So, turns out that slime-indentation contrib has the hooks for just what I needed. ...only the code had a bit of bitrot in it, as intentation specs with symbols in them ended up having strings on the Emacs side. I just committed a fix for that, so what now I can do eg: (defvar *indentation-hint-table* nil) (defun hint-slime-indentation () (let* ((swank (find-package :swank)) (tables (when swank (find-symbol (string '#:*application-hints-tables*) swank)))) (when tables (let ((table (make-hash-table :test #'eq))) (setf (gethash 'defrule table) '(4 &lambda &rest (&whole 2 &lambda &body))) (set tables (cons table (remove *indentation-hint-table* (symbol-value tables)))) (setf *indentation-hint-table* table)) t))) (hint-slime-indentation) on the CL side to tell Slime how to indent things it's regular heuristics don't get right. Cheers, -- Nikodemus