Codex

Codex is OpenAI’s agentic coding agent—terminal CLI (Rust), IDE integrations, and cloud tasks—built to read repos, edit files, run commands, and use MCP tools under approval policies. We rate it trial: credible alternative to Claude Code when you are on ChatGPT Plus/Pro/Business plans and want OpenAI models; Claude Code is also trial here (we usually default to Cursor + cursor-agent for daily IDE work).

Blurb

Codex is OpenAI’s coding agent. It helps you build, debug, and ship faster across terminals, IDEs, web, and mobile.

Summary

Codex runs an agent loop scoped to your codebase: sandboxed execution, configurable approval modes, subagents for parallel work, and support for the Agent Skills SKILL.md format (skills from Agent Skills - Sources often port with minimal changes). It is not the legacy GPT-3 “Codex” completion API—that model family is historical; this note is the 2025+ product (openai/codex on GitHub).

Use for interactive coding, reviews, and refactors inside a repo. Like Claude Code, it is a bounded AI Agent workspace tool—not an always-on messaging bot (OpenClaw, Hermes are hold for that pattern).

Details

• Install: npm i -g @openai/codex, Homebrew cask, or GitHub release binaries; requires a paid ChatGPT plan or API access per OpenAI docs.
• Models: GPT-5.x / Codex-tuned models with adjustable reasoning; cloud and local terminal modes per release notes.
• Safety: sandboxing, network policies, and human-in-the-loop approvals—see OpenAI’s “running Codex safely” guidance for enterprise patterns.
• Fit: Tool / AI Agent—agent-loop coding tool; compare Claude Code on Anthropic plans.
• Skills: cross-compatible SKILL.md ecosystem noted in Agent Skills - Sources.