Ethereum’s core developers have announced a preliminary launch window for the much-awaited Fusaka upgrade, aiming for mainnet activation on December 3. This draft timeline, revealed during the All Core Developers’ Call (ACDC) on September 17, is still pending final confirmation, but it indicates significant progress toward one of the network’s most crucial technical updates.
The rollout plan consists of staged upgrades across various test networks. Holesky is scheduled for an upgrade on October 1, followed by Sepolia on October 14, and Hoodi on October 28. If these initial transitions proceed without issues, the Fusaka changes are poised to migrate onto the Ethereum main network in December.
Christine Kim, the former research vice president at Galaxy Digital, highlighted ongoing efforts by network developers to refine crucial details such as dates, epochs, and timing as the launch date approaches. She noted that early assessments from Fusaka Devnet-5 suggest that blob capacity could more than double in the two weeks following the activation of Fusaka.
The enhancement involves the introduction of “blobs,” temporary on-chain data containers resulting from EIP-4844. These blobs allow Layer 2 rollups to post transaction data to Ethereum at a significantly reduced cost. Designed to expire after roughly two weeks, blobs are aimed at minimizing storage demands while preserving data integrity, leading to lower costs for rollups and enhanced scalability for the Ethereum network.
To mitigate potential risks associated with the upgrade, developers have agreed to implement the changes incrementally via Blob Parameter Only (BPO) forks. This approach allows for a gradual increase in blob capacity rather than a one-time adjustment. The first BPO fork is anticipated on December 17, which will raise blob targets from 6/9 to 10/15, followed by a subsequent increase on January 7, 2026, raising limits to 14/21.
In a related development, the Ethereum Foundation recently announced a $2 million security contest designed to bolster the upgrade’s safety. Running from September 15 to October 13 on the Sherlock testnet, this initiative encourages researchers to pinpoint vulnerabilities related to the Fusaka update. To incentivize early participation, submissions made in the first week will garner double points, while those submitted in the second week will qualify for a 1.5x scoring multiplier.
