A production rollout exposes a contract mismatch between the UI boundary and the owning service. The affected area is API transaction.
Repair the API transaction command handling implementation so it accepts first operations, recognizes safe repeats, and rejects key reuse with a different payload.
Evidence
- Affected surface: Full-stack backend focus / API transaction.
- Observed failure family: enforce idempotent operations.
- Scope policy: tenantId must equal tenant-primary.