Rein Security raises $25M Series A to guard enterprise AI agents, total funding hits $35M
Rein Security raised a $25 million Series A co-led by Glilot Capital and Sienna Venture Capital, lifting total funding to $35 million for AI agent defense.
Rein Security has $25 million in fresh Series A money, and enterprise AI agents are about to get a very well-funded chaperone. The round brings total funding to $35 million, according to Rein.
Glilot Capital and Sienna Venture Capital co-led, SecurityWeek reported, with Corner Ventures, Atlacle and RNP Capital Advisors. Rein's own post names only Corner Ventures among the rest. The coverage gives no valuation.
The company, founded in 2024 and co-headquartered in New York City and Tel Aviv, says it has seen 8x revenue growth and 5x more customers since its January 2026 launch. SiliconANGLE lists Flex Ltd., Swimlane Inc., Lemonade Inc. and Dun & Bradstreet Holdings Inc. among its deployments.
In its announcement, Rein says it operates at runtime, at the point where an agent executes an action, and blocks harmful actions before they run, without routing company or customer data through a gateway or proxy. It plans to use the new capital for faster product innovation, deeper research through its Agent Breakers team, and hiring in New York and Tel Aviv.
Context: Rein cites Gartner projecting that spending on securing AI will reach nearly $4.8 billion in 2027, up 68.7% from 2026, and nearly $7.7 billion by 2028.
My take? Rein says it secures thousands of agents executing millions of actions. Add an 8x growth claim in under a year and two lead investors in the room. When the agents are this busy, somebody gets paid to hold the leash, and today that somebody is very well funded.
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The 8x revenue growth and 5x customer growth come from Rein's own blog post, and the post gives no baseline. Eight times a small number is still a small number, but I admire the confidence.
It runs as a lightweight sidecar and says it does not route your data through a proxy or gateway, which is the right architecture for not rebuilding your stack. Pricing is not in any of the coverage.
