Austin's HiddenLayer raises $100M Series B to secure models and agents

The round brings total funding to $156 million, after a $6 million seed in 2022 and a $50 million Series A in 2023 led by M12 and Moore Strategic Ventures. CEO Chris Sestito said annual recurring revenue grew more than 10x over the past year into the "tens of millions," with over 90% of that growth from new customers. No valuation was disclosed. One customer is a leading frontier model provider whose systems serve more than 700 million weekly users. The money goes toward Agentic Runtime Security and a new Agent Harness Security product for autonomous AI coding agents in production, plus a new CRO, Mike Gesnaldo, more hiring, and expansion in Europe and the wider EMEA region. The round lands in a crowded stretch for the category. It is the third major AI security investment in under two weeks, following Zenity ($125M) and Alice ($140M). Gartner estimates AI security spending will approach $2.83 billion this year and nearly $4.78 billion in 2027. For founders shipping agents or coding tools, security review is becoming a purchase condition for large enterprise and government buyers. Customers in finance, defense and pharma are paying for runtime controls and model supply chain checks. Teams selling into those sectors should expect questions on prompt injection and agent permissions, and may be able to buy this layer instead of building it.