SLIME could be useful if you want to use Emacs and Emacs Lisp for the front-end. Luckily, I already have an Emacs Lisp frontend :). SLIME also supports multiple connections to the same Lisp process, but that's not very well tested. (swank:create-server has :dont-close argument for this purpose.) OK, I'll take a look at that. Any other advice from people who have already tried this would be appreciated. Of course, implementing your own protocol/server (instead of using SLIME) has also some advantages: [...] A good strategy might be to use SLIME as front-end until some key parts of your application work. Then you can decide whether you need your own protocol/server for the communication with the font-end. Yeah, that seems reasonable.