What Is OpenAI Codex?Start Here
OpenAI's coding agent explained: the open-source CLI, the IDE extension, and Codex Cloud, the models it runs, approval modes, and how it is included across ChatGPT plans.
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AI Coding Assistant
OpenAI's coding agent runs across three surfaces: an open-source command-line tool written in Rust, an extension for VS Code and JetBrains, and a cloud workspace at chatgpt.com/codex. The local tools connect to Codex Cloud to offload long-running jobs and apply the resulting diffs back to your machine.
Codex CLI
Open-source terminal agent in Rust, Apache 2.0, that runs locally with an interactive TUI
IDE Extension
Works in VS Code and its forks Cursor and Windsurf, plus JetBrains editors
Codex Cloud
Launch long-running tasks at chatgpt.com/codex, then preview and apply diffs locally
Approval Modes
Chat, Agent, and Agent (Full Access) control how much the agent can do unattended
GPT-5.5 & GPT-5.4, MCP, Image Inputs
Switch models and reasoning effort, connect third-party tools over MCP, and pass images (vendor-reported)
OpenAI Codex is a coding agent that meets you wherever you work. The Codex CLI is an open-source terminal agent written in Rust and released under Apache 2.0; the IDE extension brings the same agent into VS Code, its forks Cursor and Windsurf, and JetBrains editors; and Codex Web runs in the cloud at chatgpt.com/codex. The local surfaces connect to Codex Cloud so you can offload long jobs and apply the diffs back when they finish. All details below are vendor-reported and verified 2026-06-16.
Run Codex from the terminal with the open-source CLI, inside your editor with the VS Code or JetBrains extension, or in the browser through Codex Web. The interactive TUI, a local code-review agent, and non-interactive scripting let you fit Codex into both hands-on sessions and automated pipelines.
GPT-5.5 is the latest model Codex references, with GPT-5.4 also available. You can switch models with the /model command and choose a reasoning effort of low, medium, or high. The exact model list moves over time, so confirm the current options in OpenAI's documentation.
Approval modes (Chat, Agent, and Agent with Full Access) decide how much Codex can do without checking in, and you preview cloud diffs before applying them. Codex is included with ChatGPT Plus, Pro, Business, Edu, and Enterprise. For current plans and rate limits, see OpenAI's pricing pages.
Vendor-reported, verified 2026-06-16. Model names, surfaces, and plan inclusion move quickly; confirm current details at openai.com/codex and developers.openai.com/codex.
3
Surfaces: CLI / IDE / Cloud
GPT-5.5
Latest Model Referenced
Apache 2.0
Open-Source CLI License
3
Approval Modes
In-depth coverage of what OpenAI Codex is, how to use the open-source CLI, and how it compares with GitHub Copilot. Researched with vendor documentation and honest trade-offs.
OpenAI's coding agent explained: the open-source CLI, the IDE extension, and Codex Cloud, the models it runs, approval modes, and how it is included across ChatGPT plans.
A walkthrough of the open-source terminal agent: installing it, signing in with a ChatGPT account or API key, working in the interactive TUI, and using approval modes and cloud tasks.
The open-source coding agent against the in-IDE assistant: Codex's CLI-first, cloud-delegating approach versus Copilot's broad editor support and multi-vendor model catalog, with an honest read on where each fits.
Explore the ChatGPT plans that include Codex, a rival in-IDE coding assistant, and the broader AI Tools Hub.
ChatGPT Hub
OpenAI's chat product and the Plus, Pro, Business, and Enterprise plans that include Codex.
GitHub Copilot Hub
The in-IDE AI pair programmer compared head to head with OpenAI Codex.
Cursor Hub
The agent-native code editor, one of the VS Code forks the Codex extension supports.
AI Tools Hub
Breakdowns, comparisons, and guides across the leading AI vendors.
AI Governance
Responsible AI, code provenance, the EU AI Act, and compliance for generative tools.
Important context for responsible AI adoption
OpenAI Codex sends your prompts, the code in your project, and the agent's actions to OpenAI's models. The open-source CLI runs locally, but a ChatGPT or API sign-in is required, and cloud tasks process your repository on OpenAI's infrastructure. Approval modes let you limit what the agent touches before review. Business, Edu, and Enterprise plans differ from individual plans in the controls available, so review OpenAI's current privacy and data-handling documentation, and prefer enterprise controls before processing sensitive or proprietary code.
Coding agents like OpenAI Codex speed up output, but long agent-driven sessions can blur into overwork, and the ease of generating code should not replace rest, review, or real connection. If you are experiencing distress:
AI systems can produce plausible-sounding but incorrect guidance. For mental health, medical, legal, or financial decisions, always consult a qualified professional.
See the NIST AI Risk Management Framework for structured guidance on AI risk assessment.
Under GDPR (EU) and CCPA (California), you have the right to access, correct, and delete your personal data. AI coding tools can produce confident but wrong output, so review every diff Codex proposes before applying it, and validate generated code against your own tests and security review. Approval modes exist precisely so a human stays in the loop.
The EU AI Act sets transparency obligations for generative AI, including disclosure of AI-generated content. Organizations adopting AI coding tools remain responsible for meeting these provisions and for the code they ship.
This publication is editorially independent. AI tool coverage reflects independent research, vendor documentation, and editorial judgment. Where affiliate links are present, they are clearly disclosed and do not influence conclusions.