Compare Codex and Claude Code on your own work, or use both.

Know what each one is

Claude Code is Anthropic’s coding agent. It runs in the terminal, in IDEs and the Claude desktop app, and in cloud sessions you can reach from the web and the Claude mobile app. Codex is OpenAI’s coding agent, with a CLI, an IDE extension, a desktop app and Codex cloud for running tasks in parallel cloud environments.

Both can work in a local repository on your own machine, and both have cloud options. Plans, usage limits and available models change often, so check each provider’s current documentation and pricing before you plan a team rollout. This guide does not rank them.

Compare them on the same brief

Pick two or three real tasks: a bug with a reproducible failure, a small feature with acceptance criteria and a refactor covered by tests. Give each agent the same brief, the same repository state and the same limits, and run them on separate branches or worktrees so their changes do not collide.

Then review both results as you would a colleague’s change. Record what you measured and when: models and usage limits change, so a comparison is a dated snapshot, not a permanent verdict.

• Did the change meet the acceptance criteria and pass the relevant tests?
• How much review and correction did it need before it was usable?
• Did the agent ask useful questions, or make changes nobody requested?
• How much of your plan’s usage did it take?

Share one set of instructions

Codex reads project instructions from AGENTS.md files. Claude Code reads CLAUDE.md, and from version 2.1.277 it also reads AGENTS.md when the repository has no CLAUDE.md or CLAUDE.local.md in the working directory or above it.

If you keep both files, Claude Code reads CLAUDE.md only. To keep one source of truth, put the shared rules in AGENTS.md, import it from CLAUDE.md with an @AGENTS.md line and add anything specific to Claude Code below it.

• AGENTS.md only: both agents read it.
• AGENTS.md and CLAUDE.md: Claude Code reads CLAUDE.md only, unless it imports AGENTS.md.
• CLAUDE.md that imports @AGENTS.md: one shared file, plus notes for Claude Code.

Use both on one piece of work

You do not have to choose one agent for everything. A team can give an implementation to one agent and ask the other to review it, or run both on the same brief and keep the better result. What matters is that the brief, both results and the review decision stay together.

In TM8, people coordinate Claude Code and Codex sessions from one shared workspace, using their own logins, on a hosted seat or on their own machine or server. A Claude Code session and a Codex session can work in parallel on the same task, and both results come back to the same place for review. The decision to ship stays with a person.

Common questions