So, the interesting part for me was:
"Who runs the fleet Anthropic, its own E2B, rented, third party"
Like that's the only option, a bespoke platform or a rented SaaS for agent sandboxes.
Disclaimer: I am tooting my own horn here - we built SlicerVM.com (Firecracker + Apple Virtualization framework) so that people don't have to pick between those two options.
Especially when you have your own 1500-7000 USD MacBook right under your fingers.
For remote access, (and this happened by accident one night in January) we built superterm.dev - initially as a tmux manager, then as a way to run and monitor agents. Our team sits with 6-24 long running tasks with dictation available, great mobile experience, and can combine both for secure agents + high amounts of feedback.
If anyone's curious - Superterm has a CE edition - free for unlimited personal use. Slicer has a free trial and then a personal edition is available after that.