feat(sdk): expose live event stream (#34098)

packages/server/src/handlers/event.ts

@@ -1,16 +1,19 @@
 import { EventV2 } from "@opencode-ai/core/event"
-import { Effect, Stream } from "effect"
+import { OpenCodeEvent } from "@opencode-ai/protocol/groups/event"
+import { Effect, Schema, Stream } from "effect"
 import { HttpServerResponse } from "effect/unstable/http"
 import { HttpApiBuilder } from "effect/unstable/httpapi"
 import * as Sse from "effect/unstable/encoding/Sse"
 import { Api } from "../api"
 
+const subscriberCapacity = 256
+
 function eventData(data: unknown): Sse.Event {
   return {
     _tag: "Event",
     event: "message",
     id: undefined,
-    data: JSON.stringify(data),
+    data: JSON.stringify(Schema.encodeUnknownSync(OpenCodeEvent)(data)),
   }
 }
 
@@ -24,13 +27,16 @@ export const EventHandler = HttpApiBuilder.group(Api, "server.event", (handlers)
           type: "server.connected",
           data: {},
         }
+        const output = Stream.unwrap(
+          Effect.gen(function* () {
+            // Acquiring the bounded stream installs its listener before readiness is observable.
+            const live = yield* EventV2.allBounded(events, subscriberCapacity)
+            return Stream.make(connected).pipe(Stream.concat(live))
+          }),
+        ).pipe(Stream.map(eventData), Stream.pipeThroughChannel(Sse.encode()))
+        const heartbeat = Stream.tick("15 seconds").pipe(Stream.map(() => ": heartbeat\n\n"))
         return HttpServerResponse.stream(
-          Stream.make(connected).pipe(
-            Stream.concat(events.all()),
-            Stream.map(eventData),
-            Stream.pipeThroughChannel(Sse.encode()),
-            Stream.encodeText,
-          ),
+          output.pipe(Stream.merge(heartbeat, { haltStrategy: "left" }), Stream.encodeText),
           {
             contentType: "text/event-stream",
             headers: {