--- title: "Michał Pierzchała" description: "Michał Pierzchała leads open source and R&D at Callstack, and created the React Native Testing Library project. Get to know the engineers behind Callstack." url: https://www.callstack.com/team/michal-pierzchala updated: 2026-10-22T14:18:28.064Z --- # Michał Pierzchała Michał Pierzchała leads open source and R&D at Callstack, and created the React Native Testing Library project. Get to know the engineers behind Callstack. _Principal Engineer_ Principal Engineer leading Callstack's Open Source and R&D efforts, ensuring continuous innovation in app development. Passionate about building OSS tools for JavaScript developers and creator of React Native Testing Library. Also, he likes rockets! [LinkedIn](https://www.linkedin.com/in/thymikee/) · [X](https://twitter.com/thymikee) · [GitHub](https://github.com/thymikee) ## What I’ve been shipping - [From Design to Shipped: A Modern App Development Meetup](https://www.callstack.com/events/from-design-to-shipped-a-modern-app-development-meetup) (Meetup, 10/22/2026): Join Callstack, JetBrains, and Expo in Amsterdam on October 22 for talks on AI agents, UI development, and verification across web and mobile. - [Agentic Mobile Testing With e2e and agent-device](https://www.callstack.com/blog/agentic-mobile-testing-with-e2e-and-agent-device) (Article, 10/13/2026): See how e2e uses agent-device for AI-driven iOS and Android tests, combines exact assertions with agent actions, and replays cached steps without model calls. - [Automating Mobile QA with Cloud Agents](https://www.callstack.com/events/automating-mobile-qa-with-cloud-agents-2) (Talk, 10/7/2026): Michał Pierzchała shows how cloud-based QA agents can test real iOS and Android user flows and bring screenshots, recordings, and logs into pull requests. - [Apex Is Now Generally Available: Agentic Coding Model for Mobile and Web, Specialized in React](https://www.callstack.com/blog/apex-agetic-coding-for-mobile-and-web-spcialied-in-react) (Article, 10/1/2026): Apex is now publicly available. Explore Callstack’s coding model for React Native and Next.js, with API pricing, benchmarks, and self-hosting options. - [Automating Mobile QA With Cloud Agents](https://www.callstack.com/blog/automating-mobile-qa-with-cloud-agents) (Article, 8/4/2026): Code review and green CI checks do not prove a mobile app still works. Learn how cloud agents, agent-device, and runtime evidence can verify app behavior before merge. - [Migration to React Native in 2026 Starts With a Delivery Question](https://www.callstack.com/blog/migration-to-react-native-in-2026-starts-with-a-delivery-question) (Article, 8/3/2026): Choosing between brownfield and greenfield React Native migration? Learn where risk sits, when to use a checkpoint, and what to prove before committing. - [3 Minutes With an Agent, 9 Seconds on Replay](https://www.callstack.com/blog/3-minutes-with-an-agent-9-seconds-on-replay) (Article, 7/30/2026): See how agent-device replay cuts repeated mobile QA flows from minutes to seconds, reduces model calls, and shows when repair is worth the cost. - [Behavior Review for AI-Native Delivery](https://www.callstack.com/events/behavior-review-for-ai-native-delivery) (Webinar, 7/21/2026): AI can increase code output faster than teams can verify the real app. See why behavior review matters before merge. - [Mobile QA with Cloud Agents at AI Coding Summit London](https://www.callstack.com/events/mobile-qa-with-cloud-agents-at-ai-coding-summit-london) (Talk, 7/6/2026): Michał Pierzchała will speak at AI Coding Summit London 2026 about mobile QA agents for iOS and Android pull request workflows. - [The Missing QA Loop for Mobile Agents](https://www.callstack.com/podcasts/the-missing-qa-loop-for-mobile-agents) (Podcast, 6/25/2026): A conversation with Michał Pierzchała on how agents use simulators, logs, screenshots, and accessibility data to verify mobile apps in real workflows. - [Building Mobile QA Agents With Vercel Eve](https://www.callstack.com/blog/building-reviewable-mobile-qa-agents-with-vercel-eve) (Article, 6/19/2026): See how Eve helps turn a mobile QA agent into a reviewable, durable part of a CI workflow. - [Automating Mobile QA with Cloud Agents](https://www.callstack.com/events/automating-mobile-qa-with-cloud-agents) (Talk, 6/17/2026): Michał Pierzchała will present Automating Mobile QA with Cloud Agents at Ship London on 17 June 2026. - [Callstack x Expo AI Meetup](https://www.callstack.com/events/callstack-x-expo-ai-meetup) (Meetup, 6/3/2026): Join Callstack and Expo in San Francisco for practical talks on AI-native mobile development, Expo Agent, Cloud Agents and autonomous mobile QA. - [How AI Is Changing React Native Development and Testing](https://www.callstack.com/podcasts/how-ai-is-changing-react-native-development-and-testing) (Podcast, 5/13/2026): Zack Ebenfeld joins React Universe On Air to talk about how AI is changing React Native workflows, testing, QA, and day-to-day engineering work. - [How We Optimized Agent Device for Mobile App Automation](https://www.callstack.com/blog/how-we-optimized-agent-device-for-mobile-app-automation) (Article, 4/3/2026): Discover how we optimized Agent Device to reduce LLM token consumption by over 50% and speed up AI-driven mobile app automation. - [Agent Device, AI workflows, and mobile testing in practice](https://www.callstack.com/events/agent-device-ai-agents-meet-mobile-automation) (Live Stream, 3/19/2026): A discussion on Agent Device, AI-driven workflows, and testing mobile apps using simulators and accessibility data. - [Announcing React Native Evals](https://www.callstack.com/blog/announcing-react-native-evals) (Article, 3/5/2026): We built an open-source benchmark to measure how AI coding models handle real React Native tasks, such as animations, async state, navigation, and more. - [Agent Device: iOS & Android Automation for AI Agents](https://www.callstack.com/blog/agent-device-ai-native-mobile-automation-for-ios-android) (Article, 2/17/2026): Agent Device is a lightweight CLI for AI-driven mobile automation on iOS and Android, with structured snapshots and deterministic replay. - [Announcing: React Native Best Practices for AI Agents](https://www.callstack.com/blog/announcing-react-native-best-practices-for-ai-agents) (Article, 1/16/2026): We're turning React Native optimization knowledge into agent-ready skills (JS, native, bundling) mapped to FPS and TTI, built from real-world production work - [React Native Wrapped 2025: A Month-by-Month Recap of The Year](https://www.callstack.com/blog/react-native-wrapped-2025-a-month-by-month-recap-of-the-year) (Article, 12/22/2025): Seven major React Native releases in 2025, React Native turns 10, the New Architecture becomes the default, and 1.0 moves into view. A recap of 2025’s biggest RN updates. - [The Offline AI: On-Device LLMs in React Native With AI SDK](https://www.callstack.com/events/the-offline-ai-on-device-llms-in-react-native-with-ai-sdk) (Talk, 12/5/2025): Learn how to run on-device LLMs in React Native using Vercel’s AI SDK from Michał Pierzchała's talk at DevAI by Data Science Summit. - [Vega Developer Meetup](https://www.callstack.com/events/vega-developer-meetup) (Talk, 11/17/2025): Learn how to integrate React Native into Android TV apps at the Vega Developer Meetup. Workshop, roadmap, and community talks, live in Munich. - [Testing Native Modules Reliably With JavaScript](https://www.callstack.com/events/testing-native-modules-reliably-with-javascript) (Talk, 11/14/2025): Learn how React Native Harness bridges the gap between mocking and E2E testing: real device tests, full native access, Jest-style simplicity. - [From Unit to E2E: A Guide to Testing React Native TV in 2026](https://www.callstack.com/blog/testing-react-native-tv-apps) (Article, 10/3/2025): Standard mobile testing tools fail for React Native TV apps due to D-pad navigation. This guide shows how to build custom helpers for React Native Testing Library that emit hardware key events and how to configure Appium for end-to-end testing on tvOS and Android TV. - [Debugging Android Connectivity Issues with Metro Bundler](https://www.callstack.com/blog/debugging-android-connectivity-issues-with-metro-bundler) (Article, 9/16/2025): A practical guide to fixing the "Unable to load script" error in React Native when the Android emulator can’t connect to Metro. - [Native Apps Without a Build Step](https://www.callstack.com/events/native-apps-without-a-build-step-2) (Talk, 9/13/2025): Discover Rock by Callstack: the open, modular, self-hosted framework for React Native. Built to help teams scale, migrate, and deliver faster in the evolving React Native ecosystem. - [React Universe Conf 2025 Keynote](https://www.callstack.com/events/react-universe-conf-2025-keynote) (Talk, 9/3/2025): Explore React Native’s past, present, and future with insights from Meta and Callstack on stability, new architecture, and enterprise-ready tooling. - [React Native Enterprise Framework is now Rock](https://www.callstack.com/blog/react-native-enterprise-framework-is-now-rock) (Article, 8/18/2025): Rock is the new name for the React Native Enterprise Framework (RNEF). A solid foundation for enterprise-grade, cross-platform apps. Faster CI, build caching, iOS ad-hoc installs, and more. - [Announcing Node-API Support for React Native](https://www.callstack.com/blog/announcing-node-api-support-for-react-native) (Article, 7/10/2025): We are bringing Node-API to React Native to simplify native module development. Learn how this ABI-stable, cross-runtime system can unlock faster builds, better maintainability, and broader ecosystem interoperability. - [Brownfield Incremental React Native Adoption x Rock](https://www.callstack.com/events/brownfield-incremental-react-native-adoption-x-rock) (Talk, 6/24/2025): Learn how to smoothly adopt React Native in your existing apps using Callstack’s Rock for easier setup, faster deployment, and seamless integration. - [React Universe Meetup, New York](https://www.callstack.com/events/react-universe-meetup-new-york-june-2025) (Meetup, 6/24/2025): Join us in NYC or online for React Universe Meetup: tech talks, real-world insights, and networking with React Native devs. June 24, 2025. - [Caching React Native Builds on S3 and R2 With Rock](https://www.callstack.com/blog/caching-react-native-builds-on-s3-and-r2) (Article, 6/19/2025): Learn how to cache your React Native builds and store them on Amazon S3 or R2 to reuse across your team. - [Build Faster and Scale Smarter With Rock](https://www.callstack.com/podcasts/build-faster-with-rock) (Podcast, 6/10/2025): Discover how Rock cuts build times, streamlines CI, and simplifies large-scale app development for growing teams. - [Adding React Native to iOS and Android Apps Has Never Been Easier](https://www.callstack.com/events/adding-react-native-to-ios-and-android-apps-has-never-been-easier) (Webinar, 5/27/2025): Learn how to easily add React Native to your iOS and Android apps with a modern brownfield setup powered by Callstack’s open-source tooling. - [React Native Legal: Zero-Config OSS License Screens for Your App](https://www.callstack.com/blog/react-native-legal-acknowledge-open-source-libraries-in-your-app) (Article, 5/13/2025): Add license acknowledgments to your React Native app with ease using React Native Legal-a zero-config tool for OSS compliance across iOS, Android, tvOS, and AndroidTV platforms. - [From Hours to Minutes: Making Your React Native CI Builds 20x Faster](https://www.callstack.com/events/from-hours-to-minutes-making-your-react-native-ci-builds-20x-faster) (Webinar, 5/12/2025): Discover how to skip 90% of native builds in React Native CI using Rock. Includes a live demo and cost-saving insights from Expensify’s setup. - [Native Apps Without a Build Step](https://www.callstack.com/events/native-apps-without-a-build-step) (Talk, 4/24/2025): Learn how Callstack’s new React Native framework slashes CI times and simplifies enterprise-scale mobile development. - [React Universe Meetup: San Francisco](https://www.callstack.com/events/react-universe-meetup-san-francisco) (Meetup, 4/24/2025): Missed the React Universe Meetup SF? Watch the livestream recording soon, talks on RN performance, optimization, and build-free workflows await. - [How to Run E2E Tests on Every PR and Don’t Burn All Your CI Credits](https://www.callstack.com/events/how-to-run-e2e-tests-on-every-pr-and-dont-burn-all-your-ci-credits) (Talk, 4/1/2025): End-to-end tests are notoriously slow and costly, especially in mobile development. This talk introduces new tools and techniques to make E2E testing fast and efficient, so you can run tests on every pull request without draining CI resources. - [Why You Need Rock](https://www.callstack.com/events/why-you-need-rock) (Webinar, 3/27/2025): Learn more about Callstack's Rock straight from its creators. - [We’re Building a New React Native Framework](https://www.callstack.com/blog/were-building-a-new-react-native-framework) (Article, 3/14/2025): Meet a React Native framework designed for enterprise apps, optimizing build reuse, CI speed & cloud integration while staying flexible and self-hosted. - [New React Native Framework for Enterprise Announcement](https://www.callstack.com/events/new-react-native-framework-for-enterprise-announcement) (Live Stream, 3/4/2025): We know what it takes to make React Native work for serious-scale applications. That’s why we created Rock, so enterprise teams can build with confidence, efficiency, and full control over their stack. - [Shaping the Future of Super Apps in React Native](https://www.callstack.com/blog/shaping-the-future-of-super-apps-in-react-native) (Article, 9/12/2024): Discover how Re.Pack, Rspack, Module Federation, and Zephyr Cloud are shaping the future of super app development in React Native. - [Welcome to the React Universe](https://www.callstack.com/events/welcome-to-the-react-universe) (Talk, 9/5/2024): This is the Keynote talk presented at React Universe Conf 2024, the largest community conference that unites developers and thought leaders to explore trends, share insights, and push the boundaries of React and React Native. - [How to Scale Teams, Product Development, and Release Process With Re.Pack](https://www.callstack.com/events/scale-teams-product-development-and-release-process-re-pack) (Webinar, 7/8/2024): Join us to learn how Re.Pack helps manage complexity in React Native apps, enables scalable teams, and boosts release processes. - [Apple Vision Pro: Insights From Conferences and Beyond](https://www.callstack.com/blog/apple-vision-pro-insights-from-conferences-and-beyond) (Article, 6/10/2024): Explore key insights from introducing Apple Vision Pro at tech events. Discover its intuitive interface, immersive experiences, and the challenges faced. - [Spatial Computing With React](https://www.callstack.com/events/spatial-computing-with-react) (Talk, 5/16/2024): JavaScript powers a React Native journey on Apple Vision Pro, adapting to spatial apps and visionOS quirks for a unique dev experience. - [Top 5 Metrics You Need to Track When Optimizing Your React Native App](https://www.callstack.com/events/top-5-metrics-you-need-to-track-when-optimizing-your-react-native-app) (Webinar, 2/15/2024): Watch a webinar on optimizing React Native apps to learn the top 5 metrics every React Native team should track to improve performance, reduce load time, and boost user experience. - [React Native for Apple Vision Pro and visionOS](https://www.callstack.com/podcasts/react-native-for-apple-vision-pro-and-visionos) (Podcast, 12/21/2023): In this episode, Łukasz invites Oskar and Michał to discuss their experimental journey of bringing React Native to Apple Vision Pro and visionOS. - [Introducing E2E Tests to React Native Core](https://www.callstack.com/blog/introducing-e2e-tests-to-react-native-core) (Article, 9/12/2023): Learn how End-to-End (E2E) tests were introduced to React Native core through collaboration between Callstack, Microsoft, and Meta engineers. - [The Invisible Architect](https://www.callstack.com/events/the-invisible-architect) (Talk, 9/7/2023): Learn how communication shapes your app development, from code to design. Discover React’s role and leverage Conway’s Law for success. - [React Native Performance Q&A](https://www.callstack.com/podcasts/performance-questions-and-answers) (Podcast, 5/11/2023): In April 2023, we enjoyed talking about performance optimization in the US. We went to San Francisco, Los Angeles and Detroit to meet some amazing folks from the React Native community - we loved the intense thought exchange there! - [Callstack OSS Update](https://www.callstack.com/podcasts/callstack-oss-update) (Podcast, 4/27/2023): April 2023 Callstack OSS Update: RFC for Expo Config Plugins, Re.Pack & Paper news. - [How to Make Your Open Source Project Repository Contributor Friendly](https://www.callstack.com/blog/make-open-source-project-repository-contributor-friendly) (Article, 3/15/2023): Check out 5 tips on making the repository of your Open Source project more contributor friendly for both new maintainers & users. - [Automated Performance Regression Testing With Reassure](https://www.callstack.com/events/automated-performance-regression-testing-with-reassure) (Talk, 2/24/2023): Developers often fix performance issues in React apps, but this is unsustainable and prone to regressions. Reassure, a testing library, helps spot problems before production, enhancing automated testing suites. - [State of React Native](https://www.callstack.com/podcasts/state-of-react-native) (Podcast, 2/22/2023): In this Coffee Talk Michał Pierzchała, Oskar Kwaśniewski, and Łukasz Chludziński comment on the results of the State of React Native survey. Check it out! - [NPM Kiosk and Open Source Monetization](https://www.callstack.com/podcasts/npm-kiosk-and-open-source-monetization) (Podcast, 2/21/2023): Explore the pros, cons, and lessons from gating access to open source libraries, plus insights on handling payments with tools like NPM Kiosk and Reassure. - [Webpack & Callstack Experts' Take on Next.js Conf](https://www.callstack.com/podcasts/webpack-callstack-experts-take-on-next-js-conf-coffee-talk-6) (Podcast, 10/28/2022): Join Callstack and Webpack experts as they discuss the most interesting tech announcements from the Next.js Conf 2022. - [Continuous App Performance Monitoring Made Simple With Reassure](https://www.callstack.com/blog/app-performance-monitoring) (Article, 9/21/2022): Discover Reassure - an open source library for measuring performance regression of React and React Native components of your app. - [Reassure - Open Source Tool Measuring Performance Regression](https://www.callstack.com/podcasts/reassure-performance-regression-measurement-tool) (Podcast, 7/28/2022): Explore Reassure, an Open Source tool for measuring performance regression in React Native apps. - [React Native News and App.js Conf](https://www.callstack.com/podcasts/coffee-talk-4-react-native-news-app-js-conf) (Podcast, 6/22/2022): Join Michał Pierzchała and Abi Thiao as they discuss the most interesting talks at App.js Conf 2022 and other React and React Native news. - [Callstack Experts on Open Source](https://www.callstack.com/podcasts/coffee-talk-3-open-source) (Podcast, 6/7/2022): Learn how to get started with Open Source, find the right project to contribute to, and explore top React Native libraries from the Callstack community. - [Scaling Teams With Federated Super Apps](https://www.callstack.com/events/scaling-teams-with-federated-super-apps) (Talk, 5/19/2022): App developers shape code, but communication with others truly designs products. This talk explores how React and Conway’s law influence this process. - [React v18.0 & React Native 0.68](https://www.callstack.com/podcasts/coffee-talk-1-react-v18-0-react-native-0-68) (Podcast, 4/27/2022): Introducing Coffee Talks! Dive into the latest news in React and React Native with our hosts. - [Migrating React and Native Apps To React Native - Everything You Need To Know](https://www.callstack.com/blog/migration-to-react-native) (Article, 4/19/2022): Migrate seamlessly from native to React Native - greenfield, brownfield, and best practices covered! - [Look into the Future of React Native Testing Library](https://www.callstack.com/podcasts/look-into-the-future-of-react-native-testing-library) (Podcast, 8/11/2020): The first episode of React Universe On Air (formerly known as The React Native Show) provides insights into React Native Testing Library. Mike and his guest give a quick glimpse into the very concept of Testing Library and tell the story behind React Native Testing Library. - [Merge of React Native Testing Libraries](https://www.callstack.com/blog/merge-of-react-native-testing-libraries) (Article, 7/30/2020): We’re merging React Native Testing Library and Testing Library together! Check out what's the story behind that and how it will make your testing easier. - [React Native Testing Library 2.0 - What’s New?](https://www.callstack.com/blog/react-native-testing-library-2-0) (Article, 5/28/2020): React Native Testing Library 2.0 is out now! Read the article and find out what's new. Check our migration guide. - [Meet the Team your Open Source Project Wants](https://www.callstack.com/blog/meet-the-team-your-open-source-project-wants) (Article, 3/19/2016): Read about Michał Pierzchała's thoughts on a month spent with Recat Native Open Source Evangelists JOIN US ## Build the AI-native React Native future Work with engineers who contribute to the ecosystem and turn new technology into real products. At Callstack, AI is part of how we build, learn, and ship software. [Join Us](https://www.callstack.com/careers) [About us](https://www.callstack.com/about-us)