FOCIL Breakout #21, October 7, 2025

[jihoonsong]

UTC Date & Time

October 7, 2025, 14:00 UTC

Agenda

• FOCIL on native rollups
• Development updates

Call Series

FOCIL Breakout

🔧 Meeting Configuration

Duration

60 minutes

Occurrence Rate

bi-weekly

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[akashkshirsagar31]

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[jihoonsong]

FOCIL opens the door for rollups to easily implement forced transactions.

Research

FOCIL and Native Rollups

• In a world where L1 full nodes can perform the state transition function statelessly, this capability can be used to verify rollup states. With the EXECUTE precompile exposing this functionality, a native rollup could leverage Ethereum’s execution client code as-is for its own state transitions, without the complexity coming from custom proof systems and governance.

• Rollups implement forced transactions so users can withdraw even when a centralized sequencer crashes or censors them. Forced transactions are hard to implement though; they are usually implemented either by defining new transaction types or by operating as a based rollup for a certain time window, which may degrade UX.

• Once we have FOCIL in L1, native rollups can use it to implement forced transactions. FOCIL introduces inclusion_list_transactions parameter to state_transition in the execution spec. Native rollups can pass forced transactions to this parameter during its state transitions. In other words, rollup users can submit their forced transactions to a rollup smart contract in L1 and those queued forced transactions are passed as IL transactions during state transitions of native rollups.

• A non-native rollup can also adopt this approach if they want, which eases the burden of implementing forced transactions.

Q: FOCIL allows omitting IL transactions, if it's invalid or there is not enough gas left. What happens when a forced transaction via FOCIL mechanism is validly omitted?
A: The user would need to resubmit a forced transaction. It's an open problem but we're quite optimistic that a good solution can be found.

Implementation Updates

• Reth has fixed a bug that caused unsatisfied IL blocks due to an encoding misconfiguration and has been implementing on execution metrics.
• Lodestar has adopted basis points configs so now it can run on 6s slots for faster testing, and has fixed a bug that passed empty ILs to forkchoiceUpdated calls.

Testing

• Jihoon has been working on adding unit tests for InclusionListStore.

FOCIL Metrics

• Katya has shared FOCIL execution metrics PR.
• Pelle has been implementing the FOCIL execution metrics in Reth.

Links

• The Native Rollups Book
• FOCIL on Native Rollups
• FOCIL execution metrics PR