Fusaka Is Live: Scaling Optimism and the Superchain
Ethereum’s Fusaka hardfork is live on mainnet, unlocking the next major leap in data scalability for rollups. This upgrade incorporates core contributions made by the engineering teams in the Superchain – including Blob Parameter Only (BPO) and changes to L1 consensus clients - and delivers the most meaningful expansion of Ethereum’s data availability capacity since EIP-4844. With Fusaka activated, OP Stack chains can immediately take advantage of these enhancements, giving builders, users, and ecosystem partners faster throughput, lower fees, and a more scalable foundation to grow on.
Over the past year, activity across the Superchain has grown to the point where Ethereum’s existing blob capacity was once again nearing saturation. Blobs from EIP-4844 delivered a major step forward, but the ecosystem quickly began pushing up against the limits of what the current data layer could support. Without deeper protocol changes on Ethereum itself, rollups would hit a ceiling on throughput and would have limited room to continue reducing fees.
Fusaka addresses this bottleneck directly. The upgrade introduces two foundational improvements to Ethereum’s data layer: PeerDAS, a more efficient protocol for verifying data availability, and EIP-7892, the “Blob Parameter Only” (BPO) mechanism that lets Ethereum safely increase blob capacity between hardforks. Together, these upgrades create the next stage of scalability—expanding Ethereum’s data bandwidth while keeping the network secure, decentralized, and predictable for the L2s that depend on it.
Scaling Blobs: Lower Costs, More Capacity
EIP-7594 introduces PeerDAS, a new networking protocol that lets nodes verify blob data availability through sampling rather than needing to download all the data. This is a foundational step toward increasing blob throughput while preserving Ethereum’s security and decentralization.
Since the Dencun upgrade, demand for L2 blockspace has outstripped the throughput provided by Ethereum’s current 9-blob limit. PeerDAS enables Ethereum to raise that limit safely. It uses erasure coding to let nodes sample small portions of blob data while still providing cryptographic guarantees that the full data is available across the network. This mechanism unlocks the path toward higher blob targets envisioned in Ethereum’s scaling roadmap.
For rollups, the impact is straightforward: more blob capacity unlocks greater throughput and lower fees. As L1 data availability throughput scales beyond today’s limits, L2 users can transact more cheaply without any impact on the security and trust assumptions they are accustomed to
Following PeerDAS activation, Ethereum will use Blob-Parameter-Only (BPO) forks to safely raise blob capacity without tying these adjustments to major named upgrades. Fusaka includes two planned BPO parameter adjustments on mainnet starting December 9, 2025. See the BPO schedule below for further details.
Blob Parameter Only (BPO) Fork Schedule
Following the main Fusaka activation, the network will implement Blob Parameter Only forks to gradually increase blob throughput. BPO1 will increase the per-block blob target to 10 and maximum to 15.
BPO Fork (target/limit) | Epoch | Date & Time (UTC) | Unix Timestamp |
BPO 1 (10/15) | 412672 | 2025-12-09 14:21:11 | 1765290071 |
BPO 2 (14/21) | 419072 | 2026-01-07 01:01:11 | 1767747671 |
L1 🤝L2 Collaboration Wins
Fusaka is the result of a year of close collaboration across Ethereum’s core dev and the broader L2 ecosystem. Engineers from OP Labs, Base, Soneium, and multiple Ethereum client teams contributed to designing, testing, and validating the upgrade. You can read more about it in our previous blogs:
OP Labs developers proposed the Blob Parameter Only model, which became EIP-7892. This gives Ethereum a mechanism to safely increase blob capacity between major hardforks – allowing for a more responsive scaling plan as L2 usage grows.
Teams across the Superchain helped test PeerDAS in early devnets, confirming its performance for both execution clients and consensus clients under real rollup workloads.
“Fusaka represents steady, shared engineering between Ethereum’s core developers and the Superchain,” said Mark Tyneway, Co-Founder and Head Systems Engineer at Optimism. “PeerDAS and BPO make scaling more predictable and cost-efficient, showing how aligned development across layers keeps the network moving forward.”
Looking Ahead
With Fusaka now in production, rollups will gather real-world usage data to guide future BPO forks planned for early 2026. These forks will gradually raise Ethereum’s data capacity, giving L2s more bandwidth to scale. In parallel, OP Labs is preparing a Superchain upgrade, expected in early 2026, to adopt Fusaka EIPs into the OP Stack itself.
Scaling Ethereum is a collective effort, and each upgrade compounds the last. Optimism remains committed to driving that progress – improving performance, lowering costs, and keeping the network secure, usable, and open to all.