Idempotency Key. A stable identifier for one intended effect, used to recognize retries, replays, duplicated dispatch, or recovery attempts as the same work rather than new work.
An idempotency key does not make an effect safe by itself. It must bind to the durable work record, approval binding, payload, actor or scope, and external effect so repeated attempts can be refused, replayed, reconciled, or treated as already complete without double-applying the consequence.