(Feel free to update this bug's summary to be more specific.)
Component Readiness has found a potential regression in the following test:

[sig-arch][Feature:ClusterUpgrade] Cluster should remain functional during upgrade [Disruptive] [Serial]

Extreme regression detected.
Fishers Exact probability of a regression: 100.00%.
Test pass rate dropped from 100.00% to 30.77%.

Sample (being evaluated) Release: 4.21
Start Time: 2025-11-18T00:00:00Z
End Time: 2025-11-25T16:00:00Z
Success Rate: 30.77%
Successes: 4
Failures: 9
Flakes: 0
Base (historical) Release: 4.20
Start Time: 2025-09-21T00:00:00Z
End Time: 2025-10-21T23:59:59Z
Success Rate: 100.00%
Successes: 79
Failures: 0
Flakes: 0

View the test details report for additional context.

Seems to be nearly every job run. Separate from the recent problem where multi-arch upgrade jobs were trying to jump 4.19 to 4.21.

Filed by: dgoodwin@redhat.com