Ethereum has reached a pivotal moment as it enters the last testnet phase of its Fusaka upgrade, set to take place before the mainnet launch anticipated on December 3. This significant update introduces a transaction gas cap of approximately 16.78 million units, aimed at optimizing block efficiency and laying the foundation for future parallel execution.

This change, already effective on the Holesky and Sepolia testnets, is designed to prevent single transactions from exhausting an entire block’s gas. Historically, individual transactions could utilize the complete block gas limit of around 45 million, creating risks for denial-of-service and constraining scalability.

A gas cap limits the processing power utilized by a single transaction, ensuring fair usage across the network.

By implementing this cap, Ethereum seeks to enhance block composition and ensure that multiple smaller transactions can coexist within a block. This adjustment supports Ethereum’s broader strategy towards parallel execution, a key aspect of its roadmap aimed at allowing simultaneous transaction processing.

This upgrade follows the launch of the Fusaka upgrade on the Sepolia testnet, which increased the complete block gas limit from around 45 million to 60 million.

The next milestone of the Fusaka upgrade will be unveiled on the Hoodi testnet on October 28, with the final deployment projected for December 2025.

Understanding the Fusaka Upgrade

The Fusaka upgrade (EIP-7825) is an essential milestone in Ethereum’s roadmap and follows the Dencun upgrade in March 2024 as well as the Pectra upgrade on May 6, 2025.

This upgrade brings several changes: raising Ethereum’s default block gas limit to 60 million, setting a per-transaction gas cap of 16.77 million under EIP-7825, and introducing PeerDAS — the primary feature of the upgrade.

PeerDAS, or Peer Data Availability Sampling, allows Ethereum nodes to store only small, random portions of layer 2 “blob” data instead of the entire data set. This approach maintains network security while reducing hardware demands and facilitating more cost-effective, high-throughput scaling for layer-2 networks.

The subsequent upgrade, Glamsterdam, will focus on Ethereum’s execution layer and unveil EIP-7928, marking the network’s initial significant step towards parallel transaction processing.

Gabriel Trintinalia, Protocol Engineer at Consensys’ client Besu, stated, “These testnet upgrades are crucial in building confidence ahead of the mainnet fork, allowing client teams, validators, and the ecosystem to validate performance, detect edge cases, and fine-tune parameters before activation.”