[Gloas] Light Client API support timeline for ePBS (EIP-7732)?

[yoshidan]

Question

We are planning to use the Light Client API (/eth/v1/beacon/light_client/finality_update) on Gloas/ePBS devnets and testnets.

Currently, the API returns stale pre-Gloas data after the fork transition and does not update.

We would like to know:

1. Is there a plan to support Light Client API for Gloas/ePBS?
2. If so, what is the expected timeline? (e.g., before Sepolia fork, before mainnet, etc.)

We are aware that there is no Light Client spec under https://github.com/ethereum/consensus-specs/tree/master/specs/gloas yet.

Context

We observed the following in epbs-devnet-1:

• persistPostBlockImportData has an early return for Gloas blocks with TODO comment:

  // TODO GLOAS: Light-client updates for Gloas are pending spec work.
  if (ForkSeq[fork] >= ForkSeq.gloas) {
    return;
  }

• After Gloas epoch, finality_update returns the last pre-Gloas values indefinitely
• Gloas removes latestExecutionPayloadHeader from BeaconState, which affects LightClientHeader structure

[matthewkeil]

We just started to talk about this yesterday. There is currently no spec yet as you mentioned. We will see what we can do to push that spec forward but cannot give a timeline as there is still a lot of Gloas stuff left to do.

cc @nflaig @ensi321

[ensi321]

We probably won't have a gloas light client spec for at least 1-2 months.

We had this conversation a while ago: https://discord.com/channels/595666850260713488/874767108809031740/1442323269041520733
So we will need to get epbs to stabilized first (probably devnet 2 or 3), then we have a decision on the remaining CFI'ed EIPs for gloas in ACDC, then we will see a gloas light client spec.