fix: adopt UIScene lifecycle so iOS 27 apps launch

[thang2162]

Summary

Apps generated from this 0.87 template crash immediately on launch when built with Xcode 27 / the iOS 27 SDK. UIKit asserts in ___UIApplicationEvaluateRuntimeIssueForNoSceneLifecycleAdoption because the template still creates UIWindow from AppDelegate and does not declare a scene manifest.

This migrates the iOS template to the UIScene lifecycle using APIs that already exist on React Native 0.87 (startReactNative(withModuleName:in:launchOptions:)). It does not depend on RCTSceneDelegate or connectionOptions:, which only landed on 0.88+/main.

Related:

• [iOS] CLIENT OF UIKIT REQUIRES UPDATE: This process does not adopt UIScene lifecycle. This will become an assert in a future version. react/react-native#54739
• feat: adopt SceneDelegate #246 (main / 0.88+ SceneDelegate APIs)

Changelog

[IOS] [FIXED] - Adopt UIScene lifecycle so apps built with Xcode 27 launch on iOS 27

Test Plan

• Generated app from this template pattern and ran on iOS 27 simulator (iPhone 18 Pro)
• Confirmed the previous AppDelegate-only bootstrap SIGTRAPs in NoSceneLifecycleAdoption
• Confirmed the SceneDelegate bootstrap reaches Metro and shows the Welcome screen
• yarn test in this repo

Made with Cursor

[cortinico]

cc @cipolleschi

[cipolleschi]

Thanks for putting this together and for testing it on iOS 27.

Unfortunately, we can’t merge this PR into 0.87-stable. React Native 0.87 does not contain the complete UISceneDelegate support added in 0.88. Although this workaround allows the app to launch, it would introduce regressions:

• Cold-start deep links and Universal Links would be lost because they arrive through UIScene.ConnectionOptions, not the AppDelegate’s launchOptions.
• Links received while the app is running would not reach Linking, because 0.87 lacks the SceneDelegate forwarding APIs.
• Some window resizing, external-display, and development loading-view behavior may be incorrect because the corresponding scene-aware fixes are also absent from 0.87.

Backporting only the template changes would therefore leave 0.87 in a partially supported state. A safe solution would require backporting and releasing the relevant React Native core machinery as well, which is too broad and risky for the stable branch.

Thanks again for identifying the issue and proposing a solution. Full SceneDelegate support will be available starting with 0.88.