I agree this is where enum coupling is beneficial. What I'm saying is that, if those fields are later used for other things in your system (like persisting to a

I agree this is where enum coupling is beneficial. What I'm saying is that, if those fields are later used for other things in your system (like persisting to a DB or running reports or something), you likely don't want to be re-validating the strings as closed enums, that's probably over-coupled. I don't think there's a silver bullet here, or some rule of thumb that can save us from these schema issues. It's messy and imperfect; we have static type systems that can help us locally but they are not global silver bullets. Unfortunately we still have to use our judgment to find the right balance, because the "perfect" solution requires knowledge of the future.