OpenAI Codex CLI

TL;DR

OpenAI's open-source Rust coding agent — 549K lines, 88 crates, native OS sandboxing on macOS/Linux/Windows. The Guardian pattern uses a second AI to risk-score every action, auto-approving below threshold. 17K lines of sandbox code across 3 platforms — more than most entire CLI tools.

Key Finding: Queue-pair arch, Guardian AI approval, 3-OS sandbox (17K LoC)