GNU Emacs Lisp Reference Manual

15.4.6.1: Global Break Condition

A global break condition stops execution when a specified condition is satisfied, no matter where that may occur. Edebug evaluates the global break condition at every stop point. If it evaluates to a non-nil value, then execution stops or pauses depending on the execution mode, as if a breakpoint had been hit. If evaluating the condition gets an error, execution does not stop.

You can set or edit the condition expression, stored in edebug-global-break-condition, using the X command (edebug-set-global-break-condition).

The global break condition is the simplest way to find where in your code some event occurs, but it makes code run much more slowly. So you should reset the condition to nil when not using it.