Hide the API away too? You don't need to add another field to an existing API while in development, use a different endpoint altogether, to obscure the fact tha

Hide the API away too? You don't need to add another field to an existing API while in development, use a different endpoint altogether, to obscure the fact that it even exists. Then, part of the "keystone" can be merging it with the existing API. This is very specific to your example, but I guess my point is it is almost always possible to design your in-progress state in a way such that new features are obscured.