FOCIL Breakout #40, August 18, 2026

Protocol Calls & happenings
1

Agenda

  • Development updates
  • Spec updates
  • Testing updates
  • and more

Meeting Time: Tuesday, August 18, 2026 at 13:00 UTC (60 minutes)

GitHub Issue

1 Like
2

Meeting Summary:

The meeting focused on updates and discussions related to the Fossil Breakout 40 and FOCIL development progress across different clients and the specification. Fabio reported on porting Besu to Glamsterdam DevNet 8 and implementing the latest spec changes. Nico shared that fossil changes were rebased on DevNet 8, and Mehdi confirmed TECO was on DevNet 8 with work on a DevNet 0 branch for FOCIL. Cristian provided an update on Lighthouse’s groundwork for FOCIL, noting that their implementation was not yet ready for DevNet 0. Jihoon discussed spec updates, including a merged PR for EL and ongoing discussions about changes to the CL spec, particularly around handling state and committee parameters in functions related to inclusion lists. The group debated naming conventions and the best way to pass necessary data to functions, with a preference for passing the committee rather than the full state. Barnabas inquired about the timeline for launching DevNet 0, and the group tentatively discussed targeting the end of August, depending on client readiness. The conversation ended with a plan to reconvene in two weeks.

Click to expand detailed summary

The team discussed development progress on various client implementations for DevNet 8. Fabio reported porting Besu to Glamsterdam DevNet 8 and implementing the latest spec changes. Nico confirmed that their fossil changes have been rebased on devnet-8, with CI tests looking good. Mehdi mentioned that Teku is working on a devnet-0 branch for FOCIL, while Marc indicated Nethermind needs to rebase on devnet-8. The discussion concluded with concerns about potential interop issues related to dependent root changes affecting containers.

The team discussed the potential release of Alpha 14, with Justin noting that ACDT client didn’t need it but FOCIL could benefit from it. Jihoon proposed merging dependent route changes PR and making an Alpha 14 release so CL clients could work on top of it, as ANSI indicated LoadStore is based on Offer 13. Cristian provided an update on Lighthouse’s FOCIL implementation, stating that while groundwork was laid, their implementation isn’t ready for Devnet 0 yet. Jihoon also mentioned a PR from Evan that fixed several issues and was merged, but noted that the execution spec needs to reflect the latest engine APIs like PayloadStatusV2, which he plans to discuss with Steel.

Jihoon discussed the FOCIL test on Hive, mentioning that some hype tests exist but may be missing edge cases. He also provided updates on two PRs related to sales, including one merged PR (5512) and another PR (5544) that requires feedback on function parameters. Jihoon asked for input on whether to store the committee in the store or pass it as a parameter instead of state.

The team discussed resolving state handling in a function, with Nico suggesting loading the state directly inside the function and Justin favoring passing the committee as a parameter instead of the full state. After considering various approaches including passing fork choice store or committee directly, they agreed to proceed with using committee as a parameter for the function. Jihoon planned to implement this change and create additional PRs for testing cases after the current release for fossil defense zero.

The team discussed launching W04 for sale, with Barnabas suggesting targeting the end of August, which aligns with the next Breakout Call on August 31st. The group agreed to aim for this tentative deadline, pending client readiness and successful testing. The conversation ended with the team committing to work toward the first DevNet for FOCIL, with a follow-up scheduled in two weeks.

Next Steps:

  • Fabio: Complete the implementation of the latest spec changes for get inclusion list for choice, targeting readiness for Clamsterdam DevNet 8 in one or two days.
  • Jihoon: Discuss with Steel tomorrow about updating the execution spec to reflect the latest engine APIs (PayloadStatusV2).
  • Jihoon: Check with the team about the FOCIL test on Hive and get back to Barnabas.
  • Jihoon: Update the PR 5544 to pass the committee as a parameter to the bitlist functions instead of the state, and then proceed with the release for fossil definite zero.
  • Jihoon: Make several PRs to add test cases after the PR 5544 is finalized.
  • All Clients: Prepare for the potential launch of DevNet 0 for FOCIL, tentatively targeting the next Breakout Call on August 31st.

Recording Access:

3

YouTube recording available: https://youtu.be/FqxsuTRP0YI

4

The first FOCIL devnet aims to launch on August 31st.

Development Updates

  • Besu is on glamsterdam-devnet-8 and is now implementing the latest spec changes.

  • Lodestar is on glamsterdam-devnet-8 and focil-devnet-0. It includes all features from the consensus-specs’ alpha.13 release, execution-apis, and the unmerged beacon-APIs.

  • Nethermind will be rebased onto glamsterdam-devnet-8 soon.

  • Teku is on glamsterdam-devnet-8 and is working on focil-devnet-0.

  • Lighthouse has laid the groundwork for FOCIL and is working on the IL store, gossip validation and IL publishing.

  • ethrex is on glamsterdam-devnet-8 and focil-devnet-0, and is giving finishing touches on some remaining work.

Spec Updates

EL Spec Updates

  • execution-specs#3370, opened by Ivan to fix several issues with test filling, has merged and is rebased on top of Amsterdam.

  • Jihoon will talk to STEEL about updating the execution spec to reflect the latest engine API changes such as PayloadStatusV2 and about running the Hive tests.

CL Spec Updates

  • consensus-specs#5512, opened by NC to group IL and timeliness together, had support from developers and has merged.

  • consensus-specs#5544 changes the IL store key from the IL committee root to a pair of slot and dependent root. The PR will soon be merged as people addressed the open questions during the call.

  • Jihoon will make the alpha.14 release for focil-devnet-0.

Devnet Timeline

  • We will target launching the first FOCIL devnet on August 31st and discuss its progress on the next breakout call, which is the day after.
1 Like