Technical notes on web development, DevOps, and AI integration.
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A lock checked once at startup guards the door, not the data. Fencing tokens validated at every state write, plus a heartbeat lease, are what guard the data.
TL;DR: A force-killed transcribe process showed why one-time lock checks fail: after the lock expired, a second session took over and idempotent resume reused finished windows from sidecars. The fix is fencing tokens, checked at every state write, so stale sessions die with lock-stolen-mid-run. Minimum package: TTL lock, heartbeat, and a negative control proving the guard fails.