Rein Security raises $25m Series A to secure AI agents at runtime

Rein Security raises $25m Series A to secure AI agents at runtime

8 October 2026: Rein Security has raised a $25 million Series A, taking its total funding to $35 million. The company, which hires in New York and Tel Aviv, says the round was co-led by Glilot Capital and Sienna Venture Capital with participation from Corner Ventures. SiliconANGLE adds Atlacle and RNP Capital Advisors to the list of investors.

Rein sells security for AI agents and works at runtime, at the point where an agent carries out an action. In its announcement the company says it traces each action back to the line of code that triggered it, lets security teams define what each agent may and may not do, and blocks harmful actions before they run, including exploits for which no patch exists. It says it does this without routing company or customer data through a gateway or proxy. Chief executive Matan Bar-Efrat told SiliconANGLE the platform runs as a lightweight sidecar that watches prompts, API calls and database access, builds a baseline of each agent's normal behaviour and stops only the deviating action rather than the whole agent process.

Rein says it has grown revenue eightfold and customers fivefold since launching in January 2026, and that it secures thousands of agents executing millions of actions. It names Lemonade and Dun & Bradstreet as customers; SiliconANGLE also lists Flex and Swimlane.

The new money goes into product development, the company's Agent Breakers research team and hiring. Agent Breakers, the company says, showed at Black Hat USA 2026 how it compromised the AI shopping agent of a major US retailer.

The market figures in the post, including IDC's finding that 95% of companies run AI agents in production and Gartner's projection of nearly $4.8 billion spent on securing AI in 2027, are cited by Rein from those firms and were not checked here.

The company, which its post describes as not yet two years old, was also named to the TechCrunch Startup Battlefield 200.

Company profile on TrustList: Rein Security

Sources

• Rein Security: We Raised A $25M Series A to Secure the Agent Economy, 8 October 2026
• SiliconANGLE: Rein Security raises $25M to rein in insecure AI agents, 8 October 2026