What exactly is changing? Are these completely separate pieces as in can they be separately deployed services? Or are you talking about a View layer, middle/bus

What exactly is changing? Are these completely separate pieces as in can they be separately deployed services? Or are you talking about a View layer, middle/business layer, db layer in the same app? If they can be separate apps, then create APIs with agreed upon interfaces. Then do not change those interface contracts. Version them if they need to change then the other components can still use the old version while upgrading to the newer version of the interface contract if needed