How to Use Codex in VS Code (From Setup to Efficient Real-World Workflow)

Fri, 20 Mar 2026 00:00:00 +0000

Codex can help you write code, fix bugs, understand projects, and run commands directly from the VS Code sidebar.

1. Preparation

Before you start, make sure:

VS Code is updated to a recent stable version.
You can access OpenAI services normally.
Your project is opened locally (preferably in a Git repository).

2. Install the Extension

Open the VS Code Extensions panel.
Search and install: Codex - Codex - OpenAI's coding agent.
Complete the sign-in/authorization flow.

You can open it in either way:

Click Open Codex Sidebar in the top-right area of the editor.
Use Command Palette (Ctrl + Shift + P), search Codex, and open it.

After opening, Codex reads the current workspace context and becomes ready for chat.

4. Common Usage Patterns

4.1 Ask It to Explain Code

Example prompt:

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Please explain the core logic of this file,
and point out the 3 areas most likely to fail.

Great for quickly understanding legacy code.

4.2 Ask It to Implement Features

Example prompt:

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Add a /healthz endpoint to the existing API.
It should return app version and database connectivity status,
and include basic tests.

If you clearly state constraints and acceptance criteria, output quality is usually much more stable.

4.3 Ask It to Fix Issues

Example prompt:

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This endpoint intermittently returns 500 under concurrency.
First identify the root cause, then propose a minimal-change fix,
and finally list regression test points.

“Diagnose first, then fix” helps reduce accidental over-refactoring.

5. High-Quality Prompt Template

You can reuse this template directly:

Background: This is a <tech stack> project. Current goal: <goal>
Constraints: Do not modify <module/interface>; keep compatibility with <version/platform>
Output:
1) File list to change
2) Key code explanation
3) Validation steps
4) Risks and rollback plan

This is especially useful for large projects and team collaboration.

6. FAQ

6.1 About Free Quota

Type \ in the input box, then choose status to view quota/reset-time related information.

6.2 Changes Are Not as Expected

After changes are generated, open the review panel to inspect details. If not satisfied, use undo/revert. You can split large requirements into smaller steps and execute incrementally. Use Git and keep small commits for easier rollback.

Ai-Coding-Practice on KnightLi Blog

How to Use Codex in VS Code (From Setup to Efficient Real-World Workflow)

1. Preparation

2. Install the Extension

3. Open the Codex Sidebar

4. Common Usage Patterns

4.1 Ask It to Explain Code

4.2 Ask It to Implement Features

4.3 Ask It to Fix Issues

5. High-Quality Prompt Template

6. FAQ

6.1 About Free Quota

6.2 Changes Are Not as Expected