claimSteering matched steering rows by runId even after they were
claimed, and still returned them when updateMany updated zero rows.
That could inject duplicate user context into an active run.
Filter findMany to claimedAt: null and return nothing when the claim
update does not land.
Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: cynarAI <cynarAI@users.noreply.github.com>
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