C# Dev Kit 3.20.x: “Run project associated with this file” no-ops on Linux

[RealShiftless]

Describe the Issue

After updating C# Dev Kit, the editor top-right run button / “Run project associated with this file” no longer works on Linux.

Clicking it does nothing: no visible error, no DevTools console error, and no useful output in the C# Dev Kit, C#, Projects, or Extension Host output panels.

This reproduces even in a fresh dotnet new console project, so it does not appear to be caused by my actual project.

Downgrading C# Dev Kit to 3.10.12 restores the expected behavior. The issue reproduces with C# Dev Kit 3.20.197 and 3.20.199.

Steps To Reproduce

1. Install C# Dev Kit 3.20.197 or 3.20.199 on Linux.

2. Create a fresh console project:

   dotnet new console -o DevKitButtonProbe
   code -n DevKitButtonProbe

3. Open Program.cs.

4. Wait for C# Dev Kit / the project system to finish loading.

5. Click the editor top-right play button dropdown.

6. Select “Run project associated with this file”.

Expected:
The console project runs.

Actual:
Nothing happens. No visible error appears.

I also reproduced this in a real mixed CMake + .NET workspace. Downgrading only C# Dev Kit to 3.10.12 makes the same run-button workflow work again.

Expected Behavior

Clicking “Run project associated with this file” should run the console project associated with the currently open Program.cs file, the same way it does in C# Dev Kit 3.10.12.

Environment Information

OS:

• Arch Linux x64

VS Code:

• Currently tested with VS Code 1.122.1
• I also originally reproduced this on VS Code 1.106.2 before updating VS Code.

Extensions tested:

• C# Dev Kit 3.20.199: broken
• C# Dev Kit 3.20.197: broken
• C# Dev Kit 3.10.12: works
• C# extension 2.140.8
• .NET Runtime Install Tool 3.0.2

.NET:

• .NET SDK 10.0.104
• MSBuild 18.0.11

[Mostafa-Ehab]

I can reproduce a related behavior when the workspace contains test projects, even if those test projects are not part of the active solution.

With C# Dev Kit 3.20.197/3.20.199, clicking "Run project associated with this file" does not appear to consistently launch the executable project associated with the current file. Instead, when test projects exist anywhere in the workspace, the generated command targets those test projects.

For example, when invoking the command from a source file in an executable project, I observed a command similar to:

dotnet test /path/to/MyApp.Tests/MyApp.Tests.csproj

even though the expected behavior would be to run the application project, for example:

dotnet run --project /path/to/MyApp/MyApp.csproj

Notably, this occurs even when:

• The active file belongs to a non-test executable project.
• The correct startup project is selected.
• The test projects are excluded from or commented out in the .slnx file.
• The command is invoked from a source file in the application project.

The behavior suggests that project resolution may be considering test projects discovered in the workspace rather than the selected project. In my case, test projects that were no longer present in the solution were still being referenced by the generated build command.

Downgrading to C# Dev Kit 3.10.14 restores the expected behavior, where "Run project associated with this file" launches the executable project corresponding to the currently open file and does not appear to be influenced by unrelated test projects elsewhere in the workspace.

Environment:

• Arch Linux x64
• VS Code 1.122.1

[Jomontalvo]

Hi Kayla (@RealShiftless)
It appears to be a problem with the update on ARM processors. I have the exact same problem with a MacBook M4, both on macOS and in a Windows 11 virtual machine. And if you look at the output of C# Dev Kit - Test Explorer, you'll see the following when clicking in Run project associated with this file /Debug project associated with this file:

2026-06-02 03:46:44.628 [info] Created Test Controller (Lightweight Test Experience)
2026-06-02 03:46:44.628 [info] Log verbosity: Info
2026-06-02 03:46:44.628 [info] C# Dev Kit version: 3.20.199
2026-06-02 03:46:45.971 [info] Initialized Test Explorer Server [70474]
2026-06-02 03:46:45.978 [info] The dotnet SDK was found in /usr/local/share/dotnet/sdk/10.0.300.
2026-06-02 03:46:46.039 [info] Initializing 1 project(s) from cache.
2026-06-02 03:47:03.549 [warning] No test projects to run.
2026-06-02 03:48:34.474 [warning] No test projects to run.

[matthiasbaitsch]

Had the same problem in my programming class today, the "Run Project" button consistently failed to work on all of the ~25 student's private computers.

[sotskopa]

Looks related to #3172, which has been fixed in the 3.21.* - prerelease.

[H3nryM4]

Looks related to #3172, which has been fixed in the 3.21.* - prerelease.

Has this bug been fixed in the official version?

[cyberps96]

Still not fixed as of today. The play button ("Run project associated with this file") is completely unresponsive on Linux.
Downgrading to 3.10.14 immediately resolved the issue for me.
Microslop really needs to test their Linux extensions before pushing broken updates.