The process-wide 4-worker pool retained the stdlib executor's unbounded
queue: four hung summaries wedged every slot, a fifth compression queued
silently, waited out its whole budget without starting, and remained
eligible to run later as an expensive stale job whose fence was already
cancelled (the first fence check used to sit AFTER the summary call).
- Bounded admission: submission fails fast (messages returned unchanged,
loud warning) when all pool slots are occupied; slots are freed by a
future done-callback. Recovery contract documented at the constant: new
work fails fast while wedged, wedged workers are fence-cancelled and
restore service when they return; a worker that never returns costs its
slot — bounded, observable degradation instead of unbounded queueing.
- Not-yet-started futures are cancel()ed on timeout.
- The cancelled fence is checked BEFORE any expensive summary work, both
in the pooled wrapper (stale queued job) and inside compress_context
(pre-summary gate), so a stale job never burns an LLM call or acquires
session state.
Saturation regression: 4 event-blocked summaries wedge the pool, a 5th
submission fails fast (asserted while the four are provably still
blocked), the refused job never runs after worker recovery, and a fresh
submission after recovery succeeds.
PR #76354 review, blocking finding 6 / merge gate 7.
Teknium
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