TL;DR

Any UIKit app built with the iOS 27 SDK (Xcode 27) that hasn't adopted the UIScene lifecycle won't launch. React Native apps are UIKit apps, so every RN app is affected, whatever the RN version.

Deadline: the day you build with Xcode 27. Binaries built with Xcode 26 keep launching on iOS 27; Apple says it strives for binary compatibility but won't guarantee zero issues.

RN 0.88+: move startup into a SceneDelegate using the new startReactNative(withModuleName:in:connectionOptions:) , forward links to RCTLinkingManager , add UIApplicationSceneManifest to Info.plist .

RN 0.79–0.87: same shape, but you build the root view yourself from reactNativeFactory.rootViewFactory and handle cold-start links by hand.

RN 0.74–0.78: keep your RCTAppDelegate subclass, but build the window in a SceneDelegate from its rootViewFactory .

RN below 0.74: create the root view in SceneDelegate from the RCTBridge the AppDelegate owns, with RCTRootView(bridge:moduleName:initialProperties:) .

Watch: deep links, Universal…