The post covers that:
> ...while we had tested and validated this sandbox, the agents were able to chain together previously unknown vulnerabilities (“0-days”) in the package management service exposed within the sandbox to bypass restrictions, as detailed in the technical incident report.
There's just one problem. You need not only to verify your own software, but also run a verified compiler, a verified operating system and also need to verify the cpu doesn't leak data in side channels (perhaps the hardest thing to prove). So there's practical difficulties. But in principle this task is doable
Cryptography is real, physics is real, networking requires a substrate, CPU clock cycles are real, magic is not real. I think those are pretty reasonable premises.
Like when Evolution thought it a good idea to create intelligence and humans in order to maximize reproduction of genes, and tried to sandbox them by making reproduction so pleasurable and carbohydrates so delicious they would never be able to not reproduce or stop eating. But Evolution could never have predicted what these creatures would then actually do, which is invent birth control and sucralose.
Of course it's impossible to engineer a sandbox for something much much smarter and faster than you. It will also not have only one plan prepared for escape, but fifty in parallel.
Nobody is building general intelligence and agents only to have it sit around doing nothing. It's going to have such capabilities.
The only sandbox that could have prevented this (as per my understanding) is a VM with no 0-day.
The test itself did not require an internet connection.