Ethereum core developers have officially finalized the Consensus Layer (CL) specification for the Fusaka upgrade. During the ACDC #159 call held on June 26, 2025, teams agreed that with the successful merging of four critical pull requests (PRs), the CL spec is now considered complete and stable enough to move forward.
Four Key PRs Locked In
The following four PRs were confirmed as the final changes to the CL spec:
- PR #4393 – Remove peer sampling in Fulu
- PR #4394 – Serve DataColumnSidecarsByRoot for finalized epochs
- PR #4406 – Add some clarifications around new ENR changes
- PR #4407 – Clarify NFD Disconnect Conditions
These updates reflect weeks of client discussions, testing, and refinements across implementations, and their successful integration signals a high degree of coordination and readiness across the ecosystem.
No Further CL Changes Expected Before Mainnet
With these PRs merged, developers now consider the Fusaka CL spec to be “frozen” moving into Devnet 3, expected to launch in approximately two weeks. Devnet 3 will act as the final test environment before mainnet activation. Crucially, there are no expected changes to the CL spec between Devnet 2 and Devnet 3, meaning that testing will focus on confirming the stability and correctness of already-agreed changes.
While the CL scope is frozen, developers clarified that this freeze does not yet apply to the Execution Layer (EL). A final discussion and freeze decision for EL specs will take place during the next All Core Devs call. This layered approach allows client teams to finalize testing on both sides independently, reducing last-minute bottlenecks.
Conclusion
Assuming no major regressions surface during Devnet 3, the frozen CL spec will proceed unchanged into the Fusaka mainnet release. Execution Layer changes are expected to be finalized within the next two weeks, after which coordinated testnet and mainnet client releases can begin.
If you find any issues in this blog or notice any missing information, please feel free to reach out at yash@etherworld.co for clarifications or updates.
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