
Promptfoo: The Open-Source Red Teaming Tool That OpenAI Just Acquired for $86M
Promptfoo is the most widely adopted open-source AI red teaming tool, with 18K+ GitHub stars and use at 25% of Fortune 500 companies. OpenAI acquired it in March 2026 for approximately $86M. This post covers how Promptfoo’s automated red teaming works, the 50+ vulnerability types it catches, how it compares to alternatives like PyRIT and Garak, and what the acquisition signals about the future of AI agent security testing.








