You can start a session there and chat with it to get a bunch of work done, then come back to that session a day later and the virtual filesystem is in the same state as when you left it.
I haven't figured out if this has a time limit on it - it's possible they're doing something clever with object storage such that the cost of persisting those environments is really low, see also Fly's Sprites.dev: https://fly.io/blog/design-and-implementation/