test(companion): cover waitForIdle pending RPC lifecycle

docs/plans/state.json

@@ -990,6 +990,17 @@
       ],
       "test_status": "pnpm test:run src/companion/platformClients.integration.test.ts src/companion/platformClients.test.ts src/companion/runtimeClient.test.ts src/companion/heartbeatLoop.test.ts + pnpm typecheck passing"
     },
+    "companion-runtime-wait-for-idle-pending-rpc-coverage": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Added runtime regression coverage for `waitForIdle()` pending-RPC behavior, verifying idle resolution after pending requests are rejected on teardown.",
+      "files_modified": [
+        "src/companion/runtimeClient.test.ts",
+        "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/runtimeClient.test.ts

@@ -730,6 +730,49 @@ describe('CompanionRuntimeClient', () => {
     await pendingWait;
   });
 
+  it('waitForIdle resolves after pending RPC requests are rejected', 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();
+
+    const pendingCall = client.call('system.capabilities').catch(() => undefined);
+    expect(client.pendingRequestCount).toBe(1);
+
+    const idle = client.waitForIdle({ timeoutMs: 1_000, pollIntervalMs: 5 });
+    setTimeout(() => {
+      client.disconnect();
+    }, 20);
+
+    await expect(idle).resolves.toBeUndefined();
+    await pendingCall;
+    expect(client.pendingRequestCount).toBe(0);
+    expect(client.hasPendingWork).toBe(false);
+  });
+
   it('waitForIdle supports AbortSignal cancellation', async () => {
     const client = new CompanionRuntimeClient({
       url: 'ws://127.0.0.1:1',