Vitalik Buterin Proposes “Extremely Lean Chain” to Reduce Ethereum Beacon Chain Validator State

Vitalik Buterin has released a new proposal titled “The Extremely Lean Chain,” outlining a plan to significantly reduce the amount of state stored per validator on Ethereum’s current Beacon Chain. According to Foresight News, the proposal’s core idea is to streamline validator-stored data—such as public keys, withdrawal credentials, and activation or exit epochs—down to 6 bytes, retaining only 1 byte for effective balance and 5 bytes for a deposit tree index. Under the proposal, validators would be responsible for tracking their own deposit Merkle proofs. Effective balances and participation records would be updated asynchronously using daily STARK proofs, rather than being processed on-chain in real time each epoch. The plan is described as a multi-stage rollout. The first stage would remove on-chain public key storage, switch to using a deposit tree index, and rely on daily STARK proofs for balance updates. A later stage would introduce a daily public key refresh mechanism intended to provide strong anonymization of validator identities and to naturally support Single Secret Leader Election (SSLE). The proposal argues the design is feasible in the context of “Lean” upgrades such as single-slot finality (SSF) and recursive STARKs. It aims to reduce consensus-layer state overhead and computational load, support scaling the validator set to the millions, and provide stronger privacy protections in more advanced versions.