Exact same bug as Bug 1012784 which is apparently not resolved in version 41.0a2 (2015-07-25). How to cause this bug: Attempt to drag a tab from a window to outside the window. Expected result: The tab in the original window will disappear, a new window will open, and the tab will be successfully moved to the new window. Actual result (bug): The tab remains in the original window, is unable to be deleted and, once another tab is switched to, one cannot switch back to that tab. Additionally, a new window is created, but with a blank tab rather than the desired tab. This only happens while e10s is enabled.

This was broken by bug 936092

I am not sure if this is the same bug, but intermittently, dragging the tab results in nothing instead of a new window (see attachment). This is happening on the latest Nightly (7/31) on MacOS X.

[Tracking Requested - why for this release]: Appears to have user impact, tabs do not work intermittently on latest Nightly. Setting status to 'affected' because affected in Nightly.

We can track this for now, but don't need to track it for 42 beyond aurora, since e10s is turned off in beta/release.

Yeah so I can't reproduce the problem listed in the first comment, all I can see is that from comment 3.

So I can't reproduce this and the issue I could reproduce is being tracked in bug 1156703 so I can't really work on this. Matt, can you reproduce this on a current nightly build?

Well I just now updated to 41.0a2 (2015-08-05) to give it a try. It's mixed results, but in short, yes. I was able to initially drag a tag to create a new window, but when attempting to drag it back to the main window, it creates a blank new tab on the main window - this tab doesn't load and cannot be opened again. The second window still shows the tab you try to drag, along with a new tab. If you close that new tab, the entire window closes (both tabs). So it's still a bit buggy, but unfortunately it's a bit harder to define now.

(In reply to Matt W. from comment #8) > Well I just now updated to 41.0a2 (2015-08-05) to give it a try. It's mixed > results, but in short, yes. This is a developer channel build, not a nightly build. But I can't reproduce this on developer channel either. Can you disable all your add-ons and try again?

Yeah, after some tinkering with a few add-ons I've discovered it's the "Private Tab" add-on which is quite disappointing. With that add-on disabled, it works fine now. It's a shame that isn't a native feature in Firefox; private tabs would be far easier than windows.

e10s is disabled in 42, so get this off the radar.

Is there a way to remove this bug or at least remove the flags on my two prior comments? I just narrowed down a recent burst of spam at my private email to being when I first posted this bug. I already changed my account's email but I need the commend flags GONE.