Ethereum's Fusaka upgrade activated on the Hoodi testnet on October 29, 2025, at 18:53 UTC, completing the final testing phase before mainnet deployment on December 3. The upgrade will increase the block gas limit from 30 million to 150 million units and expand blob capacity through Peer Data Availability Sampling. Core developers confirmed the timeline during the ACDC #165 call, following earlier activations on Holesky and Sepolia testnets.