Calling a model successfully is not the same thing as building a reliable AI product.
A prototype can often be created quickly. Send some context to a model, receive a response, place it inside an interface, and an AI feature appears to work.
Production changes the requirements. Real users arrive. They have different permissions. Data changes. APIs fail. Knowledge becomes outdated. Model behavior varies. Outputs need validation. Sensitive workflows need review.
At that point the core engineering question is no longer simply which model to call.
The question becomes: what complete software system is required to make the intelligence useful, observable, secure, maintainable, and appropriate for the work?