Ethereum’s Fusaka upgrade is live on mainnet, introducing changes to the way the network handles data used by rollups. Optimism’s activation report identifies PeerDAS and the Blob Parameter Only mechanism as the central additions for Layer-2 scaling.
The immediate development is an upgrade to data availability. The larger capacity increases are staged through separate parameter changes, rather than all arriving as one jump on activation day.
Sampling reduces the burden on nodes
Rollups publish data to Ethereum so that their activity can be checked. Blobs provide a dedicated form of data space for that purpose, but available capacity can become a constraint as use grows.
PeerDAS, introduced through EIP-7594, lets nodes verify data availability by sampling portions of the data instead of downloading every blob in full. The design uses erasure coding so that the network can assess whether the complete data is available.
The practical objective is to increase data throughput without requiring each node to take on the full additional download burden. For rollups, more available capacity can ease a cost and throughput constraint, although an individual user’s fee also depends on the rollup’s own pricing and demand.
Capacity changes have their own schedule
EIP-7892 introduces Blob Parameter Only, or BPO, forks. These let Ethereum adjust blob limits between larger named upgrades.
The published schedule sets the first adjustment for December 9, raising the target to 10 blobs per block and the maximum to 15. A second adjustment is scheduled for January 7, 2026, with a target of 14 and a maximum of 21.
Those are planned follow-up steps at the time of activation. They should not be confused with capacity already in use on December 4.
Optimism says teams from OP Labs, Base, Soneium and Ethereum client projects contributed to development and testing. It also describes a future OP Stack upgrade, separate from Ethereum’s current mainnet change.
