Editor not working after Visual Studio 18.4.0 update

[julealgon]

I immediately stopped getting any handling on .props files after opening Visual Studio after just having updated it to version 18.4.0 today.

The files open with zero highlighting:

Same behavior observed in other file types, such as csproj:

[espenrl]

• Visual Studio 2026 Community Insiders [11605.296] (March 2026)
• Visual Studio as Arm64 native process (Windows on ARM)

I'm experiencing the same for all MSBuild files. The features are not working, no colorization, no auto-complete.

The following exception is shown at startup

System.ArgumentException: Failed to get the editor factory manager for 4c9bc7a2-907a-44aa-99ea-d1b57b1a20f8.
   at Microsoft.VisualStudio.PlatformUI.Packages.ShellService.EditorFactories.EditorFactoryRegistrar.<GetMatchingEditorFactoryAsync>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Platform.WindowManagement.WindowFrame.<>c__DisplayClass86_0.<<CreateEditorInstanceAsync>g__GetEditorFactoryAsync|0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Platform.WindowManagement.WindowFrame.<CreateEditorInstanceAsync>d__86.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Platform.WindowManagement.WindowFrame.<LoadDocumentFrameInternalAsync>d__85.MoveNext()

It's related to MSBuild Editor as I found the guid in the source code.

MonoDevelop.MSBuildEditor/MonoDevelop.MSBuild.Editor.VisualStudio/PackageConsts.cs

Line 14 in c77880a

public const string EditorFactoryGuid = "4C9BC7A2-907A-44AA-99EA-D1B57B1A20F8";

Even though the editor seems to be registered.

NOTE: I'm also using ReSharper though it doesn't change anything when I disable ReSharper.

[espenrl]

Seems to be an issue with loading assemblies. Log output from devenv /log

ActivityLog.xml

[espenrl]

Seems like the logic behind IntrinsicFunctions have diverged between MSBuild and the replicated logic in this repository. But I'm not entirely sure. See https://github.com/dotnet/msbuild/commits/337c1237984c11add49298f8682b1ab1a3a7db12/src/Build/Evaluation/Expander/WellKnownFunctions.cs

[jmoralesv]

I noticed the same as the others, the highlighting in the props and csproj files is missing. I've disabled the extension in the meantime.

My main concern is that the extension was not updated since 2024, so maybe we will not see an update in the near future?