Steps to reproduce: - Use Aurora as your main browser - When Firefox Developer Edition (FDE) is released, download it - Launch FDE, note that it does not use your Aurora profile - Open the profile manager with /Applications/FirefoxDeveloperEdition.app/Contents/MacOS/firefox-bin -P - Select your old default profile (not the new FDE one) and tick the box to make it always use that profile - Wait for FDE to start, notice that it's now using your default profile - Quit FDE - Re-open FDE Expected: it should remember to use your default profile on restart Actual: it always goes back to the FDE profile. In other words, switching to the new default profile is not sticking across restarts. As a work around I manually copied my old default into the new FDE profile.

Note that at first I allowed Aurora to auto-update to FDE. This worked at first but at some point it crashed and went back to the FDE profile. I think maybe this was the crash but there were a couple. https://crash-stats.mozilla.com/report/index/377425fb-271e-4249-926a-e0db12141111

AIUI you should be able to open the preferences and untick the "allow Firefox Developer Edition and Firefox to run side by side" pref (or whatever the exact wording is) and have this work the way you want it to work. Does it not?

That did switch me back to the default profile, thanks. It still seems like a bug that you can't select it manually but I guess if 'use at the same time' is set than it wouldn't make sense to manually select your default profile. Feel free to close the bug ;)

Closing per comment 3.