Ethereum co-founder Vitalik Buterin has a fresh set of takeaways on "Lean Ethereum," the multi-year plan to rebuild nearly every major part of the network, following research meetings.

He termed it the third major iteration of Ethereum after the 2022 Merge that switched the network from mining to a stake-based system, with almost every major piece of the protocol set to be replaced over three to four years while keeping disruption to existing applications low.

The ambitious Lean Ethereum idea was first laid out in July 2025 as a technical framework for the network's next decade, built around superior cryptography compared with most methods currently in use.

Buterin's update – accompanied by a revised roadmap internally called a strawmap – gave further details on where the effort is heading and what has moved up in priority.

Quantum safety has moved sharply up the list of priorities. Reigning theories state a powerful enough quantum computer could eventually break the cryptography that secures blockchains, a risk the industry increasingly treats as worth preparing for even if it remains years away.

But Ethereum now treats replacing every quantum-vulnerable part with a quantum-safe alternative as urgent, Buterin said, including a redesign of the cheap data storage that rollups, the layer-2 networks built on top of Ethereum, depend on.

Privacy has been raised to what Buterin called a 'first-class goal' rather than an afterthought. The plan calls for designing core network components so that private, intermediary-free transactions can pass through them by default.

The way the network checks itself is also changing. Instead of every node re-running every transaction, Ethereum plans to rely on recursive STARKs. This cryptographic proof method allows a node to verify a compact proof that the work was done correctly, rather than repeating it. That shift is meant to make the network faster and lighter to run.

As such, the change Buterin flagged as most disruptive is to what Ethereum calls state. State is a blockchain's current memory, the complete snapshot of everything that exists on a network at a specific point in time.

Think of it as the running record of every account balance and all the data those contracts hold (such as who owns which NFT, how much is in a lending pool, every token ledger), as of the latest block.

Every transaction is essentially an edit to that record – send ETH and a user's balance goes down, someone else's goes up, and the state updates to reflect it.

Each node running Ethereum must store the entire state and keep it up to date to validate transactions. As more people use the network, that record grows, and the bigger it gets, the more expensive and demanding it becomes to run a node, which pushes toward fewer, bigger operators and away from the decentralization that's the point.

The Lean Ethereum plan proposes keeping the current flexible "dynamic" state but only allowing it to grow moderately, and adding new, more restrictive types of state that are far cheaper to scale. Doing so will allow the network to hold vastly more (from the current 2 terabytes old-style to over 100 terabytes in 2030) without every node having to carry all of it the old way.

Meanwhile, Ethereum may also outgrow its core engine. Buterin said the network will need a virtual machine beyond the EVM, the software that runs its smart contracts, with the open chip architecture RISC-V among the leading candidates.

His own preference is for the EVM to become a higher-level convenience while the protocol itself runs on the simpler base, though he cautioned that this is still far off.

Running through the plan is a steady lift in capacity, with the network's transaction ceiling rising, data limits growing and block times shrinking repeatedly over roughly five years.

Buterin pointed to a large capacity increase with the upcoming Glamsterdam upgrade, and said the fork after it, Hegotá, is likely Ethereum's last before the Lean era fully begins.

The roadmap is a long-horizon bet, most of it years from shipping, and it commits Ethereum to quantum defense and privacy well before much of the industry treats either as pressing.

The thoughts land as ether rose more than 12% on the week to about $1,777, per CoinDesk data, among the strongest of the majors.