A task soft-deleted concurrently with a heartbeat-driven moveTask raised
TaskDeletedError from the engine's own board path, leaving the agent in `error`
with a non-empty lastError and requiring a stop/start cycle to recover.
The race is benign by construction: the task is gone, so the move is a no-op.
The heartbeat now classifies it via isConcurrentSoftDeleteRaceError (matching the
canonical message and serialized/typed forms), keeps the agent active, clears
stale error/recovery state, and emits agent:heartbeat-move-skipped-soft-delete
with ids/counts-only metadata. Concurrent operator pauses are preserved.
Squash-merged by hand from fusion/fn-8004. The engine's AI merge approved this
content twice (squash a3a3cc6a8) but could not land it: main advances every ~8
minutes and each merge cycle took ~10, so every attempt lost to a concurrent
advance and rebuilt. Each cycle also burned a corrective pass on a first-pass
review rejection with no stated reason — the issue #1946 class of bug that this
task's own report cites as a sibling.
Reconciled against #2157, which refactored transient-error-detector.ts: the new
classifier coexists with the extracted transient-error-patterns.ts leaf. Verified
on the merged tree — 123 tests green across FN-8004's suites and #2157's,
engine typecheck clean.
Fusion-Task-Id: FN-8004
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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