Subcontracting / Outside Processing Purchase Order

A production router includes an outside-processing (subcontract) operation (e.g., heat treat, plating). When the work order reaches that operation, the system automatically generates a subcontract purchase order to the designated vendor, referencing the work order and specifying the service, quantity, and price. The production team ships the semi-finished goods to the subcontractor, recording a transfer-to-subcontractor inventory transaction. The subcontractor completes the service and ships back. The receiving clerk records the return receipt against the subcontract PO, which closes the outside-processing operation on the work order and triggers three-way match for invoice payment. The subcontract service cost is absorbed into the work order's actual cost alongside internal labor and overhead.

subcontract_pos { po_id: string, work_order_id: string, op_id: string, vendor_id: string, service_description: string, qty: numeric, unit_price_minor: int64, currency_code: char(3), status: enum, external_id: string };
subcontract_receipts { receipt_id: string, po_id: string, received_qty: numeric, received_at: timestamp, landed_cost_minor: int64, currency_code: char(3) };
(reference, product may differ).

POST /v1/subcontract-pos { work_order_id, op_id, vendor_id, qty, unit_price_minor, currency_code } -> 201 { po_id };
POST /v1/subcontract-pos/{id}/ship-to-vendor -> 200 { transfer_txn_id };
POST /v1/subcontract-pos/{id}/receive { received_qty } -> 200 { receipt_id, three_way_match_status };
emits subcontract.received event;
idempotent via external_id.

DRAFT -> SENT -> GOODS_SHIPPED -> RECEIVED -> INVOICED -> CLOSED;
terminal CANCELLED;
guard: three-way match must pass before PO moves to CLOSED;
CANCELLED blocks receipt posting.