- Codex CLI is OpenAI's terminal coding agent, shipped as one compiled Rust binary. Safety comes from an OS-level sandbox, and OpenAI still labels the project experimental.
- Install the scoped npm package `@openai/codex`. An unscoped `codex` package with a similar name is unrelated.
- Signing in with ChatGPT uses plan credits and usage limits, while an API key bills per token. They behave like two different products.
- Models are chosen per task, and named profiles in `~/.codex/config.toml` can route work to cheaper or stronger ones.
- Three approval modes set how much autonomy it has, and `codex exec` runs it headless for CI.
- The author suggests using it for cheap autonomous work and a stronger agent for high-stakes changes.
This is a summary in our own words, not the article itself. Read the original for the full text.