## We Pinned Our Model Version to Stay Safe. The Provider Deprecated It Anyway. The recurring cost of production AI is not inference. It is re-qualification: the eval reruns, prompt retuning, and regression testing you owe every time a model changes under you. Here is what that tax actually covers, and how to budget for it before it surprises you. The email arrived on a Tuesday. A model we had been running in production for the better part of a year, pinned to a specific version on purpose, was being deprecated. We had a window to migrate. After that, the endpoint would start returning…