# Builder API: EIP-4844 and Capella changes Changes will be required on both the beacon API and builder API. - Beacon API: [proposed changes](https://github.com/ethereum/beacon-APIs/pull/271) - Builder API: [proposed changes](https://github.com/ethereum/builder-specs/pull/58) ![](https://i.imgur.com/8B3KtKc.png) ### Open questions - Does make sense to add a new `submitBlindedBlockV2` endpoint, that includes `blobs_sidecar` in the response (`SignedBeaconBlockAndBlobsSidecar`). - Chris (@metachris) > from the discussions i've had with EF/CL peers, there seems to be a preference for reusing the existing API call, rather than introducing a new V2 one. - Enrico (@tbenr) > It makes sense to me to have a V2 returning the entire `SignedBeaconBlockAndBlobsSidecar`. It reduces complexity and the overhead is minimal since `ExecutionPayload` and `BlobsSidecar` are the biggest objects we need to get anyway. - Alex (@ralexstokes) > I think we should mirror the existing APIs and it seems like we can get away with just using the V1 ### Action items - Implement builder spec changes left to be done on lighthouse. - Generate test vectors. - Share test vectors with falshbots so they can test early and share potential issues with CL teams. --- If you have any feedback you can reach [@jimmygchen](https://github.com/jimmygchen) or [@0xGabi](https://github.com/0xGabi).