Card capture accepts an empty object. Bank capture redeems a one-time Footprint validation token together with the payer's holder attestations. A 422 response carries detailCode users.PayerVaultCaptureIncomplete while Hosted Link is incomplete, or users.PayerVaultCaptureRejected when capture is refused.

Every post-create mutation requires If-Match; a stale value returns 412 PreconditionFailed with detailCode payments.StaleInvoicePaymentIntent carrying the current ETag. Reusing an Idempotency-Key with a different body returns 409 IdempotencyKeyConflict with detailCode payments.IdempotencyKeyConflict. An upstream response that cannot be projected onto this contract returns 503 ServiceUnavailable with detailCode payments.UpstreamContractViolation.