I don't use it this way yet, but aider has a watch mode that would be fun with vim:

https://aider.chat/docs/usage/watch.html

I imagine with vim, from the document you're editing, you'd go:

:ter

to get a terminal. Fire up aider with --watch-files in the terminal. Hop back up to the file and start telling it what to do. Hit L when it's done to see the changes.

That's just a guess but after writing it out I kinda want to try it.

When I use aider it's via its chat interface and then I load the file with vim in another terminal tab to follow along but I think --watch-files with vim would be fun.