Patronus AI Raises $50M to Stress-Test AI Agents

Patronus AI, founded by former Meta researchers, has raised $50 million in a Series B round led by Greenfield Partners to expand its AI agent testing platform. The startup builds simulated digital environments where AI agents are stress-tested using reinforcement learning, helping model makers identify shortcuts and failures before real-world deployment. Revenue has grown 15-fold over the past year, with nearly every frontier AI lab among its customers. Currently focused on software engineering and finance, Patronus plans to expand into harder-to-verify domains, with ambitions to run agents through simulations lasting days or even weeks.