Agents stop heartbeating during long legitimate work (e.g. a verification
step blocked on a multi-minute test command). The 5-minute floor could
misread a busy agent as dead and reclaim its in-progress task mid-run.
Raise MIN_HEARTBEAT_STALENESS_MS to 10 minutes and strengthen the floor
test (7-minute-silent fast-interval agent stays healthy — would have read
stale under the old 5-minute floor). Engine typecheck clean; heartbeat
suite 148/148 pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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