Worked on the openai/codex repository to resolve a sandbox policy issue that blocked numpy usage within secure environments. Addressed a critical bug by modifying the seatbelt base policy, specifically enabling read access to hw.physicalcpu, which restored numpy import functionality inside the sandbox. This targeted fix improved parity between sandboxed and host environments, allowing numpy-dependent data processing and testing workflows to function reliably without workarounds. The work involved applying expertise in sandbox security and system configuration, utilizing the Seatbelt Policy Language to implement the change. The update enhanced the stability and usability of numpy in sandboxed contexts for ongoing experimentation.