# Week 14 & 15 EPF Update

## Kurtosis Interop Testing

I spent the last two weeks doing more in-depth interop testing with Lodestar, Geth, and Lighthouse.

### Lighthouse
I opened a PR to fix the IL cache indexing and serialization issues (UncleBill said he'll take a look): https://github.com/eserilev/lighthouse/pull/22

Upon further inspection, Lighthouse currently supports neither `engine_updatePayloadWithInclusionListV1` nor `engine_forkchoiceUpdatedV4`. This explains the missed payloads produced with Reth during testing. These methods will hopefully be added in the future as Fusaka’s work ramps down.

### Lodestar
I helped Nico fix the same issue Lighthouse suffered from. There is still an issue with `engine_forkchoiceUpdatedV4` not passing ILs to Reth, which results in about 1 out of 20 blocks failing to include all IL transactions.

{
  "id": 2261,
  "jsonrpc": "2.0",
  "method": "engine_forkchoiceUpdatedV4",
  "params": [
    {
      "finalizedBlockHash": "0xcb024775bc3b2e436ca02710ea4265e352aa49ec1be58c741b290b9e2b0f78e2",
      "headBlockHash": "0x002633140292252d4c73e68eb62ff1ef3b2af38d7f13d83c29f8fd6cb24e89b2",
      "safeBlockHash": "0x0df0880207780e816873715e1b16740cf8f3ab03a4f27b2d8cd6d2f642965745"
    },
    {
      "inclusionListTransactions": [], // ILs are failing to be passed in engine_forkchoiceUpdatedV4
      "parentBeaconBlockRoot": "0x9c5cd903e4e528acd60f0c581a92fa38faaaf10ad21bcfa42d2f52dfc24502a1",
      "prevRandao": "0xd1a7575fd282550548ba52678a4133bcd316caf33e4a7fe72c744d19afef3466",
      "suggestedFeeRecipient": "0x8943545177806ed17b9f23f0a21ee5948ecaa776",
      "timestamp": "0x68db258e",
      "withdrawals": []
    }
  ]
}

## Conclusion

I’ve been making good progress in helping other clients prepare for interop testing after the Fulu rebase and Engine API spec changes. We are close to having the first fully spec’d Reth interop test. All previous runs, while successful, lacked a complete EL.

## Next Steps

- Work with Nico to fix engine_forkchoiceUpdatedV4 issues in Lodestar
- Get Lighthouse changes merged
- Implement Katya’s metric logging to help with further FOCIL devnets: https://github.com/ethereum/execution-metrics/pull/4