RunSybil builds an AI agent called Sybil that continuously probes live applications to find, exploit and document real security vulnerabilities without humans in the loop. Its approach focuses on testing running systems—exploring, chaining vulnerabilities and testing authentication boundaries—rather than analyzing source code pre-deployment. The company was co-founded in 2023 by Ari Herbert-Voss, who previously led security research at OpenAI, and Vlad Ionescu, who led offensive security red teams at Meta. RunSybil reports working with startups (including Cursor, Turbopuffer, Notion, Baseten and Thinking Machines Lab) as well as several major financial institutions and Fortune 500 customers. Customers have reported that Sybil discovered critical vulnerabilities missed by traditional penetration tests and red teams. Investors and founders position the product as particularly relevant for regulated industries facing strict audit and compliance requirements as AI-driven development accelerates.

Total raised

$40M

Funding rounds

1

Latest round

Series A

Latest activity

Mar 2026