• Ethereum will launch the Fusaka upgrade on Dec. 3 after testnet activations in October.
• Fusaka will raise blob capacity and expand gas limits to support higher transaction throughput.
• The Ethereum Foundation has started a $2M security contest to test Fusaka before mainnet launch.

Ethereum core developers have outlined a launch window for the Fusaka upgrade, with mainnet activation targeted for Dec. 3. The tentative date came during the All Core Developers Call on Sept. 17. Final confirmation on timing and epoch numbers is expected in the coming days.

Testnet Rollout Ahead of Mainnet

The rollout will progress through several test networks before reaching the mainnet. Holesky will implement the upgrade on Oct. 1, followed by Sepolia on Oct. 14 and Hoodi on Oct. 28. These phased activations are meant to confirm system readiness and stability before December.

Developers plan to adjust technical parameters gradually to minimize risk. They intend to apply Blob Parameter Only forks, which will raise blob limits in stages. The first fork, scheduled for Dec. 17, will lift targets from 6/9 to 10/15. A second fork on Jan. 7, 2026, will increase them further to 14/21.

Scalability and Data Handling

Fusaka is set to expand Ethereum’s scalability while maintaining security and decentralization. The upgrade introduces Peer Data Availability Sampling, allowing validators to check large datasets by sampling smaller sections from peers. This reduces data burdens while ensuring accuracy.

Blobs, added under EIP-4844, form a central part of the upgrade. These are temporary data containers designed for rollups, which lower costs by storing transaction data for around two weeks. The mechanism helps reduce permanent storage needs while maintaining transaction reliability. Developers expect blob capacity to double within two weeks of Fusaka activation.

Technical Enhancements

The hard fork includes several new proposals. The block gas limit will rise from 30 million to 150 million units. This increase is expected to support higher transaction throughput.

Verkle Trees will also be integrated, improving proof efficiency with smaller sizes and optimizing storage. In addition, enhancements to Ethereum Virtual Machine performance will enable faster smart contract execution. Together, these updates are intended to support growing network demand.

Security and Future Roadmap

In preparation, the Ethereum Foundation launched a four-week security contest on Sept. 15, hosted on the Sherlock testnet. The contest runs until Oct. 13 and offers up to $2 million in rewards. The initiative is designed to identify vulnerabilities before the Fusaka upgrade goes live.

Looking ahead, Ethereum’s next planned overhaul is Glamsterdam in 2026. That upgrade is expected to focus on scalability improvements, including the full EVM Object Format and faster block times.