I like the bubblewrap approach, it just happens to be Linux-only unfortunately. And once privileges are dropped for a process it doesn't appear to be possible to reinstate them.
What other dev OSs are there?
> once privileges are dropped [...] it doesn't appear to be possible to reinstate them
I don't understand. If unprivileged code could easily re-elevate itself, privilege dropping would be meaningless ... If you need to communicate with the outside, you can do so via sockets (such as the bind-mounted X11 socket in one of the readme Examples).
Consider one wanted to replicate the human-approval workflow that most agent harnesses offer. It's not obvious to me how that could be accomplished by dropping privileges without an escape hatch.
And I think that what CC's /sandbox uses on a Mac