# Dev Update Week 12 This week: - Completed and merged in PR defining the [SSZ serialization of `GetLightClientUpdatesByRange`](https://github.com/ConsenSys/teku/pull/6685) in teku - This endpoint has a custom octet encoding defined in [`beacon-apis`](https://github.com/ethereum/beacon-APIs/blob/master/apis/beacon/light_client/updates.yaml#L37) that requires a different handling than that of the default SSZ library in teku. The JSON and SSZ output types differ, requiring us to define a custom SSZ type - This was the last piece remaining to define the interface to LightClientUpdates, meaning we can begin the internal implementation - Implemented a set of [API changes from etan wrapping light client data in a `LightClientHeader` object](https://github.com/ConsenSys/teku/pull/6692) - Wrapping in a parent object makes the API more extensible to adding light client data in the future, e.g. the [`ExecutionPayloadHeader` in Capella](https://github.com/ethereum/consensus-specs/pull/3151) - Change was made to the Altair defintions, so we implemented it now to preserve compatibility - Synced up with teku mentor Paul Harris about the remainder of the light client work - Tracking in [issue](https://github.com/ConsenSys/teku/issues/4230#issuecomment-1357933576) - The big remaining piece to tackle before we have an e2e flow is the internals of `GetLightClientUpdatesByRange` - After that endpoint is implemented, we should be able to test an e2e light client sync using a tool like [`helios`](https://github.com/a16z/helios) synced against a teku node - [This article](https://mycelium.xyz/research/world-of-light-clients-ethereum) has a good example of this sync Next week we will mainly take on the [implementation of `GetLightClientUpdatesByRange`](https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/full-node.md#create_light_client_update). Time permitting, we can begin implementing the [gossip topic of `GetLightClientBootstrap`](https://github.com/ethereum/consensus-specs/blob/dev/specs/altair/light-client/p2p-interface.md#getlightclientbootstrap).