US startup Obsidian Security announced a $85 million Series D round, valuing the company at $1.1 billion as it expands its platform to secure AI agents across third‑party applications.

Obsidian Security, a US‑based startup specializing in AI agent protection, closed an $85 million Series D financing round, pushing its valuation to $1.1 billion. The funding will fuel the company’s push to broaden its platform, which safeguards AI‑driven agents embedded in third‑party applications from misuse and cyber‑threats.

Funding round and investors

The Series D round was led by Sequoia Capital with participation from existing backers including Accel and Bond Capital. The $85 million injection adds to the $120 million previously raised, underscoring growing investor confidence in AI security solutions.

Expanding the AI agent security platform

Obsidian’s core technology monitors the behavior of autonomous AI agents, detecting anomalous actions and preventing data exfiltration. The latest platform updates enable protection for agents that operate within third‑party SaaS tools, expanding the company’s addressable market beyond native enterprise environments.

According to the company, the enhanced suite will offer real‑time policy enforcement, automated threat hunting, and detailed audit trails, helping organizations meet compliance requirements while deploying AI‑driven automation.

Market context and competition

The AI security niche has attracted several startups as enterprises grapple with the rapid adoption of large‑language models and autonomous agents. Obsidian’s focus on agent‑level protection differentiates it from broader AI risk platforms that primarily target model training or inference layers.

  • Detects unauthorized API calls by AI agents
  • Enforces data‑access policies in real time
  • Generates compliance‑ready reports for auditors
Securing AI agents is becoming as critical as securing the underlying infrastructure, especially as they gain autonomous decision‑making capabilities.

The valuation milestone places Obsidian among the few AI‑security firms crossing the billion‑dollar mark, a sign that investors see lasting demand for tools that can tame the expanding attack surface introduced by autonomous agents.

AI Magazine coverage of Obsidian Security’s $1.1 bn valuation