A browser you left open comes back where it was.
A reopened session already gave you back who its browsers were. Now it gives you back their pages too: the urls are saved beside the identity, and the first command aimed at a declared browser starts it and reopens the tabs it had. Click a pane that says "not up" and it wakes, with a stopwatch on it - starting an engine takes seven to fourteen seconds and an interface that goes quiet for that long is telling you nothing.
It happens once. After the wake, the tabs are the browser's own business.
A browser that dies mid-command is rebuilt the same way now: the same person, back on the same pages. Before this it came back correct and empty, and the only way to notice was to go looking for your own work.