Kotlin v2.4.20-RC released!

NewsBot · 12 August 2026 12:24

Kotlin v2.4.20-RC has been released.

Changelog

Backend. J2KLIB

KT-88165 Add Support for -XheaderModeType=compilation to improve header compilation performance

KT-86239 [JKLIB] Investigate which type system context is needed in JklibIrLinker

KT-88306 [JKLIB] Unbound symbols for kotlin.coroutines.SuspendFunctionN

KT-88120 [JKLIB] Add -jvm-target to K2JKlibCompilerArguments

KT-88176 [JKLIB] DeserializationStrategy.WITH_INLINE_BODIES when deserializaing dependencies

KT-88163 Allow to disable firAggressivePrunner for Jklib

Compiler

KT-87499 ClassCastException “Float cannot be cast to Unit” when a suspend function’s result is discarded in a when-branch

KT-87983 CCE on member extension property delegated to bound property reference

KT-85403 kotlin.NoWhenBranchMatchedException on Kotlin Native with sealed interface

KT-87922 K1FakeDescriptorsForReferencesKt classes duplicated between kotlin-scripting-compiler-embeddable and kotlin-build-tools-impl

KT-86657 Native: turn on incremental compilation by default

Compose compiler

b/543684938 Fix composable singleton in function with type parameters

b/537617330 Fixed a bug that caused miscompilation of cross-module calls
to getters and setters, causing spurious runtime errors.

JVM. Reflection

[KT-87369](https://youtrack…

Link: Release Kotlin 2.4.20-RC · JetBrains/kotlin · GitHub