In-depth explanation of Fusaka: How does the December upgrade fit into Ethereum's long-term development roadmap?

Author: Cointelegraph

Compiled by: White55, Mars Finance

On December 3, 2025, Ethereum will activate the “Fusaka” upgrade on the mainnet, marking the second major hard fork of the year following the “Pectra” upgrade in May. The name Fusaka is derived from the combination of two internal upgrade code names, Osaka (execution layer upgrade) and Fulu (consensus layer upgrade).

What is the Fusaka upgrade?

Rollups currently handle most of the transactions and fee revenue on Ethereum, but they are still limited by the amount of data published back to L1 and the associated costs.

The Fusaka upgrade aims to alleviate this pressure. Its main feature, PeerDAS (Peer Data Availability Sampling), allows validators to verify Rollup data blocks without downloading everything, thereby reducing bandwidth and storage requirements while significantly increasing data throughput.

At the same time, the “Blob-Only Parameter” (abbreviated as BPO), new gas and block size limits, as well as adjustments for historical expirations, enable the blockchain to adapt to multiple capacity upgrades.

This article will analyze the changes brought by the Fusaka upgrade, its positioning in the Surge, Verge, and Purge roadmaps, and the potential impacts it may have on users, Rollups, and the entire Ethereum ecosystem in the coming years.

From Merge to Fusaka: Roadmap

To understand the positioning of Fusaka, it might be helpful to revisit the development history of Ethereum.

The Merge (2022) “Merge” transitioned Ethereum from a proof-of-work mechanism to a proof-of-stake mechanism, reducing energy consumption by approximately 99.9%.

Shapella (2023) enabled the withdrawal of staked Ether, transforming the one-way staking system into a liquidity system, attracting more validators.

Dencun (March 2024) introduced Ethereum Improvement Proposal (EIP) 4844 “blob”, which is a cheaper temporary data channel for Rollup, also known as protodanksharding.

Pectra (May 2025) added EIP-7702 account abstraction features and readjusted staking parameters such as the validator cap of 2048 Ether.

These upgrades align with Vitalik Buterin's brief roadmap: Merge, Surge, Verge, Purge, and Splurge. Surge aims to scale Ethereum through Rollup and better data availability, while Verge and Purge focus on lighter clients and clearing old history.

Fusaka is the first upgrade to simultaneously promote all these features. It expands Rollup data as part of Surge and optimizes historical records and a lighter synchronization mechanism as part of Verge and Purge. It also sets clear goals for a modular Ethereum stack, aiming to increase L2 throughput on top of L1 settlement to achieve over 100,000 transactions per second (TPS).

PeerDAS, blobs, and larger blocks

Fusaka's core scaling solution is EIP-7594, namely PeerDAS.

PeerDAS no longer requires each full node to download the complete Rollup data block, but instead splits it into smaller units and uses sampling and erasure coding techniques, allowing validating nodes to only obtain random fragments. If enough available fragments exist, the network can be confident that the complete data is present.

This can reduce the bandwidth and storage of each node and lay the foundation for the eventual realization of an 8-fold increase in blob capacity without forcing stakers to upgrade their hardware.

To make this growth more flexible, EIP-7892 introduces the BPO fork, which is a small hard fork that only changes three parameters related to Blobs: target value, maximum value, and base fee adjustment factor.

After Fusaka, Ethereum can increase blob capacity in a smaller, more frequent manner based on the growth of L2 demand, without having to wait years for a major fork as in the past.

In terms of execution, Fusaka has updated the gas and block size:

The target value for effective block gas has been significantly increased from the current 45 million. EIP-7825 restricts the amount of gas that can be used per transaction, while EIP-7934 increases the recursive length prefix (RLP) block size limit to 10 MB to reduce the risk of denial-of-service (DoS) attacks.

EIP-7823 and EIP-7883 repriced and restricted the MODEXP precompile to prevent a heavy cryptographic call from stalling the entire block.

In short, Fusaka provides more space for Ethereum to store Rollup data and complex transactions, while adding security mechanisms to ensure that blocks remain verifiable by ordinary nodes.

User experience, security, and developer tools

The improvements of Fusaka are not only focused on capacity; several EIPs also focus on user experience, security, and ease of operation for developers.

EIP-7917 makes the proposer schedule for the next epoch fully deterministic and accessible on-chain via the beacon root. This is crucial for Rollup-based and pre-confirmation schemes, as these schemes need to know in advance which validator will propose a given block in order to provide fast and reliable Soft Finality guarantees.

In terms of user experience, EIP-7951 adds a secp256r1 precompile, enabling Ethereum to natively support P-256 signatures, which are adopted by Apple’s Secure Enclave, Android Keystore, Fast Identity Online 2 (FIDO2), and WebAuthn keys. This allows wallets to rely on device-level biometrics and keys instead of mnemonic phrases, bringing L1 closer to the login processes of mainstream platforms.

Developers received EIP-7939, which is an opcode for calculating the number of leading zeros in a 256-bit word. It lowers the cost and difficulty of implementing bitwise mathematical operations, large integer operations, and some zero-knowledge proof circuits.

Finally, EIP-7642 extends Ethereum's historical data expiration mechanism, allowing clients to discard more pre-merge and earlier data while publishing the range of data they provide. This can save hundreds of GB of space for each node and significantly speed up the synchronization of new validators.

Who benefits: L2 nodes, validator nodes, and Ethereum holders

For the L2 ecosystem, the combination of PeerDAS and BPO forks makes data cheaper and richer.

Analysts estimate that the Fusaka along with the first BPO fork could reduce L2 data fees by 40% to 60% for a period of time, especially for high-throughput application scenarios such as DeFi, gaming, and social. Lower data fees mean more room for experimentation and could trigger a new round of Rollup competition around price and user experience.

For node operators and validators, Fusaka alleviates some burdens but also adds others. Sampling and historical expiry reduce the amount of data that nodes need to download and store, making it easier for new nodes to synchronize to the latest blocks.

However, as the BPO fork pushes the blob count higher, well-equipped validators and infrastructure providers will bear more upload bandwidth, which could push the network towards larger operators if client implementations and guidance are not cautious enough.

Institutional and equity staking service providers often view Fusaka as a strategic empowerment rather than a one-time speed boost. More predictable data throughput, more secure gas and block size limits, and clearer historical management all make large-scale validator operations easier to plan.

The impact is evident for ETH holders. The underlying Ethereum network is being adjusted to a Layer 2 level for high-capacity settlement and data engines, with minimum fees and blob pricing also being adjusted to attract more trading activity to settle on Ethereum, which could affect the fee market and validator rewards.

However, this adjustment also comes with trade-offs. The protocol becomes more complex, and if ordinary users do not perceive a significant improvement in terms of cost and experience, it may invite criticism.

After Fusaka: Glamsterdam and the Road to 100,000 TPS

The next upgrade called Glamsterdam is expected to be launched in 2026, with two major highlights: proposer-builder separation (ePBS) and block-level access lists (BAL).

ePBS is committed to strengthening the Maximum Extractable Value (MEV) supply chain by separating block construction and proposal at the protocol level, rather than relying solely on external relays.

BALs aim to achieve more efficient execution and better handling of state access, including future increases in blob capacity.

PeerDAS and BPO forks have driven the development of Surge. The extension of historical record expiration time and adjustments in peer-to-peer (P2P) reflect the themes of Verge and Purge. User experience upgrades such as Proposer Lookahead and P-256 support enable large-scale implementation of pre-confirmation and passkey wallets.

If Ethereum can maintain this pace, then Fusaka will be seen more as a turning point. It marks the transition of the roadmap from a decentralized plan to a coherent and value-focused scaling solution. Its goal is to support a modular stack capable of 100,000 transactions per second without sacrificing the decentralized characteristics that originally gave the network its value.