[CI] iOS monotouch app launches but never connects to XHarness

[dalexsoto]

Summary

The iOS simulator monotouch test app intermittently launches but never connects to the XHarness test server. XHarness cancels the launch after three minutes and reports LaunchTimedOut after 15 minutes.

• Stable signature: ios27-monotouch-harness-startup-timeout
• Classification: genuinely flaky test / simulator startup failure
• Distinct monitored PRs: 2
• Confirmed occurrences: 4
• First observed by the monitor: 2026-08-12 02:31 UTC
• Latest observed: 2026-08-12 05:09 UTC

Confirmed occurrences

• [AutomaticAssessmentConfiguration] Update bindings up to Xcode 27.0 Beta 5 #26432, head 266d164665536f387afbf8717eea43781e28fdaf, build 14944204
  • Attempt 1: Debug (PrepareAssemblies) in T: monotouch_ios launched the app but never established the harness connection.
  • Attempt 2: the same signature moved to Debug (interpreter).
  • Attempt 3: the same signature moved to Release (interpreter).
  • Attempt 4 succeeded; final retry accounting was 3 lifetime / 3 head requests.
• [Bindings] Update multiple frameworks up to Xcode 27.0 Beta 5 #26438, head 1c46ed7045bad084f46a529392b8d6ccf1fdb64b
  • Build 14946633, attempt 1, T: monotouch_ios
  • Debug (PrepareAssemblies) launched com.xamarin.monotouch-test, but the app never connected; XHarness logged Test failed to start in 3 minutes and ultimately LaunchTimedOut.

Impact and investigation

The failing variation changes between attempts, while other variations in the same job pass. The app process is created successfully, but the test harness never receives a connection. This is not the NSUrlSession test hang and is not a deterministic product assertion failure.

Workaround

Rerun only the failed T: monotouch_ios job after confirming the PR is conflict-free and retry budgets permit it. Azure logs and artifacts are retention-limited.

[dalexsoto]

PR #26438 retry/head update:

• The failed-job retry for head 1c46ed7045bad084f46a529392b8d6ccf1fdb64b was superseded when the PR advanced to c12070bcb25ea8e62f8ed751289073f3bbb2d32b.
• Fresh package, API-diff, and simulator builds are now active on the new head.
• Retry accounting remains 1 PR-lifetime / 0 current-head retries for the new revision.

No additional retry was submitted, and the new head will be diagnosed independently if the startup signature recurs.

[dalexsoto]

New recurrence on PR #26438 head c12070bcb25ea8e62f8ed751289073f3bbb2d32b:

• Build 14949997, T: monotouch_ios attempt 1 timed out in both Debug (LinkSdk) and Release (all optimizations).
• In both configurations the app process launched, never established the XHarness connection, and the run reported Test run never launched after the 15-minute timeout.
• Classification: genuinely flaky recurring simulator startup failure matching this issue.
• An Azure DevOps failed-job retry was attempted through the API, but was conclusively rejected because the current identity lacks Update build information permission. No retry attempt was created and the request was not resubmitted.
• Accepted retry accounting remains 2 PR-lifetime / 1 current-head.

Current canonical count: 2 distinct PRs / 6 confirmed occurrences. This issue has no Additional info to collect checklist.