Swift 6.3 made Swift on Android official, which changes the question for mobile teams. It is no longer "can this run?" but "what is worth sharing?" In this session I will walk through a pragmatic architecture: native SwiftUI on iOS, native Compose on Android, and Swift used for the product logic that should not be written twice. We will look at boundaries, async APIs, generated interop, local persistence, and team ergonomics. This is not about replacing Kotlin or forcing one architecture onto two platforms. It is about using Swift where it creates leverage, while keeping each app feeling native. You will leave with a practical model for deciding what to share, what to keep platform-specific, and what tradeoffs to expect.