[Flaky Test] Microsoft.Build.Engine.UnitTests.MSBuildServer_Tests.ServerSpawnAndReuseAreLoggedToBuildLog

**Flaky-test key** (automated de-duplication — do not edit):
```text
flaky-test-id: Microsoft.Build.Engine.UnitTests.MSBuildServer_Tests.ServerSpawnAndReuseAreLoggedToBuildLog
```

## Evidence

- **Assembly**: `Microsoft.Build.CommandLine.UnitTests`
- **Fully-qualified name**: `Microsoft.Build.Engine.UnitTests.MSBuildServer_Tests.ServerSpawnAndReuseAreLoggedToBuildLog`
- **Distinct sources**: 3 (0 PRs + 3 rolling builds)
- **Rolling builds**: [1514373](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1514373), [1517682](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1517682), [1527742](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1527742)
- **Legs**: FullOnWindows Release
- **TFMs**: net472
- **First seen**: 2026-07-17 | **Last seen**: 2026-07-27
- **Total failures**: 3
- **Error hashes**: 3 distinct (`f2f3ee09`, `4af42ebc`, `347b6841`)

### Sample error

```
Shouldly.ShouldAssertException : output.ShouldNotContain(reusedMessage)
```

See [sample build](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1514373) for details.

## Action

This test will be quarantined with `[ActiveIssue("")]` (from `Microsoft.DotNet.XUnitV3Extensions`, namespace `Xunit`) until the underlying nondeterminism is fixed. The quarantine pipeline (def 344) will continue running it to gather signal.

> [!WARNING]
>
> Firewall blocked 2 domains
>
> The following domains were blocked by the firewall during workflow execution:
>
> - `awmgmcpg`
> - `southcentralus0.in.applicationinsights.azure.com`
>> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter:
>
> ```yaml
> network:
> allowed:
> - defaults
> - "awmgmcpg"
> - "southcentralus0.in.applicationinsights.azure.com"
> ```
>
> See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information.
>
>

> Generated by [Flaky Test Triage](https://github.com/dotnet/msbuild/actions/runs/30267259222) · sonnet46 · 153.8 AIC · ⌖ 6.72 AIC · ⊞ 14.7K · [◷](https://github.com/search?q=repo%3Adotnet%2Fmsbuild+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Fmsbuild%2Fflaky-test-detector.agent%22&type=issues)

Start with Microsoft.Build.Engine.UnitTests.MSBuildServer_Tests.ServerSpawnAndReuseAreLoggedToBuildLog in the Microsoft.Build.CommandLine.UnitTests assembly and review the rolling-build failures, especially the reusedMessage assertion. Use the quarantine pipeline results to identify the nondeterminism. Done means the test no longer flakes on FullOnWindows Release net472 and the quarantine can be removed.

Written by the indexing model from the issue text.