The devtools toolbox includes a button to make the toolbox vertical, and a button to make it a standalone window: https://developer.mozilla.org/en-US/docs/Tools/Tools_Toolbox#Toolbox_controls. If I make an add-on using "dev/panel" that adds a new panel to the toolbox, then switch to my new panel, then try pressing these buttons, things break. Specifically, it looks as if the frame for the toolbox switches, but all the content stays where it is, and various things no longer work properly. I get this error in the Browser Console: > A promise chain failed to handle a rejection. > Did you forget to '.catch', or did you forget to 'return'? ...with a link to toolbox.js, line 1322. This is with Nightly (35.0a1 (2014-09-30)), using a fresh checkout of the SDK, and: cfx run -b /path/to/nightly -o

I am experiencing the same problem with Firebug 3 Honza