> The repo you’re working on, sure. But all files?

Yes, any tool, including any coding agent, has access to all files $USER has access to.

Sandbox it explicitly to give access to only the current directory - https://github.com/ashishb/amazing-sandbox

Not sure what that's about, I was just copying the wording from OP. Their harness probably has the same restrictions as most other coding harnesses. That is, the read tool gives all project files by default without prompting, and everything else requires manual approval (or opting into auto-run all). If you decide to run it from your home directory however, then your "project" is all your files.