Claude has been pretty good at F# so far. Sometimes it makes mistakes as if it was OCaml but other than that I found the output actually better than C#. That is - the C# output has higher likelihood of being correct, but because there is so much absolutely terrible code out there - you have to coerce it to give you good output, which you don't need to do with F#.

And of course Github Copilot autocomplete works well just as it does for most other languages.