Builds native iOS and Android apps, creates cross-platform mobile applications using React Native or Flutter, configures mobile build systems, and debugs platform-specific issues including crashes, permissions, and store rejections. Use when the user asks about mobile app development, iOS or Android projects, Swift, SwiftUI, Kotlin, Jetpack Compose, React Native, Flutter, mobile UI design, push notifications, offline sync, in-app purchases, .ipa or .apk builds, or app store submission.