This is a hard one as it's not easily repro'ed. Sometimes, when I close Cud with no explicit session file loaded, the changes in the current session (which should be saved in "history session.json") are not saved at all. Upon restarting Cud I get the session as it was when Cud was loaded last time, ie I start Cud and have three files t{1,2,3}.txt loaded. I close t2.txt and load t4.txt and close and restart Cud and get t{1,2,3}.txt.
Alas, this does not happen always. Sometimes a changed session is indeed saved but I can't see any logic or pattern to this.
There's a hint though: This happens both with Windows and Linux, v113.2, but it doesn't happen with v107.
Any ideas?