{
  "context": "Tests whether the agent proactively adds idempotency protection to a payment endpoint, even though the task only says 'build a POST /api/payments endpoint' and mentions it should be 'production-quality.' A skilled agent should recognize that a payment endpoint absolutely needs idempotency to prevent double-charges.",
  "type": "weighted_checklist",
  "checklist": [
    {
      "name": "Idempotency key accepted",
      "description": "The server accepts an idempotency key from the client — either as an 'Idempotency-Key' header or as a field in the request body — and uses it to prevent duplicate payment creation",
      "max_score": 18
    },
    {
      "name": "UNIQUE constraint on idempotency key",
      "description": "The payments table DDL includes a UNIQUE constraint on an idempotency key column (or equivalent unique identifier supplied by the client) to prevent duplicate insertions at the database level",
      "max_score": 16
    },
    {
      "name": "Duplicate returns existing record",
      "description": "When a duplicate payment is detected (via constraint violation or cache hit), the service returns the existing payment record rather than an error, allowing safe retries",
      "max_score": 14
    },
    {
      "name": "Non-duplicate errors re-thrown",
      "description": "If the code catches constraint violations, it only suppresses the specific duplicate error — other database errors are re-thrown, not swallowed",
      "max_score": 10
    },
    {
      "name": "Processing state tracked",
      "description": "The service tracks a 'processing' or 'in-progress' state for each idempotency key so that concurrent duplicate requests can be detected while the first is still executing",
      "max_score": 14
    },
    {
      "name": "409 or retry for concurrent duplicates",
      "description": "When a concurrent request arrives with an idempotency key that is currently being processed, the service returns 409 Conflict or an equivalent signal rather than creating a duplicate",
      "max_score": 12
    },
    {
      "name": "5xx errors not cached",
      "description": "If idempotency caching is implemented, server errors (5xx) are NOT cached — the key is cleared so the client can retry",
      "max_score": 10
    },
    {
      "name": "schema.sql present with idempotency column",
      "description": "The schema.sql file includes an idempotency_key column (or equivalent client-supplied unique identifier) in the payments table",
      "max_score": 6
    }
  ]
}