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Ethereum is entering the final testnet phase for its highly anticipated Fusaka upgrade, the last major step before the expected mainnet rollout on December 3, 2025. This upgrade introduces a per-transaction gas cap, aiming to improve block efficiency, reduce potential denial-of-service risks, and set the stage for parallel transaction execution in future updates like Glamsterdam.
Already active on Holesky and Sepolia testnets, the Fusaka upgrade marks a critical milestone in Ethereum’s ongoing roadmap, designed to ensure the network can handle growing demand and scalability challenges.
Key Changes: Per-Transaction Gas Cap and Block Efficiency
A central feature of the Fusaka upgrade is the implementation of a per-transaction gas cap of approximately 16.78 million units. Previously, a single transaction could consume the entire block gas limit, around 45 million units, creating bottlenecks and potential denial-of-service vulnerabilities.
By limiting how much gas a single transaction can consume, Ethereum ensures that multiple smaller transactions can fit into a block. This change improves overall block composition efficiency and predictability, allowing the network to process activity more evenly across all users.
According to developers, this adjustment is critical for maintaining network stability and avoiding scenarios where one oversized transaction monopolizes resources, delaying others and reducing throughput.
Testnet Rollouts: Holesky, Sepolia, and Hoodi
The Fusaka upgrade has already been tested on the Holesky and Sepolia testnets. These deployments allowed developers to simulate real-world network activity and identify potential issues before the mainnet rollout.
The next phase of testing will occur on the Hoodi testnet, scheduled for October 28, 2025. This stage is designed to stress-test the network under higher traffic loads, evaluate the gas cap’s effectiveness, and validate performance across different Ethereum client implementations.
By conducting these rigorous tests, Ethereum developers aim to ensure a smooth transition on December 3, reducing the risk of bugs or network disruptions during the mainnet upgrade.
PeerDAS: Improving Data Storage and Efficiency
Another critical component of the Fusaka upgrade is the introduction of Peer Data Availability Sampling (PeerDAS). PeerDAS allows Ethereum nodes to store only small, random portions of Layer 2 “blob” data, rather than maintaining the entire dataset.
This approach has two key benefits: it significantly lowers hardware requirements for node operators, making it easier for participants to run nodes, and it enables faster, more cost-effective Layer 2 scaling. By reducing storage demands while maintaining security, PeerDAS helps Ethereum accommodate increasing transaction volumes without sacrificing decentralization or performance.
Preparing for Parallel Execution: The Road to Glamsterdam
Fusaka also lays the groundwork for Ethereum’s next major upgrade, Glamsterdam, which will focus on execution layer improvements. Glamsterdam will introduce EIP-7928, Ethereum’s first major step toward parallel transaction processing.
Parallel execution allows multiple transactions to process simultaneously, increasing throughput and reducing latency across the network. Fusaka’s per-transaction gas cap is a prerequisite for this development, ensuring that no single transaction can block other operations from being executed concurrently.
Mainnet Launch Scheduled for December 3, 2025
Ethereum developers have confirmed that the mainnet rollout of the Fusaka upgrade is scheduled for December 3, 2025. Ahead of the upgrade, the testnet phases will validate performance, detect edge cases, and fine-tune network parameters.
Gabriel Trintinalia, a protocol engineer at ConsenSys’ Besu client, emphasized the importance of these testnets: “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.”
Fusaka in Context: Following Dencun and Pectra Upgrades
Fusaka follows Ethereum’s Dencun upgrade in March 2024 and the Pectra upgrade on May 6, 2025. Each update has focused on scalability, efficiency, and preparing Ethereum for more advanced features like parallel execution.
With Fusaka, Ethereum continues its trajectory toward higher throughput, lower latency, and a more predictable block structure. The combination of the per-transaction gas cap and PeerDAS ensures that Ethereum is ready to meet the growing demand of decentralized applications (dApps), DeFi platforms, and enterprise adoption.
Conclusion: Fusaka Sets Stage for Ethereum’s Future
The Fusaka upgrade represents a critical juncture in Ethereum’s development roadmap. By improving block efficiency, introducing a per-transaction gas cap, and deploying PeerDAS, Ethereum is ensuring a smoother, more secure, and scalable network.
As the final testnet phases conclude and the mainnet rollout approaches on December 3, 2025, the Ethereum community and developers remain focused on making this upgrade a success. Fusaka not only addresses current network challenges but also lays a solid foundation for parallel execution and future upgrades like Glamsterdam, positioning Ethereum for long-term growth and resilience in the increasingly competitive blockchain ecosystem.
