What is OpenAI Codex? (2026)
Published June 30, 2026
TLDR
OpenAI Codex is a family of AI models from OpenAI that specialize in code. The original Codex model powered GitHub Copilot. In 2025, OpenAI launched a new Codex as an autonomous AI coding agent, similar to Claude Code, that can write, run, and debug code in a sandboxed environment.
The name "Codex" has meant two different things from OpenAI at different times. The original Codex, released in 2021, was a language model specifically trained on code. It became the engine behind GitHub Copilot and could autocomplete code, translate between languages, and explain code snippets. It has since been superseded by more capable models.
In 2025, OpenAI launched a new Codex, this time as an autonomous coding agent integrated into ChatGPT. The new Codex can write software from scratch, fix bugs, answer questions about a codebase, and run terminal commands, similar to how Claude Code operates. It runs in a sandboxed cloud environment, which means it can execute code safely without touching your local machine.
The new Codex is notable for running tasks in the background. You can give it a coding assignment, and it works on it while you do other things, reporting back when it is finished or when it needs input. This is different from models that require you to wait and read each response.
Codex and Claude Code represent a new category of AI tool: the coding agent. Unlike autocomplete tools that suggest the next line, agents can plan and execute multi-step coding tasks: reading a codebase, designing an approach, writing code, running tests, and fixing failures, all in sequence.
In practice
Building a feature from a description
You describe a feature in plain English. Codex reads the relevant parts of the codebase, writes the implementation across multiple files, and returns a summary of what it changed.
Automated bug fixing
Paste a bug report or error log. Codex analyzes the code, identifies the root cause, writes a fix, and runs tests to verify the fix works before reporting back.
Codebase questions
Ask questions about an existing codebase in natural language: "How does the authentication flow work?" or "Which functions call this module?" Codex reads the code and answers accurately.
Frequently asked questions
Is OpenAI Codex the same as GitHub Copilot?+
Not exactly. GitHub Copilot was originally powered by the Codex model, but has since moved to newer OpenAI models. The new Codex (2025) is a separate autonomous agent product, not the same as Copilot.
Is Codex available to everyone?+
As of 2026, the Codex agent is available to ChatGPT Pro and Team subscribers. Access and pricing may have changed, so check the current status at openai.com.
How does Codex compare to Claude Code?+
Both are autonomous coding agents, but they differ in architecture. Codex runs in a sandboxed cloud environment and works well for background tasks. Claude Code runs locally in your terminal with direct access to your file system.
Can Codex work on any programming language?+
Yes. Like other large language models, Codex has broad language support including Python, JavaScript, TypeScript, Go, Rust, Java, C++, and more.
Bottom line
OpenAI Codex is a family of AI models from OpenAI that specialize in code. The original Codex model powered GitHub Copilot. In 2025, OpenAI launched a new Codex as an autonomous AI coding agent, similar to Claude Code, that can write, run, and debug code in a sandboxed environment.