Fusaka upgrade one month away: Ethereum's boldest scaling bet yet

Author: Jason Nelson

Translation: Luffy, Foresight News

Summary

• Ethereum's Fusaka upgrade is scheduled for December 2025, introducing data scaling, DoS protection, and developer tools.

• Peer Data Availability Sampling (PeerDAS) increases blob throughput by a factor of 8 by sampling data instead of requiring full nodes to store complete data.

• New EIPs will set blob fees, limit block size, and add features such as pre-confirmations and P-256 signature support.

The next major upgrade to the Ethereum network is on the horizon. This upgrade, named Fusaka (short for Fulu-Osaka), is set to launch in December 2025 and will bring significant changes to both the execution and consensus layers of Ethereum.

Fusaka marks another milestone following Ethereum's 2022 Merge. The 2023 Shapella upgrade introduced staked ETH withdrawals; the 2024 Dencun upgrade brought proto-Danksharding technology and blobs; and the 2025 Pectra upgrade enhanced validator flexibility and Layer 2 interoperability.

According to the roadmap, the Fusaka upgrade aims to expand data capacity, strengthen defenses against DoS attacks, and introduce new tools for developers and users.

This upgrade is far-reaching. Fusaka is not a minor patch but involves a redesign of Ethereum’s data availability management, blob pricing, and transaction protection mechanisms. Its success will depend on whether Ethereum can scale to meet growing Layer 2 demands without causing network splits or overburdening node operators.

PeerDAS: Sample Instead of Storing All Data

The core feature of the Fusaka upgrade is PeerDAS, a new method for handling blobs.

In Ethereum, blobs are temporary data packets introduced during the Dencun upgrade alongside proto-Danksharding technology. They allow Rollups to submit large volumes of transaction data to the mainnet at low cost, enhancing scalability without permanently increasing blockchain state.

This ensures redundancy, but as demand grows, it creates bottlenecks. Under the current model, every full node on Ethereum must store all blobs submitted by Layer 2 networks to the chain.

PeerDAS changes this logic. Each node stores only a portion of the blobs (approximately one-eighth), relying on cryptographic reconstruction techniques to fill in missing data segments. The design uses random sampling to verify data availability, with an extremely low error probability—between one in 10²⁰ and one in 10²⁴.

Through this distributed storage approach, Ethereum could theoretically increase blob throughput by up to 8 times without requiring node operators to upgrade hardware or bandwidth. Rollups that rely on blobs to publish compressed transaction data are expected to benefit most directly.

Blob Economics and Flexibility

The Fusaka upgrade also reshapes blob pricing and management mechanisms.

A key change is EIP-7918, which introduces a minimum reserve fee for blobs. Under current rules, when execution layer gas fees dominate, blob prices can drop close to zero, encouraging inefficient usage. A minimum reserve fee ensures there is always a baseline cost for blob usage, forcing Layer 2s to pay for the storage and bandwidth they consume.

Another mechanism is EIP-7892, which introduces forks that adjust only blob parameters. This allows Ethereum clients to modify blob throughput without a full hard fork, enabling developers to respond flexibly to unpredictable Layer 2 demand without waiting for the next scheduled upgrade.

Strengthened Attack Defense

Scaling also means expanding Ethereum’s attack surface. The Fusaka upgrade includes a series of adjustments to limit extreme scenarios and protect the network from DoS attacks:

• EIP-7823: Limits input size for MODEXP operations to 8192 bits;

• EIP-7825: Sets a per-transaction gas limit of 2²⁴ units;

• EIP-7883: Increases gas costs for large exponents in MODEXP to better reflect computational workload.

• EIP-7934: Caps execution layer block size at 10MB.

These adjustments collectively reduce the risk of client overload, propagation stalls, or network instability caused by extreme transactions or oversized blocks.

New Tools for Users and Developers

The Fusaka upgrade also focuses on improving usability.

For users, EIP-7917 introduces pre-confirmation support. This enables wallets and applications to preview validator proposal schedules, allowing users to lock in certainty about which upcoming block their transaction will be included in, thereby reducing latency and uncertainty around transaction confirmations.

For developers, the Fusaka upgrade adds two important features:

• CLZ opcode, useful for cryptographic algorithms and contract optimization;

• EIP-7951, providing native secp256r1 (P-256) signature verification. This elliptic curve is widely used in hardware devices and mobile systems, and its inclusion will enhance compatibility and account abstraction capabilities.

These changes aim to lower the barrier for application developers and pave the way for new wallet designs and security models.

What ETH Holders Need to Know

For ordinary Ethereum users, no action is required for the Fusaka upgrade. Account balances, tokens, and applications will continue to function normally. The official Ethereum website emphasizes that users should beware of scams asking them to "upgrade ETH" or make transfers, as no such actions are needed.

The responsibility mainly falls on validators and node operators, who must synchronize upgrades to both execution and consensus layer clients. Coordination is critical: failure to do so could result in network downtime or temporary forks.

Following a series of successful testnet activations, the Fusaka upgrade is scheduled to go live on the Ethereum mainnet on December 3, 2025.

The Future of Ethereum After Fusaka

The Fusaka upgrade is one of the boldest steps on Ethereum’s roadmap since the Merge. It attempts to simultaneously achieve three major goals—increased blob capacity, stronger defenses, and updated developer tools—through a single coordinated release.

Testing and development are ongoing, with client teams focusing on PeerDAS performance, blob pricing models, and compatibility between execution and consensus layer software. If successful, Fusaka could become a turning point for Ethereum in handling the next wave of Layer 2 adoption and enhancing its scalability.