[browser] Wasm.Build.Tests BuildThenPublishWithAOT (Chrome) times out due to ChromeDriver port-binding race (Connection refused) #134534

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1594894
Build error leg or test failing: Wasm.Build.Tests.BuildPublishTests.BuildThenPublishWithAOT (Chrome) / Workloads-ST-Wasm.Build.Tests.BuildPublishTests.WorkItemExecution
Pull request: #133387

Error Message

{
  "ErrorMessage": ["Process timed out", "Connection refused", "ChromeDriver was started successfully"],
  "ErrorPattern": "",
  "BuildRetry": true,
  "ExcludeConsoleLog": false
}

Details

On Ubuntu.2604.Amd64.Open, BuildThenPublishWithAOT (Chrome host) times out with:

System.AggregateException : One or more errors occurred. (Process timed out. Last 20 lines of output:
[wasm test-browser] Connection refused [::ffff:127.0.0.1]:45663 (localhost:45663)
[wasm test-browser] Connection refused [::ffff:127.0.0.1]:45663 (localhost:45663)
[wasm test-browser] Starting ChromeDriver 126.0.6478.0 (...) on port 45663
[wasm test-browser] Only local connections are allowed.
...
[wasm test-browser] ChromeDriver was started successfully.

Console log: https://helixr1107v0xd1eu3ibi6ka.blob.core.windows.net/dotnet-runtime-refs-pull-133387-merge-296b7f4f97714f0dae/Workloads-ST-Wasm.Build.Tests.BuildPublishTests/1/console.88065f7e.log?helixlogtype=result

Interestingly, later in the same log the app under test actually runs to completion (test-main.js exiting ... with result 42), but the harness/xharness wrapper still reports the overall process as timed out, and the paired Workloads-ST-Wasm.Build.Tests.BuildPublishTests.WorkItemExecution work item on the same Helix job reports BadExit. This suggests a startup race between the xharness client connecting and ChromeDriver finishing binding to its local port, rather than a genuine test/product regression — the failing PR (#133387) only bumps runtime-assets test-data dependencies and does not touch WASM/mono/xharness code.

Build Analysis reports non-trivial historical hit rates for these two legs (0.29% and 2.27% respectively) but there is currently no open Known Build Error tracking them.

A prior, similarly-worded issue (#104349, "[browser] Connection refused in 127.0.0.1") existed but was explicitly closed as a "misleading catch-all filter" that hid other distinct bugs (per maintainer comments), rather than being root-caused/fixed. This issue is filed narrower (requiring both the Connection refused and ChromeDriver was started successfully lines to match) to avoid repeating that problem.

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1594894
Error message validated: [Connection refused ChromeDriver was started successfully]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 9/23/2026 6:23:40 PM UTC