### What needs to get done With certain exceptions, `build-base` and `base` should not be able to differ from each other. `build-base` is thus optional but must match `base`. Currently known exceptions: - `base: bare` allows any build base, but it requires `build-base` to be defined. - Any in-development base must be matched with its appropriate build-base. (Craft Application provides those mappings, but the app can apply supplemental mappings. An in-development base is defined as one that exists in either of those mappings.) - An app may implement a method that provides specific overrides, but the use of this method is discouraged and only there for legacy purposes ### Why it needs to get done Currently apps are enforcing this (or not enforcing it) ad-hoc. We should move to this being strictly enforced with the app being able to loosen those requirements if needed.