System.Net.Quic.QuicException : Connection handshake was canceled due to the configured timeout

```
System.Net.Quic.QuicException : Connection handshake was canceled due to the configured timeout of 00:00:10 seconds elapsing.
Stack Trace:
/_/src/libraries/System.Net.Quic/src/System/Net/Quic/QuicConnection.cs(96,0): at System.Net.Quic.QuicConnection.g__StartConnectAsync|2_0(QuicClientConnectionOptions options, CancellationToken cancellationToken)
/_/src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs(222,0): at System.Net.Quic.Tests.QuicTestBase.CreateConnectedQuicConnection(QuicClientConnectionOptions clientOptions, QuicListener listener)
/_/src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs(257,0): at System.Net.Quic.Tests.QuicTestBase.CreateConnectedQuicConnection(QuicClientConnectionOptions clientOptions, QuicListener listener)
/_/src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs(191,0): at System.Net.Quic.Tests.QuicTestBase.CreateConnectedQuicConnection(QuicClientConnectionOptions clientOptions, QuicListenerOptions listenerOptions)
/_/src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs(191,0): at System.Net.Quic.Tests.QuicTestBase.CreateConnectedQuicConnection(QuicClientConnectionOptions clientOptions, QuicListenerOptions listenerOptions)
/_/src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicTests.cs(604,0): at System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError(String ipString, Boolean expectsError)
```

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1591361
Build error leg or test failing: System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError
Pull request: https://github.com/dotnet/runtime/pull/133598

## Error Message

**DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK** otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "System.Net.Quic.QuicException : Connection handshake was canceled due to the configured timeout",
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1591361
**Error message validated:** `[System.Net.Quic.QuicException : Connection handshake was canceled due to the configured timeout`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 9/10/2026 10:36:11 PM UTC

### Report

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1596878](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596878)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596878&view=ms.vss-test-web.build-test-results-tab&runId=44082626&resultId=198010)|dotnet/runtime#133922|
|[1596502](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596502)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596502&view=ms.vss-test-web.build-test-results-tab&runId=44073612&resultId=184710)|dotnet/runtime#133914|
|[1596300](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596300)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1596300&view=ms.vss-test-web.build-test-results-tab&runId=44069142&resultId=197792)|dotnet/runtime#133890|
|[1594854](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594854)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594854&view=ms.vss-test-web.build-test-results-tab&runId=44028778&resultId=209651)|dotnet/runtime#133833|
|[1594689](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594689)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594689&view=ms.vss-test-web.build-test-results-tab&runId=44024442&resultId=201455)|dotnet/runtime#133826|
|[1594357](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594357)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594357&view=ms.vss-test-web.build-test-results-tab&runId=44012196&resultId=194233)|dotnet/runtime#133803|
|[1594354](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594354)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594354&view=ms.vss-test-web.build-test-results-tab&runId=44012152&resultId=209614)|dotnet/runtime#133802|
|[1594179](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594179)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594179&view=ms.vss-test-web.build-test-results-tab&runId=44007060&resultId=170029)||
|[1593908](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593908)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593908&view=ms.vss-test-web.build-test-results-tab&runId=43995694&resultId=201841)|dotnet/runtime#133774|
|[1593761](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593761)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593761&view=ms.vss-test-web.build-test-results-tab&runId=43991252&resultId=201599)|dotnet/runtime#133739|
|[1593630](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593630)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1593630&view=ms.vss-test-web.build-test-results-tab&runId=43988238&resultId=212081)|dotnet/runtime#133199|
|[1592602](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592602)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592602&view=ms.vss-test-web.build-test-results-tab&runId=43965000&resultId=191955)|dotnet/runtime#133690|
|[1592367](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592367)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592367&view=ms.vss-test-web.build-test-results-tab&runId=43958302&resultId=218631)|dotnet/runtime#130407|
|[1592254](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592254)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592254&view=ms.vss-test-web.build-test-results-tab&runId=43953524&resultId=144847)||
|[1591361](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1591361)|dotnet/runtime|[System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1591361&view=ms.vss-test-web.build-test-results-tab&runId=43928982&resultId=196541)|dotnet/runtime#133598|
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|3|15|15|

Start with src/libraries/System.Net.Quic/src/System/Net/Quic/QuicConnection.cs and the connection helpers in src/libraries/System.Net.Quic/tests/FunctionalTests/QuicTestBase.cs. Run System.Net.Quic.Tests.MsQuicTests.ConnectWithCertificateForLoopbackIP_IndicatesExpectedError and compare the repeated build failures in the report. Done means the test no longer fails with the handshake-timeout error.

Written by the indexing model from the issue text.