I moved a while back when Claude started refusing to do security audits and also failed to run properly in my sandbox without a lot of wrangling. Renamed Claude.md to agents.md and had no problems at all. There’s almost 0 switching cost.

I’ve been using both at the same time, but fable had me hitting my limits; even less will have me get 2x codex max instead of one of each.

No. Here's a data point: I tried it for a few days. While it worked fine I didn't see any benefit to switching since it costs the same ($100) and I've spent a year getting up to speed on Claude usage and quirks.

I for one, and I know of plenty others.