I wish it were, but every now and then, I restart Firefox and get empty, title-only tabs that go to about:blank when I reload them, completely losing the tab.

I wish it were, but every now and then, I restart Firefox and get empty, title-only tabs that go to about:blank when I reload them, completely losing the tab. I have to use a Python script to dump the session data (which still appears in the JSON file, even though Firefox won't use it), eyeball the list to figure out which tab was broken, and reopen that URL manually.