CUE’s core operations are defined so that the order in which configurations are combined is unimportant.
We say that order is irrelevant in CUE.

This crucial property explains how CUE is able to handle a field being specified multiple times. Because each occurrence of a field is as important as every other, all occurrences must not conflict with each other.

Order irrelevance makes it easy for humans and machines to reason about values, and makes advanced tooling and automation possible.

a: {X: 1, O: int}
a: {X: int, O: 2}

b: {X: int, O: 2}
b: {X: 1, O: int}

$ cue eval file.cue
a: {
    X: 1
    O: 2
}
b: {
    X: 1
    O: 2
}