Kotlin ksp becomes unstable when using KSP Gradle plugin #225

Summary

Applying the KSP Gradle plugin (com.google.devtools.ksp) to a module makes the Kotlin LSP unstable. After the plugin is applied, imports from external libraries are no longer resolved: they don't get semantic highlighting, hover/peek doesn't work, and Ctrl+Click navigation silently fails (the cursor turns into the pointer hand on hover, suggesting navigation is available, but clicking does nothing).

The project itself compiles fine via Gradle — this is purely an LSP/editor experience issue.

Reproduction

libs.versions.toml:

[versions]
ksp = "2.3.9"

[plugins]
ksp = { id = "com.google.devtools.ksp", version.ref = "ksp" }

Root build.gradle.kts:

plugins {
    alias(libs.plugins.ksp) apply false
}

app/build.gradle.kts:

plugins {
    alias(libs.plugins.ksp)
}

Applying KSP to the module is enough to trigger the regression — no processors need to be registered as ksp(...) dependencies for the symptoms to appear.

Expected behavior

• External library imports are recognized and semantically highlighted.
• Ctrl+Click on an import or symbol from a library navigates to its declaration (decompiled source or attached sources).
• Hover/peek shows documentation and type info.

Actual behavior

• External library imports are not semantically highlighted.
• Ctrl+Hover shows the pointer-hand cursor as if navigation were available, but Ctrl+Click does nothing.
• No "Go to Definition" target is offered for library symbols.
• The behavior degrades the moment KSP is applied; removing the plugin restores normal LSP behavior.

Project-internal symbols (within the same module/codebase) still seem to resolve, but anything coming from a .jar dependency stops working.

Environment

• VS Code version: 1.126.0
• Kotlin by JetBrains extension version: 0.0.5
• Kotlin version: 2.3.21
• KSP version: 2.3.9
• Gradle version: 9.4.1
• JDK: 17.0.1 (openjdk)
• OS: Linux Mint 22.3 (zena) - Linux 7.0.0-14-generic (x86-64)

Additional notes

Gradle build, compilation, and KSP code generation all work correctly from the CLI. The issue is strictly with the LSP-driven editor experience after the KSP plugin is applied to a module.