Ethereum's Fusaka Upgrade: A Deep Dive into Scalability, User Experience, and Security

Key Takeaways

• Introduction to the upcoming Ethereum Fusaka Upgrade
• PeerDAS and its impact on Rollup scalability
• Blob-Only Parameter (BPO) and gas adjustments
• User experience and security enhancements with Fusaka
• Winners and Losers: L2s, validator nodes, and ETH holders
• Looking ahead to Glamsterdam upgrades and beyond

Fellow digital finance enthusiasts,

Brace yourselves, as Ethereum is poised to deploy the 'Fusaka' upgrade on its mainnet in December 2025, a landmark following the 'Pectra' upgrade in May. Fusaka, a clever portmanteau of the internal code names Osaka (execution layer upgrades) and Fulu (consensus layer upgrades), represents a pivotal leap forward in Ethereum's quest for scalability and optimal performance.

What is the Fusaka Upgrade?

Rollups currently serve as the backbone for transaction processing and fee generation on Ethereum. However, they are constrained by the amount and cost of data posted back to Layer-1 (L1). Fusaka aims to alleviate these bottlenecks. Its core feature, PeerDAS (Peer Data Availability Sampling), allows validators to verify Rollup data blocks without needing to download the entire thing. This significantly reduces bandwidth and storage requirements while drastically increasing data throughput. Concurrently, the 'Blob-Only Parameter' (BPO), new gas and block size limits, and historical expiry adjustments enable the blockchain to adapt to multiple capacity increases.

We will dissect the changes brought by the Fusaka upgrade, its positioning in the Surge, Verge, and Purge roadmaps, and the potential impacts on users, Rollups, and the entire Ethereum ecosystem in the years to come.

From Merge to Fusaka: The Roadmap

To understand Fusaka's place, let's recap Ethereum's evolution. 'The Merge' (2022) transitioned Ethereum from Proof-of-Work to Proof-of-Stake, slashing energy consumption by approximately 99.9%. Shapella (2023) enabled the withdrawal of staked ETH, transforming the one-way staking system into a liquid one, 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 functions and recalibrated staking parameters such as the 2048 ETH validator cap. These upgrades align with Vitalik Buterin's succinct 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 cleaning up old historical records. Fusaka is the first upgrade to push all of these functions simultaneously. It scales Rollup data as part of Surge and optimizes archives and lighter sync mechanisms as part of Verge and Purge. It also sets a clear goal for a modular Ethereum stack, adding L2 throughput on top of an L1 settlement foundation, achieving over 100,000 transactions per second (TPS).

PeerDAS, Blobs, and Bigger Blocks

The core of Fusaka’s scaling solution is EIP-7594, aka PeerDAS. Instead of requiring every full node to download entire Rollup data blocks, PeerDAS splits them into smaller units and uses sampling and erasure coding techniques, enabling validating nodes to acquire only random fragments. If enough fragments are available, the network can be confident the complete data exists. This reduces the bandwidth and storage needed per node and paves the way for an eventual eightfold growth in blob capacity without forcing stakers to upgrade hardware.

To make this growth more flexible, EIP-7892 introduces the BPO fork, a small hard fork that only changes three blob-related parameters: target values, maximum values, and base fee adjustment factor. Post-Fusaka, Ethereum can increase blob capacity in smaller, more frequent ways in response to L2 demand growth, without having to wait years for a major fork like before.

Executionally, Fusaka updates gas and block size: the effective block gas target value is increased substantially from the current 45 million. EIP-7825 limits the amount of gas a single transaction can use, while EIP-7934 increases the 10 MB Recursive Length Prefix (RLP) block size limit to reduce the risk of Denial-of-Service (DoS) attacks. EIP-7823 and EIP-7883 reprice and restrict the MODEXP precompile to prevent a single heavy crypto call from stalling an entire block. In short, Fusaka gives Ethereum more room to store Rollup data and complex transactions while adding security mechanisms that ensure blocks remain verifiable by ordinary nodes.

User Experience, Security, and Developer Tools

Fusaka’s improvements aren’t just about capacity; several EIPs also focus on user experience, security, and developer operability. EIP-7917 makes the proposer schedule for the next epoch fully determinate and accessible on-chain via the beacon root. This is critical for Rollups and pre-confirmation-based schemes that require advance knowledge of which validator will propose a given block in order to provide fast and reliable soft finality guarantees.

From a user experience perspective, EIP-7951 adds the secp256r1 precompile, making Ethereum natively support P-256 signatures, a curve used 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 seed phrases, bringing L1 closer to the login flow of mainstream platforms.

Developers get EIP-7939, the count leading zeros opcode, which counts the number of leading zeros in a 256-bit word. It makes bitwise math, big integer operations, and some zero-knowledge proof circuit implementations cheaper and easier to implement. Finally, EIP-7642 extends Ethereum’s historical data expiry mechanism, allowing clients to discard more pre-Merge and older data while advertising the range of data they provide. This saves hundreds of gigabytes of space per node and can significantly speed up the synchronization of new validators.

Who Benefits: L2 Nodes, Validator Nodes, and Ethereum Holders

For the L2 ecosystem, PeerDAS and the BPO fork combine to make data cheaper and more plentiful. Analysts estimate that Fusaka plus the first BPO fork could reduce L2 data fees by 40% to 60% for a time, especially for high-throughput use cases like DeFi, gaming, and social media. Lower data fees mean more room for experimentation and could ignite a new round of Rollup competition around price and user experience.

For node operators and validators, Fusaka lightens some burdens but adds others. Sampling and historical expiry 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-scale operators if client implementation and guidance aren’t careful enough.

Institutions and staking-as-a-service providers often see Fusaka as a strategic enabler 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.

For ETH holders, the impact is straightforward. Ethereum is being adjusted to become a high-capacity L2-level settlement and data engine, with minimum fees and blob pricing adjusted to attract more transaction activity to settle on Ethereum, potentially impacting the fee market and validator rewards. However, there are trade-offs with this adaptation. The protocol becomes more complex and may draw criticism if average users don’t feel tangible cost and experience improvements.

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

The next upgrade, codenamed Glamsterdam, is projected to launch in 2026, with two highlights: proposer builder separation (ePBS) and block-level access lists (BALs). ePBS aims to harden 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 enable more efficient execution and better handle state access, including future blob capacity increases. PeerDAS and the BPO fork advance Surge. The extension of historical expiry and peer-to-peer (P2P) adjustments reflect the themes of Verge and Purge. User experience upgrades like Proposer Lookahead and P-256 support enable pre-confirmation and passkey wallets at scale.

If Ethereum can maintain this pace of progress, Fusaka will more likely be seen as an inflection point. It signals a shift in the roadmap from a fragmented plan to a coherent, value-oriented scaling solution. The goal is to support a modular stack of 100,000 transactions per second without giving up the decentralization characteristics that made the network valuable in the first place.