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.
- 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`.
- 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.
- 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.`
- 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:
- 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.
1. [CONFIRMED] OpenCode emitted `session.idle` while the latest assistant message was still incomplete and still had pending/running tool parts, so OMO idle hooks treated a malformed live turn as safe to resume.
2. [CONFIRMED] OMO background completion wake logic only checked `finish === "tool-calls"`, so an unfinished assistant with `finish: null` and running tool state could still receive a background wake prompt.
3. [CONFIRMED] Existing tool-result recovery could recover missing tool results but only from storage readers and without a status filter, so it could not safely synthesize results for only interrupted `pending`/`running` parts from the latest idle message.
4. [REFUTED AS COMPLETE FIX] Waiting for upstream OpenCode alone is enough. Sibling `../opencode` contains upstream commit `e76cf967e60995986a4dd99d818fc900fa82f904` (`fix(session): finalize interrupted assistant messages (#27254)`), but the installed CLI is still 1.15.3 and the plugin must defend against this malformed idle state.
- Log evidence from `/Users/yeongyu/.local/share/opencode/log/2026-05-17T052321.log`:
- `InstanceRef not provided rejection`
- child sessions cancelled with `Aborted process`
- main session emitted `session.idle` while the DB retained the unfinished assistant and dangling tools.
## 3.17.x / OpenCode Comparison
- OpenCode `prompt_async` was accept-only / fire-and-forget in both older and current routes, so prompt acceptance alone is not the distinguishing regression.
- Sibling OpenCode already has `e76cf967e60995986a4dd99d818fc900fa82f904`, which finalizes interrupted assistant messages on interrupt.
- The observed installed runtime lacks that protection: an idle event can coexist with unfinished assistant/tool state.
- OMO must therefore treat idle-with-interrupted-tool-parts as a recoverable malformed state before any normal idle continuation/background/team wake hooks run.
## Root Cause
OpenCode 1.15.3 can publish `session.idle` after an interruption path without finalizing the latest assistant turn. The latest assistant message can remain `completed = null`, `finish = null`, and contain `pending` or `running` tool parts with valid call IDs. OMO then sees an idle edge and multiple hooks may try to resume or wake the same parent session, but the provider is still waiting for tool results that will never arrive. This creates the apparent forever hang.
The fix is defensive and minimal: when a `session.idle` event arrives, OMO now checks the latest assistant message first. If it is unfinished and has interrupted tool parts, OMO injects synthetic error `tool_result` parts only for those pending/running call IDs, dedupes the recovery by assistant message id, and skips later idle hooks for that event. Background completion wake also refuses to fork a prompt into any latest assistant turn containing pending/running tool state, even when `finish` is null.
- Test-only mock now exports all names required by the storage barrel during full one-process Bun suite runs.
## Manual QA
Scenario: recreate the exact stale shape from `ses_1cb9c3013ffesUOy5H3QOIya4K` with one completed tool plus the two bad call IDs.
Observed output:
```json
{"recovered":true,"dispatched":1,"recoveredToolUseIds":["toolu_015rqEhGgnYKiB73hQbwGgwT","toolu_01UPe3AyVwAoMebpGcuGPV4N"],"text":"Tool execution was interrupted before producing a result.","agent":"Sisyphus - Ultraworker","model":{"providerID":"anthropic","modelID":"claude-opus-4-7"},"variant":"max"}
```
Expected: only interrupted `running` / `pending` call IDs are recovered, completed tool results are left alone, and session agent/model/variant are preserved.
## Validation
- Focused tests:
- `bun test src/features/background-agent/task-completion-cleanup.test.ts --test-name-pattern "running tool state without finish"`: pass.
- `bun test src/hooks/session-recovery/recover-tool-result-missing.test.ts --test-name-pattern "recoverStatuses"`: pass.
- `bun test src/hooks/session-recovery/hook.test.ts --test-name-pattern "interrupted idle recovery"`: pass.
- `bun test src/plugin/event.test.ts --test-name-pattern "idle recovery handles"`: pass.
- Combined focused suite:
- `bun test src/hooks/session-recovery/recover-tool-result-missing.test.ts src/hooks/session-recovery/hook.test.ts src/features/background-agent/task-completion-cleanup.test.ts src/plugin/event.test.ts --bail`
- Result before test-only mock fix: failed with path-space encoded import issues and one storage mock export issue; storage mock was fixed and its file passes standalone.
- Full suite in no-space validation worktree with the same patch after the final `tool_use.id` precheck adjustment:
- Product behavior change: only malformed idle events with unfinished latest assistant messages and `pending` / `running` tool parts get synthetic interrupted tool results.
- Behavior preserved:
- Normal idle hook fanout remains unchanged when there is no interrupted latest assistant turn.
- Completed tool results are not re-emitted by the recovery filter.
- Background wakes still run when the latest assistant turn is finished or has no live tool state.
- Upstream OpenCode finalization remains compatible; this OMO defense becomes a no-op when OpenCode stores a finished/error assistant.
