Meet Codex
OpenAI's agentic CLI. Different posture from Claude Code, same family of skills.
Codex is OpenAI's coding agent — an open-source CLI (plus an IDE extension and a cloud mode) that reads your repo, edits files, and runs commands inside a sandbox. Where Claude Code gates individual actions with approval prompts, Codex expresses trust as a mode you pick up front: Read Only, Auto (the default — free to read, edit, and run commands inside the workspace, asks before leaving it or touching the network), or Full Access. Knowing which mode you're in is the difference between flowing with it and getting bitten by it.
For mobile we'll use Codex specifically — the GPT-5.1 Codex models are tuned for long, tool-heavy engineering sessions and are exceptional at React Native and Swift/Kotlin. Iterating on a UI feels great: scaffold, run, screenshot, adjust.