fix(plugin): await session.idle + server.instance.disposed handlers

[Alezander9]

Summary

Await plugin event handlers for session.idle and server.instance.disposed so lifecycle plugins (e.g. bcode-laminar) can finish draining before process.exit().

Why

packages/opencode/src/index.ts:252-266 (PR #50) added a top-level provider.forceFlush() race before process.exit() to recover the final agent LLM span. That helped, but forceFlush() only exports ended spans. The deeper bug — already called out in PR #50's own comment — is that bus dispatch at packages/opencode/src/plugin/index.ts:249 is void hook["event"]?.(...), so the bcode-laminar plugin's session.idle and server.instance.disposed handlers (which span.end() the open turn span and await processor.forceFlush() / await sdk.shutdown()) are fire-and-forget. The turn span is therefore still open when forceFlush() runs, so it never reaches the wire before process.exit() kills the in-flight export.

Verified empirically in V4 cloud staging: long-task runs land every turn span except the last one in BrowserCode-CLOUD Laminar. Exact symptom of the existing comment.

Change

-        // Subscribe to bus events, fiber interrupted when scope closes
+        // Subscribe to bus events, fiber interrupted when scope closes.
+        // session.idle and server.instance.disposed are plugins' only chance to
+        // drain async work (e.g. OTel span exporters) before src/index.ts's
+        // top-level finally runs forceFlush and calls process.exit() — await
+        // those handlers; keep the rest fire-and-forget for throughput.
         yield* bus.subscribeAll().pipe(
           Stream.runForEach((input) =>
-            Effect.sync(() => {
+            Effect.promise(async () => {
+              const awaitHook = input.type === "server.instance.disposed" || input.type === "session.idle"
               for (const hook of hooks) {
-                void hook["event"]?.({ event: input as any })
+                const ret = hook["event"]?.({ event: input as any })
+                if (awaitHook && ret) {
+                  try {
+                    await ret
+                  } catch (err) {
+                    log.error("plugin event hook failed", { error: err })
+                  }
+                }
               }
             }),
           ),
           Effect.forkScoped,
         )

Narrow scope by design:

• Only the two disposal-class events block on plugin handlers. session.message, session.created, etc. keep their existing fire-and-forget semantics — no latency increase, no new deadlock surface, no ordering changes for the hot paths.
• Handler errors are caught and logged via the same log.error pattern the config hook already uses, so one bad plugin can't stall the bus.
• The PR fix(laminar): drain OTel processors before process.exit() to stop losing final agent spans #50 forceFlush race upstairs stays in place as a generic safety net for any future OTel plugin.

Verification plan

1. Land this PR; cut bcode v0.1.7 from main.
2. Bump cloud/backend/sandboxes/v4-worker/Dockerfile to --version 0.1.7; CP auto-deploys to AgentCore.
3. Re-run V4 staging long-task smoke (~30s+ runtime, multiple turns).
4. Confirm BrowserCode-CLOUD Laminar shows the complete trace tree including the final turn, with all AI-SDK sub-spans nested correctly.

Yellow-zone note

Documented in memory/browsercode/EXCEPTIONS.md under "Phase F (cont.) — await disposal/idle plugin events". This is a real upstream-grade fix (PR #50's comment already identifies the underlying bug). Upstreamable to anomalyco/opencode once we've validated it in production for a week.

---

Summary by cubic

Await plugin handlers for session.idle and server.instance.disposed so lifecycle plugins (e.g., bcode-laminar) can end the final turn span and flush OTel before process exit. Also log errors from fire‑and‑forget handlers to avoid unhandled rejections.

• Bug Fixes
  • Await promises for session.idle and server.instance.disposed; all other events stay fire-and-forget.
  • Wrap the whole invocation in try/catch to catch sync throws and awaited rejections; keep the subscription fiber and other plugins running.
  • For fire-and-forget events, attach .catch(log.error) to handler promises to surface async failures instead of unhandledRejection.
  • Keep top-level provider.forceFlush() as a fallback.

^{Written for commit e008c31. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/opencode/src/plugin/index.ts">

<violation number="1" location="packages/opencode/src/plugin/index.ts:257">
P2: Synchronous exceptions from `hook["event"]` are not caught, so a throwing plugin can fail the bus subscription fiber instead of being logged and isolated.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.
Fix all with cubic | Re-trigger cubic}

[cubic-dev-ai]

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/opencode/src/plugin/index.ts">

<violation number="1" location="packages/opencode/src/plugin/index.ts:259">
P2: Non-awaited plugin event Promises can reject without being caught, so async handler failures on non-disposal events are still unhandled and not logged.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.
Fix all with cubic | Re-trigger cubic}