Lowers the fulfillment-order and order credits the shipment wrote, returns to the source location exactly what its stock movements took (never more), and reserves again at most what they released when the fulfillment order still holds a reservation. A shortfall correction the shipment recorded is kept. No postage is refunded. Already canceled: outcome unchanged. DSCO channels: 409.

Scope: shipments:write, channel:write or admin.

Idempotency: send Idempotency-Key; a retry with the same key replays the first answer.

Rate limit: write class, 1,200 requests per minute per tenant by default (read class 6,000). Every response carries X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset; a refusal is 429 rate_limited with Retry-After.