Ethereum core developers have officially announced the rollout timeline for the Fusaka network upgrade across public testnets, following the previous Pectra upgrade. The deployment phase begins on the Holesky testnet at slot 5,283,840, scheduled for October 1, 2025, at 08:48:00 UTC. Subsequent testnet upgrades are set for Sepolia on October 14, 2025, and Hoodi on October 28, 2025. Ethereum developers noted that Fusaka represents the final upgrade for the Holesky network, which will be decommissioned shortly after testing completes.

Fusaka's flagship feature is Peer Data Availability Sampling, introduced via EIP-7594. PeerDAS permits nodes to verify data availability using erasure coding and cryptographic sampling rather than downloading full data blobs. This networking protocol optimization expands blob throughput for Layer-2 rollups without placing excessive bandwidth burdens on individual node operators, paving the way for reduced L2 transaction fees while preserving Layer-1 security guarantees.

Following the initial testnet activations, Ethereum will introduce Blob Parameter Only hardforks to incrementally scale capacity. These minimal, configuration-only adjustments aim to raise the per-block blob target and maximum metrics from the current 6 and 9 limits. Under BPO1, the target and maximum will increase to 10 and 15, respectively, followed by a second phase, BPO2, which expands the parameters to 14 target and 21 maximum blobs. Holesky is scheduled for BPO adjustments on October 7 and October 13, 2025.

In addition to data availability enhancements, Fusaka incorporates several key changes designed to scale execution and optimize user experience. EIP-7935 increases the network's default gas limit to 60 million, reflecting developers' target for L1 capacity scaling. Meanwhile, EIP-7825 introduces a protocol transaction gas limit cap of 16,777,216 gas to guard against denial-of-service vector attacks and enable future parallel processing. EIP-7642 simplifies network communications by introducing eth/69, which removes legacy pre-merge fields.

User experience improvements in Fusaka include EIP-7951, which introduces a precompiled contract supporting the secp256r1 elliptic curve. This addition allows direct smart contract interactions with secure hardware enclaves found in modern mobile and web devices. Additionally, EIP-7939 adds the Count Leading Zeros opcode to lower zero-knowledge proof costs and optimize mathematical calculations. Node operators must upgrade both execution and consensus clients to supported releases to remain synchronized during the testing sequence.