Failed ci jobs:
https://qe-private-deck-ci.apps.ci.l2s4.p1.openshiftapps.com/view/gs/qe-private-deck/logs/periodic-ci-openshift-openshift-tests-private-release-4.18-multi-nightly-4.18-cpou-upgrade-from-4.15-aws-ipi-mini-perm-arm-f14/1842004955238502400

https://qe-private-deck-ci.apps.ci.l2s4.p1.openshiftapps.com/view/gs/qe-private-deck/logs/periodic-ci-openshift-openshift-tests-private-release-4.18-arm64-nightly-4.18-cpou-upgrade-from-4.15-azure-ipi-fullyprivate-proxy-f14/1841942041722884096

The 4.15-4.18 upgrade failed at stage of 4.17 to 4.18 update while authentication operator degraded and unavailable due to APIServerDeployment_PreconditionNotFulfilled

$ omc get clusterversion
NAME      VERSION                                    AVAILABLE   PROGRESSING   SINCE   STATUS
version   4.17.0-0.nightly-arm64-2024-10-03-172957   True        True          1h44m   Unable to apply 4.18.0-0.nightly-arm64-2024-10-03-125849: the cluster operator authentication is not available

$ omc get co authentication
NAME             VERSION                                    AVAILABLE   PROGRESSING   DEGRADED   SINCE
authentication   4.18.0-0.nightly-arm64-2024-10-03-125849   False       False         True       8h

$ omc get co authentication -ojson|jq .status.conditions[]
{
  "lastTransitionTime": "2024-10-04T04:22:39Z",
  "message": "APIServerDeploymentDegraded: waiting for .status.latestAvailableRevision to be available\nAPIServerDeploymentDegraded: ",
  "reason": "APIServerDeployment_PreconditionNotFulfilled",
  "status": "True",
  "type": "Degraded"
}
{
  "lastTransitionTime": "2024-10-04T03:54:13Z",
  "message": "AuthenticatorCertKeyProgressing: All is well",
  "reason": "AsExpected",
  "status": "False",
  "type": "Progressing"
}
{
  "lastTransitionTime": "2024-10-04T03:52:34Z",
  "reason": "APIServerDeployment_PreconditionNotFulfilled",
  "status": "False",
  "type": "Available"
}
{
  "lastTransitionTime": "2024-10-03T21:32:31Z",
  "message": "All is well",
  "reason": "AsExpected",
  "status": "True",
  "type": "Upgradeable"
}
{
  "lastTransitionTime": "2024-10-04T00:04:57Z",
  "reason": "NoData",
  "status": "Unknown",
  "type": "EvaluationConditionsDetected"
}

 4.18.0-0.nightly-arm64-2024-10-03-125849
 4.18.0-0.nightly-multi-2024-10-03-193054

    always

    1. upgrade from 4.15 to 4.16, and then to 4.17, and then to 4.18
    2.
    3.
    

    upgrade stuck on authentication operator

    upgrade succeed

    The issue is found in a control plane only update jobs(with paused worker pool), but it's not cpou specified because it can be reproduced in a normal chain upgrade from 4.15 to 4.18 upgrade.