I think it's pretty clearly not a bug. Chrome behaves the same way. Private session is cleared when all windows are closed. I am curious though. What happens i

I think it's pretty clearly not a bug. Chrome behaves the same way. Private session is cleared when all windows are closed. I am curious though. What happens if you drag a private tab into its own window? Is state shared with the original private window? How is this communicated to the user? And what if I drag a different private window tab into the new private window? Does each tab retain it's original window? Edit: you might be interested in the Firefox add-on Temporary Containers. You can open a new tab in its own container that isn't shared with anything else