DeepMind's AlphaProof Code has achieved a breakthrough in verifying complex software at depth by writing three million lines of proofs in Lean, a formal verification system. This milestone demonstrates the potential of large language models in formal verification, a crucial process in ensuring the correctness and reliability of software, particularly in safety-critical systems. The successful application of AlphaProof Code to Signal's core encryption verifies the correctness of its cryptographic protocols, providing an additional layer of security for users. This advancement matters to people building and operating AI agents because it showcases the efficiency and scalability of large language models in formal verification, enabling the creation of more secure and trustworthy software.