Kotlin: Unknown JVM target version: 25

IntelliJ Platform
1

I am writing a simple plugin for the Simula language.
The compiler produces an executable .jar and I want to execute it using JDK 25.

I tried to run my plugin, I got:
error: simula/plugin/extensions/lang/SimulaFileType has been compiled by a more recent version of the Java Runtime (class file version 69.0), this version of the Java Runtime only recognizes class file versions up to 65.0,

Then, During rebuild project, I got:
Kotlin: Unknown JVM target version: 25
Supported versions: 1.8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24

I use:
IntelliJ IDEA 2025.3.1
Build #IU-253.29346.138, built on December 18, 2025
Source revision: 9478cb03fae44
Runtime version: 21.0.9+1-b1163.86 amd64 (JCEF 137.0.17)
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.awt.windows.WToolkit
Windows 11.0
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 2048M
Cores: 16
Registry:
ide.experimental.ui=true
Non-Bundled Plugins:
org.jetbrains.completion.full.line (253.29346.138)
intellij.webp (253.28294.218)
Subversion (253.29346.170)
DevKit (253.29346.50)
com.intellij.spring (253.29346.157)
com.jetbrains.restClient (253.29346.170)
intellij.jupyter (253.29346.138)
org.jetbrains.plugins.kotlin.jupyter (253.29346.138)
org.jetbrains.idea.maven (253.29346.138)
com.intellij.mcpServer (253.29346.142)
Kotlin: 253.29346.138-IJ

With settings:
IntelliJ Project Settings
Project SDK: Go to File | Project Structure | Project:
SDK: 25 java version “25”
Language level: 25 - Compact source files, module imports
Project SDK: Go to File | Project Structure | Modules:
Module SDK: Project SDK 25

  • main: Module SDK: Project SDK 25
    • Kotlin: JVM 25
  • test: Module SDK: Project SDK 25
    • Kotlin: JVM 25

IntelliJ Plattform Settings
SDK: 25 - C:\Program Files\Java\jdk-25

In build.gradle.kts:
kotlin {
compilerOptions {
jvmToolchain(25)
}
}

PS C:\GitHub\WorkSpaces\Intellij\SimulaPlugin> ./gradlew --version

Gradle 9.2.1

Build time: 2025-11-17 13:40:48 UTC
Revision: 30ecdc708db275e8f8769ea0620f6dd919a58f76

Kotlin: 2.2.20
Groovy: 4.0.28
Ant: Apache Ant™ version 1.10.15 compiled on August 25 2024
Launcher JVM: 25 (Oracle Corporation 25+37-LTS-3491)
Daemon JVM: C:\Program Files\Java\jdk-25 (no JDK specified, using current Java home)
OS: Windows 11 10.0 amd64

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