Sessions are cards that tell you what they're doing.
Sessions sit in a sidebar, not a tab strip, because each one carries real state. Ember reads the state off the screen itself: working, waiting on you, or idle. A small animated sprite on each card shows it, so you can see which agent needs you without opening anything.
Cards also carry the git branch and dirty count, and the one waiting on you tints amber with a quiet chime. Nothing goes to the notification centre.