Ethereum Developers Confirm Fusaka Upgrade for December 3

Ethereum developers have officially set a date for the next major network upgrade. The new update, called Fusaka, is scheduled to go live on the Ethereum mainnet on December 3, 2025. 

The announcement was made during the latest All Core Developers Consensus (ACDC) call, number 165. This upgrade follows earlier changes like Dencun and Pectra and is expected to bring more improvements to scalability, fees, and validator performance.

Before the full launch, the Fusaka upgrade will be tested on three separate testnets in October. This staged rollout is meant to make sure everything works properly before it reaches the main network.

During the ACDC call, developers agreed on a clear rollout plan. The Fusaka upgrade will go through three public testnets in the following order: Holesky on October 1, Sepolia on October 14 and Hoodi on October 28.

If no major issues come up during testing, Fusaka will be activated on Ethereum’s mainnet on December 3, 2025.

Christine Kim, the former Vice President of Research at Galaxy Digital, shared these details on X. She added that developers still need to finalize the exact epoch numbers and timings for each launch. These details will be confirmed in the coming days.

Although the date is now public, developers emphasized that it is still tentative and could change if problems come up during testnet deployments. Originally, the team had aimed for a November release, but that plan was delayed.

Even so, the Fusaka upgrade is moving faster than expected. If the schedule holds, it will go live just seven months after the previous major upgrade, Pectra, which launched on May 7, 2025. By comparison, earlier upgrades took longer to develop and roll out.

What Fusaka Will Change on Ethereum

The Fusaka upgrade is one of the most important updates to Ethereum in recent years. It includes 12 Ethereum Improvement Proposals (EIPs), most of which aim to improve how Ethereum handles data and transactions.

One of the biggest changes is the increase in blob capacity. Blobs are a special type of data that helps reduce costs for Layer 2 (L2) networks. These networks rely on Ethereum to finalize transactions, but they process them off-chain to save space and fees. 

By increasing blob capacity, Fusaka will help these L2 chains run more efficiently and at a lower cost. The blob increase will happen in two steps. In the first week after launch, blob limits will rise from 6/9 to 10/15. In the second week, the limits will rise again to 14/21.

These changes are expected to double the amount of blob data that Ethereum can handle. This will help support more L2 transactions and lower the cost of using the network.

Developers tested these changes earlier on Devnet-5, and the results showed that blob capacity could more than double within two weeks of activation. This would be a big win for projects building on Ethereum.

Fusaka also introduces Peer Data Availability Sampling (PeerDAS). This feature helps validators by allowing them to verify data by checking samples from other nodes, instead of downloading all the data themselves. This reduces the strain on validators and speeds up the process.

Another update is a higher gas limit. Ethereum’s gas limit will be raised to 150 million units, giving the network more room to process transactions during busy times.

Together, these changes are expected to increase Ethereum’s speed, reduce fees, and improve the user experience, especially for developers building decentralized apps (dApps) and financial products on L2 networks.

Ethereum is also working on Verkle tree integration and faster block times, which will come in later upgrades. Fusaka helps lay the foundation for those improvements.

Security, Testnet Changes, and What’s Next

To make sure the Fusaka upgrade is safe, the Ethereum Foundation launched a four-week security audit on September 15. This audit is hosted on the Sherlock platform, a community-based bug bounty service. 

The Foundation has offered a $2 million prize pool to anyone who can find bugs or vulnerabilities in the upgrade’s code.

The goal is to catch any problems before the upgrade goes live on the mainnet. The audit is one of the largest ever run for an Ethereum upgrade.

At the same time, Ethereum is making changes to its testnets. The Holesky testnet, which is the first to receive the Fusaka upgrade, will be deprecated two weeks after the update. Developers made this decision due to technical issues that happened during the Pectra deployment on Holesky.

The testnet shutdown is meant to simplify development and remove unnecessary complexity. Other testnets like Sepolia and Hoodi will continue to be used for ongoing testing.

Fusaka is part of Ethereum’s broader “Surge” roadmap. The goal of the Surge is to make Ethereum more scalable, faster, and able to handle more users. Developers hope Fusaka will push Ethereum closer to handling 12,000 transactions per second, a major improvement from current levels.

Following Fusaka, Ethereum is planning another upgrade called Glamsterdam, expected sometime in 2026. That upgrade will focus on further improvements in storage, transaction speeds, and validator performance.

Impact on ETH and Layer 2 Networks

The Fusaka upgrade is not just a technical update, it also affects the economics of using Ethereum.

After the Dencun upgrade in March 2024, which first introduced blob transactions, costs for L2 projects dropped sharply. Some projects reported that their monthly fees fell from $15,000 to just $1,500 after they switched to using blobs. In addition, transaction fees fell by as much as 73%.

The Pectra upgrade in May 2025 continued that trend. It improved wallet features and raised the validator limit from 32 ETH to 2,048 ETH, making staking more efficient. This allowed larger institutions and staking providers to join more easily.

With Fusaka, Ethereum aims to cut costs even further. The upgrade will help make L2s less reliant on calldata, a more expensive method of storing data. Instead, they’ll be able to use blobs more often, reducing their footprint on Ethereum’s Layer 1.

Currently, over 93% of all Ethereum transactions happen on Layer 2 chains. These chains, however, carry only 13.69% of the total economic value. Most large-scale decentralized finance (DeFi) activity still takes place on Layer 1. This gap shows that while scalability is improving, Ethereum still relies on strong liquidity to attract users.

Right now, Base is the biggest user of blob space, paying around $6,250 in daily rent. Other networks are active too but are able to keep their Layer 1 costs low by using blobs efficiently. As blob capacity increases with Fusaka, these networks will save even more.

Interestingly, the announcement of the Fusaka upgrade did not affect ETH’s price much. ETH continued trading around $4,563.17, showing that such updates are now considered routine.

Ethereum’s AI Efforts and Future Plans

In another development, Ethereum is also exploring artificial intelligence. Developer Davide Crapis announced that the Ethereum Foundation has started a new research group called the dAI Team. This team will focus on building AI agents that can manage payments, make decisions, and run decentralized governance systems without needing human control.

The dAI Team will also work on building systems that are open, transparent, and protected from censorship. These tools are expected to support Ethereum’s long-term vision of decentralization and self-governance.

While this AI effort is still in the early stages, it shows that Ethereum is looking beyond just scaling and fees. The network is preparing for a future where smart agents, robots, and machine learning could play a role in managing blockchain-based systems.

The Fusaka upgrade is one of the most important Ethereum updates in 2025. It brings real changes to how the network handles data, validators, and fees. With testnets scheduled for October and a mainnet launch set for December 3, Ethereum is once again moving fast.

As Layer 2 adoption grows and developers push for faster, cheaper, and more efficient systems, upgrades like Fusaka are key. Combined with strong security audits, support from the Ethereum Foundation, and new research in AI, Ethereum is laying the groundwork for the next phase of blockchain technology.