the ai running part of your business has a shutdown date. the vendor sets it, and you find out in an email.

you did not buy a tool. you rented a model version that lives on the vendor's calendar, and that calendar is now moving. openai retired gpt-4o and several others from chatgpt in february, told developers in june that older gpt-5 and o3 snapshots come out of the api in december, and set the assistants api to shut off in august. if you pinned a workflow to one of those, the fix everyone reaches for is to point it at the newest model and move on. that is not a swap, it is a silent behavior change: the new model reads your prompts differently, trips your guardrails differently, and passes the cases the old one failed while failing the ones it used to pass, with nothing on screen to tell you. the danger is not the shutdown notice, it is trusting the replacement without re-checking it. before the forced date, pull ten real inputs your automation handles, run them on the new model, and compare the output to what the old one produced. keep those test cases and the rules in your own files, not the vendor's, so the next time they change the engine under you it takes an afternoon to prove whether the business still works.