Selects the order's fulfillment orders oldest first (created, then id), at most limit (default every one), and cancels the open ones: each releases exactly its open reservation (reservation_short when a legacy reservation was smaller). Already canceled and closed (shipped) ones are left as they are and listed as skipped. The order itself is not changed. Nothing open: outcome unchanged.

Scope: fulfillment:write, channel:write or admin. A permission group made before the Channel API scopes existed grants it as fulfillment-orders:manage.

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.