Detailed Explanation of Fusaka: How the December Upgrade Integrates into Ethereum's Long-Term Development Roadmap?

Translated by: Felix. PANews

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 Ethereum's transactions and fee revenue, 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" (BPO), new gas and block size limits, and adjustments to historical expiration enable the blockchain to adapt to multiple capacity increases.

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

From Merge to Fusaka: The Roadmap

To understand the positioning of Fusaka, it is helpful to review the development history of Ethereum.

The Merge (2022) 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," a cheaper temporary data channel for Rollups, 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 Rollups and better data availability, while Verge and Purge focus on lighter clients and clearing old history.

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

PeerDAS, Blobs, and Larger Blocks

The core scaling solution of Fusaka is EIP-7594, namely PeerDAS.

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

This reduces the bandwidth and storage requirements for each node and lays the groundwork for achieving an 8-fold increase in blob capacity without forcing stakers to upgrade their hardware.

To make this growth more flexible, EIP-7892 introduced the BPO fork, a minor 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 L2 demand growth, without having to wait years for a major fork as in the past.

In terms of execution, Fusaka updates gas and block size:

The effective block gas target value is significantly increased from the current 45 million. EIP-7825 limits the amount of gas that can be used in a single 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 reprice and limit the MODEXP precompile to prevent a heavy cryptographic call from stalling the entire block.

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

User Experience, Security, and Developer Tools

The improvements in Fusaka are not solely focused on capacity; several EIPs also concentrate on user experience, security, and developer convenience.

EIP-7917 fully determines the proposer schedule for the next epoch, which can be accessed 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 to provide fast and reliable soft finality guarantees.

In terms of user experience, EIP-7951 adds secp256r1 precompile, enabling Ethereum to natively support P-256 signatures, a curve 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 mainstream platform login processes.

Developers gain EIP-7939, which computes the number of leading zeros in a 256-bit word. It lowers the cost and difficulty of bit-level mathematical operations, large integer calculations, and the implementation of some zero-knowledge proof circuits.

Finally, EIP-7642 extends Ethereum's historical data expiration mechanism, allowing clients to discard more pre-merge and older 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 the BPO fork makes data cheaper and richer.

Analysts estimate that Fusaka, along with the first BPO fork, could reduce L2 data costs by 40% to 60% for some time, especially for high-throughput application scenarios like DeFi, gaming, and social. Lower data costs mean more room for experimentation and could spark a new round of competition around pricing and user experience for Rollups.

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

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

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

For ETH holders, the impact is evident. The underlying Ethereum network is being adjusted to a high-capacity settlement and data engine at the L2 level, with minimum fees and blob pricing adjusted to attract more transaction 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 experience significant improvements in cost and experience, it may invite criticism.

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

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

ePBS aims to strengthen the maximum extractable value (MEV) supply chain by separating block building and proposing 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 the BPO fork drive the development of Surge. The extension of historical record expiration times and peer-to-peer (P2P) adjustments reflect the themes of Verge and Purge. User experience upgrades such as proposer lookahead and P-256 support enable pre-confirmation and passkey wallets to be implemented on a large scale.

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 initially gave the network value.

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