Lean now ships a proof-checking kernel that Claude wrote and proved consistent
Lean v4.35.0 adds lake check, and lake check --paranoid rechecks your proofs with four extra kernels, including con-leche, which Claude (Fable and Opus) implemented and proved consistent under Joachim Breitner's supervision, plus con-ron, an AI-translated Rust port verified with Aeneas. Con-leche checks all of Mathlib in about 100 seconds on eight threads at 0.69x the official kernel's instruction count (GitHub).
