I strive to make this NOT the case, by fixing up my skills or agents.md whenever they don't work how I want in one provider or the other. I mean, yeah, it would be awesome if I was a virtuoso with all the agents/models I use. But I am switching all the time, either because one leapfrogs the other, or because I hit limits (I'm on $200/mo on both Claude and Codex, and also subscribe to some others when I hit limits on both of those simultaneously).