Adopt
OpenAI Codex is OpenAI's agentic coding system: an open-source CLI (Apache 2.0, written in Rust) plus IDE extensions, cloud agents and integration into the ChatGPT desktop app. Powered by the GPT-5.x model family.
Key Features
- OS-level sandboxing by default (macOS Seatbelt, Linux Landlock/seccomp, network off unless allowed) - Codex's main differentiator.
- Feature set on par with Claude Code: subagents, hooks, MCP support, auto-review.
- Cloud handoff: start tasks locally, delegate long-running work to cloud agents and review results asynchronously.
- Headless execution (
codex exec) for CI and automation.
Assessment
The open-source CLI lowers the entry barrier, but model usage requires a ChatGPT plan or API access. Strong choice for teams standardized on OpenAI models or with strict process-isolation requirements.
Related: Claude Code, OpenCode, Harness Engineering