Ethereum’s core developers mapped the launch window for the much-anticipated Fusaka upgrade on December 3rd, with the mainnet activation still penciled in.
The draft schedule shared on September 17th is shared across all Core Developer Calls (ACDC), but while final confirmation is still needed, it shows momentum increasing towards one of Ethereum’s most important technical overhauls.
The rollout begins in stages in the test network. Holesky is scheduled to upgrade to October 1st, with Sepolia to continue on October 14th and Hoodi to continue on October 28th. Once these rehearsals run smoothly, the changes will be ready to move to Ethereum’s main network in December.
Gradual blob fork
Christine Kim, former Vice President of Research at Galaxy Digital, emphasized that network developers will continue to refine dates, times and timing over the coming weeks.
She added:
“They also agreed that, based on some preliminary analyses on Fusaka Devnet 5, the BLOB capacity should be more than doubled over the two weeks following Fusaka activation.”
Blobs, introduced through EIP-4844, is a temporary on-chain data container that allows Layer 2 rollups to post transactional data to Ethereum at a low cost. Unlike persistent call data, blobs expire after about two weeks, helping to reduce storage demand while maintaining data integrity.
This mechanism is designed to reduce rollup costs and improve Ethereum scalability.
To minimize risk, the Ethereum developers have agreed to gradually deploy via the BLOB Parameter Only (BPO) fork. So instead of increasing the blob volume in a single step, the threshold increases in the stage.
As a result, the first BPO fork, expected on December 17th, will raise the BLOB target from 6/9 to 10/15. The second fork on January 7th, 2026 will push these limits up to 14/21.
Meanwhile, Fusaka’s imminent developments came just days after the Ethereum Foundation launched its $2 million security contest. Hosted on Sherlock TestNet from September 15th to October 13th, the initiative encourages researchers to identify upgrade vulnerabilities.
To encourage early participation, findings submitted in the first week earned double points, while second week submissions qualify for a 1.5x multiplier.