Ethereum enters final testnet for 'Fusaka' upgrade…scheduled for mainnet on December 3

Ethereum has entered the final testnet phase ahead of the 'Fusaka' upgrade, scheduled for December 3. The upgrade aims to set a per-transaction gas cap to increase block efficiency and reduce the risk of denial-of-service (DoS) attacks, while laying the technical foundation for future scalability based on parallel processing.

These changes are already being applied on the Holesky and Sepolia testnets and are designed to prevent a single transaction from monopolizing the entire block gas (about 45 million units). Under the new structure, transactions are limited to about 16.78 million gas units each, allowing multiple transactions to be included in a block more efficiently.

The gas cap limits the amount of computation a single transaction can use, preventing a block from being filled by a single transaction. This improves block composition efficiency and predictability, and is expected to enhance overall network processing stability.

This measure is a key foundation for Ethereum's long-term move toward a 'parallel execution' system. Once parallel execution is introduced, multiple transactions can be processed simultaneously, significantly improving throughput and scalability.

The Fusaka upgrade was implemented after the Sepolia testnet last week increased the block gas limit from about 45 million to 60 million. The next step, applying to the Hoodi testnet, is scheduled for October 28, and the mainnet upgrade is set to be rolled out in December.

Fusaka (EIP-7825) is a major step following the March 2024 Dencun upgrade and the May 6, 2025 Pectra upgrade, and includes raising the block gas limit to 60 million and capping gas per transaction at 16.77 million units. It also introduces the core feature PeerDAS·Peer Data Availability Sampling to have nodes store only samples of Layer 2 data rather than the entire dataset, maintaining security while reducing hardware burden and improving scalability.

The subsequent planned upgrade, Glamsterdam, intends to introduce parallel transaction processing focused on the Ethereum execution layer (EIP-7928).

Gabriel Trintinalia, protocol engineer for the Besu client at Consensys, said, "This testnet upgrade is very important for performance validation, parameter tuning, and checking exceptional cases before mainnet deployment," adding, "It is a key step to give Ethereum developers, validators, and the broader ecosystem confidence."