Kubernetes' node tests fail a lot. Most of the time someone re-runs them, they go green, and everyone moves on.

Over the past week I picked four failures in SIG Node territory and refused to move on — I kept reading the logs until the timeline explained the failure. Three were CI flakes. The fourth was a second, separate bug hiding inside a reported kubelet 1.37 memory regression. In every case, the bug wasn't where the error message pointed.

Status, to be upfront: as of October 10, 2026, all four of my fixes are open pull requests, triaged or awaiting review, not merged. This post is about the investigations — which is the part I'd want to read anyway.

How I read a failing CI run

Every Kubernetes CI run on Prow keeps its artifacts: the build log, the JUnit results, the kubelet and containerd logs from the node, and for node tests, the VM's serial console. TestGrid shows the history, so you can tell a one-off from a pattern.

My loop for each flake:

Find the pattern in TestGrid.…