Fusaka launch window shifts to December with Hoodi check
December instead of November: Fusaka is delayed to thoroughly test network parameters and roll out changes incrementally.
Fusaka is the next major Ethereum hard fork. It includes PeerDAS (peer data availability sampling) to make layer‑2 transactions cheaper and faster, as well as post-fork Blob Parameter Only (BPO) stages to raise “blob” throughput after activation. All accompanying EIP changes have a single aim: reduce costs (gas usage) and improve the network’s scalability without sacrificing stability.
Developers have pencilled in mainnet fork activation for Dec. 3, 2025, pending successful Hoodi testnet activation on 28 October. After several successful tests and unanimous support from client teams on an All Core Devs call, the date is effectively set.
Pre‑release client builds are slated for 3 November, giving node operators roughly a month to upgrade.
On the closed network Sepolia, about 99% of validators are reported ready for Fusaka. Core developers agree to retire the Holesky testnet used for Dencun: validator stress‑testing moves to Hoodi, while application‑level testing remains on Sepolia.
Why was Fusaka moved to December?
Developers emphasized caution, echoing Vitalik Buterin’s view that Ethereum upgrades should prioritize safety over speed. In the summer, several client teams requested four extra weeks beyond the initial November plan, arguing they needed a safety buffer after Devconnect to test PeerDAS and network parameters before mainnet deployment. The launch window was therefore shifted to December to ensure stability and sufficient validation time.
In October, developers further refined the December timeline. During core-dev calls, dates discussed included December 3, 9, and 17, with the current proposal setting December 3 for mainnet activation and BPO stages scheduled for December 9 and January 7 (2026).
These BPO stages (phased parameter updates that gradually increase network load for safe testing) are designed to ensure stability and allow quick rollbacks if needed. Developers highlighted seasonal risks related to year-end holidays and emphasized keeping the main fork separate from the BPO stages.
What are the odds for December? Both Holesky and Sepolia testnets ran smoothly, and developers agree the network is ready. Client release candidates are expected in early November, so a December launch looks likely. Final confirmation will come after the Hoodi testnet, which is the last major checkpoint; if problems appear there, the date could still change.
Bottom line: the November→December shift reflects Ethereum’s safety-first engineering culture – better slightly later with thorough testing and minimal operational risk. If Hoodi proceeds smoothly, a December 3 mainnet activation remains the base case.
