F18. A single last_error slot destroyed causal evidence twice. Run 7
kept only the last of four failures. In run 11 a five-second retry loop
on a dead task pinned the slot for twenty-six minutes, so the live
task's own expiry was never visible at all, and run 12 lost diagnosis
time to the same thing before F58 removed the flood.
WorkerHealth now carries up to sixteen distinct observations, each with
its repeat count and first/last times. Collapsing is by message rather
than by position, because a loop interleaved with other failures would
otherwise still flush the ring. Eviction drops the least recently seen.
last_error and error_at keep their wire names and still report only the
newest failure, so nothing reading them has to change.
The ring lives in memory beside last_error and is not persisted, which
is the behaviour last_error already had across a restart.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CVbaKucEYBjMqVeUgJUsc1
kami
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