Edit: I remembered the problem. It's not closing the last tab, it's closing the window that closes all tab groups for that window. More generally, the problem for me is that tab groups are local to a window. In practice this basically means that if you want to use tab groups, you can't also use multiple windows, because managing multiple windows each with multiple tab groups pretty much guarantees that you'll go insane trying to keep track of where everything is and which windows are safe to close.

I think I would much prefer if tab groups were shared across windows, and each window would "claim" a tab group as its own. Closing that window would either close that tab group or even just "detach" from it, leaving the tab group available for another window to claim it. Essentially, it would work sort of like tmux only with windows and tab groups instead of terminals and shells. (Possibly with the limitation that only one window can view a given tab group at once.)

I'd love to use tab groups to organize a large number of tabs, but ultimately, the fact that your tab groups are always a single close button away from being blown away is a deal breaker. (I know I can restore the window to get them back, but that's only if I remember while that closed window is still in the "Recently Closed Windows" menu.)

It's a pity, they really were a guiding light of open source.

> The Tab Groups (Panorama) feature will be removed from Firefox in version 45. We know this may be inconvenient and we apologize. Removing the Tab Groups feature will make it easier for us to improve Firefox.

This is plain stupid. How much effort could it be to maintain this feature? Compared to Hello, or Rust, or Servo? None of these are useful to most Firefox users, but tab groups were. How more complex is this than the WebMaker or Persona, stuff that practically no-one uses? Is this harder that writing their current homepage, with blocks, pictures and fancy? I'm not touching a Mozilla product again.