feat(companion): expose pending request observability

README.md

@@ -1190,7 +1190,7 @@ Methods:
 - `system.capabilities` returns gateway protocol and node policy snapshot.
 
 Companion runtime helper:
-- `src/companion/runtimeClient.ts` provides a typed Node/WebSocket client for companion runtimes (macOS/iOS/Android workers) with wrappers for `node.register`, `node.capabilities.get`, `node.location.set/get`, `node.status.set`, `node.push_token.set`, `system.capabilities`, `system.nodes`, and canvas artifact RPCs (`canvas.put/get/list/delete/clear`), plus convenience helpers (`bootstrapNode`, optional `autoConnect`, `dispose()`) and event helpers (`subscribeEvents()`, `subscribeEvent()`, `subscribeAgentStream()`, `subscribeAgentTyping()`, `subscribeContextWarning()`, `waitForEvent()` with timeout/predicate/abort support, non-empty event-name validation, and deterministic teardown cancellation (including socket-close rejection), `waitForAnyEvent()` (with non-empty event-name-list validation), `waitForAgentStream()`, `waitForAgentTyping()`, `waitForContextWarning()`, `clearEventSubscriptions()`, `listKnownEventNames()`, `eventSubscriptionCount`).
+- `src/companion/runtimeClient.ts` provides a typed Node/WebSocket client for companion runtimes (macOS/iOS/Android workers) with wrappers for `node.register`, `node.capabilities.get`, `node.location.set/get`, `node.status.set`, `node.push_token.set`, `system.capabilities`, `system.nodes`, and canvas artifact RPCs (`canvas.put/get/list/delete/clear`), plus convenience helpers (`bootstrapNode`, optional `autoConnect`, `dispose()`) and event helpers (`subscribeEvents()`, `subscribeEvent()`, `subscribeAgentStream()`, `subscribeAgentTyping()`, `subscribeContextWarning()`, `waitForEvent()` with timeout/predicate/abort support, non-empty event-name validation, and deterministic teardown cancellation (including socket-close rejection), `waitForAnyEvent()` (with non-empty event-name-list validation), `waitForAgentStream()`, `waitForAgentTyping()`, `waitForContextWarning()`, `clearEventSubscriptions()`, `listKnownEventNames()`, `eventSubscriptionCount`) plus in-flight RPC observability via `pendingRequestCount`.
 - `src/companion/platformClients.ts` provides platform-focused wrappers:
   - `MacOSCompanionClient` (`platform: "macos"`, APNs push registration)
   - `IOSCompanionClient` (`platform: "ios"`, APNs push registration)
@@ -1201,6 +1201,7 @@ Companion runtime helper:
   - optional `defaultSessionId` for canvas helper calls so `sessionId` can be omitted per call
   - lifecycle passthroughs for connection state/teardown (`connected`, `dispose(code?, reason?)`)
   - stream passthrough helpers (`subscribeEvents`, `subscribeEvent`, `clearEventSubscriptions`, `listKnownEventNames`, `eventSubscriptionCount`, `subscribeAgentStream/Typing/ContextWarning`, `waitForEvent`, `waitForAnyEvent`, `waitForAgentStream/Typing/ContextWarning`)
+  - runtime observability passthroughs (`pendingRequestCount`, `connected`)
 - `src/companion/heartbeatLoop.ts` provides `CompanionHeartbeatLoop` for periodic heartbeat scheduling (`publishHeartbeat`) with start/stop safety, optional interval jitter (`jitterRatio`) to spread load, `tickNow()` for manual sends, success/error hooks, loop observability (`successCount`, `lastSuccessAt`, `failureCount`, `lastFailure`, `getState()`), and optional auto-stop after repeated failures.
 
 ## Canvas / A2UI Foundation

docs/plans/state.json

@@ -843,6 +843,21 @@
       ],
       "test_status": "pnpm test:run src/companion/heartbeatLoop.test.ts src/companion/platformClients.test.ts src/companion/runtimeClient.test.ts src/companion/platformClients.integration.test.ts + pnpm typecheck passing"
     },
+    "companion-runtime-pending-request-observability": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Added runtime `pendingRequestCount` observability and platform passthrough getters so companion runtimes can inspect in-flight RPC request cardinality.",
+      "files_modified": [
+        "src/companion/runtimeClient.ts",
+        "src/companion/runtimeClient.test.ts",
+        "src/companion/platformClients.ts",
+        "src/companion/platformClients.test.ts",
+        "README.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/heartbeatLoop.test.ts src/companion/platformClients.integration.test.ts + pnpm typecheck passing"
+    },
     "browser-tools-activation-clarity": {
       "status": "completed",
       "date": "2026-02-17",

src/companion/platformClients.test.ts

@@ -38,6 +38,7 @@ function createRuntimeMock(): {
   waitForContextWarning: ReturnType<typeof vi.fn>;
   waitForAnyEvent: ReturnType<typeof vi.fn>;
   eventSubscriptionCount: number;
+  pendingRequestCount: number;
   connected: boolean;
 } {
   const connect = vi.fn(async () => undefined);
@@ -77,6 +78,7 @@ function createRuntimeMock(): {
   const waitForContextWarning = vi.fn(async () => ({ thresholdPct: 75, estimatedPct: 90 }));
   const waitForAnyEvent = vi.fn(async () => ({ event: 'agent.stream', data: { token: 'any' } }));
   const eventSubscriptionCount = 3;
+  const pendingRequestCount = 2;
   const connected = true;
 
   const runtime = {
@@ -112,6 +114,9 @@ function createRuntimeMock(): {
     get eventSubscriptionCount() {
       return eventSubscriptionCount;
     },
+    get pendingRequestCount() {
+      return pendingRequestCount;
+    },
     get connected() {
       return connected;
     },
@@ -149,6 +154,7 @@ function createRuntimeMock(): {
     waitForContextWarning,
     waitForAnyEvent,
     eventSubscriptionCount,
+    pendingRequestCount,
     connected,
   };
 }
@@ -294,6 +300,13 @@ describe('platform companion clients', () => {
     expect(client.eventSubscriptionCount).toBe(mock.eventSubscriptionCount);
   });
 
+  it('platform pendingRequestCount forwards runtime getter value', async () => {
+    const mock = createRuntimeMock();
+    const client = new IOSCompanionClient({ runtime: mock.runtime, nodeId: 'ios-node' });
+
+    expect(client.pendingRequestCount).toBe(mock.pendingRequestCount);
+  });
+
   it('macOS client forwards canvas methods to runtime client', async () => {
     const mock = createRuntimeMock();
     const client = new MacOSCompanionClient({ runtime: mock.runtime, nodeId: 'mac-node' });

src/companion/platformClients.ts

@@ -275,6 +275,10 @@ export class MacOSCompanionClient {
     return this.runtime.eventSubscriptionCount;
   }
 
+  get pendingRequestCount(): number {
+    return this.runtime.pendingRequestCount;
+  }
+
   waitForAnyEvent<TData = unknown>(
     eventNames: readonly (CompanionEventName | string)[],
     options?: {
@@ -517,6 +521,10 @@ export class IOSCompanionClient {
     return this.runtime.eventSubscriptionCount;
   }
 
+  get pendingRequestCount(): number {
+    return this.runtime.pendingRequestCount;
+  }
+
   waitForAnyEvent<TData = unknown>(
     eventNames: readonly (CompanionEventName | string)[],
     options?: {
@@ -757,6 +765,10 @@ export class AndroidCompanionClient {
     return this.runtime.eventSubscriptionCount;
   }
 
+  get pendingRequestCount(): number {
+    return this.runtime.pendingRequestCount;
+  }
+
   waitForAnyEvent<TData = unknown>(
     eventNames: readonly (CompanionEventName | string)[],
     options?: {

src/companion/runtimeClient.test.ts

@@ -593,6 +593,44 @@ describe('CompanionRuntimeClient', () => {
     );
   });
 
+  it('tracks pendingRequestCount for in-flight RPCs', async () => {
+    class FakeWebSocket extends EventEmitter {
+      readyState: number = WebSocket.CONNECTING;
+
+      constructor() {
+        super();
+        queueMicrotask(() => {
+          this.readyState = WebSocket.OPEN;
+          this.emit('open');
+        });
+      }
+
+      send(_payload: string, callback?: (error?: Error) => void): void {
+        callback?.();
+      }
+
+      close(_code?: number, _reason?: string): void {
+        this.readyState = WebSocket.CLOSED;
+        this.emit('close');
+      }
+    }
+
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+      websocketFactory: () => new FakeWebSocket() as unknown as WebSocket,
+      requestTimeoutMs: 10_000,
+    });
+    await client.connect();
+    expect(client.pendingRequestCount).toBe(0);
+
+    const pending = client.call('system.capabilities');
+    expect(client.pendingRequestCount).toBe(1);
+
+    client.disconnect();
+    await expect(pending).rejects.toThrow('Disconnected');
+    expect(client.pendingRequestCount).toBe(0);
+  });
+
   it('connects and performs node registration + capability discovery', async () => {
     if (!LISTEN_ALLOWED) {
       return;

src/companion/runtimeClient.ts

@@ -302,6 +302,10 @@ export class CompanionRuntimeClient {
     return this.eventHandlers.size;
   }
 
+  get pendingRequestCount(): number {
+    return this.pending.size;
+  }
+
   async connect(): Promise<void> {
     if (this.connected) {
       return;