Ethereum's Fusaka Upgrade Activates, Boosting Rollup Throughput and Gas Efficiency

Introduction: A Major Step on the Scaling Roadmap

Ethereum's execution layer has undergone a significant transformation with the activation of the Fusaka upgrade on December 3. This hard fork represents a concentrated effort to enhance the network's core scalability infrastructure, directly targeting the efficiency and cost-effectiveness of Layer-2 rollups. By deploying a suite of carefully engineered Ethereum Improvement Proposals (EIPs), Fusaka introduces PeerDAS data-availability sampling, doubles the default block gas limit, rewires the blob fee market, and adds native support for modern cryptographic standards like passkeys.

Named after the star Fulu (‘auxiliary road’) and the city of Osaka (‘slope or hill’), Fusaka continues Ethereum's tradition of celestial and terrestrial name pairings. This upgrade is not a singular event but part of a phased rollout, with two subsequent "Blob Parameter Only" forks—BPO1 on December 9 and BPO2 on January 7—scheduled to further expand capacity. As the most throughput-focused upgrade since the introduction of proto-danksharding (EIP-4844) in March 2024, Fusaka's primary mission is clear: to provide more abundant and economically stable data availability for rollups, thereby creating a path for cheaper user transactions and a more robust foundation for decentralized application growth.

PeerDAS: Unlocking the Next Order of Magnitude in Data Availability

The cornerstone of the Fusaka upgrade is the implementation of PeerDAS (Peer Data Availability Sampling), formalized in EIP-7694. This protocol marks a fundamental shift in how nodes verify the existence of data blobs. Prior to Fusaka, nodes were required to download entire blobs to confirm their availability, a process that became a scaling bottleneck following the initial success of EIP-4844.

PeerDAS elegantly solves this by allowing nodes to verify data by sampling small, random pieces of a blob instead of consuming it in its entirety. This breakthrough is critical because it removes a key constraint on blob throughput. By decoupling verification workload from data size, PeerDAS creates a technical pathway to increase blob capacity by roughly an order of magnitude over time. For end-users, this technical evolution translates directly into lower Layer-2 transaction fees. Rollups compress thousands of user transactions into single blobs posted to Ethereum; more efficient and abundant blob space means rollups can post data more cheaply, savings they can pass on to their users.

This advancement builds directly on the foundation laid by EIP-4844. Where EIP-4844 introduced blobs as a new transaction type dedicated to rollup data, Fusaka's PeerDAS ensures that system can scale efficiently without overburdening network participants.

Doubling Down: The Block Gas Limit Increase and Blob Parameter Expansions

Complementing the PeerDAS innovation, Fusaka executes a substantial increase in network capacity through a straightforward yet impactful change: it doubles the default gas limit per block to 60 million gas, up from the 30 million configuration that has been in place since the Merge. This adjustment effectively doubles the immediate budget for both standard execution-layer transactions and blob processing on Layer 1.

The increase provides immediate headroom for network activity. However, its most significant synergy is with the upcoming blob-specific upgrades. Fusaka itself is followed by two targeted forks: BPO1 on December 9 and BPO2 on January 7. These "Blob Parameter Only" forks are designed to adjust key parameters—like the number of blobs per block—without requiring additional code changes from node operators. This phased approach allows developers, node operators, and rollup teams to monitor network performance and client stability after each incremental increase, ensuring a smooth and controlled expansion of data availability capacity.

Rationalizing Economics: Rewiring the Blob Fee Market with EIP-7918

A critical component of sustainable scaling is ensuring that underlying markets function rationally. EIP-7918 addresses a potential economic distortion by tying the minimum base fee for blobs to the execution gas price. Prior to this change, it was possible for blob fees to collapse to near-zero levels while execution-layer gas prices remained high during periods of network congestion. This divergence could create arbitrage opportunities and distort the economic incentives for rollups, potentially leading to inefficient data posting behavior.

EIP-7918 stabilizes this relationship. By linking the two fee markets, it ensures that the cost of data availability maintains a sensible correlation with the overall demand for block space. This creates a more predictable and economically rational environment for rollup operators as they budget for their fixed costs of securing data on Ethereum's base layer. A stable fee market is essential for long-term planning and for the business models of Layer-2 networks.

Hardening the Network: Security and Predictability Enhancements

Beyond scaling and economics, Fusaka includes several proposals aimed at improving network security and client performance predictability. A suite of EIPs targets potential denial-of-service (DoS) vectors and heavy computational workloads:

• EIP-7823 & EIP-7825: These proposals target the ModExp (Modular Exponentiation) precompile, capping its input sizes and raising its gas cost. This precompile is used in cryptographic operations like zk-SNARK verification.
• EIP-7883: Introduces an absolute ceiling for transaction gas limits.
• EIP-7934: Enforces a strict limit on block size in their RLP (Recursive Length Prefix) encoded form.

Collectively, these changes reduce the attack surface available to malicious actors and make worst-case client workloads more predictable and manageable for node operators. This hardening is a proactive measure to maintain network stability as capacity and complexity grow.

Empowering Developers: New Opcodes and Cryptographic Primitives

Fusaka also delivers valuable new tools for smart contract developers, expanding Ethereum's virtual machine capabilities.

• EIP-7939 - Count Leading Zeros (CLZ): This new opcode provides a cheap and simple way to perform bit-manipulation and calculate integer logarithms on-chain. It offers significant gas savings and simplicity for DeFi protocols, cryptographic contracts, and algorithms that rely on efficient bitwise operations.
• EIP-7917 - Deterministic Proposer Lookahead: This upgrade gives validators a fixed schedule showing which validator will propose blocks in future slots. MEV (Maximal Extractable Value) relays and large staking operators can use this precise timeline to coordinate their activities more safely and efficiently, reducing uncertainty in block production workflows.
• EIP-7951 - Native secp256r1 Precompile: Perhaps the most user-facing developer feature, this addition introduces native support for the secp256r1 elliptic curve. This is the same cryptographic standard used by Apple’s Secure Enclave, Android Keystore, and WebAuthn/FIDO2 security keys.

The inclusion of secp256r1 support is a landmark for user onboarding. It allows wallets and smart account schemes (like ERC-4337 account abstraction wallets) to verify passkey-style signatures directly on-chain. This removes a major friction point, enabling seamless authentication flows using FaceID, TouchID, or hardware security keys without requiring custom bridging circuits or off-chain verification services. It paves the way for mainstream applications that demand both high security and user convenience.

Conclusion: A Foundation for the Next Wave of Growth

The Fusaka upgrade is a multifaceted enhancement firmly focused on strengthening Ethereum's foundational layer for the age of rollups. By simultaneously attacking scalability bottlenecks (PeerDAS), expanding immediate capacity (gas limit increase), rationalizing economics (EIP-7918), hardening security, and providing better developer tools (new opcodes, secp256r1), it represents a holistic step forward.

The immediate impact will be felt most acutely in the Layer-2 ecosystem. With more efficient and predictably priced blob space, leading rollups like Arbitrum One, Optimism Mainnet, Base, zkSync Era, and Starknet have the runway to further reduce fees for their users while maintaining robust economic security derived from Ethereum. The phased parameter expansions through January will test this new capacity under real-world conditions.

For readers and participants in the ecosystem, key developments to watch next include:

1. Monitoring Layer-2 Fee Trends: Observing how rollups utilize the new blob space and whether cost savings are consistently passed to end-users.
2. Adoption of New Primitives: Tracking how wallet providers and dApp developers integrate native passkey (secp256r1) support to improve user experience.
3. Network Performance: Ensuring client diversity remains healthy and node operator workload stays manageable through the BPO1 and BPO2 parameter increases.

Fusaka does not alter staking mechanics or validator incentives; its changes are precisely targeted at execution-layer throughput and developer experience. By successfully deploying this upgrade, Ethereum continues its methodical progression along its scaling roadmap, reinforcing its position as a stable and evolving settlement layer capable of supporting an ever-expanding universe of decentralized applications