FOCIL Breakout #42, September 15, 2026

Protocol Calls & happenings
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Agenda

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

Meeting Time: Tuesday, September 15, 2026 at 13:00 UTC (60 minutes)

GitHub Issue

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Meeting Summary:

The meeting focused on updates for Fossil Breakout 42, covering DevNet progress and the interaction between FOCIL and FRAMES. NC reported on issues with Teku and Lothar clients due to RPC limits, with a PR submitted to increase the limit from 4MB to 10MB, while other clients like Nethermind, Bessel, and Lighthouse provided updates on their readiness and ongoing work. The main discussion centered on the interaction between FOCIL and FRAMES, where Tomas presented EIP 8369 outlining VOPS profiles for FOCIL eligibility and discussed the need to define state boundaries and validation mechanics for frame transactions. The team discussed whether to prioritize Fossil and FRAMES DevNet or continue with CL/EL only DevNets, with preference expressed for moving quickly on the FOCIL and FRAMES interaction given their importance as headline features. Key technical questions were raised about BuilderIndex implementation and witness objects for transaction omission validation, with agreement to follow up on implementation details in future breakout sessions.

Click to expand detailed summary

Justin Traglia announced he would be taking Wednesday through Friday off and asked Jihoon to cover in his absence. The team then began their Fossil Breakout 42 meeting focused on DevNet updates and the interaction between FOCIL and FRAINS. NC reported that Teku was experiencing issues with batched gos sip objects exceeding incoming limits, causing Lothar to drop Teku as a peer, and shared a PR to increase the limits from 4MB to 10MB. Iván mentioned that while his team had no new updates, there were still some PRs pending on the execution specs repo to fix failing test cases in Hive.

The team provided updates on their readiness for DevNet-0 launch. Nethermind and Bessel reported they are ready, while Lighthouse is making progress but not yet ready. Fabio discovered failing IP tests that appear to be related to recent Glamsterdam changes, and Pellekrab mentioned fixing some failing tests but noted that EIP 7610 may no longer be included. Jihoon emphasized that shipping to Amsterdam remains the top priority, and the team is working on developing a testing framework for post-conditions to address the non-deterministic nature of collateralized testing.

The team discussed the blocker for DevNet Zero launch, which was related to issues between CL clients including Lothar and Teku making their own chains. Jihoon explained that they need at least two CL clients working before launch, and with three EL clients ready, they are close to meeting the requirements. The team confirmed they are not waiting for all clients to be ready but need to reach the minimum 2x2 configuration with two working CL clients.

Soispoke presented EIP 8369, which defines the interaction between FOCIL and FRAMES transactions, focusing on VUPS profiles and the boundaries of state that nodes should maintain. The discussion highlighted a trade-off between including more states in VUPS to benefit more transactions from FOCIL guarantees versus maintaining smaller VUPS for better decentralization. Soispoke also introduced the BuilderIndex mechanism for checking FOCIL validity in frame transactions and requested feedback on both the state boundary definitions and the technical implementation details.

The team discussed validation limits in VOPS, with soispoke explaining that limits would need to be defined along two dimensions: state requirements and compute capacity. Soispoke indicated that the minimal validation requirements would likely include signature validity, nonce placement, and root recency checks, potentially with 2-4 additional storage slots. Jihoon provided an overview of current Fossil validity requirements, which include checking transaction completion, intrinsic validity, nonce and balance requirements, and gas availability. The team also discussed future DevNet plans, with Jihoon noting uncertainty about whether to implement CL and EL only DevNets before Hegora DevNet or vice versa, and suggesting that learning from AetherX’s frame implementation could be beneficial.

The team discussed prioritizing the integration between FOCIL and FRAMES, with soispoke advocating for an early and fast approach since these features are considered essential for the fork’s shipment. Marc reported that EtherX and Nethermind are collaborating on FRAMES DevNet, though interop testing with FOCIL and frames is still pending. The group identified the need for a common specification document, with Iván mentioning he is close to submitting a PR with specs, which would help align the team on the mechanism and determine where the changes should be implemented.

The team discussed the implementation of transaction omission validation and witness requirements for builders. They identified the need to clarify how the witness data should be stored and propagated, whether in P2P objects or envelope, and agreed to follow up on the implementation details in the next breakout room. The group also outlined upcoming work including spec PRs for EL and CL, and MaxVerifyGas benchmarks, with Iván committing to have the PR ready by the end of the week or early next week.

The team discussed maintaining a two-track approach for FOCIL DevNet Zero development while also exploring interactions with fossil and frame specs. Soispoke suggested focusing on identifying specific use cases that would benefit from FOCIL’s inclusion guarantees, particularly highlighting privacy transactions as a key example. The group agreed to discuss stack changes, benchmarks, and potential use cases in the next breakout call, with Marc committing to share links to his work for others to review.

Next Steps:

  • NC: Share the link to the PR that increases the incoming RPC limits from 4MB to 10MB.
  • Iván: Share the links to the PRs on the execution specs repo that fix failing test cases in Hive.
  • Fabio: Share the name of the failing IP test for Rizzo in the Discord channel.
  • Pellekrab: Check if the failing tests for EIP 7610 need to be removed, as they are not meant to be included anymore.
  • Jihoon: Collaborate with others on GATT enclosure-laced testing and share updates.
  • NC: Finalize the fix for the issue between Teku and Lohstar (CL clients) to enable the launch of DevNet Zero.
  • soispoke: Share insights and potentially invite EtherX or Nethermind to discuss their progress on Fossil and Frames DevNet.
  • Marc: Try out interop testing with FOCIL and Frames enabled.
  • soispoke: Follow up on how the BuilderIndex/witness for transaction omission is being handled in the prototype implementations.
  • Jihoon: Discuss spec changes and benchmarks for Max Verify Gas in the next breakout call.
  • Iván: Aim to have the PR for the failing test cases ready before the next breakout.
  • Marc: Share links to the benchmarking work being done on Max Verify Gas.
  • All participants: Think about use cases that should absolutely benefit from FOCIL and discuss them in the next breakout.

Recording Access:

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YouTube recording available: https://youtu.be/skrZKWT5fNg