Kotlin Multiplatform Jan 8, 2026 Pre-release

v2.3.20-Beta1

What's New

Kotlin v2.3.20-Beta1 introduces Collection Literals inference, unnamed local variables, and expanded contract support for property accessors. WebAssembly gains single module compilation with TypeScript generation and improved performance through eliminated unnecessary conversions. The Analysis API receives significant enhancements including KDoc extraction, functional type builders, and context parameter support, while the compiler fixes numerous edge cases in type inference, generic handling, and interoperability.

Highlights

Breaking Changes

  • K1 API deprecation level changed from Warning to Error
  • Nested type aliases from libraries forbidden for sources with language version below 2.3
  • Context receivers resolution removed in K2 compiler

Deprecations

  • KaFunctionType.arity deprecated in favor of parameter count methods
  • KaType.enhancedType renamed for clarity regarding Java nullability enhancement

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