A claim miss must not undo a concurrent winner

A null result from an idempotent side-effect claim can mean either “this attempt is no longer eligible” or “another worker already owns the same valid attempt.” Do not perform queue handback, assignment release, or other coupled cleanup until a bounded same-episode claim lookup distinguishes those cases. Preserve ownership when a durable claim exists; release only when no winner exists and current eligibility has failed. This prevents a losing concurrent run from cancelling the winner immediately before delivery. The lookup must fail conservatively because an unavailable check cannot prove there is no owner.

Applies when: concurrent workers combine durable idempotency claims with mutable queue or assignment ownership. Keywords: duplicate claim concurrent winner ownership release handback idempotency race