Many mobile teams reach a point where maintaining duplicate implementations across iOS and Android becomes unsustainable. React Native promises a unified approach, but a full rewrite is rarely an option - in practice, most migration efforts are discarded as infeasible. RN Brownfield is the solution - a set of tools for embedding RN apps in native apps as self-contained libraries, which allows for a gradual adoption of React Native in native applications.

In this talk, we will do a deep dive into the internals of Brownfield: how RN apps are packaged, what tooling is needed (nav, state), why we had to implement a custom Gradle Plugin, a few things about real-life problems with transitive dependency handling, SO stripping, how Hermes V1 is handled on Android, how prebuilt RN core on iOS (0.81+) is handled with backwards compatibility, SPM support, and how integration of this complex library with Expo is handled using just 1 line of code for the end user, thanks to an Expo config plugin.