fix(amicode-service): reconcile re-opens the dead LOCAL fan-in arm (#1601)

[jeonghun-jj-lee]

Closes #1601.

What

FanInConnection.reconcile() now re-opens the LOCAL fan-in arm when it is
absent from this.sources — idempotently, resuming from the LOCAL namespace's
live cursor, mirroring start().

Why (the freeze)

On a role: server machine with ≥1 serving peer, the webview's GET /global/event
runs through SseFanInDriver, which fans in a LOCAL arm (→ local engine) plus
peer arm(s). start() opened the LOCAL arm once; pump() removes any dead
source (LOCAL included) when its upstream ends; but reconcile() only iterated
agg.activeArms(), which is peers-only by construction ([...peerArms],
never local). So once the LOCAL upstream ended, the LOCAL arm was never
restored until a full webview reload — while peer frames kept the composite
stream non-silent, so the client stream-liveness watchdog (#1584) never fired.
Result: local chat sessions freeze / go stale until a window reload (#1583,
Problem B — event delivery). This is server-side; #1587 (client watchdog) was
necessary but insufficient, and #1594 (engine lifecycle, Problem A) is unrelated.

The fix

13 lines in reconcile(), appended after the peer close loop: guarded on
!this.sources.has(LOCAL_NAMESPACE), calling openArm(LOCAL_NAMESPACE, localEventUrl(), authHeader, resume.get(LOCAL_NAMESPACE)). No change to
start(), pump(), openArm, peer-arm behavior, or the aggregator; the
downstream res is never ended.

Tests

New describe("#1601 …") in sse_fanin_driver_pump.test.ts (mirrors the #1566
peer-arm test for the LOCAL namespace): asserts the LOCAL arm opens once, a
pre-drop frame is delivered, the arm is re-opened after its upstream ends +
reconcile(), a post-reopen frame is delivered, the downstream res is never
ended, and fleet-of-one idempotence (a healthy LOCAL arm + no peers is never
re-opened/duplicated across repeated reconcile ticks). RED before the fix (arm
not re-opened → expected 1 to be 2), GREEN after.

Gates (all run locally on this branch)

• Fan-in unit suite: 30/30 (was 28; +2 new; [A2] Fix dead arm zombie: cleanup source on pump exit #1566/Remote agent output never reaches the observer: SSE fan-in binds /event, but the app/engine speak /global/event #1580 preserved)
• Full extension fast suite: 4992 passed, 0 failed (294 files)
• Typecheck (tsc --noEmit): clean
• build:binary: DONE (v1.18.30, OPENCODE_CHANNEL=dev)
• Boot smoke: PASS (GET /event → 200 text/event-stream)

Base is feature/free-tier-fleet (not main). Draft until a human reviews;
merge is human-only.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 69a54a15-9caf-4d23-932d-79de2de90bc8

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}