A colleague pointed me to a sandbox that actually handles egress control properly. Spent the weekend testing it.
One of our platform engineers mentioned a new sandbox launch he came across. Said it does something he had not seen before with network egress controls. I was skeptical but spent the weekend poking at it.
The problem we have is agents executing code we did not write and calling APIs we cannot fully predict. Most sandbox solutions give you full network access or nothing. Neither works for us.
What I found is that each sandbox is a Firecracker micro-VM with its own kernel, so there is no shared kernel risk. The egress enforcement happens at the kernel level through eBPF with a per-sandbox allowlist for outbound traffic, bandwidth quotas, and no inbound by default. The part that actually surprised me is the overlay networking with DNS between sandboxes. You can run a distributed workload inside isolated sandboxes and have them talk to each other. Pause and resume works, and you can fork a running sandbox into N copies for parallel evaluation through a server-side copy that does not pull data to the host. There is a self-host option for teams that need data residency.
A few things to be aware of. It is alpha. SOC 2 is on the roadmap, not shipped. Create latency is in seconds, not milliseconds. No Python SDK yet, TypeScript works anywhere JS runs.
I am not associated with the project. Just passing along what I found in case it saves someone else a weekend of research.