An architectural doctrine for NestJS projects: a breakdown of typical codebase degradation scenarios and the structural constraints that keep them from emerging as the feature set grows. For three parts we've watched how an "ordinary" NestJS project arrives at forwardRef and the rest of the wall. It's time to answer the question, "how not to do this." This is the moment to say "Clean Architecture" — and immediately offer a caveat. Anyone who has read about it for more than five minutes knows: there are so many contradictory interpretations grazing around this term that for two different people "Clean Architecture" means two different systems. It isn't a single approach, and it isn't the circles Bob Martin drew in the form of commandments. It's a family of ideas that converges on a single thesis: business logic is separated from infrastructure, and dependencies flow in only one direction . Everything else is implementation choices.…