https://openai.com/index/updating-our-preparedness-framework... goes through the process. Anthropic has a similar framework, that's why Mythos was never publically accessible once initial tests like the one in OP revealed it's capabilities.
Appendix C Illustrative safeguards, controls, and efficacy assessments has specific examples like:
- Agent actions are all logged in an uneditable database, and asynchronous monitoring routines review those actions for evidence of harm
- Limiting internet access and other tool access
- Limiting credentials
- Limiting access to system resources or filesystem (e.g., sandboxing)
- Limiting persistence or state