The Ethereum Foundation announced that the Fusaka mainnet upgrade is scheduled to activate at slot 13,164,544, corresponding to epoch 411392 on December 3, 2025, at 21:49:11 UTC. Following previous activations on the Hoodi, Holesky, and Sepolia testnets, Fusaka succeeds the Pectra upgrade to advance Ethereum's layer-1 performance, layer-2 data availability, and user experience.

PeerDAS and Blob Throughput Scaling

Fusaka's primary feature is Peer Data Availability Sampling (EIP-7594, or PeerDAS), a networking protocol that allows nodes to verify blob data availability using erasure coding sampling instead of downloading full blobs. This mechanism aims to scale layer-2 blob throughput without proportionally increasing node bandwidth demands. Following activation, Ethereum will implement Blob Parameter Only (BPO) config forks to expand blob capacity. BPO1 is scheduled for December 9, 2025 (epoch 412672), raising per-block blob targets and maximums from 6 and 9 to 10 and 15, while BPO2 is set for January 7, 2026 (epoch 419072) to increase them to 14 and 21.

Layer-1 Performance and Execution Changes

To optimize layer-1 execution, Fusaka raises Ethereum's default gas limit to 60M (EIP-7935) and imposes a 16,777,216 transaction gas limit cap (EIP-7825) to protect against denial-of-service attacks and lay groundwork for parallel EVM execution. It also adjusts ModExp precompile costs and upper bounds (EIP-7883 and EIP-7823) and transitions to eth/69 (EIP-7642), removing pre-merge fields and receipt Bloom to reduce sync bandwidth.

User Experience and Node Requirements

For user experience, EIP-7951 introduces a secp256r1 curve precompile for hardware authenticators like Apple Secure Enclave and FIDO2/WebAuthn, while EIP-7939 adds the CLZ opcode. Node operators and stakers must update execution clients (Besu, Erigon, go-ethereum, Nethermind, Reth) and consensus clients (Grandine, Lighthouse, Lodestar, Nimbus, Prysm, Teku) to maintain network compatibility, whereas regular ETH holders and wallet users do not need to take action.