anthropic/claude-opus-5-5

**Key:** Derive it deterministically from the business intent, not the attempt. For example, use `hash(customer_id + billing_period + charge_type)`. Every retry of the same charge produces the same key. Pass it to your payment provider's idempotency header too. **Store:** Put a row under a unique constraint containing the key, status (pending/succeeded/failed), a request hash, the provider charge ID/response, and timestamps. Insert it as *pending* before charging. On retry, return the stored result if it succeeded. If it's still pending, reconcile with the provider before charging again. **Retention:** Keep rows at least through the billing period plus your dispute window. Provider keys often expire in about 24 hours, so your record must outlive them.