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

Author: Cointelegraph; Translator: Felix. PANews

On December 3, 2025, Ethereum will activate the "Fusaka" upgrade on its mainnet, marking the second major hard fork this year following the "Pectra" upgrade in May. The name Fusaka is a merger of two internal upgrade code names: Osaka (execution layer upgrade) and Fulu (consensus layer upgrade).

What is the Fusaka upgrade?

Rollups currently carry the majority of Ethereum's transaction and fee revenue, but they are still limited by the amount of data to be 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 validate Rollup blocks without downloading all content, thus reducing bandwidth and storage requirements while significantly increasing data throughput. Meanwhile, "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 about by the Fusaka upgrade, its position in the Surge, Verge, and Purge roadmaps, and its potential impact on users, Rollups, and the entire Ethereum ecosystem in the coming years. From Merge to Fusaka: A Roadmap To understand Fusaka's positioning, it's helpful to review the development history of Ethereum. The Merge (2022) transformed Ethereum from a Proof-of-Work to a Proof-of-Stake mechanism, reducing energy consumption by approximately 99.9%. Shaphala (2023) enabled the withdrawal of staked Ether, transforming the one-way staking system into a liquidity system and 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 and recalibrated staking parameters such as the validator cap of 2048 Ether. These upgrades align with Vitalik Buterin's concise roadmap: Merge, Surge, Verge, Purge, and Splurge. Surge aims to scale Ethereum through Rollups and improved data availability, while Verge and Purge focus on lighter-weight clients and clearing old history. Fusaka is the first upgrade to push all of these features simultaneously. It expands Rollup data as part of Surge and optimizes history and lighter-weight synchronization mechanisms as part of Verge and Purge. It also sets a clear goal for a modular Ethereum stack: to increase L2 throughput on top of L1 settlement, achieving 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 block; instead, it breaks it down into smaller units and uses sampling and erasure coding techniques to ensure that validators only receive random fragments. If enough fragments are available, the network can be confident that the complete data exists. This reduces the bandwidth and storage required per node and lays the foundation for eventually achieving an 8x increase in blob capacity without forcing stakers to upgrade their hardware. To make this growth more flexible, EIP-7892 introduced the BPO fork, a small hard fork that changes only three Blob-related parameters: target value, maximum value, and base fee adjustment factor. Following Fusaka, Ethereum can increase blob capacity more frequently and in smaller increments based on L2 demand growth, instead of waiting years for a major fork as before. In terms of implementation, Fusaka updated gas and block size: The effective block gas target has been 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 adds a 10 MB Recursive Length Prefix (RLP) block size limit to reduce the risk of denial-of-service (DoS) attacks. EIP-7823 and EIP-7883 repriced and limited MODEXP pre-compilation to prevent a single heavy cryptographic call from halting the entire block. In short, Fusaka provides Ethereum with more space to store Rollup data and complex transactions while adding security mechanisms to ensure that blocks remain verifiable for ordinary nodes. User Experience, Security, and Developer Tools Fusaka's improvements are not only focused on capacity; several EIPs also focus on user experience, security, and ease of use 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 rollups and pre-confirmed schemes, which 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 the secp256r1 pre-compilation, 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, rather than mnemonic phrases, bringing L1 closer to the login process of mainstream platforms. Developers obtained EIP-7939, an opcode for calculating leading zeros, used to count the number of leading zeros in a 256-bit word. This makes bit-level math operations, large integer operations, and some zero-knowledge proof circuits easier and less costly to implement. 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 per 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, coupled with the first BPO fork, could reduce L2 data fees by 40% to 60% for some time, especially for high-throughput applications like DeFi, gaming, and social networking. Lower data fees mean more room for experimentation and could trigger a new round of Rollup competition surrounding price and user experience. 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, potentially pushing the network toward larger operators if client implementations and guidance are not careful enough. Institutions and staking service providers often view Fusaka as a strategic enabler rather than a one-off speed boost. More predictable data throughput, more secure gas and block size limits, and clearer history management all make large-scale validator operations easier to plan. For ETH holders, the impact is obvious. The Ethereum network is being tuned to a high-capacity settlement and data engine at the L2 level, and minimum fees and blob pricing have also been adjusted to attract more transaction activity to settle on Ethereum, which may affect the fee market and validator rewards. However, this adjustment also involves trade-offs. The protocol has become more complex, and if ordinary users do not feel a significant improvement in cost and experience, it may attract criticism. After Fusaka: Glamsterdam and the Road to 100,000 TPS The next upgrade, called Glamsterdam, is expected to launch in 2026, with two major highlights: proposer-builder separation (ePBS) and block-level access lists (BALs). ePBS aims to strengthen the maximum extractable value (MEV) supply chain by separating block building and proposal at the protocol level, rather than relying solely on external relays. BALs are designed for more efficient execution and better handling of state access, including future increases in blob capacity. The PeerDAS and BPO forks have driven the development of Surge. The extension of historical record expiration times and adjustments to peer-to-peer (P2P) scaling reflect the themes of Verge and Purge. User experience upgrades such as Proposer Lookahead and P-256 support enable pre-confirmed and pass-key wallets to be implemented at scale. If Ethereum can maintain this pace, then Fusaka will be seen more as a turning point. It marks a shift in the roadmap from a decentralized plan to a coherent and value-oriented scaling solution. Its goal is to support a modular stack of 100,000 transactions per second without abandoning the decentralized characteristics that initially made the network valuable.