I’ve been struggling on and off to get KPAX to work for the past few days. It turns out that the default method SLIME uses to communicate with the Lisp interpreter causes problems with the way s-sysdeps sets up the socket listening function in SBCL. The workaround is to set swank:communication-style to :fd-handler, but it has to be set before SLIME starts, so put the following form in ~/.swank.lisp

(defparameter swank:communication-style :fd-handler)

Now to get KPAX to work with mod_lisp…