Hacker News Reader

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

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 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.