FOCIL Breakout #23, November 4, 2025

[jihoonsong]

UTC Date & Time

November 04, 2025, 14:00 UTC

Agenda

• Development updates
• FOCIL in Glamsterdam

Call Series

FOCIL Breakout

🔧 Meeting Configuration

Duration

60 minutes

Occurrence Rate

bi-weekly

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⚡ Protocol Call Resources:

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[akashkshirsagar31]

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[jihoonsong]

To FOCIL or not to FOCIL, that’s the question.

FOCIL in Glamsterdam

FOCIL landscape

• Teku is fine with SFI’ing FOCIL. As soon as Teku has a working ePBS implementation, they could further voice this opinion.
• Lodestar published a blog post when choosing the headliner for Glamsterdam and supported both ePBS and FOCIL. Since there are many proposed EIPs for Glamsterdam, Lodestar needs to review them to see if their opinion has changed. It’s not expected to have changed much though.
• Nethermind supports FOCIL for Glamsterdam.
• Most opinions at the EF are to ship FOCIL for the H* fork. One of the reasons is to ship forks on a regular cadence, which is not a technical one. We should decide based on technical reasons, not political ones.
• The community has strongly signaled preferences for FOCIL inclusion. Some people are against it because it touches both layers, delays the fork, etc. However, the same argument applies to the H* fork as well. The later we try to ship it, the more difficult it will become.

FOCIL and gas repricings

• Gas repricings and FOCIL are not very comparable. They provide very different things and are difficult in different ways.
• Gas repricings consist of many EIPs, and there are many different ways to group them. As these groups interact with each other in hard-to-reason-about manners, they create scheduling and testing burdens. Gas repricings were advocated for Glamsterdam as it is a scaling hard fork, but scaling has had developers’ attention for the past three years.
• Gas repricings and ePBS are orthogonal. In other words, having gas repricings before or after ePBS won’t matter much.
• Gas repricings and BALs have overlapping testing efforts that could add some complexity. For example, in BALs construction, creating a list of state accesses is intertwined with gas repricings.

The added complexity by FOCIL

• The added complexity by FOCIL should not be underestimated. Even the ePBS spec is not finalized yet, and both ePBS and FOCIL set deadlines within a slot, which should be run in testnets to make sure that they work in a decentralized manner.

People have been working on FOCIL and will be

• Client teams are already working on FOCIL and will continue working on it regardless of delay. There were more people implementing FOCIL than ePBS just a few weeks ago. FOCIL will be implemented on top of ePBS anyway.
• Originally, a working implementation was required to be SFI’d. FOCIL meets this requirement more than any other EIP proposed for Glamsterdam.

Implementation Updates

• A PR rebasing FOCIL onto Gloas has re-opened.
• Lodestar has no update. Mostly focused on ePBS.
• Teku has no update. Mostly focused on ePBS.
• Reth has worked on the spec tests. Currently, 9 test cases are passing.
• Erigon has just finished the initial implementation and will work on interop with other EL clients.

Metrics

• Lodestar has already implemented the beacon metrics, and both the execution metrics and Reth’s implementation are nearly complete.

Links

• A PR rebasing FOCIL onto Gloas