Implement Robust Mobile Deeplink Handling

The skill implements deeplink systems for iOS and Android apps, built around a consistent URL design - hierarchical paths like myapp://category/item/12345 with a fallback web URL for universal links, human-readable and versioned so app updates don't break old links. Platform guidance is explicit: iOS should prioritize Universal Links over custom URL schemes for security, Android should implement App Links with verified intent filters, and cross-platform frameworks (React Native, Flutter) need consistent link-parsing behavior on top of the native mechanism.

Use it to implement Universal Links on iOS - handling NSUserActivity/webpageURL in AppDelegate or SceneDelegate and serving an Apple App Site Association file that maps URL paths to the app - or App Links on Android via an autoVerify intent filter plus onNewIntent/Intent parsing in the activity. It also covers React Native routing through the Linking API (getInitialURL() for cold start, the url event for a running app), deferred deeplinking (holding a link in memory until the user finishes authentication), and generating shareable or campaign links with UTM parameters and a download fallback. It is not a general navigation/routing skill - it is scoped to how a link reaches and is parsed by the app, not the in-app navigation stack itself.

Input is an incoming URL (universal/app link or custom scheme) or a request to generate one. Output is either routed in-app navigation (mapping a path like /product/123 to a product screen) or a generated link string. Testing is done per platform from the command line:

# Test Universal Links
xcrun simctl openurl booted "https://myapp.com/product/123"

# Test URL Schemes
xcrun simctl openurl booted "myapp://product/123"

# Validate AASA file
curl -I https://myapp.com/.well-known/apple-app-site-association

Android has equivalent adb shell am start commands plus adb shell pm get-app-links to verify domain verification status.

On iOS it integrates with AppDelegate/SceneDelegate and the AASA file served from .well-known; on Android with AndroidManifest.xml intent filters and domain verification; on React Native with the core Linking module. It recommends monitoring deeplink analytics to catch broken links and track engagement.

Security guidance is explicit throughout: validate every deeplink parameter to prevent injection, require HTTPS for universal/app links, and test link handling across app states - cold start, background and foreground - since the same URL can arrive through three different code paths.

Mobile developers implementing or debugging deeplinks who need working platform-specific setup - Universal Links, App Links, deferred linking, link generation - and a security checklist covering parameter validation, HTTPS-only links, and graceful fallbacks for malformed or unhandled URLs.