Ethereum co-founder Vitalik Buterin says the network’s next major overhaul, an initiative researchers are calling “Lean Ethereum,” will take three to four years to complete and will rival the scope of the Merge, Ethereum’s 2022 transition away from proof-of-work.

In a post on X following a June meeting of Ethereum researchers in Berlin, Buterin described Lean Ethereum as the protocol’s “third major iteration.” He said the upgrade will touch nearly every core layer of the network, including how transactions are verified, the cryptography protecting the chain from future quantum computers, how quickly transactions reach finality, and how Ethereum stores its data.

This story is an excerpt from the Unchained Daily newsletter.

The plan builds on the “strawmap,” a draft long-term roadmap that Ethereum Foundation researcher Justin Drake introduced in February outlining seven upgrades through 2029. Buterin said this year’s Hegota fork will likely be Ethereum’s last “pre-Lean” hard fork, meaning nearly every subsequent change will be part of the broader rebuild.

Buterin called Lean Ethereum’s planned storage redesign “probably the single most disruptive part of the plan.” Ethereum today stores all of its state data, from token balances to smart contract code, in one expensive format. Under Lean Ethereum, that system would remain for complex applications like Uniswap, while a new, cheaper storage tier would be added for simpler tokens and NFTs. Migrating could cut transaction fees by more than tenfold, Buterin said.

Buterin also said quantum resistance has gone up in priority, saying work on quantum-safe blob designs has been underway for months. He also said privacy is now a “first-class goal” and “no longer an afterthought.” Longer term, he said Ethereum would need an alternative virtual machine, touting RISC-V and leanISA as the most likely contenders at present.

Buterin’s post has drawn a flurry of responses, including some pushback. Ethereum Foundation researcher Dankrad Feist slammed the three-to-four-year window as “very slow,” saying AI-assisted development could compress the work into roughly a year.

Buterin’s remarks on Ethereum’s roadmap arrives as the Ethereum Foundation works through a major reset. The foundation recently announced it has cut a fifth of its staff and 40% of its budget, with Buterin saying the changes would reduce annual spending from roughly 15% of treasury assets to about 5% by 2030.

Ether was most recently trading at $1,765, down over 40% year-to-date, amid a broader crypto market slump and questions around its tokenomics.

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