GitHub Actions Failing to Build .NET 9.0 Project

[ZjzMisaka]

Description:
I recently updated my project to target .NET 9.0 after its release. I modified the csproj file to set the TargetFramework to .NET 9.0 and successfully built the project on my local machine. However, after committing the changes, the GitHub Actions workflow fails during the build step with the following error:

The current .NET SDK does not support targeting .NET 9.0. Either target .NET 8.0 or lower, or use a version of the .NET SDK that supports .NET 9.0. Download the .NET SDK from https://aka.ms/dotnet/download

This suggests that the version of the .NET SDK being used in the GitHub Actions environment does not yet support .NET 9.0.

Questions:

1. Is .NET 9.0 supported in GitHub Actions?
2. Do I need to configure my workflow specifically for .NET 9.0?

Task version:
actions/setup-dotnet@v3

Platform:

• Ubuntu
• macOS
• Windows

Runner type:

• Hosted
• Self-hosted

Repro steps:
https://github.com/ZjzMisaka/PowerThreadPool/blob/main/.github/workflows/test.yml

Expected behavior:
Successfully build

Actual behavior:
Build step with the following error:

The current .NET SDK does not support targeting .NET 9.0. Either target .NET 8.0 or lower, or use a version of the .NET SDK that supports .NET 9.0. Download the .NET SDK from https://aka.ms/dotnet/download

[hongbo-miao]

I may get a similar issue (?)

When I upgrade global.json from

{
  "sdk": {
    "version": "8.0.404",
    "quality": "release"
  }
}

to

{
  "sdk": {
    "version": "9.0.100",
    "quality": "release"
  }
}

I got error in my build:

Unhandled exception: System.Exception: The build host could not be found at '/usr/share/dotnet/sdk/9.0.100/DotnetTools/dotnet-format/BuildHost-net472/Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.exe'
   at Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager.AssertBuildHostExists(String buildHostPath)
   at Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager.GetDotNetFrameworkBuildHostPath()
   at Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager.CreateMonoBuildHostStartInfo()
   at Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager.GetBuildHostAsync(BuildHostProcessKind buildHostKind, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager.GetBuildHostWithFallbackAsync(BuildHostProcessKind buildHostKind, String projectOrSolutionFilePath, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadProjectFileInfosAsync(String projectPath, DiagnosticReportingOptions reportingOptions, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadProjectInfosFromPathAsync(String projectPath, DiagnosticReportingOptions reportingOptions, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.Worker.LoadAsync(CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.LoadSolutionInfoAsync(String solutionFilePath, IProgress`1 progress, ILogger msbuildLogger, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildProjectLoader.LoadSolutionInfoAsync(String solutionFilePath, IProgress`1 progress, ILogger msbuildLogger, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.MSBuild.MSBuildWorkspace.OpenSolutionAsync(String solutionFilePath, ILogger msbuildLogger, IProgress`1 progress, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Tools.Workspaces.MSBuildWorkspaceLoader.LoadAsync(String solutionOrProjectPath, WorkspaceType workspaceType, String binaryLogPath, Boolean logWorkspaceWarnings, ILogger logger, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Tools.CodeFormatter.OpenMSBuildWorkspaceAsync(String solutionOrProjectPath, WorkspaceType workspaceType, Boolean noRestore, Boolean requiresSemantics, String binaryLogPath, Boolean logWorkspaceWarnings, ILogger logger, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Tools.CodeFormatter.FormatWorkspaceAsync(FormatOptions formatOptions, ILogger logger, CancellationToken cancellationToken, String binaryLogPath)
   at Microsoft.CodeAnalysis.Tools.FormatCommandCommon.FormatAsync(FormatOptions formatOptions, ILogger`1 logger, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Tools.Commands.RootFormatCommand.FormatCommandDefaultHandler.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)
   at System.CommandLine.Invocation.InvocationPipeline.InvokeAsync(ParseResult parseResult, CancellationToken cancellationToken)

[aparnajyothi-y]

Hello @ZjzMisaka, Thank you for creating this issue and we will look into it :)

[ZjzMisaka]

Hello @ZjzMisaka, Thank you for creating this issue and we will look into it :)

Hi, thank you for the help, is there any progress, or something need my help?

[mahalakshmi-rekadi]

Hello @ZjzMisaka,
GitHub Actions supports .NET 9.0, but to use it, you need to install it externally and configure your workflow to use the correct SDK version. Since ubuntu-latest runners support up to .NET 8.0 version, you need to specify the .NET 9.0 SDK version in actions/setup-dotnet@v4 step.

Workflow Configuration:
To resolve this, update your workflow file to specify the .NET 9.0 SDK version as shown below:

steps:

• uses: actions/checkout@v4
  name: Checkout code
• name: Setup .NET
  uses: actions/setup-dotnet@v4
  with:
  dotnet-version: 9.0.x
• name: Restore dependencies
  run: dotnet restore PowerThreadPool/PowerThreadPool.csproj
• name: Build
  run: dotnet build PowerThreadPool/PowerThreadPool.csproj --no-restore

1.The specified Target Framework Monikers (TFMs) indicate compatibility with multiple .NET versions.
2.The .NET SDK version in the workflow determines the highest framework version supported during the build process.
3.Using the .NET 9.0 SDK ensures compatibility with all specified TFMs, including the newest framework versions.

For more details, refer to the Select which .NET version to use - .NET | Microsoft Learn.

Please let us know if you have any further questions or need additional support

[ZjzMisaka]

@mahalakshmi-rekadi Thank you, your suggestion works well. However, I’d like to know if the ubuntu-latest runner will support .NET 9.0 in the near future?
If native support for .NET 9.0 becomes available, I can re-run the previously failed Actions. While new GitHub Actions are running successfully, the failed ones remain in a failed state.

[hongbo-miao]

(I saw @ZjzMisaka 's change at https://github.com/ZjzMisaka/PowerThreadPool/pull/81/files and succeed. Strange, mine still failed, I will test more and if still no luck, will create a new ticket as @ZjzMisaka 's original question has been resolved. Thanks!)

[ZjzMisaka]

@hongbo-miao I'm not sure but maybe you should try to add this?

      - name: Setup .NET
        uses: actions/setup-dotnet@v4
        with:
          dotnet-version: 9.0.x

[hongbo-miao]

(Thanks @ZjzMisaka @mahalakshmi-rekadi for helping! Glad @ZjzMisaka 's original issue has been resolved. However, I was happy too early as I found my issue is complete different. I posted details at #563)

[mahalakshmi-rekadi]

Hello @ZjzMisaka ,

The timeline for native support of .NET 9.0 on ubuntu-latest is not specified.

If .NET 9.0 support becomes available, you can re-run the failed Actions to see if they pass. For now, continue specifying the .NET 9.0 SDK version in your workflow as recommended.

To stay updated on supported software versions for GitHub Actions runners, check these resources:

GitHub Actions Runner Images
GitHub Actions Blog

Please feel free to reach out if you have any concerns or need additional assistance.

Thanks!

[ZjzMisaka]

@mahalakshmi-rekadi Hi,
My action failed again and this time the log shows the following

App: /home/runner/work/PowerThreadPool/PowerThreadPool/UnitTest/bin/Debug/net6.0/testhost.dll
Architecture: x64
Framework: 'Microsoft.NETCore.App', version '6.0.0' (x64)
.NET location: /usr/share/dotnet/
The following frameworks were found:
  8.0.11 at [/usr/share/dotnet/shared/Microsoft.NETCore.App]
  9.0.0 at [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Learn more:
https://aka.ms/dotnet/app-launch-failed
To install missing framework, download:
https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=6.0.0&arch=x64&rid=linux-x64&os=ubuntu.[24](https://github.com/ZjzMisaka/PowerThreadPool/actions/runs/12430730648/job/34726171175#step:4:25).04
. Please check the diagnostic logs for more information.

Does that mean ubuntu-latest does not natively support .NET 6.0 now? should I edit test.yml again, or just wait?

[ZjzMisaka]

I found that this issue occurs when switching to use ubuntu-24.04 in the ubuntu-latest pipelines.

---

Update: I temporarily resolved this issue by upgrading the project's TargetFramework from NET6 to NET8. However, I still don't want GitHub Actions to have failure records caused by environmental factors.

May I ask if this issue will be resolved in the future, allowing me to rerun the Action to clear the existing failure records?