[testing] Random failures on CI iOS device tests: app fails to start after install with xharness

[rmarinho]

Description

We're experiencing random failures on CI device tests for iOS. After installing the app on the simulator using xharness, the app fails to start.

Failed build log excerpt:

dbug: Xamarin.Hosting: Simulator device failed to launch com.microsoft.maui.essentials.devicetests.
dbug: Underlying error (domain=FBSOpenApplicationServiceErrorDomain, code=4):
dbug: The request to open "com.microsoft.maui.essentials.devicetests" failed.
dbug: error HE0042: Could not launch the app 'com.microsoft.maui.essentials.devicetests' on the device 'iOS 18.5 (22F77) - iPhone Xs': simctl returned exit code 4
dbug: Test run failed
dbug: Could not find pid in mtouch output.

• Link to failed build: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=12016739&view=logs&j=98722e33-6750-50cb-8419-95b2cae9d431&t=299b78b0-3620-5696-8ea1-1e27a1166e9b&l=559
• Link to a successful build on the same machine: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=12015415&view=logs&j=bcab9ef3-1348-5aa3-7545-b5f3f972e9ad&t=8f50c246-a37a-572c-c729-238cc6def949&l=2517

This seems to be intermittent, as the same machine can have both good and bad runs. Please investigate possible causes for the simulator app launch failure after install, and if there are any known workarounds or fixes for this scenario.

Steps to Reproduce

1. Run CI device tests for iOS with xharness.
2. The app installs on simulator, but fails to launch.
3. Observe failure on random runs; other runs on same machine succeed.
4. See provided build links for detailed logs.

Is this a regression from previous behavior?

Not sure, did not test other versions

Affected platforms

iOS

Affected platform versions

iOS 18.5 (22F77) - iPhone Xs

Relevant log output

dbug: Xamarin.Hosting: Simulator device failed to launch com.microsoft.maui.essentials.devicetests.
dbug: Underlying error (domain=FBSOpenApplicationServiceErrorDomain, code=4):
dbug: The request to open "com.microsoft.maui.essentials.devicetests" failed.
dbug: error HE0042: Could not launch the app 'com.microsoft.maui.essentials.devicetests' on the device 'iOS 18.5 (22F77) - iPhone Xs': simctl returned exit code 4
dbug: Test run failed
dbug: Could not find pid in mtouch output.

More logs

CoreSimulator_2B700A95-6B62-415D-90DB-7B0BC510A9D9_2025-07-23-11-59-11.zip
DiagnosticReports_2B700A95-6B62-415D-90DB-7B0BC510A9D9_2025-07-23-11-59-11.zip

test-results.zip