Swift 6 Migration Checklist for an Existing Xcode 16 App

This article provides a detailed migration checklist for moving an existing iOS app to Swift 6 using Xcode 16. It emphasizes treating the migration as compiler-assisted cleanup rather than a dramatic flag flip, with opt-in language mode and complete concurrency checking. The guide covers inventorying targets, enabling strict concurrency checking in Swift 5 mode first, fixing root causes like UI state isolation, Sendable conformance, and shared mutable state, then switching the language version. It includes practical advice on handling third-party dependencies, public APIs, and main actor isolation, making it a valuable resource for iOS developers upgrading their codebase to Swift 6.