Lean v4.35.0 ships verified kernels — one written and proven consistent by Claude
geoffreyirving · x · 2026-10-16
Leonardo de Moura announced Lean v4.35.0 now ships with verified kernels, responding to AI agents repeatedly finding kernel bugs. New lake check rechecks projects in a sandbox via leanchecker, and --paranoid runs all bundled kernels (nanoda, lean4lean, con-leche, con-ron) including a hardened-allocator official-kernel variant. Highlight: con-leche, the first Lean kernel written in Lean and proven consistent — implemented and proven by Claude (Fable and Opus) under Joachim Breitner's supervision — eliminating kernel implementation bugs at 0.69x instruction count, checking all of Mathlib in 100s on 8 threads. Geoffrey Irving predicts --paranoid will become the default as standard paths get verified.
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