Ask HN: Agents get dumber before release of new model version?

I've noticed an effect with openai where my codex agents seem to perform worse in the week(s) leading up to a new release. I'm wondering if the vendors tweak effort params at all to free up hardware to host the new version. It's a double win as the new model will look night and day better to their regular users when the new model is released presumably with effort back at normal levels.

Is this a known phenomenon? Are any folks trying to measure any of this objectively?