YeonGyu-Kim
38732b426e
PR #3825's fac90d69f introduced a shared bootstrap context to fix delegated child-session fallback when the first prompt fails before any session history is persisted. PR #4044 reverted that fix because its own regression test failed on a clean root suite (6828 pass / 1 fail). The bug remains unaddressed in v4.2.0; reland is deferred.
This commit documents the symptom, history, workaround, and tracking issue so users have visibility.
Closes BLOCKER-4 via Path B (documentation).
Refs PR #3825, PR #4044, issue #4059.
2.3 KiB
Known Issues
Tracks bugs that are present in the current release but have been intentionally deferred. Each entry should explain the symptom, the history, any workaround, and the planned resolution.
v4.2.0 - Delegated child-session early-failure fallback (PR #3825 deferred)
Symptom
A delegated child session that fails on its very first promptAsync call (for example, the provider rejects the request before any session history is persisted) may not advance to the configured fallback models. The session ends in early failure instead of retrying with the next fallback in the chain.
This affects subagents launched via the delegate-task tool (background or sync) where the first provider call fails immediately and session.messages is still empty.
History
PR #3825 (tw-yshuang/fix/delegated-child-session-early-failure-fallback, merged as commit fac90d69f on 2026-05-07) introduced a shared bootstrap context (src/shared/delegated-child-session-bootstrap.ts) to capture the retry payload before the first prompt dispatch, so empty-history failures could still retry with the fallback chain.
After the merge landed on dev, the PR's own regression test (delegated child-session empty-history fallback retries with captured bootstrap prompt in src/hooks/runtime-fallback/index.test.ts) failed on a clean root bun test --timeout 30000 run (6828 pass / 1 fail). PR #4044 (code-yeongyu/revert/3825-delegated-bootstrap, merged on 2026-05-15) reverted the merge to keep dev green (6823 pass / 0 fail / 6 skip across 709 files).
The original failure-mode the PR targets remains in v4.2.0.
Workaround
- For delegated subagents, prefer providers that succeed reliably on the first call (rarely fail with auth/quota errors at request time).
- Configure fallback models conservatively in
categories[].fallback_modelsand accept that the very first failure may not auto-retry. - The existing runtime-fallback persisted-history retry path still works after the subagent produces any history.
Planned Resolution
Reland will target v4.2.1 once the regression test is stabilized against the post-#4032 schema-compatible synthetic tool result shape and the prompt-async-gate's dispatch timeout + post-dispatch hold semantics. A follow-up issue will be filed to track this work.