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In a recent X post, Ethereum co-founder Vitalik Buterin expands on earlier thoughts about "Lean Ethereum," the multi-year plan to rebuild nearly every major part of the network.
Here, Buterin shares insights on upgrades to the consensus chain with respect to the "Lean" roadmap, which will entail adding strong validator privacy.
In a blog post titled "The Extremely Lean Chain," Buterin explained a pathway to make the Lean Ethereum consensus chain aggressively more "lean," add strong validator privacy, a ZK-unlink deposit from staking activity at withdrawal, and re-anonymize stakers daily.
Buterin explained how the Ethereum consensus chain, in the context of "Lean" upgrades, can be designed to aggressively minimize state requirements by pushing responsibility to stakers to manage and occasionally ZK-prove their state. These include three phases: Phase 1A entails eliding the pubkey tree.
Instead of storing a validator's pubkey (48 bytes) in the beacon chain state, the index is stored in the deposit tree (5 bytes). Phase 1B: ZK-proving balances will remove all logic related to reward and penalty processing from the beacon chain state transition function.
Phase 2: Privacy will see several major adjustments made to the beacon chain design. First, the "active validator registry" becomes a separate structure per day, as there is no concept of a long-term validator index.
Second, the pubkey registration is moved to the balance-proving step, with each validator providing a fresh pubkey each day. Third, a form of BFT consensus is assumed where validators send a message per round, and there are no "surround slashings."
Lean Ethereum: What Is It?
The Lean Ethereum idea was first unveiled in July 2025 as a vision for Ethereum's next 10 years.
According to Buterin, "Lean Ethereum" is not a single one-shot upgrade but a collection of improvements that will occur over the next three or four years. Buterin calls it the third major iteration of Ethereum, in the same way that the Merge was the second, as almost every major piece of the Ethereum protocol will be replaced.
In a recent update, Buterin shared a revised roadmap internally called a "strawmap" and gave further details on where the "Lean" effort is heading and what has moved up in priority.
The Ethereum co-founder noted that quantum safety has shifted up a lot in priority; privacy is also no longer an afterthought, having become a first-class goal.
Dan Burgin
U.Today Editorial Team
