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OpenAI Codex

coding

by openai

OpenAI's cloud based autonomous coding agent that runs tasks in a sandbox and delivers pull requests.

Key features

Cloud Sandbox Execution
Autonomous Task Completion
GitHub Integration
Multi-file Editing
Codex CLI
Parallel Task Execution
Pricing

From $20/month

Best For

Developers who want a fully autonomous coding agent that works in the background without tying up their local machine

Verdict

Runs in an isolated cloud sandbox; cannot break your local environment, corrupt files, or access your local services.

What it does

Cloud Sandbox Execution

Every task runs inside an isolated cloud container (a temporary, disposable computer in the cloud). Your local machine stays untouched while Codex works remotely.

Learn more

Autonomous Task Completion

Describe what you need in plain English and Codex handles the rest: reading your code, planning changes, writing new code, and running tests to verify everything works.

GitHub Integration

Codex connects directly to your GitHub repositories. When a task is complete, it creates a pull request (a proposed set of changes) that you can review before merging.

Multi-file Editing

Codex can read, modify, and create files across your entire project. It understands how different parts of your codebase connect and makes coordinated changes.

Codex CLI

An open source terminal tool you install locally. Unlike the ChatGPT version, it runs on your machine and supports multiple AI providers beyond OpenAI.

Learn more

Parallel Task Execution

Run multiple Codex tasks at the same time. Each one gets its own sandbox, so you can tackle several parts of a project simultaneously.

Environment Customization

Configure the sandbox to match your project: install dependencies, set up build tools, and define environment variables before Codex starts working.

Code Review and Iteration

Review Codex's output, leave feedback, and ask it to iterate. Codex reads your comments and makes adjustments, similar to working with a remote teammate.

ChatGPT Integration

Access Codex directly from the ChatGPT interface. Connect a GitHub repo, describe your task, and Codex works in the background while you continue chatting.

Learn more

Test Generation and Verification

Codex writes tests for its changes and runs your existing test suite to verify nothing breaks. It follows a test driven approach by default.

Automated PR Reviews

Codex can review pull requests from your team, checking for bugs, suggesting improvements, and leaving detailed review comments.

AGENTS.md Configuration

A project level configuration file that tells Codex your conventions, setup commands, and testing requirements. Similar to CLAUDE.md for Claude Code.

Learn more

Container Based Isolation

Each task runs in its own container with restricted network access. Codex cannot reach the internet during execution, preventing unintended side effects and supply chain risks.

Pricing

Best Value

ChatGPT Pro

$20/month

Access Codex through your ChatGPT Pro subscription. Includes a limited number of Codex tasks per month alongside all other ChatGPT Pro features.

  • Codex in ChatGPT sidebar
  • Limited Codex tasks per month
  • GitHub repository connection
  • Pull request creation
  • All ChatGPT Pro features included
Most popular

ChatGPT Plus

$200/month

Higher Codex task limits and priority access. Designed for developers who use Codex frequently and need faster execution with fewer queue delays.

  • Everything in Pro
  • Significantly higher task limits
  • Priority queue access
  • Faster task execution
  • Extended context for larger codebases
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Pros & Cons

Pros

  • Runs in an isolated cloud sandbox; cannot break your local environment, corrupt files, or access your local services.
  • Deep GitHub integration; creates pull requests automatically with clear descriptions and diffs for easy review.
  • Can execute multiple tasks in parallel, each in its own sandbox, dramatically speeding up multi part projects.
  • No local setup required for the ChatGPT version. Connect a GitHub repo and start immediately from your browser.
  • Codex CLI is open source and works with multiple AI providers, giving you flexibility beyond the OpenAI ecosystem.
  • Follows a test driven workflow by default, writing and running tests to verify changes before submitting them.

Cons

  • Cloud execution means no access to local tools, databases, or services. If your project depends on a local database or API, Codex cannot reach it.
  • Requires a ChatGPT Pro or Plus subscription ($20 to $200 per month) for the hosted version. The CLI requires an API key with separate usage costs.
  • Slower feedback loop than local tools. Tasks take minutes, not seconds, because Codex spins up a container, clones your repo, and installs dependencies each time.
  • Limited extensibility compared to Claude Code. No equivalent to MCP servers, hooks, or custom agent systems for workflow automation.
  • Still relatively new with fewer community resources, tutorials, and established patterns compared to more mature tools like Claude Code or GitHub Copilot.

How to get started

1

Subscribe to ChatGPT Pro or Plus

Sign up for a ChatGPT Pro ($20/mo) or Plus ($200/mo) subscription. Codex is included with both plans at different usage limits.

ChatGPT pricing
2

Connect your GitHub repository

In ChatGPT, open the Codex panel and connect your GitHub account. Authorize access to the repositories you want Codex to work with.

Codex in ChatGPT
3

Open Codex in the ChatGPT sidebar

Navigate to the Codex section in ChatGPT. You will see your connected repositories and a prompt field where you can describe tasks.

4

Describe your first task

Write a clear task description like "Add input validation to the signup form" or "Fix the failing test in src/utils/parser.test.ts." Codex works best with specific, concrete instructions.

5

Review the pull request Codex creates

Codex works in the background and creates a GitHub pull request when finished. Review the changes, leave feedback, or merge. You can also ask Codex to make adjustments based on your review.

6

(Optional) Install Codex CLI for terminal usage

For a local terminal experience, install the open source Codex CLI with npm. This version runs on your machine and supports multiple AI providers.

Codex CLI on GitHub

Deep dive

Detailed guides with comparisons, tips, and visuals for each feature.

How Codex Works

The cloud sandbox model: how Codex spins up containers, clones your repo, executes tasks, and delivers pull requests.

ChatGPT Pro, Plus, Team, Enterprise·2 min read

Codex CLI

The open source terminal tool for running Codex locally with multiple AI provider support.

Free (open source), requires API key·1 min read

Codex in ChatGPT

How to use Codex inside the ChatGPT interface: connect repos, describe tasks, and receive pull requests.

ChatGPT Pro ($20/mo), Plus ($200/mo), Team, Enterprise·1 min read

AGENTS.md Configuration

Project level instructions that tell Codex your conventions, setup commands, and testing requirements.

All versions (ChatGPT and CLI)·1 min read

Codex vs Claude Code vs Cursor vs GitHub Copilot

How OpenAI Codex compares to other AI coding tools across execution model, autonomy, pricing, and extensibility.

All plans·1 min read

Security and Isolation

How Codex's sandbox model provides safety through container isolation, network restrictions, and review workflows.

All plans·1 min read

Get notified about updates

We'll email you when this tool's pricing or features change.

Last updated: 2026-02-18