LABEL_PRINTING_CONTRACT.md

Pescamar — Physical Label Printing Contract

Scope

This control connects live packing_units to already validated product_labels, versioned label_templates, registered physical printer devices and the auditable label_print_jobs queue.

Invariants

1. A physical print request starts from an existing live packing unit; it never creates or reinterprets a lot.
2. The label must belong to the same reception and have status = validated before it can enter the queue.
3. Species, grade and net weight remain consistency gates when those values exist on both the packing unit and label.
4. The template must be active and either global or scoped to the packing unit plant.
5. The printer must be an active printer device on an active station in the same plant.
6. Each requested physical action uses a new idempotency key. Reusing a key for different print intent is rejected.
7. New requests and reprints enter as queued. The UI and API never claim a job was physically printed without a future printer adapter confirming it.
8. Reprint can only originate from a job already confirmed as printed or reprinted and preserves source_job_id lineage.
9. PLANT_EXECUTION_WRITES_ENABLED=false is an immediate kill switch for every print mutation.
10. No printer language or protocol is assumed. ZPL, EPL, TSPL, ESC/POS, PDF or proprietary adapters are implemented only after the real printer is identified.

Operational sequence

packing unit → validated label → template version → registered printer → queued print job → adapter sends → physical confirmation

The current delivery ends at the auditable queue. sent, printed, failed and reprinted physical outcomes require a real adapter or explicitly audited device integration.