Rein Security raises $25 million for AI agent security

Rein Security raised $25 million in Series A funding, the company said in a press release. Glilot Capital and Sienna Venture Capital co led the round, with Corner Ventures, Atlacle and RNP Capital Advisors also participating.

The round brings Rein Security's total funding to $35 million. The company will use the capital for product work, AI agent security research and global hiring.

Rein Security's platform monitors AI agents while they run, tracing the code they execute and the resources they access. It also applies guardrails that can block harmful actions without routing company or customer data through a gateway or proxy. Since launching in January 2026, the company has increased revenue eightfold and expanded its customer base fivefold.