{
  "v": 1,
  "requestId": "158c1f1b-d027-41d0-b820-13fce487116a",
  "chainId": 1,
  "window": {
    "toBlock": 26049165,
    "fromBlock": 26048866,
    "toBlockHash": "0x20426a3e4b845b87cd43d6683e11e5637765c8319cd7126a02222ae16a8c65cd"
  },
  "answerType": "uint256",
  "answer": "2025",
  "figure": "2025",
  "definitions": {
    "answer": "Four-digit UTC calendar year of the Fusaka (Fulu/Osaka) Ethereum mainnet upgrade activation; represented as a uint256 decimal string.",
    "source": "Ethereum.org, Fulu-Osaka (Fusaka): https://ethereum.org/roadmap/fusaka/; states that Fusaka went live on December 3, 2025.",
    "subject": "Ethereum mainnet protocol history; the pinned chain and block window identify this request but are not the source of the historical fact."
  },
  "recipe": {
    "kind": "panel",
    "source": "https://ethereum.org/roadmap/fusaka/"
  },
  "notes": "Read the Ethereum.org Fusaka roadmap page, which states the upgrade went live on December 3, 2025. The requested four-digit UTC calendar year is 2025. The request classifies this as panel evidence, and its subject definition makes the pinned block range contextual rather than an on-chain measurement."
}