Codex Plugin for Claude Code: How to Install It, Review Code, and Delegate Tasks with Codex

Key Takeaways: The Codex plugin for Claude Code gives you a practical two-agent workflow: stay inside Claude Code for day-to-day development, then hand reviews, adversarial checks, and longer background tasks to Codex without changing tools.

What Is the Codex Plugin for Claude Code?

The Codex plugin for Claude Code is an integration that lets you use Codex directly inside your existing Claude Code workflow. Instead of switching between tools, you can trigger Codex from within Claude Code for read-only reviews, design-challenge reviews, and delegated engineering work that runs in the background.

That positioning is what makes the plugin interesting. It is not trying to replace Claude Code. It is trying to give Claude Code users a clean path to a second model and a second workflow style. Claude can stay in the foreground for interactive coding, while Codex can be used when you want another opinion, a harsher review, or a separate task thread that can run without blocking your flow.

In practice, this makes the plugin useful for teams and solo developers who already like Claude Code but want a reliable way to offload specific work. If you have ever wanted to say, “review this branch,” “challenge this architecture,” or “investigate this regression while I keep moving,” this plugin is built for that exact moment.

Why This Plugin Matters

Most AI coding workflows break down when everything has to happen in one chat loop. You code, ask for a review, then wait. You want a second opinion, then you re-prompt. You want a bug investigated, then your main thread gets consumed by that debugging session.

The Codex plugin changes that by introducing separation of roles. Claude Code remains your interactive environment. Codex becomes the specialist you call in for focused code review or delegated execution. That division is especially useful in four situations: pre-merge code review, adversarial design review, bug investigation, and long-running background tasks.

For SEO and GEO purposes, the simplest way to explain the value is this: the Codex plugin for Claude Code helps developers review code faster, stress-test implementation decisions, and delegate engineering tasks without leaving the terminal workflow they already use.

What You Need Before Installation

Before installing the plugin, make sure your machine is ready for both Claude Code plugins and Codex itself.

Requirements

You need:

• Node.js 18.18 or newer
• A ChatGPT account or an OpenAI API key for Codex authentication
• Claude Code with plugin support enabled
• A working terminal environment where global npm packages can be installed if needed

The plugin depends on your local Codex CLI setup. That means authentication and configuration are not separate from Codex; the plugin uses the same local Codex environment you would use directly.

How to Install the Codex Plugin in Claude Code

The installation process is straightforward and terminal-friendly.

Step 1: Add the marketplace

/plugin marketplace add openai/codex-plugin-cc

This tells Claude Code where to find the plugin.

Step 2: Install the plugin

/plugin install codex@openai-codex

This installs the Codex plugin into Claude Code.

Step 3: Reload plugins

/reload-plugins

Reloading ensures the new slash commands and subagent definitions are available in your current session.

Step 4: Run setup

/codex:setup

This is the most important step after installation. It checks whether Codex is installed locally and whether authentication is ready. If Codex is missing and npm is available, setup may offer to install it for you.

Step 5: Install Codex manually if needed

If setup tells you Codex is not available, install it yourself:

npm install -g @openai/codex

Then authenticate:

!codex login

Once setup succeeds, you should see the Codex slash commands and the codex:codex-rescue subagent appear in Claude Code.

Your First Successful Run

A good first-run sequence is:

/codex:review --background
/codex:status
/codex:result

This does three things. First, it confirms the review command works. Second, it shows you how background jobs are tracked. Third, it shows you where completed output lives. If you want to validate the install quickly, this is the cleanest path.

How to Use Codex from Claude Code

The plugin becomes useful when you understand the job of each command instead of treating them as interchangeable.

Use /codex:review for normal code review

/codex:review
/codex:review --base main
/codex:review --background

This command is read-only. It is the right choice when you want Codex to inspect your current changes or compare your branch against a base branch like main. If you are preparing a pull request, this is the safest default command because it gives review feedback without changing code.

Use it when you want a standard review, not a debate.

Use /codex:adversarial-review to challenge design decisions

/codex:adversarial-review
/codex:adversarial-review --base main challenge whether this was the right caching and retry design
/codex:adversarial-review --background look for race conditions and question the chosen approach

This is the sharper tool. Instead of asking Codex to simply review code, you are asking it to pressure-test the implementation. That makes it ideal before releases, migrations, auth changes, concurrency work, rollback-sensitive changes, or anything where the biggest risk is not style but hidden assumptions.

If /codex:review tells you whether the code looks sound, /codex:adversarial-review asks whether the whole direction was sound in the first place.

Use /codex:rescue to delegate work

/codex:rescue investigate why the tests started failing
/codex:rescue fix the failing test with the smallest safe patch
/codex:rescue --resume apply the top fix from the last run
/codex:rescue --background investigate the regression

This is the delegation command. It sends work to Codex through the rescue subagent, which makes it perfect for debugging, fixing, continuing prior work, or assigning smaller scoped engineering tasks while you stay focused elsewhere.

This is the command that turns the plugin from “nice reviewer” into “useful teammate.” It is especially effective for repeatable engineering tasks such as investigating CI failures, tracing regressions, finding flaky tests, or drafting the smallest safe patch for a contained issue.

How to Monitor Background Jobs

Longer Codex tasks are often better in the background, especially if you are reviewing a multi-file branch or asking Codex to investigate a bug.

Check status

/codex:status
/codex:status task-abc123

Use this to see whether a task is still running or to identify the latest completed job.

Fetch results

/codex:result
/codex:result task-abc123

This returns the final stored output for a finished task. When available, it can also expose the session ID so you can resume that run directly in Codex later.

Cancel a running task

/codex:cancel
/codex:cancel task-abc123

This is useful when a review is no longer relevant or a delegated job is going down the wrong path.

A Practical Workflow for Real Teams

A strong everyday workflow looks like this:

1. Build interactively in Claude Code.
2. Run /codex:review --background before shipping.
3. If the change is risky, follow with /codex:adversarial-review --background.
4. If a bug or regression appears, hand it off with /codex:rescue.
5. Check progress with /codex:status.
6. Pull the result with /codex:result.
7. Resume in Codex directly later if deeper follow-up is needed.

This works because it reduces context switching. You do not have to abandon your Claude Code session just to get a second opinion or parallelize investigation work.

Configuration and the Review Gate

The plugin can also use your Codex configuration files, including user-level and project-level settings. If you already customize model choice or reasoning effort in Codex, the plugin can pick that up.

A more advanced option is the review gate, which you can toggle with setup commands. When enabled, the plugin can run a targeted Codex review as part of a stop hook and block completion if issues are found.

That sounds powerful, and it is, but it should be used carefully. A review gate can create a longer Claude-and-Codex loop and consume usage faster. It is best reserved for sessions where you are actively watching outputs and want stronger guardrails.

Best Practices for Getting Better Results

The plugin works best when you treat each command as a specialized tool.

Use standard review for code quality. Use adversarial review for risk discovery. Use rescue for delegated execution. Prefer background mode for anything non-trivial. Give rescue tasks crisp scopes such as “find the cause of the flaky login test” instead of vague instructions like “look around the backend.” And if you already maintain project-specific Codex config, keep it tidy so the plugin inherits sane defaults.

The biggest mistake is expecting every command to behave like an all-purpose agent. The plugin is more effective when you give the right job to the right command.

Final Verdict

If you already live in Claude Code, the Codex plugin is one of the cleanest ways to add review depth and task delegation without changing your workflow. Installation is simple, the command set is compact, and the value is immediate: better reviews, better pressure-testing, and better background execution.

For developers evaluating AI coding workflows in 2026, this plugin stands out because it does not ask you to choose one assistant over another. It lets you combine Claude Code’s interactive flow with Codex’s review and delegation strengths in one terminal-first setup.