I am on Mac OS X 10.9.5 (Mavericks). I have a late 2013 MacBook Pro running in clamshell mode with an external 27 inch Apple monitor attached to it.

I am logged in with two users, A and B. When I do a fast user switch from user A to user B, most windows that were open for user B when I last worked with that user are resized and some windows even change their position. Maximized windows are affected the most, typically they become less in height while staying the same in width. It feels as if initiating the user switch had temporarily changed the screen size or resolution, causing windows to change their size/position to adjust for the smaller screen size.

Is this a known problem of Mac OS X in general, or of running a MacBook in clamshell mode? Has anyone experienced this as well and/or knows how to fix it?

I can't remember when exactly I have noticed this problem for the first time. I am certain that it didn't exist with older versions of Mac OS X (i.e. 10.8 and older), although I must say that when I was last using Mac OS X 10.8 I also had a different MacBook and a different monitor. The general work environment MacBook/clamshell mode/external monitor has been the same for me for years.

  • Note that the windows of user A are kept intact, only B's windows are messed up. Of course, if you log A and B out and login in the reverse order, then only A's windows get messed up. Oct 6, 2014 at 2:24

1 Answer 1


It's a known bug of the 10.9.3 update that has been reported last May. Sadly, it has yet to be fixed.

Possible workarounds:

  • Hide your windows before fast user switching. The app Notes is immune to the bug, so you can switch to that app and hide all other windows from there.

  • Use the app stay (cost $14.99, not checked)

Another workaround that works for some people (but not for me) is to kill the dock before fast user switching. Can even be automated following these instructions.

  • FWIW: Rebooting the machine also helps (for those who don't want to mess with the terminal to kill the dock)
    – herzbube
    Oct 17, 2014 at 14:44
  • @herzbube: Rebooting won't help at all, except that it might look like it because you will now be the first logged in user (unaffected by the bug). Oct 17, 2014 at 17:47
  • Hm... I haven't performed any system updates since I wrote the question, yet I can now switch between users without experiencing any window resizes. The only thing that I can think of that has changed is that I have rebooted the system once. I imagine that the dock will "go crazy" again after I leave the system running for a few more days/weeks (I usually put the machine to sleep at the end of the day, but I shut down only rarely).
    – herzbube
    Oct 18, 2014 at 0:43

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