Upgrading to 1.9.20-RC and I get the following error when trying to build with gradle: Unable to find method ''java.util.List org.jetbrains.kotlin.gradle.plugin.mpp.KotlinJsCompilation.getRelatedConfigurationNames()'' 'java.util.List org.jetbrains.kotlin.gradle.plugin.mpp.KotlinJsCompilation.getRelatedConfigurationNames()' Works fine if I go down to 1.9.10

What version of Gradle are you running? Check compatibility at https://docs.gradle.org/current/userguide/compatibility.html

8.1.1 which works fine for 1.9.10 . Do I need to upgrade to 8.4? Which would mean I need Java 21?

You don't need Java 21 for Gradle 8.4, it's the other way around: you need Gradle 8.4 for Java 21. It might be a bug in the Kotlin Multiplatform Gradle plugin; there's a new RC2 out now.

I tried RC2 as well, and it didn't work.

I don't think so. Only if you want to use Kotlin Gradle DSL with 1.9.x stuff – not to just compile Kotlin code.

Ok. So it looks like it's a bug of some kind.

I just tried an admittedly simple project and could compile with Kotlin 1.9.20-RC2 and Gradle 8.1.1

Hmm...

You could try using the upcoming Gradle 8.5 (which I guess might be released next month) at https://gradle.org/nightly/

Just tried. No luck. Same issue. Shame. I've been waiting for a bugfix in 1.9.20 for many moons.

Are you using the latest version of the plugin, not just the dependency?

plugins {
  kotlin("multiplatform") version "1.9.20-RC2"
}

Yes.