For one, I’ve been working on a generic sandbox environment

github.com/brianv0/formwork

You should be easily able to hide/lock down files, network, and MCP tools from an agent and it shouldn’t be up to the agent.

> files, network, and MCP tools

Locking that down to nothing is trivial for any harness: just don't expose those to the LLM.

The tricky part is allowing access to those.

sure it’s not tricky. But everybody does it different and OpenAI couldn’t even be bothered to do it right when benchmarking their models