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Fusaka follows the current year’s Pectra enhancement, signifying a significant advancement in Ethereum’s scaling strategy that boosts L1 performance, amplifies blob throughput, and improves user experience.
The Fusaka network upgrade is set to activate on the Ethereum mainnet at slot 13,164,544 (December 3, 2025, 21:49:11 UTC). Additionally, Fusaka introduces Blob Parameter Only (BPO) forks to effectively scale blob throughput post-PeerDAS activation. These are minimal, configuration-only upgrades that modify the blob target/max and fee update ratio. Refer to the activation table below for more details.
The Fusaka mainnet client releases are listed below.
Fusaka Overview
Fusaka’s standout feature is PeerDAS (Peer Data Availability Sampling), which facilitates substantial blob throughput scaling. It also encompasses enhancements throughout the execution layer and consensus layer to elevate L1 performance and enrich user experience. This article delineates the key improvements. For a more extensive overview, refer to ethereum.org’s guide on the upgrade.
Scale Blobs
PeerDAS
EIP-7594 introduces PeerDAS, a novel networking protocol facilitating nodes to ascertain blob data availability through sampling instead of downloading entire blobs. This represents a critical advancement in scaling blob throughput while preserving Ethereum’s security and decentralization.
Following the Dencun upgrade, layer 2 adoption has surged significantly, frequently hitting the current 9 blob per block cap. PeerDAS enables Ethereum to elevate this limit without compromising security. It achieves this by employing erasure coding to permit nodes to sample segments of blob data while still ensuring that the complete data is available throughout the network. This paves the way for higher blob targets outlined in Ethereum’s scaling roadmap.
This sampling technique directly aids layer 2 rollups by allowing greater blob throughput without proportionally increasing bandwidth demands for individual nodes. As blob capacity expands beyond current thresholds, L2 transaction fees can further decrease while upholding the security assurances of data availability on Ethereum L1.
After PeerDAS is enabled, Ethereum will utilize Blob Parameter Only (BPO) forks to prudently boost blob throughput rather than combining the blob parameter modifications with named forks. Fusaka incorporates two anticipated BPO parameter adjustments on the mainnet commencing December 9, 2025. These BPOs will elevate the per-block blob target and maximum from 6 & 9 to 10 & 15 in BPO1 and 14 & 21 in BPO2. Refer to the BPO schedule below for additional details.
Scale L1
ModExp Optimization
EIP-7883 and EIP-7823 collaborate to enhance the ModExp precompile. EIP-7883 raises gas charges to more accurately reflect computational complexity, including increasing minimal gas costs and tripling general cost assessments. EIP-7823 establishes upper limits for ModExp operations. Collectively, these modifications ensure that resource-heavy cryptographic tasks are appropriately valued and support potential future increases in block gas limits.
Transaction Gas Limit Cap
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EIP-7825 establishes a protocol-level transaction gas limit ceiling of 16,777,216 gas, averting individual transactions from utilizing excessive block gas and safeguarding against DoS assaults. This forms the foundation for concurrent transaction handling within the EVM.
Network Protocol Enhancement
EIP-7642 brings forth eth/69, which eliminates pre-merge fields and the receipt Bloom from the communication protocol. This tidying up lowers synchronization bandwidth demands, introduces a distinct history serving window for nodes to denote, and streamlines the codebase by discarding legacy elements that are unnecessary following the merge.
Gas Limit Augmentation
EIP-7935 increases Ethereum’s standard gas limit to 60M, reflecting the gas ceiling that core developers deem Ethereum L1 can presently accommodate safely. This enhancement provides more L1 execution capability and has undergone extensive testing across various client configurations to confirm network reliability and security.
Enhance UX
secp256r1 Precompile
EIP-7951 integrates native support for the secp256r1 elliptic curve via a new precompiled contract. This permits seamless compatibility with contemporary secure hardware such as Apple Secure Enclave, Android Keystore, and FIDO2/WebAuthn devices, minimizing friction for widespread blockchain adoption through familiar authentication methods.
Count Leading Zeros Opcode
EIP-7939 unveils the CLZ (Count Leading Zeros) opcode, offering a native, gas-effective means to conduct essential bit-counting tasks. This feature aids mathematical computations, compression techniques, and post-quantum signature protocols while lowering ZK proving expenditure.
Fusaka Specifications
The comprehensive list of modifications presented in Fusaka can be located in EIP-7607. The principal EIPs comprise:
Additional supportive EIPs:
Comprehensive specifications for the alterations in the execution and consensus layer can be accessed in the following releases:
Fusaka also brings about modifications to the Engine API utilized for interaction between consensus and execution layer nodes. These changes are detailed in the osaka file of the execution-apis repository.
Fusaka Activation
The Fusaka network upgrade is set to activate on the Ethereum mainnet at the commencement of epoch 411392, projected for December 3, 2025, at 21:49:11 UTC.
It was previously enabled on the Hoodi, Holesky, and Sepolia testnets.
Blob Parameter Only (BPO) Fork Timeline
Subsequent to the primary Fusaka activation, the network will execute Blob Parameter Only forks to progressively boost blob throughput. BPO1 will elevate the per-block blob aim to 10 and cap it at 15. BPO2 will further raise the target to 14 and the cap to 21.
Mainnet BPO Timeline
| BPO Fork | Epoch | Date & Time (UTC) | Unix Timestamp |
|---|---|---|---|
| BPO1 | 412672 | 2025-12-09 14:21:11 | 1765290071 |
| BPO2 | 419072 | 2026-01-07 01:01:11 | 1767747671 |
Client Updates
The subsequent client updates are appropriate for the Fusaka enhancement on the Ethereum mainnet.
Consensus Layer Updates
To operate a validator, both the Consensus Layer Beacon Node and Validator Client require updates.
Execution Layer Updates
Tools
FAQ
How do Ethereum network upgrades function?
Ethereum network upgrades necessitate explicit commitment from node operators within the network. Although client developers reach a consensus on which EIPs are included in an upgrade, they are not the final arbiters of its acceptance.
For the upgrade to be effective, validators and non-staking nodes must manually refresh their software to accommodate the protocol modifications being introduced.
Should they utilize an Ethereum client that isn’t updated to the current version (as listed above), it will disconnect from upgraded peers at the fork block, resulting in a split on the network. In this case, each group of network nodes will solely remain connected with those who possess the same (un)upgraded status.
While the majority of Ethereum enhancements are non-controversial and occurrences leading to forks have been infrequent, the ability for node operators to coordinate on whether to endorse an upgrade or not is a significant aspect of Ethereum’s governance.
For a more detailed insight into Ethereum’s governance process, see this discussion by Tim Beiko.
As an Ethereum mainnet user or ETH holder, is there any action required from me?
In summary, no.
If you are using an exchange, digital wallet, or hardware wallet, there is no action needed unless your exchange or wallet provider instructs you to perform additional tasks.
If you wish to observe the upgrade as it happens, you can participate in the online viewing event!
As a non-staking node operator, what steps should I take?
To ensure compatibility with the upgrade, refresh your node’s execution and consensus layer clients to the versions detailed in the table above.
As a staker, what actions do I need to perform?
To ensure compatibility with the upgrade, refresh your node’s execution and consensus layer clients to the versions specified in the table above. Verify that both your beacon node and validator client are up-to-date.
As a developer of applications or tools, what actions should I take?
Examine the EIPs incorporated in Fusaka to ascertain whether and how they influence your project. The introduction of PeerDAS, support for secp256r1, and the novel CLZ opcode present fascinating prospects for improved functionality and performance enhancements. Specifically, consult this article for additional details on blob submission modifications, and this write-up for extra information on alterations to the gas limit per transaction.
Why “Fusaka”?
Enhancements to the execution layer align with city names from Devcon, while improvements to the consensus layer utilize star names. “Fusaka” merges Fulu, a star located in the constellation of Cassiopeia, with Osaka, the venue for Devcon V.
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