Szymon Rybczak is the Co-Founder and CEO of TesterArmy (YC P26), an AI-native QA testing platform that deploys autonomous agents to test websites and mobile apps on every pull request, catching bugs before they reach users.

Szymon started programming at age 14 and joined Callstack as their youngest-ever developer, where he worked on React Native infrastructure, open source initiatives, and pioneered on-device LLM execution through the react-native-ai library.

Recognized as the youngest-ever React Native contributor, Szymon maintained the React Native Community CLI and spoke at international developer conferences on topics including React Server Components and on-device AI.

Prior to founding TesterArmy, Szymon led R&D and open source work at Callstack, a core React Native ecosystem partner, gaining deep expertise in mobile infrastructure and developer tooling.

TesterArmy was accepted into Y Combinator's Spring 2026 batch, attracted 500+ signups including Fortune 500 companies after a single viral demo, and is actively reshaping how engineering teams approach autonomous QA testing.