Test failure: TlsSessionTests.SocketBoundSession_DeferredOptions_MultipleSni_SelectsMatchingCert fails with Connection reset by peer on macOS #131798

Test

System.Net.Security.Tests.TlsSessionTests.SocketBoundSession_DeferredOptions_MultipleSni_SelectsMatchingCert

Added recently in #130366 (Add low-level TLS state machine API (TlsContext / TlsSession)).

Symptom

Failing in CI on the OSX.26.Arm64.Open Helix queue — 6 builds between 2026-07-24 and 2026-08-04 (pipelines runtime and runtime-nativeaot-outerloop).

System.IO.IOException : Unable to read data from the transport connection: Connection reset by peer.
---- System.Net.Sockets.SocketException : Connection reset by peer

Notes

New test from the low-level TLS state machine API (#130366); fails only on macOS 26 ARM64 so far. The sibling test SocketBoundSession_HandshakeAndPingPong_Succeeds shows the same "Connection reset by peer" symptom on macOS and is likely the same underlying issue.

Known issue core information

Fill out the known issue JSON section by following the step by step documentation on how to create a known issue.

{
  "ErrorMessage": "SocketBoundSession_DeferredOptions_MultipleSni_SelectsMatchingCert",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Additional information about the issue reported

The error message itself (Unable to read data from the transport connection: Connection reset by peer) is generic and shared with other socket tests, so ErrorMessage is set to the fully-qualified test method name to scope the match to this specific failure. Build Analysis matches the string against the failed test's reported error, which includes the test name.

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1538041
Error message validated: Unable to read data from the transport connection: Connection reset by peer
Result validation: ✅ Observed on osx.26.arm64.open in the above build (pipeline runtime, 2026-08-04). Additional failing builds: 1536154 (runtime-nativeaot-outerloop), 1532066, 1527700, 1526662 (runtime).

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1538041
Error message validated: [SocketBoundSession_DeferredOptions_MultipleSni_SelectsMatchingCert]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 8/4/2026 12:16:45 PM UTC

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Summary