #### `canvas.put`
 
 Upsert a session-scoped canvas artifact.

docs/architecture/AGENT_DIAGRAM.md

@@ -144,6 +144,7 @@ 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.
+- Canvas artifacts are persisted by the gateway so session UI surfaces can recover after daemon restarts.
 
 Key files:
 

docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md

@@ -17,6 +17,7 @@ If you only want the protocol surface, see `docs/api/PROTOCOL.md`.
 - 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.
+- Canvas artifacts are persisted per session under the gateway data directory for UI recovery across restarts.
 
 ## Component Map
 

docs/plans/state.json

@@ -6717,10 +6717,30 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/cli/companion.test.ts passing"
+    },
+    "deeper-surfaces-phase3-canvas-persistence": {
+      "status": "completed",
+      "date": "2026-02-25",
+      "updated": "2026-02-25",
+      "summary": "Added durable canvas storage backed by the gateway data directory, surfaced a lightweight canvas inspection panel in the web chat UI, and documented persistence behavior with focused tests.",
+      "files_modified": [
+        "src/gateway/canvas-store.ts",
+        "src/gateway/canvas-store.test.ts",
+        "src/gateway/server.ts",
+        "src/daemon/services.ts",
+        "src/daemon/index.ts",
+        "src/gateway/ui/pages/chat.js",
+        "src/gateway/ui/pages/chat.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/gateway/canvas-store.test.ts src/gateway/ui/pages/chat.test.ts passing"
     }
   },
   "overall_progress": {
-    "total_test_count": 2020,
+    "total_test_count": 2021,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",