Root cause: `formatTaskResult` and `formatFullSession` both call
`client.session.messages({ path: { id: task.sessionId } })` with no
timeout. The OpenCode SDK explicitly disables fetch timeout
(`req.timeout = false` in `packages/sdk/js/src/client.ts:37`), so when
`session.processor` enters an "Aborted process" loop (same condition
patched in #4086 for the Read hot path) every subsequent
`session.messages` call hangs forever.
User-visible impact: the parent agent running a heavy slash command
such as `/init-deep` fires many background `task` agents in parallel
and then calls `background_output(task_id, block=true)` for each. The
existing `timeoutMs` (max 10min) caps only the polling loop that waits
for the child task to transition out of `running`. Once the child is
`completed`, the loop exits and the code falls through to
`formatTaskResult` / `formatFullSession`. The 10min cap does not apply
to that post-completion fetch, so a wedged `session.messages` leaves
the tool call hanging indefinitely. The parent session appears stuck
to the user (the symptom they report on `/init-deep ultrafucking
deep`).
Fix: race the underlying `session.messages` call against a 5s timeout
through a new `withSdkCallTimeout` helper local to
`src/tools/background-task/` (mirrors `withFetchTimeout` in
`src/shared/dynamic-truncator.ts` and `withDispatchTimeout` in
`src/shared/prompt-async-gate.ts`). On timeout the caller returns a
clearly-marked `"Error fetching messages: ... timed out after 5000ms"`
fallback so the agent can recognise the failure and continue instead
of waiting forever.
Tests:
- New `sdk-call-timeout.test.ts` pins the fix with three BDD cases
using a never-settling mock and the new
`_setBackgroundOutputFetchTimeoutMsForTesting(50)` override:
(1) `formatTaskResult` resolves to the timeout fallback under the
fetch budget, (2) same for `formatFullSession`, (3) two parallel
callers against the wedged client both resolve cleanly.
- All three failed (timed out) before the fix and pass in 51ms each
after.
Verification:
- `bun test src/tools/background-task/` -- 33 pass.
- `bun test` (full suite) -- 7014 pass, 1 skip, 0 fail across 723
files.
- `bun run typecheck` -- clean (tsgo --noEmit).
- LSP diagnostics on the four changed files -- 0 errors.
- Manual QA harness `.local-ignore/init-deep-hang-qa.ts` (gitignored)
drove production default 5s timeout against a wedged client:
serial `formatTaskResult` resolved in 5001ms, serial
`formatFullSession` in 5002ms, 10 parallel `formatTaskResult` calls
all resolved within 5002ms with the timeout fallback. Without the
fix every call hangs indefinitely.
Refs: builds on #4086 (dynamic-truncator) which patched the Read hot
path of the same SDK hang.
Rename BackgroundTask and attempt ID fields to camelCase across background-agent consumers while moving BackgroundManager construction to a single config object.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
YeonGyu-Kim