Fusaka follows Pectra upgradeRepresenting a major step in the major step in the Ethereum scaling roadmap by introducing peerdas and key improvements that improve Blob flow, L1 performance and user experience.
This message announces the Testnet activation calendar for the first three testnets, starting with Holesky on Slot 5,283,840 (October 1, 2025, 08:48:00 UTC). See the activation table Below for the complete chronology of Sepolia and Hooddi. Fusaka also introduces the Blob parameter only (BPO) to safely develop the Blob flow after the activation of Peerdas. These are minimum and configurating upgrades that adjust the Blob Target / Max and Fee Update fraction.
The versions of the Fusaka Testnet client are listed below. Once the three testnets have been successfully upgraded, a Mainnet activation location will be chosen.
Fusaka overview
Peerdas (data availability sampling), which allows a significant scaling of data availability. The upgrade also includes optimizations through the execution and consensus layers to evolve performance L1 and improve the user experience. This message describes major improvements. For a more complete overview, see Ethereum.org guide on upgrade.
Blob on a scale: Peerdas
EIP-7594 Presented Peerdas, a new networking protocol that allows nodes to check the availability of Blob data via sampling rather than downloading full blobs. This is a key step towards the Blob flow scaling while maintaining Ethereum’s safety and decentralization.
Since the Dencun upgradeThe use of layer 2 has increased considerably, often reaching the limit of 9 current blob per block. Peerdas allows Ethereum to increase this limit without compromising security. It does so using erasure coding to allow nodes to sample parts of Blob data while guaranteeing cryptographically that complete data is available on the network. This creates a path to higher blob targets described in Ethereum Roadmap on a scale.
This sampling approach directly benefits the rollers of layer 2 by supporting the higher blob flow without proportionally increasing the bandwidth requirements for individual nodes. As the Blob capacity evolves beyond current limits, L2 transaction fees can decrease more while maintaining the security of data availability on Ethereum L1.
To securely crawl the blob flow after Peerdas is activated, Ethereum uses the Blob-Parameter forks (BPO). Fusaka includes two bpo settings planned to Holesky from October 7, 2025, with similar hours for other fabrics. These bpo will increase the Blob target per block and maximum of 6 and 9 respectively to 10 and 15 in bpo1 and 14 and 21 in BPO2.
L1 scale
MODXP OPTIMIZATION
EIP-7883 And EIP-7823 Work together to optimize ModexP precompilation. The EIP-7883 increases gas costs to more precisely reflect the calculation complexity, including the increase in minimum gas costs and the triple of general costs calculations. EIP-7823 defines the upper limits for Modexp operations. Together, these changes ensure that cryptographic operations with a high intensity of resources are properly at a price and support the potential potential increases in the gas limit for blocks of blocks.
Cap
EIP-7825 Implement a transaction gas limit ceiling at the 16,777 216 gas protocol, preventing individual transactions from consuming an excessive block of block and protecting against back attacks. This sets the basics of parallel transactions in the EVM.
Optimization of the network protocol
EIP-7642 ETH / 69 presentation, which removes pre-fusion fields and the flowering of the reception of the networking protocol. This cleaning reduces synchronization bandwidth requirements, adds an explicit historical service window for nodes to announce and simplifies the code base by removing the inherited components which are no longer necessary after merger.
Increase in the gas limit
EIP-7935 Increases the default gas limit from Ethereum to 60 mm, reflecting the gas limit that the main developers believe that Ethereum L1 can evolve in complete safety. This increase allows greater executive capacity L1 and has been carefully tested between different combinations of customers to ensure the stability and safety of the network.
Beyond these performance improvements, Fusaka also improves the experience of the user and developers with several targeted upgrades.
Improve UX
SECP256R1 Pre -pluged
EIP-7951 Add the native management of the Elliptical Courp256r1 curve via a new precompiled contract. This allows direct integration with modern secure equipment such as Apple Secure Enclave, Android Keystore and Fido2 / Webauthn devices, reducing friction for the adoption of traditional blockchain thanks to familiar authentication flows.
Count the manager of Zéros Opcode
EIP-7939 Presentation of the OPCODE CLZ (COUNT LEADING ZEROS), providing a native and gas efficient means of carrying out fundamental Bit Bit count operations. This addition supports mathematical operations, compression algorithms and post-qualitum signature schemes while reducing Prouvance ZK costs.
Fusaka specifications
The complete list of changes introduced in Fusaka can be found in EIP-7607. Basic EIPs include:
Additional support EIPS:
Complete specifications for consensus execution and layer changes are available in the following versions:
Fusaka also introduces modifications to the engine API used for communication between consensus and execution layers. These are specified in the Dosaka File of the execution-apis.
Fusaka security
Security researchers can participate in Fusaka audit competition To help identify potential problems before the deployment of the Mainnet.
Fusaka activation
Upgrading the Fusaka network will activate on Holesky, Sepolia and Hoodi tests as follows:
| Network | Slot | UTC time | TIMETAMP UNIX |
|---|---|---|---|
| Truant | 5,283,840 | 2025-10-01 08:48:00 | 1759308480 |
| Sepolia | 8,724,480 | 2025-10-14 07:36:00 | 1760427360 |
| Hood | 1 622 016 | 2025-10-28 18:53:12 | 1761677592 |
As previously announcedNote that Fusaka will be the last upgrade of the network deployed on Holesky. It will be closed shortly after upgrading the upgrade.
Blob parameter only (bpo) fork schedule
After the main activation of Fusaka, the network will implement the Blob parameters only to gradually increase the Blob flow. BPO1 will increase the Blob target per block and maximum to 10 and 15 respectively. BPO2 will further increase the objective to 14 and maximum to 21.
Bpo Holesky schedule
| Bpo | Era | Date and time (UTC) | TIMETAMP UNIX |
|---|---|---|---|
| Bpo1 | 166,400 | 2025-10-07 01:20:00 | 1759800000 |
| Bpo2 | 167 936 | 2025-10-13 21:10:24 | 1760389824 |
Sepolia bpo schedule
| Bpo | Era | Date and time (UTC) | TIMETAMP UNIX |
|---|---|---|---|
| Bpo1 | 274.176 | 2025-10-21 03:26:24 | 1761017184 |
| Bpo2 | 275 712 | 2025-10-27 23:16:48 | 1761607008 |
HOODI BPO TIME
| Bpo | Era | Date and time (UTC) | TIMETAMP UNIX |
|---|---|---|---|
| Bpo1 | 52,480 | 2025-11-05 18:02:00 | 1762365720 |
| Bpo2 | 54 016 | 2025-11-12 13:52:24 | 1762955544 |
Sorts of customers
The versions of the following customers are suitable for the fusaka upgrade on The three time tests. Other versions will activate the support on Mainnet. Once these are published, another ad will be made on this blog.
Court consensus of the Holesky, Sepolia & Hoodi versions
During the execution of a validator, the consensus layer tag and the validator’s client must be updated.
Note: Lodestar users must always use the last RC version listed on their Version page.
Implementation layer of the Holesky, Sepolia & Hoodi versions
Faq
How do Ethereum network upgrade?
Upgrades of the Ethereum network require an explicit opt-in of node operators on the network. While customer developers reach a consensus on what EIPs are included in an upgrade, they are not the ultimate decision -makers of its adoption.
For the upgrade to be put online, validators and non-stake nodes must manually update their software to take charge of the changes in the introduced protocol.
If they use an Ethereum customer which is not updated to the latest version (listed above), on the Fork block, it will disconnect improved peers, leading to a fork on the network. In this scenario, each subset of network nodes will only remain connected with those who share their status (no) upgraded.
Although most Ethereum upgrades are not thwarted and cases leading to forks have been rare, the option for node operators to coordinate on the management of an upgrade or not is a key characteristic of Ethereum governance.
For a more exhaustive overview of the Ethereum governance process, see This speech by Tim Beiko.
As an Ethereum user or carrier, is there anything I have to do?
In short, no.
This announcement only concerns Ethereum time tests. Another announcement will be made for the activation of Fusaka on the Mainnet Ethereum, but even then, the users of Mainnet Ethereum and the holders of ETH should not have to act.
As a Non-Stake Testnet node operator, what should I do?
To be compatible with upgrading one of these tests, update customers of the execution layer and the consensus layer of your node to the versions listed in the table above.
As Staker Testnet, what should I do?
To be compatible with upgrading one of these tests, update customers of the execution layer and the consensus layer of your node to the versions listed in the table above. Make sure your tag and validator client are updated.
As a non-test knot or stiker, what should I do?
Nothing for the moment. Other announcements will be made for the activation of Fusaka on Mainnet.
As a developer of applications or tools, what should I do?
Review the EIPs included in Fusaka to determine if and how they affect your project. The introduction of Peerdas, the SECP256R1 support and the new OPCODE CLZ offer exciting opportunities for improved features and performance optimizations.
Why “Fusaka”?
The upgrades to the execution layer follow the names of the city of Devcon, and those of the Consensus layer use the names of stars. “Fusaka” is the combination of Fulu, a star in the constellation of Cassiopeia and Osaka, the location of Devcon V.
