StemJSON

StemJSON is an open declarative language, based on JSON, that describes complete native app UI and logic - state, actions, expressions, navigation. Swift and Kotlin runtimes render it natively on iOS and Android. There are three ways into an app. Your AI writes it: from a prompt to a feature. Your backend pushes it: new features without a release. Your users shape it: they describe what they need and the runtime renders it natively, inside a sandbox you define - the Stem AI Area, patent pending. The format is open and versioned, so modules drop into an app you already ship, alongside hand-written code, for the parts that change often. StemStudio AI is a mobile IDE for writing and running them. An MCP server lets an AI assistant emit modules directly, there are open-source example apps for both platforms, and the runtime has a free tier with no time limit.