Leanstral 1.5 is a free Apache-2.0 licensed model with 6 billion active parameters that significantly enhances performance in formal verification. It solves 587 out of 672 PutnamBench problems, achieves state-of-the-art results on FATE-H (87%) and FATE-X (34%), and uncovers five previously unknown bugs across 57 repositories.

The cost and tooling of formal verification have become widely accessible, allowing for increased use in software development. AI is reducing the barriers to formal verification by eliminating the costs associated with writing proofs, enabling the creation of software that guarantees mathematically correct business rules.

AI agents are increasingly effective at identifying vulnerabilities in large software systems. Anthropic chose not to release the Mythos model due to concerns over its potential to discover dangerous security flaws.