TypeLoadException in MsBuildCompilation due to Google.Protobuf version conflict with ARCore Extensions

[CisDutchRose]

Unity Version: Unity 6.5

Package: ARCore Extensions for AR Foundation

Platform: macOS (also likely affects Windows)

Description:

Opening any project with ARCore Extensions installed in Unity 6.5 produces a flood of TypeLoadException errors originating from Unity's internal MsBuild compilation system. The error occurs because ARCore Extensions bundles a Google.Protobuf.dll that conflicts with the version Unity 6.5's MsBuild pipeline expects (v3.23.0).

The error persists even after deleting the Library folder, reimporting assets, and reinstalling Unity 6.5. It only resolves when ARCore Extensions is completely removed from the project.

Error Message:

TypeLoadException: Invalid type UnityEditor.Scripting.ScriptCompilation.MsBuild.MsBuildCompilation for instance field UnityEditor.Scripting.ScriptCompilation.MsBuild.MsBuildCompilationInterface:msBuildCompilation

Steps to Reproduce:

1. Install Unity 6.5
2. Create or open a project
3. Import ARCore Extensions for AR Foundation
4. Observe TypeLoadException errors flooding the Console immediately

Expected Result: No errors. ARCore Extensions' bundled Google.Protobuf.dll should not conflict with Unity's internal MsBuild compilation system.

Actual Result: Hundreds of TypeLoadException errors appear, making the editor partially unusable. Script compilation is disrupted.

[CisDutchRose]

I manually downloaded protobuf 3.23.0 and replaced the older version. That seems to have fixed the issue for now.