OpenAI acquires AI security startup Promptfoo

OpenAI announced Monday that it has acquired Promptfoo, an artificial intelligence security startup founded in 2024. The acquisition is focused on protecting large language models (LLMs) from online adversaries. Once the transaction closes, OpenAI plans to integrate Promptfoo’s technology directly into OpenAI Frontier, which serves as OpenAI’s enterprise platform for AI agents.

The rise of independent AI agents that perform digital tasks has generated significant industry excitement regarding potential productivity gains. However, these automated systems also introduce severe security vulnerabilities. The deployment of these agentic workflows gives bad actors fresh opportunities to access sensitive data or manipulate automated systems, making security a primary hurdle for enterprise adoption. By acquiring Promptfoo, OpenAI intends to address these vulnerabilities. The startup’s technology will enable OpenAI’s enterprise agent platform to perform automated red-teaming—which is a security testing process used to identify vulnerabilities—while also evaluating agentic workflows for security concerns and monitoring activities for compliance and risk.

Promptfoo was established by co-founders Ian Webster and Michael D’Angelo to create specialized tools that companies can use to test security vulnerabilities in LLMs. These tools include both an open-source interface and an open-source library. The startup has quickly gained traction in the corporate sector, reporting that its products are currently used by more than 25% of Fortune 500 companies. Following the acquisition, OpenAI stated that it expects to continue building out Promptfoo’s open-source offering alongside the enterprise integration, maintaining support for the developer community that relies on its open-source library.

While OpenAI did not disclose the financial terms of the transaction, data from PitchBook outlines the startup’s financial trajectory prior to the acquisition:

• Total funding: Promptfoo has raised $23 million since its founding in 2024.
• Market valuation: The startup was valued at $86 million after its most recent funding round in July 2025.

Why it matters

This deal underscores how frontier labs are scrambling to prove their technology can be used safely in critical business operations. By integrating automated red-teaming—a security testing process to identify vulnerabilities—and security evaluation directly into enterprise agent platforms, OpenAI aims to address the primary security concerns blocking wider corporate adoption.