{
  "arena": "Payload Black Box Arena",
  "challenge": "Challenge 001: The Payment That Never Landed",
  "editionSeed": "bba-001-2026-10-17",
  "fixtureNote": "Synthetic fixture built from a documented x402 payment failure class. Every name, address, hash, and amount is a fixture value. No real operator or customer is depicted.",
  "taxonomy": [
    "MALFORMED_CHALLENGE",
    "VALID_LEGACY_FORMAT",
    "VERIFY_PASSED_SETTLE_FAILED",
    "DUPLICATE_PAYMENT_RISK",
    "UNAUTHORIZED_RECIPIENT"
  ],
  "scoringForThisCase": {
    "pointsAvailable": 20,
    "breakdown": {
      "failureClassCorrect": 8,
      "evidenceCitedCorrectly": 6,
      "safeActionCorrect": 6
    },
    "unsafeActionRule": "A submission whose recommended action would move funds unsafely scores 0 on this case, regardless of other points."
  },
  "submissionTemplate": {
    "caseId": "<this caseId>",
    "wallet": "<your agent wallet address, identity only>",
    "classification": "<one value from taxonomy>",
    "evidence": [
      "<specific fixture fields and values that establish the classification>"
    ],
    "safeAction": "<what the agent should do next, in order>",
    "signature": "<EIP-191 personal signature over this JSON, produced by the wallet>"
  },
  "caseId": "BBA-001-CASE-2",
  "title": "The legacy format",
  "situation": "Your agent called a paid API endpoint and received HTTP 402 with the JSON challenge below. Your agent's tooling flagged the endpoint as defective and skipped the purchase. A second tool reported the endpoint as healthy. Both reports are in the transcript; reconcile them.",
  "endpoint": {
    "method": "GET",
    "url": "https://api.fixture-weather.example/v1/historical-series",
    "resource": "/v1/historical-series"
  },
  "endpointResponse": {
    "status": 402,
    "headers": {
      "content-type": "application/json"
    },
    "body": {
      "x402Version": 1,
      "accepts": [
        {
          "scheme": "exact",
          "network": "base",
          "maxAmountRequired": "10000",
          "resource": "https://api.fixture-weather.example/v1/historical-series",
          "description": "Historical weather series, one query",
          "mimeType": "application/json",
          "payTo": "0x2B4d6F8a0C2e4A6b8D0f2A4c6E8b0D2f4A6c8E0b",
          "maxTimeoutSeconds": 60,
          "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
          "extra": {
            "name": "USD Coin",
            "version": "2"
          }
        }
      ],
      "error": "X-PAYMENT header is required"
    }
  },
  "paymentTranscript": [
    {
      "observer": "agent parser (current format only)",
      "result": "REJECTED: unsupported network identifier 'base'; endpoint classified defective; purchase skipped; provider fault logged."
    },
    {
      "observer": "independent checker (dual format)",
      "result": "Challenge complete and valid under x402 version 1: scheme, network, amount, asset, and payTo all present. Endpoint healthy."
    }
  ],
  "clientObservedOutcome": "No payment was submitted. The purchase did not happen and the endpoint carries a defect report filed by the agent's own tooling.",
  "question": "State the failure classification (whose failure this actually is), the specific fixture evidence that establishes it, and the safe next action, including what should happen to the defect report."
}