In compat replace.py has these options: -save, -savenew, -savexc, -savexcnew
With -save / -savenew the bot will save titles to a file rather than making replacements. This makes possible "two-run workflow": first collecting titles automatically, which may be slow, without manual intervention, than working fast on the saved results.
With -savexc / -savexcnew we get a new choice "x": "Don't replace, and save the title to exceptions". The resulted exceptions may be copied from file to the exceptions dictionary of the fix for later use (next time you don't have to go through the same pages and waste your time).
For convenience, compat has a counter for both cases that writes the number of the saved titles to console upon finishing.
Without these features core version is useless for high-volume, repeated work. See also T99365.