Rein Security raises $25M to guard AI agents while they work

Companies have spent the past couple of years handing AI agents the keys to their systems. Now they want someone watching what those agents do with them. Rein Security, a cybersecurity startup founded in 2024, has raised $25 million in a Series A round announced on October 8, 2026. The raise brings its total funding to $35 million, and the pitch is simple: protect AI agents during the moment they actually run. The details of the round Glilot Capital and Sienna Venture Capital co-led the round. Corner Ventures, Atlacle, and RNP Capital Advisors also took part. The company is led by CEO Matan Bar-Efrat and CTO Netanel Rubin, who founded it in 2024. Rein operates out of New York and Tel Aviv with a team of 31 employees. Rein launched its product in January 2026, following an $8 million seed round. Since then, the company reports that revenue has grown 8x and its customer base has expanded 5x. Rein says its platform currently secures thousands of AI agents carrying out millions of actions. Customers span financial services, healthcare, and retail, and include names like Dun & Bradstreet and Lemonade. What a sidecar has to do with AI security Rein’s platform is built on patented sid...