This feels very broken to me, as the window seems to just disappear after accepting the dialog. Steps to produce: 1. Load a temporary extension using about:debugging 2. Check the "Enable add-on debugging" checkbox 3. Click debug and then accept the "incoming connection" dialog Expected: The Browser Toolbox window should stay in front of the browser window. Actual: The Browser Toolbox window gets moved to the back behind the browser window.

Yes, it's pretty unfortunate. It's because the Browser Toolbox opens in a separate Firefox process, but the "incoming connection" dialog is coming from the original Firefox, so interacting with the dialog focuses the original process, moving it above the Browser Toolbox process. A workaround is to disable the dialog by changing "devtools.debugger.prompt-connection" in about:config. Other bugs offer more long term approaches that solve this issue, such as bug 1013379 to automatically allow connections in some way and bug 1246715 to stop using a separate process.