I’m in the exact same boat, although Codex isn’t quite as bad.
Fable smacked me for asking it to design a secure app without obvious security flaws and to double check it wasn’t using libraries with known security problems.
Agree, out of the two, I can get Codex to design and implement security systems (Fable just refuses to discuss). I've only used K3 a little bit, but I found that being able to discuss attack vectors and their mechanics gives me details to paste back into Codex for it to ingest. I could never have gotten there through Codex alone.