feat(companion): add waitForEvent runtime helper

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 optional `autoConnect` mode and event subscriptions (`subscribeEvents()`, `subscribeEvent()`).
+- `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 optional `autoConnect` mode and event helpers (`subscribeEvents()`, `subscribeEvent()`, `waitForEvent()`).
 - `src/companion/platformClients.ts` provides platform-focused wrappers:
   - `MacOSCompanionClient` (`platform: "macos"`, APNs push registration)
   - `IOSCompanionClient` (`platform: "ios"`, APNs push registration)

docs/plans/state.json

@@ -327,6 +327,20 @@
       ],
       "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/platformClients.integration.test.ts src/companion/heartbeatLoop.test.ts + pnpm typecheck passing"
     },
+    "companion-runtime-wait-for-event-helper": {
+      "status": "completed",
+      "date": "2026-02-17",
+      "updated": "2026-02-17",
+      "summary": "Added `waitForEvent()` helper to `CompanionRuntimeClient` for promise-based event awaiting with timeout and optional payload predicate filtering.",
+      "files_modified": [
+        "src/companion/runtimeClient.ts",
+        "src/companion/runtimeClient.test.ts",
+        "src/companion/index.ts",
+        "README.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/companion/runtimeClient.test.ts src/companion/platformClients.test.ts src/companion/platformClients.integration.test.ts src/companion/heartbeatLoop.test.ts + pnpm typecheck passing"
+    },
     "browser-tools-activation-clarity": {
       "status": "completed",
       "date": "2026-02-17",

src/companion/index.ts

@@ -13,6 +13,7 @@ export type {
   CompanionRuntimeClientOptions,
   CompanionEventHandler,
   CompanionTypedEventHandler,
+  CompanionEventPredicate,
   RegisterNodeInput,
   ListNodesInput,
   SetNodeStatusInput,

src/companion/runtimeClient.test.ts

@@ -187,6 +187,48 @@ describe('CompanionRuntimeClient', () => {
     expect(streamHandler).toHaveBeenCalledTimes(1);
   });
 
+  it('waitForEvent resolves using optional predicate filter', async () => {
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+
+    const awaited = client.waitForEvent<{ seq: number }>('agent.stream', {
+      timeoutMs: 2000,
+      predicate: (data) => data.seq === 2,
+    });
+
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 48,
+        event: 'agent.stream',
+        data: { seq: 1 },
+      }),
+    );
+    (client as unknown as { handleMessage: (raw: string) => void }).handleMessage(
+      JSON.stringify({
+        id: 49,
+        event: 'agent.stream',
+        data: { seq: 2 },
+      }),
+    );
+
+    await expect(awaited).resolves.toEqual({ seq: 2 });
+  });
+
+  it('waitForEvent rejects on timeout', async () => {
+    vi.useFakeTimers();
+    const client = new CompanionRuntimeClient({
+      url: 'ws://127.0.0.1:1',
+    });
+
+    const awaited = expect(
+      client.waitForEvent('agent.stream', { timeoutMs: 100 }),
+    ).rejects.toThrow('Timed out waiting for event agent.stream');
+    await vi.advanceTimersByTimeAsync(100);
+    await awaited;
+    vi.useRealTimers();
+  });
+
   it('connects and performs node registration + capability discovery', async () => {
     if (!LISTEN_ALLOWED) {
       return;

src/companion/runtimeClient.ts

@@ -43,6 +43,7 @@ export interface CompanionRuntimeClientOptions {
 
 export type CompanionEventHandler = (event: string, data: unknown) => void;
 export type CompanionTypedEventHandler<TData = unknown> = (data: TData) => void;
+export type CompanionEventPredicate<TData = unknown> = (data: TData) => boolean;
 
 export interface RegisterNodeInput {
   nodeId: string;
@@ -365,6 +366,42 @@ export class CompanionRuntimeClient {
     });
   }
 
+  waitForEvent<TData = unknown>(
+    eventName: string,
+    options?: {
+      timeoutMs?: number;
+      predicate?: CompanionEventPredicate<TData>;
+    },
+  ): Promise<TData> {
+    const timeoutMs = options?.timeoutMs ?? this.requestTimeoutMs;
+    const predicate = options?.predicate;
+
+    return new Promise<TData>((resolve, reject) => {
+      let settled = false;
+      const unsubscribe = this.subscribeEvent<TData>(eventName, (data) => {
+        if (predicate && !predicate(data)) {
+          return;
+        }
+        if (settled) {
+          return;
+        }
+        settled = true;
+        clearTimeout(timeout);
+        unsubscribe();
+        resolve(data);
+      });
+
+      const timeout = setTimeout(() => {
+        if (settled) {
+          return;
+        }
+        settled = true;
+        unsubscribe();
+        reject(new Error(`Timed out waiting for event ${eventName}`));
+      }, timeoutMs);
+    });
+  }
+
   async call<T>(method: string, params?: Record<string, unknown>): Promise<T> {
     if (!this.connected) {
       if (!this.autoConnect) {