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Vasek Mlejnsky
Vasek Mlejnsky is the co-founder and CEO of E2B, an open-source cloud runtime that gives AI agents secure, isolated sandboxes to run code and use real tools. Raised in a small Czech town, he moved to San Francisco in 2021 through the Pioneer accelerator with his sixth-grade friend and co-founder Tomas Valenta. After pivoting through several developer-tool ideas, the pair launched E2B in 2023. By 2025 the platform was used by 88% of Fortune 100 companies and had run hundreds of millions of sandbox sessions, and E2B closed a $21M Series A led by Insight Partners.
E2B
E2B is an open-source cloud runtime that gives AI agents secure, isolated environments to execute code and use real-world tools. Built on Firecracker microVMs that boot in under 200 milliseconds, E2B lets developers and enterprises spin up disposable Linux sandboxes where AI-generated code runs without touching production systems. Founded in 2023 by Czech engineers Vasek Mlejnsky and Tomas Valenta, the company raised a $21M Series A led by Insight Partners in July 2025 and reports adoption across roughly 88% of the Fortune 100, including Perplexity, Hugging Face, Groq and Manus.