I know exactly what you mean. Earlier versions of Dagger actually took this "embedding" approach: any CUE configuration is a valid Dagger configuration, with an extra layer of annotation that describes how to make that configuration runnable. What we learned is that this model is thoroughly confusing to almost everyone except hardcore CUE enthusiasts.
Now we use CUE in a more straightforward way: as a superior replacement for YAML. There's a (simple) schema that all Dagger plans must follow; beyond that, you can import any CUE package and apply any definition into your plan. But you don't need to go upstream and annotate these packages with additional Dagger metadata.
I'm not sure if my explanation is clear - even I get confused by this embedding business sometimes.
It looks like dagger is using cue as a bit more than a YAML replacement; it hydrates cue values as it runs - which is cool! - but that's the part that seemed at odds with CUE's philosophy of pushing nondeterminism into clearly marked files.
Yes, we use CUE as more than just a YAML replacement. In particular we use CUE references to construct the DAG and "compile" it to buildkit.
And, yes, Dagger will gradually fill the missing values in the CUE tree during runtime. Essentially resolving the DAG on the fly. It is pretty cool :)
We have discussed this topic at length with the CUE developers. Our conclusion is that CUE's deterministic core is what matters, and the `_tool.cue` pattern is more peripheral: more of a reference for how other tools might use cue for non-deterministic operations. It's not realistic for CUE to be both a ubiquitous deterministic language, and a successful non-deterministic tool. Its priority is clearly the former, and we're focusing on the latter.
Now we use CUE in a more straightforward way: as a superior replacement for YAML. There's a (simple) schema that all Dagger plans must follow; beyond that, you can import any CUE package and apply any definition into your plan. But you don't need to go upstream and annotate these packages with additional Dagger metadata.
I'm not sure if my explanation is clear - even I get confused by this embedding business sometimes.