Introducing Brownie: Type-Safe Shared State for React Native Brownfield Apps

Callstack has released Brownie (@callstack/brownie) in alpha, a type-safe shared state library for React Native brownfield apps. It solves the recurring problem of teams building custom Turbo Modules to share state between native and React Native code. Brownie uses a single TypeScript schema to define state, stores it in a C++ layer exposed via JSI, and auto-generates matching Swift types via CLI. It supports SwiftUI with a @UseStore property wrapper, UIKit with a subscription API, and React Native with a useStore hook. Currently iOS-only, with Android support planned.