If the model in use is managed by a 3rd party, can be updated at will, and also gives different output each time it is interacted with, what is the main benefit?

If I chat with an agent and give an initial prompt, and it gets "aspect A" (some arbitrary aspect of the expected code) wrong, I'll iterate to get "aspect A" corrected. Other aspects of the output may have exactly matched my (potentially unstated) expectation.

If I feed the initial prompt into the agent at some later date, should I expect exactly "aspect A" to be incorrect again? It seems more likely the result will be different, maybe with some other aspects being "unexpected". Maybe these new problems weren't even discussed in the initial archived chat log, since at that time they happened to be generated in a way in alignment with the original engineers expectation.