Structured Concurrency in Swift 6 vs. Kotlin Coroutines: What Your KMP Team Needs to Unlearn

What We Will Build Let me show you a pattern I use in every production KMP project: a concurrency-at-the-edges architecture that keeps your shared Kotlin module clean while letting Swift 6 and Android each own their concurrency models. By the end, you will understand exactly where Swift 6 and Kotlin coroutines disagree, why your current shared concurrency code is a ticking bug factory, and how to restructure it in under an hour. Prerequisites A working KMP project targeting iOS and Android Kotlin 1.9+ with Kotlin/Native Xcode 16+ with Swift 6 strict concurrency enabled Familiarity with suspend functions and Swift's async/await Step 1: Understand Where the Models Diverge Here is the gotcha that will save you hours. Swift 6 and Kotlin coroutines look similar on the surface, but they enforce safety at fundamentally different levels: Concern Kotlin Swift 6 Data race prevention Runtime discipline Compile-time ( Sendable checking) Scope enforcement Convention-based Compiler-enforced Thread c