Yeah, you've certainly been able to get Opus to write a CRDT. It just needs a lot of hand-holding to make it correct. Opus always seems pretty bad at coming up with invariants and using them to make a piece of software correct. Without invariants, you end up with lots of hacky workarounds to avoidable problems.

So far at least - and its been less than a day - Fable seems better at this.

I think I also do my CRDTs differently from others. I've grown to like the pure-oplog approach after making eg-walker. LLMs are much worse at this!