This issue crops up, for example, when debugging huge strings (imagine huge text files slurped into strings), and is caused by the interactions of *PRINT-PRETTY* and *PRINT-LINES*: *PRINT-LINES* is in effect only if *PRINT-PRETTY* is non-NIL Currently swank.lisp defines |(defvar *sldb-printer-bindings* | `((*print-pretty* . NIL) [...] | (*print-lines* . 200) | (*print-escape* . t)) | "A set of printer variables used in the debugger.") So effectively *PRINT-LINES* is not obeyed, and slime prints huge strings (containing newlines) through emacs, causing much burden on all systems. I suggest changing the binding for *PRINT-PRETTY* in *SLDB-PRINTER-BINDINGS* to T if nothing else depends on it. -- Madhu