Vitalik Buterin outlines a multi-year rebuild of Ethereum's core protocol
Tech & Launches ·
Ethereum's Vitalik Buterin says the network's next major overhaul, described internally as "Lean Ethereum," will replace nearly every core protocol component and take three to four years, a scope he compares to the Merge.
According to The Block, Buterin frames the effort as rivaling the Merge, the upgrade that shifted Ethereum's consensus mechanism, both in scale and in the breadth of systems touched. Rather than a single discrete change, the plan involves swapping out foundational pieces of the protocol over the coming years, a timeline he pegs at three to four years to complete.
Corroborating accounts in the same cluster describe the effort in similar terms, with one characterizing it as comparable to the Merge in scope and another adding that the plan carries an increased focus on quantum safety, with a fork referred to as Hegota positioned as the last hard fork before the Lean transition begins. Together, these descriptions point to a staged rollout rather than a single upgrade event, with Hegota serving as a boundary marker separating the current protocol era from the Lean rebuild.
The announcement lands against a backdrop of ongoing stress in Ethereum's application layer, where WETH, the ERC-20 wrapped version of ether that underpins most DeFi activity, has been at the center of recent strain. Aave froze rsETH markets on its V3 and V4 deployments after a KelpDAO exploit drained roughly $290 million and left the protocol's WETH reserve carrying bad debt, with modeling from LlamaRisk estimating that bad debt at between $123 million and $230 million as WETH reserves hit full utilization. Aave has since taken steps to unwind the damage, restoring WETH borrowing power across six V3 markets and unfreezing WETH supply on its Ethereum Core V3 market, though loan-to-value ratios remain at zero and Layer 2 markets stay frozen.
That episode underscores the kind of composability risk that a base-layer rebuild like Lean Ethereum would need to account for, since WETH's function as a common denominator across lending markets, automated market makers, and NFT auctions means stress in one venue can ripple through reserves elsewhere. Separately, Sei has said it will disable inbound IBC transfers under a planned EVM-only transition, prompting warnings for WETH holders on that chain to bridge out ahead of the change.
What remains unspecified is which individual protocol components are slated for replacement under Lean Ethereum, how the three-to-four-year timeline breaks into discrete milestones, and how Hegota's rollout as the final pre-Lean hard fork will be sequenced against ongoing DeFi recovery efforts tied to the Kelp exploit.