Ethereum's Multi-Stage Fusaka Enhancement Drives Secure and Efficient Network Expansion

Ethereum’s upcoming significant upgrade, referred to as Fusaka, is planned to go live on the mainnet on December 3, 2025, after being gradually introduced on three public testnets starting in October title1 [ 1 ]. This upgrade seeks to boost both scalability and performance by increasing data capacity via a set of Blob Parameter Only (BPO) forks, which will step up blob limits from 6/9 to 14/21 without needing software updates from clients title2 [ 2 ]. The staged rollout is meant to safely increase Ethereum’s capabilities while preserving the stability of the network.

The testnet rollout will start with Holesky on October 1, followed by Sepolia on October 14, and Hoodi on October 28 title3 [ 3 ]. Developers highlighted that the definitive date and epoch for mainnet activation will depend on how testing progresses. Fusaka will add 11–12

Improvement Proposals (EIPs), concentrating on backend refinements such as PeerDAS (Peer Data Availability Sampling), a feature that allows validators to check data by sampling small segments of blobs instead of retrieving whole files title4 [ 4 ]. This mechanism lowers bandwidth and storage needs, improving node operation and facilitating scalability for Layer 2 rollups.

One of Fusaka’s primary innovations is the phased expansion of blob throughput. The initial BPO fork, set for December 17, 2025, will lift blob limits to 10/15 target/max, followed by a second fork on January 7, 2026, increasing them to 14/21 title5 [ 5 ]. These upgrades are projected to more than double Ethereum’s existing blob processing capacity, building on the Dencun upgrade from March 2024. Observers have noted that the average number of blobs per

has already climbed from 0.9 in March 2023 to 5.1 by September 2025, pointing to a rising need for more efficient data storage title6 [ 6 ].

The Ethereum Foundation has introduced a $2 million bug bounty initiative to review Fusaka’s code over a four-week period, indicating a strong emphasis on security as the network aims to scale title7 [ 7 ]. The roadmap also includes proposals to increase the block gas limit from 30 million to as much as 150 million, though developers remain cautious about issues like slower block propagation that might arise title8 [ 8 ]. Fusaka’s main focus is on infrastructure enhancements rather than user-facing features, in line with Ethereum’s ongoing upgrade pattern; this follows the Pectra update in May 2025, which brought account abstraction and changes to validator staking title9 [ 9 ].

Fusaka’s launch comes amid increased attention on Ethereum’s validator system. Recently, over 2.6 million ETH (about $12 billion) have entered the exit queue, resulting in wait times of over 40 days title10 [ 10 ]. Co-founder Vitalik Buterin has justified these delays as important for security, but some critics warn that such bottlenecks could drive centralization. The optimizations in Fusaka, such as reducing resource consumption for nodes and placing limits on blob transaction fees with EIP-7918, are intended to tackle these problems and encourage larger-scale Layer 2 adoption title11 [ 11 ].