The behavior is a bit of an implementation detail. We don’t provision more than a single sandbox per user, so the data on disk within that sandbox can overlap when you have multiple concurrent sessions, even though the other aspects of the execution state are separate. I agree this is a bit surprising (though it has no security impact), and we’ve been discussing ways to make this more intuitive.
That writes can affect another session violates my expectations, at least, of the boundaries that’d be set.
The behavior is a bit of an implementation detail. We don’t provision more than a single sandbox per user, so the data on disk within that sandbox can overlap when you have multiple concurrent sessions, even though the other aspects of the execution state are separate. I agree this is a bit surprising (though it has no security impact), and we’ve been discussing ways to make this more intuitive.