Rein Security raises $25M Series A for AI runtime

What did Rein Security announce?

Rein Security said on October 8, 2026, that it raised a $25 million Series A and lifted its total funding to $35 million. The company describes itself as the security layer for the agent economy, protecting enterprise-built AI agents and stopping agents that attack companies.

Independent reporting from SiliconANGLE said the round addresses the risk of enterprise agents reaching business systems and the threat from AI-driven attacks. Rein says its software operates at runtime, meaning it watches agent behavior as actions are executed rather than only analyzing them before deployment.

How does Rein's product work?

Rein describes its platform as an AI-native runtime security layer for enterprises. According to the company, it traces every agent action back to the line of code that triggered it and links that activity to business outcomes. It also says the system blocks harmful actions before they execute, including exploits that do not yet have patches.

Rein says it does not require company or customer data to be routed through a gateway or proxy. The company also says its deployments span financial services, healthcare, SaaS, data, retail and energy.

Independent reporting from SiliconANGLE described the product as a lightweight sidecar that analyzes prompts, API calls and database access, builds a baseline of normal agent behavior and then applies action-level controls to stop deviations in real time. Yahoo Finance’s PR Newswire version said the platform is built on patented sidecar technology and provides visibility into every line of code an agent runs and every resource it touches, along with governance and real-time guardrails.

Who backed the round?

Rein said the Series A was co-led by Glilot Capital and Sienna Venture Capital, with Corner Ventures participating. PR Newswire’s version, republished by Yahoo Finance, added that Atlacle and RNP Capital Advisors also took part in the financing. Techmeme later summarized the round as a $25 million Series A that brought total funding to $35 million.

The Yahoo Finance version of the PR Newswire copy quoted Dun & Bradstreet’s chief cybersecurity and technology risk officer saying, "Rein helps us see and control what our agents do at scale, so we can keep innovating with agentic AI while protecting the customers who depend on it."

What will Rein do with the money next?

Rein said it will use the new capital for product innovation, Agent Breakers research and hiring. SecurityWeek reported that the company also plans to expand its global employee base.

The company has been pushing to show traction as it raises. Rein said that since launching in January 2026, revenue has grown 8x and its customer base has grown 5x. It also said it already secures thousands of AI agents executing millions of actions. PR Newswire’s version likewise said the platform is securing thousands of agents, including deployments at Dun & Bradstreet and Lemonade, and that new customers include Flex and Swimlane.

Rein named Lemonade and Dun & Bradstreet as customers in its announcement, tying them to 3.31 million active customers and more than 240,000 customers, respectively. The company also said its Agent Breakers team demonstrated at Black Hat USA 2026 how it compromised the AI shopping agent of a major U.S. retailer.

Rein was founded in 2024 and is co-headquartered in New York City and Tel Aviv, according to PR Newswire’s copy republished by Yahoo Finance. Rein’s newsroom also shows an $8 million seed announcement in January 2026. The company said it was selected as one of eight early-stage companies to compete in the AI Conference’s Start Up Showdown.