Architecture preferences are a great example of things that we need to tell the LLMs.

We don't need to tell the LLM where the User model is. The LLM can find it.

However, IME we need to tell the LLM preferences like, "the User model should not have dependencies on other models" (you know, to avoid the God Model problem...)

To discover that preference, the LLM would (best case scenario) need to look at every model, and notice that the User model has no dependencies, but all the other models do, and infer that this is an architecture requirement. Except, some of our other leaf models might not have dependencies anyway, so it wouldn't necessarily be apparent. Or maybe it's a new project and none of the models have dependencies in which case our preference could not be deduced. Etc. All of this is token-intensive and unreliable.

(Perhaps even more ideally than placing this instruction in AGENTS.md or similar, it could be an inline comment in the User model itself. However, I have found LLMs to be very hit-or-miss when it comes to recognizing directives inside inline comments. And some architecture rules can't be easily expressed via inline comments in a particular file...)