fix(bus): acquire PubSub subscription eagerly to close /event race (#27959)

packages/opencode/test/bus/bus-effect.test.ts

@@ -44,7 +44,7 @@ describe("Bus (Effect-native)", () => {
       const done = yield* Deferred.make<void>()
       const ready = yield* Latch.make()
 
-      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+      yield* Stream.runForEach(yield* bus.subscribe(TestEvent.Ping), (evt) =>
         Effect.gen(function* () {
           if (evt.properties.value < 0) {
             yield* ready.open
@@ -71,7 +71,7 @@ describe("Bus (Effect-native)", () => {
       const done = yield* Deferred.make<void>()
       const ready = yield* Latch.make()
 
-      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+      yield* Stream.runForEach(yield* bus.subscribe(TestEvent.Ping), (evt) =>
         Effect.gen(function* () {
           if (evt.properties.value < 0) {
             yield* ready.open
@@ -98,7 +98,7 @@ describe("Bus (Effect-native)", () => {
       const done = yield* Deferred.make<void>()
       const ready = yield* Latch.make()
 
-      yield* Stream.runForEach(bus.subscribeAll(), (evt) =>
+      yield* Stream.runForEach(yield* bus.subscribeAll(), (evt) =>
         Effect.gen(function* () {
           if (evt.type === TestEvent.Warmup.type) {
             yield* ready.open
@@ -129,7 +129,7 @@ describe("Bus (Effect-native)", () => {
       const readyA = yield* Latch.make()
       const readyB = yield* Latch.make()
 
-      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+      yield* Stream.runForEach(yield* bus.subscribe(TestEvent.Ping), (evt) =>
         Effect.gen(function* () {
           if (evt.properties.value < 0) {
             yield* readyA.open
@@ -140,7 +140,7 @@ describe("Bus (Effect-native)", () => {
         }),
       ).pipe(Effect.forkScoped)
 
-      yield* Stream.runForEach(bus.subscribe(TestEvent.Ping), (evt) =>
+      yield* Stream.runForEach(yield* bus.subscribe(TestEvent.Ping), (evt) =>
         Effect.gen(function* () {
           if (evt.properties.value < 0) {
             yield* readyB.open
@@ -162,6 +162,92 @@ describe("Bus (Effect-native)", () => {
     }),
   )
 
+  // RACE 1: eager subscription means publishing immediately after yield*
+  // bus.subscribe is delivered. Regression for the old lazy `Stream.unwrap`
+  // shape where PubSub.subscribe ran on first pull and missed any publish
+  // in the hand-off window.
+  it.instance("eager subscribe: publish after yield* is delivered without consumer-activation race", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const stream = yield* bus.subscribe(TestEvent.Ping)
+
+      // Hand-off window: subscription is alive (we yielded). Publish goes
+      // straight into the subscription queue, even with no consumer running.
+      yield* bus.publish(TestEvent.Ping, { value: 99 })
+
+      const collected = yield* stream.pipe(
+        Stream.take(1),
+        Stream.runCollect,
+        Effect.timeout("400 millis"),
+        Effect.option,
+      )
+
+      expect(collected._tag).toBe("Some")
+      if (collected._tag === "Some") {
+        const arr = Array.from(collected.value)
+        expect(arr[0].properties.value).toBe(99)
+      }
+    }),
+  )
+
+  // RACE 2: same property for subscribeAll.
+  it.instance("eager subscribeAll: publish after yield* is delivered", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const stream = yield* bus.subscribeAll()
+
+      yield* bus.publish(TestEvent.Ping, { value: 42 })
+
+      const collected = yield* stream.pipe(
+        Stream.take(1),
+        Stream.runCollect,
+        Effect.timeout("400 millis"),
+        Effect.option,
+      )
+
+      expect(collected._tag).toBe("Some")
+      if (collected._tag === "Some") {
+        const arr = Array.from(collected.value)
+        expect(arr[0].type).toBe(TestEvent.Ping.type)
+      }
+    }),
+  )
+
+  // RACE 3: the /event-handler shape exactly. With eager subscription, the
+  // bus subscription is alive before Stream.concat ever starts. Publishes
+  // during the prefix consumption window are queued and delivered.
+  it.instance("eager subscribe: Stream.concat(initial, subscribe) delivers publish during prefix", () =>
+    Effect.gen(function* () {
+      const bus = yield* Bus.Service
+      const sawInitial = yield* Deferred.make<void>()
+      const sawPublish = yield* Deferred.make<number>()
+
+      type Frame = { marker?: "initial"; value?: number }
+      const subscriptionStream = yield* bus.subscribe(TestEvent.Ping)
+      const handlerStream: Stream.Stream<Frame> = Stream.make({ marker: "initial" } as Frame).pipe(
+        Stream.concat(subscriptionStream.pipe(Stream.map((evt): Frame => ({ value: evt.properties.value })))),
+      )
+
+      yield* Stream.runForEach(handlerStream, (frame) =>
+        Effect.gen(function* () {
+          if (frame.marker === "initial") {
+            Deferred.doneUnsafe(sawInitial, Effect.void)
+            return
+          }
+          if (frame.value !== undefined) Deferred.doneUnsafe(sawPublish, Effect.succeed(frame.value))
+        }),
+      ).pipe(Effect.forkScoped)
+
+      yield* Deferred.await(sawInitial).pipe(Effect.timeout("1 second"))
+
+      yield* bus.publish(TestEvent.Ping, { value: 7 })
+
+      const got = yield* Deferred.await(sawPublish).pipe(Effect.timeout("1 second"), Effect.option)
+      expect(got._tag).toBe("Some")
+      if (got._tag === "Some") expect(got.value).toBe(7)
+    }),
+  )
+
   it.live("subscribeAll stream sees InstanceDisposed on disposal", () =>
     Effect.gen(function* () {
       const dir = yield* tmpdirScoped()
@@ -174,7 +260,7 @@ describe("Bus (Effect-native)", () => {
       yield* Effect.gen(function* () {
         const bus = yield* Bus.Service
 
-        yield* Stream.runForEach(bus.subscribeAll(), (evt) =>
+        yield* Stream.runForEach(yield* bus.subscribeAll(), (evt) =>
           Effect.gen(function* () {
             if (evt.type === TestEvent.Warmup.type) {
               yield* ready.open