Unlock AI-Powered Coding: Install and Master OpenAI’s Codex in VS Code

What is Codex?

Codex is OpenAI’s 2025 coding agent built on the GPT‑5 model and fine‑tuned for programming tasks. It can generate full functions from natural‑language prompts, review code for bugs and style issues, perform batch refactoring across multiple files, and delegate large tasks to run in the cloud.

Prerequisites

Account requirements

ChatGPT Plus or higher tier (Pro, Business, Edu, Enterprise)

If you do not have a qualifying subscription, register at https://chat.openai.com and upgrade to Plus.

Software requirements

Visual Studio Code (latest version, recommended 1.80+)

Network access that can reach OpenAI services (proxy may be needed in some regions)

Plugin installation

Method 1: Quick command (recommended)

Open VS Code.

Press Ctrl + P (Mac: Cmd + P).

Enter the command ext install openai.chatgpt and press Enter.

Wait for the installation to complete.

Method 2: UI search

Click the Extensions icon in the left activity bar (or press Ctrl + Shift + X).

Search for "Codex".

Select the extension published by OpenAI named "Codex – OpenAI's coding agent".

Click Install.

After installation an OpenAI logo appears in the VS Code side bar.

Login and configuration

Account login

On first use a login prompt appears. Click "Sign in with your ChatGPT account" and authorize with your ChatGPT credentials. The plugin then links to your subscription quota.

Panel layout

Codex defaults to the left sidebar. You can drag the panel to the right side of the editor for a side‑by‑side view of code and chat.

Model selection

GPT‑5‑Codex – default model, sufficient for everyday coding.

GPT‑5‑Codex (high) – stronger reasoning for complex tasks.

Beginners should start with the default model.

Basic usage

Daily conversation

Enter natural‑language requests in the input box, for example:

帮我写一个Python函数，实现快速排序算法

解释一下这段代码在做什么

这段报错是什么意思，应该怎么修？

Codex reads the currently opened file, so open the target file before issuing a request.

Selection conversation

To act on a specific snippet:

Select the code you want to process.

Describe the desired action in the Codex input box, e.g. 优化这段代码的性能 or 给这个函数添加注释.

Direct editing

State a modification request, e.g. "把这个函数改成异步的".

Codex shows suggested changes on the right side.

Accept or reject each change.

Confirm to apply the updates to the file.

This workflow is useful for bulk refactoring.

Advanced techniques

Cloud‑side task delegation

For large‑scale changes, ask Codex to run the task in the cloud, e.g.:

帮我把这个项目的API全部迁移到RESTful风格

Codex analyses the project structure, processes files in batches, and runs the job in the background while you continue working. Progress is shown in the panel.

Code review

Codex can review pull requests and provide:

Bug and security issue detection

Style consistency checks

Concrete optimization suggestions

Inline comments in the PR

Multiple agents (desktop version)

The desktop client can run several agents in parallel, each handling a different task (e.g., refactor authentication, optimize API performance, update test cases). This feature is not yet available in the VS Code extension.

Comparison with other coding assistants (concise)

Codex : suited for complex tasks and code review; low learning curve; strong instruction following; high token efficiency; included with ChatGPT Plus.

GitHub Copilot : focused on daily code completion; very low learning curve; medium instruction following; high token efficiency; separate subscription ($10 / month).

Claude Code : emphasizes terminal development and natural‑language interaction; medium learning curve; medium instruction following; moderate token efficiency; separate subscription ($20 / month).

FAQ

Q1: "Not signed in" after installation

Ensure you are logged into a ChatGPT account with an active Plus subscription. If the issue persists, restart VS Code, re‑login, or verify network connectivity.

Q2: Slow response speed

Response time depends on network conditions and server load. Check proxy settings or switch to a more stable network.

Q3: Can free accounts use Codex?

No. Codex is only available to Plus and higher tiers.

Q4: Is Codex usable in mainland China?

It can work if OpenAI services are reachable; a proxy may be required in regions with restricted access.

Summary

Codex is an AI coding assistant that can generate, edit, and review code.

Install it in VS Code via Ctrl + P → ext install openai.chatgpt or through the Extensions UI.

Use it by opening a file, typing natural‑language requests, and accepting suggested changes.