By limiting what the harness execute. The LLM has the reasoning. The harness is what makes it an agent, it’s a while loop continuously prompting a model, and processing tool calls. You don’t have to expose tools calls that make it possible to execute any process! OpenAI decides what tool can be called and how, they have full control over this and should be hold responsible for running so many instances with basically full execution permission and very little oversight
The issue here for OpenAI is that they can limit what their harness can execute, but if they try to sell API access to the model, someone else would try to rebuild that harness, and in all likelihood be able to succeed pretty well (especially once they get things running to the point of being able to use the model's reasoning to help them come up with clever obfuscation and such).
They are a company that's built a business and crazy-high valuation on "this is 'intelligence' that we can sell to everyone as a service" but seem to have ended up instead in the much-smaller-addressable-market space of "this is a weapon that we can't sell to just any old person off the street."