Callstack

Callstack is an AI-native engineering company. We build cross-platform products with agent-driven workflows, then help teams adopt the same way of working in their own delivery. Our work combines deep React and React Native expertise with the systems teams need to ship faster: stronger engineering workflows, better delivery infrastructure, practical AI adoption, and the controls required to use AI safely at scale. We also build tooling for this shift, including Apex, our specialized model for React Native, and Agent Device, which lets AI agents control real iOS and Android apps. This work comes from more than a decade in React Native. We are Core Contributors to React Native, Founding Members of the React Foundation, and the team behind open-source software used in over 30M downloads every month.