error building IDEA 2026.2.0.1: Kotlin: Plugin classpath entry points to a non-existent location: $KOTLIN_COMPOSE_COMPILER_PLUGIN$

Hello Alan! It looks like a JPS-related issue (the build system integrated into IDEA). Can you please clarify do you use JPS intentionally?  Does the issue occur if you try to use Gradle? You can open Build settings in IntelliJ IDEA - Build Tools - Gradle and check the "Buils and run using" option. 
Do you use Windows with space symbols in your account name?

There are several tickets with the same looking message in YouTrack: KTIJ-23378, KTIJ-26333, KTIJ-26571, KTIJ-28028.

I suggest creating a separate YouTrack ticket regarding your case and provide more details about the reproduction (the exact repro steps, a repro-project, environment). 

Thank you!