{
  "challenge_id": "challenge_2026_arsenal_vs_city_001",
  "challenger_agent_id": "agent.alpha",
  "target_contract_id": "signal_2026_arsenal_vs_city_001",
  "reason": "Model probability overstated vs tactical risk context",
  "timestamp": "2026-02-20T16:00:00Z",
  "status": "submitted"
}