FOCIL Breakout #39, August 4, 2026

[jihoonsong]

UTC Date & Time

August 04, 2026, 13:00 UTC

Agenda

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

Call Series

FOCIL Breakout

Autopilot Mode

• Use autopilot (recommended defaults for this call series)

🔧 Meeting Configuration

Duration

60 minutes

Occurrence Rate

bi-weekly

Use Custom Meeting Link (Optional)

• I will provide my own meeting link

Display Zoom Link in Calendar Invite (Optional)

• Display Zoom link in invite

YouTube Livestream Link (Optional)

• Create YouTube livestream link

[github-actions]

⚡ Protocol Call Resources:

✅ Zoom: Join Meeting
✅ Calendar: View | Add to Calendar
✅ Discourse: Discussion Topic

[jihoonsong]

FOCIL's engine API has merged and the spec keeps maturing.

Development Updates

• Lodestar has no update.

• Besu has no update.

• Teku is on glamsterdam-devnet-7.

• Nethermind is on glamsterdam-devnet-7.

Spec Updates

• The engine API PR has finally merged.

• consensus-specs#5508 renames the size limit constant from MAX_BYTES_PER_INCLUSION_LIST to MAX_TRANSACTIONS_BYTES_PER_INCLUSION_LIST. The old name was ambiguous and people had asked several times how the size is measured, so the PR addresses that ambiguity.

• consensus-specs#5507 improves the readability of the IL store functions. They were written in a Pythonic way that may not read well for non-Python developers, so the PR rewrites them with plain if statements and for loops.

• consensus-specs#5487 stores signed inclusion lists so the IL store can handle req/resp.

• consensus-specs#5513 modifies on_inclusion_list to perform basic checks on ILs coming from req/resp. It came out of NC's findings: ILs obtained via req/resp have to be fed to on_inclusion_list, which had no sanity checks of its own because it was solely relying on the p2p checks. The PR also replaces the inclusion_list_committee_root field inside the IL with dependent_root, so a node processing ILs from different branches can still tell whether the validator is an includer. This PR is open for review.

• consensus-specs#5512 folds IL and timeliness into the stored entry so the IL store has one dictionary instead of two. The reason is that the two are always coupled. This PR is open for review.

IL Store Key and Pruning

• Jihoon asked how CL clients would implement the IL store. The IL store does not need to retain ILs for more than two slots. Its key is the IL committee root, which can be derived from a slot and dependent root pair. He wondered whether changing the key to a slot and dependent root would align the spec with implementations better, since ILs accessed by slot first and dependent root second can be pruned by dropping everything below the current slot minus two.

• Nico said Lodestar does something like this for proposer preferences. Mehdi also shared in chat that Teku does something similar.

• Jihoon said the key used to be a slot and IL committee root, but the slot was removed for simplicity, again thanks to NC, because a collision between IL committees within an epoch is very unlikely. He will look at how other clients handle proposer preferences and open a PR for people to chime in.

[github-actions]

This meeting occurred more than 24 hours ago. Closing automatically.