AI Agent Security Startups Zenity and Horizon3.ai Raise $375M Combined as SentinelOne Expands Autonomous SOC

Three cybersecurity companies announced major funding rounds and product expansions on August 3, 2026, as enterprises accelerate efforts to secure autonomous AI agents and adopt AI-driven security testing.

Zenity, an Israeli startup that builds a platform for securing AI agents, raised a $125 million Series C led by Norwest Venture Partners. The round brings Zenity's total funding to approximately $185 million, according to a company statement. The company plans to use the capital to expand engineering and go-to-market teams.

AI Agent Security Draws Record Investment

Horizon3.ai, whose NodeZero platform uses AI to find and exploit attack paths in production systems, announced a $250 million Series E at a valuation of more than $2 billion. The round was co-led by existing investors NightDragon and NEA, with participation from seven new investors and five returning backers. The company's valuation tripled from $650 million in just over 14 months.

Both startups address a growing concern: as organizations deploy AI agents for tasks ranging from customer service to code generation, they need tools to prevent data leakage, unauthorized actions, and privilege escalation. Zenity's platform monitors and governs AI agent behavior across enterprise applications, enforcing policies in real time. Horizon3.ai's NodeZero continuously tests production environments for vulnerabilities, replacing traditional annual penetration tests with ongoing, AI-driven assessments.

The funding rounds come as AI-driven cyberattacks escalate. Horizon3.ai's CEO said the company invented the concept of AI Hackers and spent years perfecting autonomous penetration testing. The oversubscribed round reflects accelerating global demand for safe, autonomous security validation.

• Zenity's total funding now stands at approximately $185 million.
• Horizon3.ai's valuation tripled to $2 billion in 14 months.
• SentinelOne's Autonomous SOC operates within human-defined boundaries.
• Both Zenity and Horizon3.ai report growing customer demand as AI agent deployments surge.

Autonomous Security Operations Gain Traction

SentinelOne also announced governed, closed-loop response across its Singularity Platform. The company's Purple AI and Singularity Hyperautomation now autonomously investigate alerts, reach verdicts, and execute responses. Security teams set boundaries first, deciding where AI acts on its own and where it stops for human sign-off. The Autonomous SOC now runs from alert to action at the speed and scale of AI, with the confidence and control of human defenders.

SentinelOne's update is available immediately to customers. The company says the governed AI approach ensures that automation stays within defined guardrails, reducing risk while increasing efficiency.

The simultaneous announcements underscore a broader shift: as organizations deploy more AI agents in production, they are investing in security tools that can keep pace. Zenity plans to use its new capital to expand engineering and go-to-market teams. Horizon3.ai will accelerate product development and global expansion. SentinelOne's governed AI automation is available now. The race to secure the AI-powered enterprise is only accelerating.