Kotlin Multiplatform v2.1.0-Beta2 Release Notes & Developer Guide

Kotlin 2.1.0-Beta2 delivers significant performance improvements across the Analysis API with caching and lazy resolution, adds Xcode 16 support for Apple developers, and introduces WebAssembly incremental compilation. The K2 compiler gains stability with numerous debugger and private member access fixes, while new features include Kotlin-to-Java direct actualization and Compose's PausableComposition. Breaking changes include dropping language versions 1.4-1.5 and enforcing stricter requirements for external functions in Kotlin/Native.

Highlights

• Xcode 16 support for Apple ecosystem with XCFramework fixes
• WebAssembly incremental compilation and improved array type conversions
• Analysis API performance improvements with caching and lazy resolution
• Kotlin-to-Java direct actualization for expect/actual declarations
• K2 compiler stability fixes for debugger and private member access
• Compose compiler PausableComposition feature and deep copy optimization
• JVM bytecode version 23 support and language version 1.4/1.5 removal