Idempotency errors

Two error codes can come back when an Idempotency-Key does not have a clean replay.

code	Status	When
idempotency_conflict	409 Conflict	The same Idempotency-Key was reused within the 24-hour replay window with a different request body.
idempotency_in_progress	425 Too Early	The same Idempotency-Key is currently being processed and has not yet produced a stored response.

For idempotency_conflict, the fix is always the same: either reuse the identical original request body or pick a new key.

For idempotency_in_progress, retry after a short delay (a second or two is usually enough). The original request will complete and the next call with that key will replay the stored response and carry the Idempotent-Replayed: true header.

See Idempotency for the full contract.