Expo SDK 55 Beta Arrives with React 19.2

React 19.2, included in Expo SDK 55, introduces a new `<Activity />` component designed to manage the lifecycle of components, which will be a significant change for how developers handle UI state. Previously, developers had to choose between unmounting components and losing state, or keeping them mounted and facing performance issues. The new component allows parts of the UI to be "hidden" without being fully unmounted, preserving state and improving performance. The beta also brings an opt-in for Hermes v1, a new version of the JavaScript engine optimized for React Native. This update shows early signs of significant performance improvements and better support for modern JavaScript features like ES6 classes and async/await. However, using Hermes v1 in this SDK requires building React Native from source, which can increase native build times. A major improvement for over-the-air (OTA) updates is the introduction of Hermes bytecode diffing. This feature is estimated to reduce the download size of updates by about 75% by sending only the changes (diffs) instead of the full bundle. This results in faster updates for end-users and more efficient use of bandwidth on EAS plans. Expo Router sees continued maturation with more native capabilities, including a new Colors API for dynamic styling on Android and adaptive colors on iOS. Experimental support for SplitView on tablets and native zoom transitions on iOS are also part of the updates, pushing Expo Router closer to a truly native navigation experience. For developers working with existing native applications, SDK 55 enhances "brownfield" support with a new `expo-brownfield` package. This allows for an isolated approach where the React Native part of an app can be packaged as a native library, which can then be consumed by native developers without them needing to set up a Node.js environment. React 19.2 also adds React Performance Tracks to Chrome DevTools, giving developers a clearer view of how React's scheduler works on a frame-by-frame basis. These tracks visualize internal priorities, component rendering, and effects, which aids in debugging and performance profiling. The default project template has been refreshed to more closely resemble a real-world production app structure, now including a `/src/app` directory and native tabs by default. Additionally, `expo-blur` is now stable on Android, utilizing the more efficient RenderNode API on Android 12 and newer for performant background blurs.