An AI coding agent developed by OpenAI. Since its initial release in May 2025, it has expanded across environments — CLI, IDE extensions, and cloud execution — and in July 2026 it was integrated into the ChatGPT desktop app, becoming one of the three tabs alongside Chat and Work. Rather than simple code completion, its defining trait is understanding the entire codebase and autonomously carrying out tasks such as feature implementation, bug fixes, code review, and testing. It is included in every ChatGPT plan, so you can try it with limited access even on the Free plan.
Key Features
- Agent-style task delegation: Ask it to “fix this bug” or “implement this feature,” and it autonomously works through the whole flow — investigating relevant files, making changes, and running tests. It also supports running multiple tasks in parallel
- Whole-codebase understanding: Unlike completion-style tools, it proposes changes based on the repository structure and the context of existing code. It can handle multi-repository projects and local projects spanning multiple folders
- A wide range of execution environments: Choose what fits your workflow — the terminal-based Codex CLI, IDE extensions for VS Code and others, cloud sandbox execution, and an SDK for embedding it in your own programs
- Integrated into the ChatGPT desktop app: Since July 2026, it is available as a dedicated tab alongside Chat and Work in the macOS / Windows desktop app, with inline diff editing, PR review, and built-in browser integration
- GitHub and Slack integration: Connect it to GitHub for automatic PR reviews and task creation from issues, and it also accepts task requests from Slack
- Included in ChatGPT plans: No separate subscription needed — use it directly from any ChatGPT plan, with usage limits that scale with your plan
Pricing
There is no standalone price for Codex; it is provided as part of each ChatGPT plan. The amount of task usage available varies by plan.
| Plan | Price | Codex access |
|---|---|---|
| Free | $0 | Available with limits |
| Go | $8/month | Available with limits (expanded Codex usage starts at Plus) |
| Plus | $20/month | Expanded usage allowance; the starting point for individual developers |
| Pro | From $100/month | Two tiers with 5x or 20x usage; maximum Codex tasks; for heavy users |
| Business | $25/user/month ($20 with annual billing, 2+ users) | Team usage with admin features |
| Enterprise | Contact sales | Management and security features for large organizations |
Pricing is as of August 2026. Plan structures and usage limits are subject to change — check the official site for the latest pricing.
Pros & Cons
✅ Pros
- Task-delegation style rather than code completion — it can handle implementation, fixes, and testing as a whole
- Broad choice of execution environments (CLI / IDE / cloud / desktop app) makes it easy to fit into existing workflows
- Included in ChatGPT plans, so if you already subscribe to ChatGPT there is no extra cost to get started
- Covers everything from solo development to team development, including automatic PR reviews via GitHub integration
- Cloud sandbox execution lets you run tasks without touching your local environment
⚠️ Cons
- Because it changes code autonomously, verifying and reviewing its output remains a human responsibility
- The Free plan’s usage allowance is small; practical use effectively requires a paid plan
- In large, complex codebases, unintended changes can slip into its output
- Features change quickly, so documentation and the user experience can shift over time
Comparison with Similar Services
| Comparison | ChatGPT Codex | Claude Code | GitHub Copilot | Gemini CLI |
|---|---|---|---|---|
| Provider | OpenAI | Anthropic | GitHub (Microsoft) | |
| Style | Agent (CLI / IDE / cloud / app-integrated) | Agent (terminal-centric) | Completion + agent (IDE-centric) | Agent (terminal) |
| Pricing | Included in ChatGPT plans | Claude Pro ($20/month) and up | Free tier / from $10/month | Free tier |
| Integrations | GitHub / Slack / SDK | MCP / GitHub Actions | GitHub ecosystem | Google products |
| Strength | Breadth of environments, ChatGPT integration | Long context, extensibility | Polished in-IDE completion experience | Generous free tier |
Who Is It For
- Developers who already subscribe to ChatGPT and want to try an AI coding agent at no extra cost
- Anyone who wants to move beyond code completion to a “delegate the whole task” development style
- Developers who move between multiple environments — CLI, IDE, cloud — and want to use the same agent everywhere
- Development teams that want AI to handle first-pass PR reviews and reduce their review workload
Summary
ChatGPT Codex is an agent-style coding assistant deeply integrated into OpenAI’s ecosystem. It offers a wide range of execution environments, from the CLI to the desktop app, and its inclusion in ChatGPT plans keeps the barrier to entry low. At the same time, because it changes code autonomously, final verification remains a human job. Start by trying it on the Free plan or with a small repository, and if it fits your development flow, move to Plus or higher for serious use.