# Debugging Journal — Race Condition Hang Between opencode and omo

**Date:** 2026-05-16
**Goal:** Investigate and fix a race condition / infinite hang bug between opencode (../opencode) and omo that causes prompting to hang indefinitely.

## Phase 0 — Environment Assessment

- **OMO repo:** `/Users/yeongyu/local-workspaces/omo` (plugin for OpenCode)
- **Opencode repo:** `/Users/yeongyu/local-workspaces/opencode` (OpenCode server/SDK)
- **Worktree:** `/Users/yeongyu/local-workspaces/omo-kimi-k2.6`
- **Runtime:** Bun (omo), Node/Bun (opencode with Effect 4.0.0-beta.65)

## Phase 1 — Hypothesis Formation

### Hypothesis 1: promptAsync dispatch timeout not covering hanging fetch
- `promptAsyncAfterSessionIdle` wraps `session.promptAsync()` with `withDispatchTimeout` (default 30s)
- But `Promise.race` doesn't cancel the underlying fetch — it just returns after timeout
- The reservation is then held for `postDispatchHoldMs` (250ms) before expiring
- **BUT:** If the event loop is blocked, `setTimeout` won't fire, so both promises hang

### Hypothesis 2: Effect-native event system in opencode has race condition
- Opencode commit `e11e089e4` (May 14) added Effect-native core event system
- OMO commit `b333a5280` (May 16) added dispatch timeout to prompt-async-gate
- The hang persists after both fixes
- The `promptAsync` handler in opencode uses `Effect.forkIn(scope, { startImmediately: true })`
- If `forkIn` has a bug in Effect 4.0.0-beta.65, the HTTP response might not return

### Hypothesis 3: Reservation leak in prompt-async-gate
- If `dispatchAfterSessionIdle` throws before `dispatchAttempted = true`, the finally block deletes the reservation
- If `dispatchAttempted = true` but `postDispatchHoldMs` is very large, reservation stays until `pruneExpiredReservations` runs
- But default is 250ms, so this should not cause "forever" hang

## Phase 2 — Parallel Investigation

### Key Files Read
- `omo/src/shared/prompt-async-gate.ts` — The gate logic with timeout
- `omo/src/shared/session-idle-settle.ts` — Simple settle logic
- `omo/src/plugin/event.ts` — Event handler that calls `autoContinueAfterFallback`
- `opencode/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts` — Server-side `promptAsync` handler
- `opencode/packages/opencode/src/session/prompt.ts` — SessionPrompt service with `loop()`
- `opencode/packages/core/src/event.ts` — Effect-native event system

### Key Findings
1. OMO `promptAsyncAfterSessionIdle` has 30s dispatch timeout (added May 16)
2. Opencode server `promptAsync` handler forks prompt processing into a scope
3. Opencode uses Effect 4.0.0-beta.65 — a beta version
4. The `promptSvc.prompt()` calls `loop()` which has `while (true)`
5. The SDK `createOpencodeClient` sets `req.timeout = false` on fetch

## Next Steps
1. Check for any OMO callers that bypass the gate (raw `session.promptAsync` calls)
2. Check opencode logs for hanging requests
3. Create a reproduction test
4. Fix the root cause

---

# Debugging Journal — 2026-05-17 gpt 5.5 xhigh Run

Started: 2026-05-17T13:34:00+09:00
Goal: Debug and fix the prompt hang/race between sibling `opencode` and `omo` with failing-first tests, manual QA, clean PR, CI pass, and Cubic pass.

## Environment Snapshot

- Runtime: Bun 1.3.12, Node v26.0.0
- OMO worktree: `/Users/yeongyu/local-workspaces/gpt 5.5 xhigh`
- OMO branch: `code-yeongyu/fix-prompt-hang-race`
- Base: `origin/dev` at `75223149d`
- Sibling OpenCode repo: `/Users/yeongyu/local-workspaces/opencode`
- Debug ports checked: 9229, 9230
- References read:
  - `/Users/yeongyu/.agents/skills/debugging/SKILL.md`
  - `/Users/yeongyu/.agents/skills/debugging/references/runtimes/node.md`
  - `/Users/yeongyu/.agents/skills/debugging/references/methodology/00-setup.md`
  - `/Users/yeongyu/.agents/skills/debugging/references/methodology/02-investigate.md`
  - `/Users/yeongyu/local-workspaces/omo/.agents/skills/work-with-pr/SKILL.md`
  - `/Users/yeongyu/.agents/skills/git-master/SKILL.md`

## Hypotheses

1. [OPEN] OpenCode `promptAsync` can resolve before the prompt is durably accepted, then a later `session.error` leaves OMO believing dispatch succeeded while no live parent turn will complete. Distinguishing evidence: OpenCode handler response path returns before durable session acceptance, and OMO currently releases or retains reservations in a way that allows an orphaned dispatch.
2. [OPEN] OMO has at least one raw `session.prompt` or `session.promptAsync` route outside `src/shared/prompt-async-gate.ts`, allowing concurrent idle/error/completion hooks to inject multiple internal prompts or hang one behind another. Distinguishing evidence: raw call sites outside the shared gate or a static invariant test gap.
3. [OPEN] The shared prompt gate does not bound the full dispatch lifecycle correctly when the underlying SDK fetch never resolves, leaving duplicate-injection state or optimistic loop state stuck forever. Distinguishing evidence: a failing test where unresolved `promptAsync` blocks or leaks reservation/task state past the expected timeout path.
4. [OPEN] Sibling `opencode` changed event/session semantics in a way that makes previous OMO idle-settle assumptions too weak. Distinguishing evidence: event/prompt implementation or tests in `../opencode` showing an accepted response can be followed by async prompt rejection/error edge.

## Artifacts To Revert Or Preserve

- [ ] `/Users/yeongyu/local-workspaces/gpt 5.5 xhigh` — temporary worktree. Remove after merged PR with `git worktree remove`.
- [ ] Branch `code-yeongyu/fix-prompt-hang-race` — temporary PR branch. Delete via PR squash merge or `git branch -D` only after safe cleanup.
- [ ] `.debugging` — journal update requested by user. Preserve unless final cleanup requires restoring debug-only notes.
- [ ] `src/tools/call-omo-agent/completion-poller.test.ts` — failing-first regression for 204-without-durable-message prompt acceptance. Preserve as product test.
- [ ] `src/tools/call-omo-agent/completion-poller.ts` — minimal prompt acceptance timeout fix. Preserve as product fix.
- [ ] `evidence/` — local QA/test output. Remove before final commit unless intentionally ignored.
- [ ] tmux session `ulw-qa-call-omo-agent` if created. Kill only this session, never the tmux server.
- [ ] `/tmp/ulw-call-omo-agent-qa.ts` — temporary tmux manual QA script. Remove after QA.

## Findings

### 2026-05-17T13:47:00+09:00 — OpenCode promptAsync is not durable acceptance
- Source: `/Users/yeongyu/local-workspaces/opencode/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts:295-314`
- Value: `promptAsync` forks `promptSvc.prompt({ ...ctx.payload, sessionID })` with `Effect.forkIn(scope, { startImmediately: true })` and then returns `HttpApiSchema.NoContent.make()`.
- Interpretation: OMO can receive 204 before OpenCode persists the user message or enters the busy run loop.
- Confirms: H1 and H4.

### 2026-05-17T13:48:00+09:00 — OpenCode can fail before user-message persistence
- Source: `/Users/yeongyu/local-workspaces/opencode/packages/opencode/src/session/prompt.ts:1092-1101`
- Value: `createUserMessage` publishes `Session.Event.Error` and throws when an agent name is not found, before `sessions.updateMessage(info)`.
- Interpretation: a forked promptAsync attempt can later error while `session.messages()` still returns zero messages.
- Confirms: H1.

### 2026-05-17T13:49:00+09:00 — OMO sync child poller waits on zero durable messages
- Source: `src/tools/call-omo-agent/completion-poller.ts:25-63`
- Value: loop treats idle with `currentMsgCount === 0` as not complete and only exits at `MAX_POLL_TIME_MS` with `Agent task timed out after 5 minutes.`
- Interpretation: when promptAsync returns 204 but OpenCode fails before persisting the user message, OMO waits for the generic five-minute poll timeout instead of surfacing prompt acceptance failure promptly.
- Confirms: H1; refutes H2 for this hang because production prompt routes are gate-routed.

## Root Cause (confirmed 2026-05-17T13:56:00+09:00)

- Mechanism: OpenCode `session.promptAsync` returns 204 after forking the real prompt, so OMO's sync child prompt path can begin polling before the user message is durably written. If the forked OpenCode prompt fails before `sessions.updateMessage(info)`, status remains idle or absent and `session.messages()` stays empty. `call_omo_agent` then waits for the generic five-minute poll timeout because zero messages never satisfy the stable-message completion condition.
- Evidence: `/Users/yeongyu/local-workspaces/opencode/packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts:295-314`, `/Users/yeongyu/local-workspaces/opencode/packages/opencode/src/session/prompt.ts:1092-1101`, `src/tools/call-omo-agent/completion-poller.ts:25-63`, and red test output in `evidence/task-2-red.txt`.
- Toggle proof: with the pre-fix poller, the red test receives `Agent task timed out after 5 minutes.` With the acceptance-timeout guard, the same simulated OpenCode 204-without-message sequence receives `Prompt was not durably accepted by OpenCode for session ses-undurable.`
- Fix scope: `src/tools/call-omo-agent/completion-poller.ts` and `src/tools/call-omo-agent/completion-poller.test.ts`.

### Red phase (2026-05-17T13:53:00+09:00)
- Test: `src/tools/call-omo-agent/completion-poller.test.ts`
- Command: `bun test src/tools/call-omo-agent/completion-poller.test.ts --bail`
- Output: `Expected substring: "Prompt was not durably accepted by OpenCode"; Received message: "Agent task timed out after 5 minutes."`

### Green phase (2026-05-17T13:55:00+09:00)
- Fix: `src/tools/call-omo-agent/completion-poller.ts` tracks whether any active status was observed and fails after 30s of idle zero-message polling before the generic five-minute timeout.
- Test: `bun test src/tools/call-omo-agent/completion-poller.test.ts --bail` passes with 2 tests.
- Adjacent checks:
  - `bun test src/tools/call-omo-agent/sync-executor.test.ts src/tools/call-omo-agent/sync-executor-leak.test.ts src/tools/call-omo-agent/completion-poller.test.ts --bail` passes with 23 tests.
  - `bun test src/hooks/shared/prompt-async-gate.test.ts src/shared/prompt-async-route-audit.test.ts --bail` passes with 20 tests.

### Manual QA — tmux sync prompt poller (2026-05-17T14:03:00+09:00)
- Scenario: run the real `waitForCompletion` implementation in a tmux session with an OpenCode-like client that reports idle status and zero messages after promptAsync acceptance.
- Command: `tmux new-session -d -s ulw-qa-call-omo-agent ... bun /tmp/ulw-call-omo-agent-qa.ts`
- Observed output: `Prompt was not durably accepted by OpenCode for session ses_qa.`
- Expected output: prompt acceptance failure appears promptly instead of generic five-minute timeout.
- Fix verified: yes.
- Cleanup: tmux session `ulw-qa-call-omo-agent` removed; `/tmp/ulw-call-omo-agent-qa.ts` removed.

## Scenario Notes

- Path: `/var/folders/nj/hqfr8ndn5q56cqw7jqgbrck40000gn/T/ulw-scenarios.XXXXXX.md.QVTvXtyXKK`

## Final Validation (2026-05-17T14:15:00+09:00)

- Focused regression:
  - `bun test src/tools/call-omo-agent/completion-poller.test.ts --bail`
  - Result: 2 pass, 0 fail.
- Adjacent call_omo_agent:
  - `bun test src/tools/call-omo-agent/sync-executor.test.ts src/tools/call-omo-agent/sync-executor-leak.test.ts src/tools/call-omo-agent/completion-poller.test.ts --bail`
  - Result: 23 pass, 0 fail.
- Prompt gate invariant:
  - `bun test src/hooks/shared/prompt-async-gate.test.ts src/shared/prompt-async-route-audit.test.ts --bail`
  - Result: 20 pass, 0 fail.
- Combined focused suite:
  - `bun test src/tools/call-omo-agent/completion-poller.test.ts src/tools/call-omo-agent/sync-executor.test.ts src/tools/call-omo-agent/sync-executor-leak.test.ts src/hooks/shared/prompt-async-gate.test.ts src/shared/prompt-async-route-audit.test.ts --bail`
  - Result: 43 pass, 0 fail.
- TypeScript quality:
  - `bun --install=fallback /Users/yeongyu/.config/opencode/skills/typescript-programmer/scripts/check-no-excuse-rules.ts src/tools/call-omo-agent/completion-poller.ts src/tools/call-omo-agent/completion-poller.test.ts`
  - Result: no no-excuse violations.
- Typecheck:
  - `bun run typecheck`
  - Result: pass.
- Build:
  - `bun run build`
  - Result: pass.
- Full suite in required worktree path:
  - `bun test`
  - Result: fail with 99 failures caused by Bun/test harness dynamic imports from an encoded path such as `/Users/yeongyu/local-workspaces/gpt%205.5%20xhigh/...`.
  - Interpretation: path-space-specific validation failure, not a product regression from this patch. Single-file reproduction: `bun test src/shared/load-opencode-plugins.test.ts --bail` fails before test logic with `Cannot find module '/Users/yeongyu/local-workspaces/gpt%205.5%20xhigh/src/shared/load-opencode-plugins.ts?...'`.
- Full suite in no-space validation worktree with the same patch:
  - Validation worktree: `/tmp/omo-ci-validation.9lEM4g`
  - `bun install --frozen-lockfile && bun test`
  - Result: 7014 pass, 1 skip, 0 fail across 724 files.
  - Cleanup: validation worktree removed with `git worktree remove --force /tmp/omo-ci-validation.9lEM4g`.

## Final Status Before PR

- Product behavior change: only `call_omo_agent` sync polling now fails fast when OpenCode never durably accepts a prompt after returning from `promptAsync`.
- Behavior preserved:
  - Durable message completion still requires stable idle message count.
  - Busy/non-idle child sessions continue polling as before.
  - Existing shared `promptAsync` gate and raw-prompt audit are unchanged and green.
- Remaining gates: commit, PR, GitHub CI, Cubic review, PR merge, final requested worktree cleanup.