runtime property
Runtime is the isolation boundary this sandbox GOT, which is not always the one it asked for: a caller states a preference and runtimeFor answers with what the sandbox can actually have. Reported so a person comparing two runtimes is comparing the runtimes they got rather than the ones they typed — the difference between those two is the whole reason to record it. Empty means the node's default runtime, which is a real answer and not a missing one. This is not a copy that can go stale. runtimeClassName is IMMUTABLE on a pod, a sandbox's pod is created once and never recreated (restartPolicy Never, no pool), and its name is never reused — so for as long as the pod this row names exists, it is running this runtime. The alternative, asking the apiserver on every read, buys nothing and costs a round trip per row.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? runtime;