Ethereum co-founder Vitalik Buterin publicly commended the Lean Ethereum team on September 6, 2025, for their significant progress this year toward Ethereum's long-term goals of scalability, decentralization, and resilience. "The Lean Ethereum team has been doing a truly amazing job kicking into gear this year, and delivering on all fronts to ensure Ethereum’s long-term scaling, decentralization, and resilience," Buterin stated, adding that he expects these efforts to align with short-term scaling milestones.
Lean Ethereum, or LeanVM, is a minimal zero-knowledge virtual machine (zkVM) proposal designed to be recursion-friendly for ZK-proofs, offering a stripped-down, more efficient version of Ethereum's computing engine. Buterin emphasized that LeanVM is optimized for XMSS aggregation and recursion, using a four-instruction ISA, multilinear STARKs, and logup lookups to reduce processing costs significantly compared to alternatives like Cairo. The development timeline includes finalizing specifications, with building set to begin in 2026, testing in 2027, and full completion targeted in 4-5 years, aiming to put Ethereum into "maintenance mode."
Benefits of LeanVM include reduced costs for large-scale computations, faster recursion for ZK-proofs, and maintained network decentralization and security. The next major upgrade, "Fusaka," is scheduled for November 2025 and focuses on enhancing efficiency for layer-2 rollups while improving base layer performance and accessibility.
Buterin also reflected on protocol design, stating, "Protocols are not a dirty get-it-out-there thing... Protocols are a work of art. They should look as such," underscoring the importance of elegance and simplicity over accumulated patches. This addresses ongoing criticisms of Ethereum's development pace, with proponents valuing thoroughness for 100% uptime over rushed solutions.
