How to reproduce:
1. Open the attached “IN-109015.zip” Project
2. Open the “SampleScene”
3. Select the “Test” Prefab GameObject in the Hierarchy
4. Observe the Crash

Reproducible with: 6000.2.0b12, 6000.3.0a3
Couldn’t test with: 6000.0.54f1, 6000.1.14f1 (non-fixable compilation errors in custom package due to downgrade)

Reproducible on: macOS 15.5 (M3 Pro), Windows 11 (user’s)
Not reproducible on: No other environment tested

Notes:
- Package with problematic code appears to be related to [https://github.com/Rumi727/RuniEngine]
- Reproducible in Release and Debug Modes, also reproducible with Dev Mode

Workaround:
1. Open the Project
2. Open the “FileExtension.cs” Script (Packages → Runiverse OS Core → Runtime → IO)
3. Make the “OnAfterDeserialize()” function an empty function e.g: “OnAfterDeserialize(){}”

First few lines of the stack trace:
{{0x000002A5D027E6B4 (Mono JIT Code) [.\Packages\com.rumi.runiengine.core\Runtime\Debug.cs:61] Debug:LogText (string,object) }}
{{0x000002A5D027D2A3 (Mono JIT Code) [.\Packages\com.rumi.runiengine.core\Runtime\Debug.cs:13] Debug:Log (object,string) }}
{{0x000002A5D027D243 (Mono JIT Code) [.\Packages\com.rumi.runiengine.core\Runtime\IO\FileExtension.cs:116] RuniEngine.IO.FileExtension:OnAfterDeserialize () }}
{{0x000002A5D02799A8 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void_{}this{}_ (intptr&,intptr,intptr,intptr) }}
{{0x00007FFCBE5C6D3E (mono-2.0-bdwgc) [C:\build\output\Unity-Technologies\mono\mono\mini\mini-runtime.c:3445] mono_jit_runtime_invoke}}