[github-actions]

Related issue(s): #15433, #14568, #14593

Context

Daily CI analysis found three tests failing intermittently across at least three independent rolling main builds. Quarantining them keeps normal validation stable while definition 344 continues gathering cross-platform evidence.

Changes Made

Quarantine ReusedTaskHostDiscardsOutputFromCachedWriter

Flaky-test key (automated de-duplication — do not edit):

flaky-test-id: Microsoft.Build.Engine.UnitTests.MSBuildMultithreaded_Tests.ReusedTaskHostDiscardsOutputFromCachedWriter

Adds a Windows-scoped [ActiveIssue] after 11 failures across 3 rolling builds from 2026-10-19 through 2026-10-29 on FullOnWindows and FullOnWindows Release (net11.0, net472). Tracked by #15433.

Quarantine RedundantMSBuildReferences

Flaky-test key (automated de-duplication — do not edit):

flaky-test-id: Microsoft.Build.UnitTests.CodeTaskFactoryTests.RedundantMSBuildReferences

Adds a Windows-scoped [ActiveIssue] after 4 failures across 3 rolling builds from 2026-10-19 through 2026-10-29 on Windows net472 legs. Tracked by #14568.

Quarantine BuildTaskSimpleCodeFactory_RedirectFrom4

Flaky-test key (automated de-duplication — do not edit):

flaky-test-id: Microsoft.Build.UnitTests.CodeTaskFactoryTests.BuildTaskSimpleCodeFactory_RedirectFrom4

Adds a Windows-scoped [ActiveIssue] after 4 failures across 3 rolling builds from 2026-10-19 through 2026-10-29 on Windows net472 legs. Tracked by #14593.

Compatibility

Normal CI will exclude these tests through the existing Category=failing trait. The quarantine pipeline continues running them on its dedicated schedule; product behavior, APIs, and diagnostics are unchanged.

Testing

• ./build.sh — blocked before compilation because the runner lacks the /run/user/1001 runtime directory required by the downloaded .NET SDK/NuGet first-run setup. PR CI is the first compile validation.
• git diff --check — passed.

Dependencies and Follow-up

The tracking issues remain open until separate deterministic fixes are validated and merged.

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• 169.254.169.254

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "169.254.169.254"

See Network Configuration for more information.

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