NONCE_PIN_MISMATCH

The transaction nonce is not the nonce the assignment pinned.

HTTP status	409
Group	Relay path
Retryable	No — sending it again changes nothing
Re-sign	NONE — do not ask the user to sign anything

What happened

An assignment pins the nonce it was issued for, so two signatures cannot compete for one slot.

What to do

Discard this signature. Assign again, use assignment.pinNonce, and sign that transaction.

The problem document

Every error is application/problem+json (RFC 9457) with the same shape:

{
  "type": "https://docs.co-relayer.com/errors/nonce-pin-mismatch",
  "title": "The transaction nonce is not the nonce the assignment pinned.",
  "status": 409,
  "detail": "A sentence about this specific occurrence.",
  "instance": "req_01JB…",
  "code": "NONCE_PIN_MISMATCH",
  "retryable": false,
  "resign": "NONE",
  "hint": "Discard this signature. Assign again, use `assignment.pinNonce`, and sign that transaction."
}

See the error model for what each member means and how to handle unknown codes.