Lean 4's reported lack of a consistency proof and other hurdles for formal verification

A post sharing an article says Lean 4 has no consistency proof yet and describes “sea monsters” in its type theory as bugs that cannot be systematically squashed. The poster says checking whether Lean code runs safely triggers Codex and Claude cybersecurity guardrails, which they see as an opportunity for Mistral's Leanstral. They say the article's author considers these issues fixable, while the poster sees a difficult path to widespread formal verification.