How Lean 4 appears in this material In the captured material for Beyond LLMs: New AI Architectures and Capabilities, Lean 4 shows up as the concrete tool side of the chapter's central argument: some problems — verifiable correctness, exact determinism, spatial reasoning — sit outside what LLMs can guarantee, and a different stack of architectures and tooling exists to address them [^c10ebe98-0850-5dfe-8c53-b988c268c606@0]. The conversation frames Lean 4 as the kind of formal environment where claims can be checked by a machine rather than trusted, which is exactly the property the episode's guest company bets on when pursuing verifiable, inspectable AI [^c10ebe98-0850-5dfe-8c53-b988c268c606@0].