Ah, I'm using racketmode which doesn't support live state buildup (and the builtin GUI doesn't either). What exactly is your setup? SLIME only has a Common Lisp backend, it doesn't support Racket to my knowledge.

EDIT: ok with geiser and geiser-racket incremental state buildup works really well. I rescind my objection!

I think that should work in racket-mode as well. You can easily send individual sexps to the repl and add to the live state. However, one thing that CL does that Racket doesn't do (afaik) is when you change a data type (e.g. alter a struct), it automatically ensures live code uses the new types. In Racket by contrast I have to either carefully go through all affected forms and send them to the repl, or send the whole buffer to the repl. This does make the whole experience feel more static than in CL.

Oh, my mistake. I'm using Spacemacs and it looks like it's just using racket-mode..?

https://www.spacemacs.org/layers/+lang/racket/README.html

I'm guessing via swank: https://github.com/mbal/swank-racket