Skip .NET SDK first-run experience in Helix work items#66916
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The .NET SDK first-run experience (welcome message, HTTPS dev cert generation, NuGet cache population) hangs on some macOS Helix machines during cert installation, taking >2 minutes and getting killed by the HelixTestRunner timeout (exit code 130). Setting DOTNET_NOLOGO and DOTNET_SKIP_FIRST_TIME_EXPERIENCE bypasses this entirely. The dev cert and NuGet cache are not needed for test execution. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR updates the Helix test runner’s process environment to avoid .NET SDK first-run initialization during Helix work item execution, addressing macOS Helix hangs during HTTPS dev cert installation that lead to timeouts and CI failures.
Changes:
- Set
DOTNET_NOLOGO=1to suppress the .NET CLI welcome/banner output. - Set
DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1to skip .NET SDK first-run behaviors (including dev cert generation) for alldotnetinvocations made by the HelixTestRunner.
DOTNET_SKIP_FIRST_TIME_EXPERIENCE is deprecated and no longer honored in .NET 8+. The actual hang is in HTTPS dev cert generation, so set DOTNET_GENERATE_ASPNET_CERTIFICATE=false to skip it specifically. Also add DOTNET_NOLOGO and DOTNET_GENERATE_ASPNET_CERTIFICATE to runtests.sh and runtests.cmd alongside the existing (deprecated) DOTNET_SKIP_FIRST_TIME_EXPERIENCE, covering both the outer dotnet invocation and the inner HelixTestRunner child processes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Youssef1313
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May 29, 2026
| // DOTNET_SKIP_FIRST_TIME_EXPERIENCE is deprecated and no longer honored | ||
| // in .NET 8+. The replacement is individual controls: | ||
| // - DOTNET_NOLOGO: suppresses the welcome banner | ||
| // - DOTNET_GENERATE_ASPNET_CERTIFICATE: skips dev cert generation (the hang) |
Youssef1313
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May 29, 2026
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Approving. Let's ensure we have some tracking issue to revert once the root cause is fixed.
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Root cause
The
DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1variable set inruntests.sh/runtests.cmdis deprecated and no longer honored in .NET 8+. This means the .NET SDK first-run experience (including HTTPS dev cert generation) runs on every Helix work item.On macOS Helix machines, the dev cert generation hangs for >2 minutes, exceeding the HelixTestRunner's 2-minute timeout and killing the
dotnetprocess (exit code 130). From the logs:Passing machine (dci-mac-build-365): first-run takes 64 seconds — barely fits
Failing machine (dci-mac-build-322): first-run hangs >2 minutes → killed
This is the root cause of the widespread macOS CI failures (
osx.15.amd64.openqueue) that have been blocking PRs for over a week. Runningdotnet tool installmanually on the machines works fine because the first-run has already completed from that interactive session.Fix
Replace the deprecated variable with the current equivalents:
DOTNET_GENERATE_ASPNET_CERTIFICATE=false— skips the dev cert generation (the actual hang)DOTNET_NOLOGO=1— suppresses the welcome bannerSet in three places to cover all code paths:
runtests.sh/runtests.cmd— covers the outerdotnet HelixTestRunner.dllinvocationTestRunner.cs— covers child process invocations (dotnet tool install,dotnet nuget, etc.)