Key Changes and Testnet Deployment
Ethereum is progressing through the final testnet phases for its Fusaka upgrade, with mainnet rollout anticipated on December 3. This significant update introduces a per-transaction gas cap, limiting individual transactions to approximately 16.78 million gas units. The primary goal of this change is to enhance block efficiency and pave the way for future parallel execution capabilities on the network.
The Fusaka upgrade's per-transaction gas limit has already been successfully implemented on the Holesky and Sepolia testnets. This modification addresses a critical limitation of the previous system, where a single transaction could consume the entire gas allocation of a block. By preventing single transactions from monopolizing block space, the update mitigates potential denial-of-service risks and addresses existing scalability limitations.
Under the former system, a single transaction had the potential to utilize up to the full block gas limit, which was approximately 45 million gas units. This scenario could lead to one large transaction dominating an entire block, thereby reducing overall network efficiency and creating vulnerabilities to specific types of attacks.
The new gas cap effectively limits the processing power that any individual transaction can consume. This ensures that no single transaction can disproportionately occupy block space, allowing the Ethereum network to manage activity more equitably across multiple transactions and thereby improving overall throughput.
Ethereum's objective with the per-transaction gas limit cap is to make block composition more efficient and predictable. This mechanism ensures that a greater number of smaller transactions can be accommodated within each block, optimizing network capacity and reducing congestion during periods of high user activity.
Path to Parallel Execution and Future Upgrades
The introduction of the per-transaction gas cap is a crucial step in Ethereum's broader transition towards parallel execution. This upcoming feature is a major milestone in the network's development roadmap, promising to enable the simultaneous processing of multiple transactions instead of sequential execution, which will significantly increase network capacity.
The implementation of limited transaction gas caps occurred approximately one week after Ethereum launched the Fusaka upgrade on the Sepolia testnet. The initial deployment on Sepolia also increased the full block gas limit from approximately 45 million to 60 million units, thereby expanding the network's overall capacity.
The next planned phase for the Fusaka upgrade involves deployment on the Hoodi testnet, scheduled for October 28. Following successful testing across these multiple testnets, the mainnet deployment is expected to proceed in December 2025, officially bringing these enhancements to Ethereum's production environment.
The Fusaka upgrade operates under Ethereum Improvement Proposal (EIP) 7825. It follows previous significant upgrades, including the Dencun upgrade in March 2024 and the Pectra upgrade on May 6, 2025. The current update introduces several technical changes, notably raising Ethereum's default block gas limit to 60 million and establishing the per-transaction gas cap at 16.77 million.
A headline feature of the Fusaka upgrade is PeerDAS, which stands for Peer Data Availability Sampling. This technology allows Ethereum nodes to store only small, random portions of layer-2 blob data, rather than the entire data sets. This approach maintains network security while reducing hardware demands, ultimately enabling cheaper and higher-throughput scaling solutions for layer-2 networks.
Following Fusaka, the next upgrade will be Glamsterdam. This future update will concentrate on Ethereum's execution layer and introduce EIP-7928. This EIP represents a significant advancement, marking the network's first major step towards parallel transaction processing capabilities, which are expected to dramatically enhance scalability.
Importance of Testnet Validation
Gabriel Trintinalia, a protocol engineer at Consensys working on the client Besu, highlighted the critical importance of testnet upgrades. He emphasized that these upgrades are essential for building confidence before mainnet deployment. Testnets provide a vital environment for client teams, validators, and the broader ecosystem to validate performance, identify potential edge cases, and fine-tune parameters before the changes are activated on the live network.