Rein Security raises $25 million to secure AI agents during execution
The AMW Read
The financing incrementally updates the agent-security player map, with reported deployment growth supporting subsegment relevance but no independent evidence of broader market impact.
Rein Security raises $25 million to secure AI agents during execution
Rein Security has raised a $25 million Series A, bringing total funding to $35 million. Glilot Capital and Sienna Venture Capital co-led the round, with participation from Corner Ventures, Atlacle and RNP Capital Advisors. Founded in 2024 by Matan Bar-Efrat and Netanel Rubin, the Israeli startup employs 31 people and has offices in Tel Aviv and New York. Rein says revenue has increased eightfold and its customer base fivefold since its product launched in January 2026; neither growth figure includes an absolute baseline.
The round highlights a security requirement within the agent market: controlling software that can act on business systems, rather than only screening what a model says. Rein describes its patented sidecar technology as operating inside the customer's cloud environment at runtime, providing visibility into executed code and accessed resources, with guardrails intended to block harmful actions. Its focus on internally developed agents puts enforcement alongside enterprise agent deployment. The company says it currently secures thousands of agents executing millions of actions, although those activity counts do not establish the platform's effectiveness.
For builders and investors, the concrete diligence question is whether runtime controls stop unauthorized actions in actual workflows. Rein reports blocking a prompt injection hidden in a PDF opened by an enterprise agent, and its Agent Breakers research team presented a compromise of a major U.S. retailer's shopping agent at Black Hat USA 2026. These examples make action-level protection a relevant purchasing criterion, but the article supplies no independent efficacy measurements. Buyers should test enforcement against their own agent permissions and workflows; investors should seek absolute revenue and customer figures behind the reported growth multiples.
