Grzegorz Mandziak

Announcing Apex: agentic coding model for mobile and web, specialized in React. We built Apex from a single idea: can an open-weight model deliver frontier-level performance at lower cost? Yes. Apex is SOTA in React Native and Next.js. Try it now: apex.callstack.com

We’re excited to share this one: the Agent Conf talks are live on YouTube. A huge thank you to every speaker who helped us shape this conference. Watch Agent Conf on YouTube 👉clstk.com/4hIGiG7 Which talk are you starting with?

🎉 @margelo_com Joins Callstack to Advance High-Performance React Native Engineering Vienna, Austria. 1 September 2026. Callstack, a leader in React Native and cross-platform development, today announced that Margelo, the Vienna-based high-end engineering company behind Nitro Modules, VisionCamera and react-native-mmkv, is joining Callstack in a transaction valuing Margelo at more than EUR 20 million. Margelo builds high-performance technology for React Native. Nitro Modules (34M downloads) lets developers write fast, type-safe native modules in C++, Swift or Kotlin, and quickly gained widespread traction across the ecosystem. VisionCamera (40M downloads), Margelo's enterprise-grade open-source Camera framework and react-native-mmkv (67M downloads), a key-value storage library, power countless React Native apps today. Callstack has spent a decade helping large organizations adopt, scale and operate React Native, contributing to the framework and its open-source ecosystem along the way. Together, the two teams give clients the strongest React Native performance expertise in the market, backed by delivery proven in complex enterprise environments. Margelo's technology and Callstack's delivery experience will now be available to the same clients. The timing reflects a fundamental change in how software is built. AI is making implementation faster and cheaper, but architecture, performance, native integration, validation and release safety are becoming more important, not less. These are the fundamentals on which both companies have built their reputations and on which they will continue to build together. "Margelo has built some of the strongest performance technology in React Native. Callstack has spent a decade helping large organizations adopt and scale the framework. Bringing those strengths together gives us the team and reach to solve more of the hard problems that determine whether software succeeds in production," said Mike Grabowski, CEO and Founder of Callstack. "At Margelo, we’ve built high-performance technology that developers already rely on. We’re excited to partner with Callstack to bring it to more clients and scale its impact. As software development becomes increasingly agentic, we want that technology to provide the foundation teams need to build reliable software with agents," said Marc Rousavy, CEO and Founder of Margelo. Margelo's existing open-source libraries will remain open source. Marc will continue to lead their development and help shape the combined company's offering. The transaction follows Callstack's 2025 growth investment and supports its strategy to expand technology and open-source capabilities while growing internationally.