Codex

AI Coding

Codex is OpenAI's AI coding agent with a coding-specialized model, a two-layer workspace-plus-thread architecture, scheduled automations, skill packs, and sandboxed execution. It covers feature development, refactoring, and unattended operations across desktop, editor, and CLI.

Human verified · 2026-07-21 · Submit a correction

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Editor's note

Best for professional developers and engineering teams that want to delegate development, refactoring, and ops work to an AI agent; not for non-programmers or users who only need simple code completion.

CategoryAI Coding

Human verified2026-07-21

What is Codex

Key features of Codex

Describing tasks in natural language and letting Codex implement fixes and features with reviewable diffs
Running parallel agents for complex refactoring and code migration to shorten delivery cycles
Scheduling Automations for log inspection, issue triage, and other unattended operations
Installing Skills so AI output follows team engineering conventions and code standards

Good for

Two-layer workspace and thread architecture prevents context pollution across tasks
Coding-specialized model with sandboxed cloud execution for safe, controlled runs
Unified access via desktop app, editor plugins, and CLI under one ChatGPT account

Watch out

The coding-specialized model is only available inside Codex, not on the main ChatGPT site
The free tier is limited; heavy use effectively requires a Plus or Pro subscription
Granting repository and system access to an AI agent requires careful permission setup

How to use Codex

Download Codex from the official site and log in with your ChatGPT account
Connect a GitHub repository or add a local project folder as a workspace
Create a new thread, keeping one thread per task
Describe the requirement in natural language and let Codex analyze and modify the code
Review the changes, then commit to the branch or open a pull request

Who Codex is for

Difficulty: Intermediate

Describing tasks in natural language and letting Codex implement fixes and features with reviewable diffs
Running parallel agents for complex refactoring and code migration to shorten delivery cycles
Scheduling Automations for log inspection, issue triage, and other unattended operations
Installing Skills so AI output follows team engineering conventions and code standards

FAQ

Is Codex free?

Codex is freemium: the free tier covers basic features, while ChatGPT Plus and Pro subscribers get doubled allowances. Check OpenAI's official site for exact tier pricing.

How is Codex different from coding with ChatGPT?

Codex runs a coding-specialized model available only inside the Codex app, and wraps it in a full engineering workflow with workspaces, threads, sandboxed execution, and code review.

Can Codex work directly on my local projects?

Yes. Codex connects to local project folders or GitHub repositories and executes code in an isolated cloud sandbox, with multi-level permissions such as Local and Full access to control its reach.