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

NEW YORK and TEL AVIV, 8 October 2026. Rein Security, a runtime security company for enterprise AI agents, announced a $25 million Series A co-led by Glilot Capital and Sienna Venture Capital. The company says its total funding is now $35 million.

Rein is co-headquartered in New York City and Tel Aviv. It did not disclose a valuation.

How much did Rein Security raise and who invested?

Rein raised $25 million in Series A financing, according to its own release issued at 06:00 ET on 8 October 2026. Glilot Capital and Sienna Venture Capital co-led. Corner Ventures, Atlacle and RNP Capital Advisors participated.

Pulse 2.0 and Dealroom both reported the same lead investors and participants on 8 October 2026. Both drew on the company's release, so they confirm the details rather than add independent reporting.

Glilot Capital is not new to Rein. SecurityWeek named it as the backer when Rein emerged from stealth on 28 January 2026.

What does Rein Security do?

Rein sells a platform that watches what AI agents do while they run inside a company's systems. Pulse 2.0 reports that the platform uses "patented sidecar technology that operates at runtime, where AI agents execute actions across business systems, data, and workflows."

The company says this gives security teams visibility into the code an agent executes and the resources it accesses. It also says the design allows real-time controls meant to block harmful activity. Rein says enterprises do not have to route company or customer data through a gateway or proxy.

The release describes the product as tracing "every action to the line of code that triggered it" and connecting it to its business outcome. These are the company's descriptions. No independent test of the platform has been published.

Rein's pitch has shifted since its first announcement. In January 2026, SecurityWeek described a patent-pending application security product that adds a single line of code to an application and baselines its normal behavior. By October 2026 the company describes itself as an AI-native runtime security platform focused on enterprise AI agents. The "patent-pending" label in January and the "patented" label in October are both the company's own wording, and no patent number appears in either source.

Who founded Rein Security?

The release describes Matan Bar-Efrat as co-founder and CEO. SecurityWeek identified Netanel Rubin as CTO. SecurityWeek spells the CEO's surname "Bar Efrat"; this article uses the spelling from the company release.

The background details come from a single source, SecurityWeek, and the release does not repeat them. The company says it was founded in 2024.

How much has Rein Security raised in total?

Rein says total funding is $35 million. The figures reported so far add up to less than that.

Crypto Briefing also reported that the product launched in January 2026 after an $8 million seed round. The distinction matters: a single round is not a cumulative total. Here the $25 million is the new money, and the $35 million is the company's own running tally.

What traction does Rein Security report?

The company says that since its January 2026 launch it has increased revenue by 8x and grown its customer base by 5x. It gives no absolute revenue or customer count. RuntimeWire noted that these multiples lack underlying revenue and customer figures.

According to Pulse 2.0, the company's customers include Flex, Swimlane, Dun & Bradstreet and Lemonade. It says the platform is securing thousands of AI agents that execute millions of actions. Crypto Briefing also named Dun & Bradstreet and Lemonade.

All of these are company-reported figures. A growth multiple from an unstated base can describe a very small or a very large business, and the release does not say which.

How big is the market Rein is chasing?

Rein cites Gartner figures in its announcement. Pulse 2.0 reports that, according to Gartner figures cited by Rein, the market for securing AI is expected to reach nearly $4.8 billion in 2027, up 68.7% from 2026. The same figures put it at nearly $7.7 billion in 2028. Dealroom repeated the 2027 and 2028 projections.

These are forecasts, and they reach this article through the company, not from the Gartner report itself. Treat them as the company's framing of its opportunity, not as an audited market size.

What will the money be used for?

The company says it will use the new capital to accelerate product innovation, advance agentic research and support global hiring. Pulse 2.0 gives the same list, phrased as product development, expanded agentic AI security research and global hiring.

The release gives no hiring numbers, no spending split and no product dates. Anything more specific than those three items would be speculation.

What's still unclear?

Several points remain open as of 13 October 2026.

• The funding total. The company states $35 million. The reported seed of $8 million plus the $25 million Series A is $33 million. Dealroom's page carries the $35 million figure in its text and shows a "$33M raised" figure in its summary widget. The company has not explained the difference.
• Valuation. Not disclosed.
• Absolute revenue and customer counts. The 8x and 5x growth figures have no stated base.
• Independent validation. The product claims, including blocking harmful activity in real time, come from the company. No third-party test results have been published.
• Second lead's name. Data provider Preqin's public preview calls the second lead "Sienna Investment Managers". The company release and the outlets above say Sienna Venture Capital, and this article uses the release wording.
• Headquarters. The company says it is co-headquartered in New York City and Tel Aviv. Preqin's preview lists only Israel.

The weakest part of the story is the traction claim. Strong growth multiples are the usual reason a young company can raise a Series A, but without a base number they cannot be compared with any other company.

The figures here rest on the company's release and press coverage, not on a regulatory filing.