Codex VS Code extension: installation, sign-in, and permissions (2025)

Codex VS Code extension: installation, sign-in, and permissions

The Codex IDE extension is one of the most important updates for developers in 2025. Until now, AI coding assistants mostly lived in chat windows or provided autocomplete in your editor. Codex changes the game: it integrates directly into VS Code with a full agent that can propose diffs, run commands, and even delegate tasks to the cloud.

In this article, we’ll cover:

• How to install the Codex VS Code extension step by step
• Different login flows (ChatGPT account vs API key)
• The three permission modes and what they mean
• How to delegate work to Codex Cloud
• Best practices for safety and productivity
• Real-world workflows where the extension shines
• Common pitfalls and troubleshooting

This isn’t just a quick install guide—it’s a 1,500+ word deep dive designed to help you use Codex effectively in daily development. For a broader view of how Codex connects CLI, editor, and cloud, check out our complete integration guide.

Why the VS Code extension matters

Most AI assistants give you code suggestions but don’t integrate into your actual workflow. Codex is different. Instead of typing a vague prompt and copy-pasting results, you:

1. Ask Codex to solve a problem in your codebase.
2. Review the diff it generates before applying.
3. Run your own validation scripts (tests, builds, linters).
4. Accept or reject changes just like any pull request.

This “plan → patch → validate” loop brings AI into the real developer workflow without breaking safety practices. VS Code is the perfect place for this because it’s where millions of developers already spend most of their day.

Installing the Codex extension

The extension is available directly in the Visual Studio Code Marketplace.

1. Open VS Code and go to the Extensions view (Ctrl+Shift+X / Cmd+Shift+X on macOS).
2. Search for “Codex” (OpenAI).
3. Click Install.
4. Reload VS Code to complete installation.

If you’re working behind a firewall or want offline installation:

# download the .vsix package
code --install-extension openai.chatgpt-x.y.z.vsix

Pro tip: Pin the extension version in your onboarding docs so your team runs the same build. Avoid unexpected upgrades in the middle of a sprint.

Sign-in options

Codex supports two authentication flows:

1. ChatGPT account sign-in

• Works with Plus, Pro, Team, Edu, and Enterprise accounts.
• Click “Sign In” in the sidebar panel.
• Your browser opens, you log in, and Codex links automatically.

This is the fastest way to get started locally.

2. API key login

For automation or CI/CD, use an API key:

1. Generate a key in your OpenAI account.
2. In VS Code: Settings → Extensions → Codex → API Key.
3. Paste the key and reload the extension.

Use API keys when setting up shared scripts, pipelines, or server-side tasks. For personal experimentation, account sign-in is easier.

Permission modes explained

The extension offers three modes of operation:

• Agent (default): Codex can propose diffs and run local scripts, but you must approve changes.
• Chat: Text-only mode. Great for planning or Q&A without touching your files.
• Agent (Full Access): Codex edits and executes without asking. Use only in sandboxes.

Switch modes from the sidebar panel. You’ll see an icon indicator showing which mode is active.

Delegating tasks to Codex Cloud

Some jobs are too heavy for local execution—long migrations, complex refactors, or performance debugging. Codex Cloud solves this by running tasks remotely:

• Cloud runs don’t block your machine.
• Logs and results sync back into VS Code.
• Context is preserved so you can continue locally afterward.

Use cloud delegation for:

• Flaky bug reproduction
• Performance experiments
• Multi-step migrations

Best practices for daily use

1. Default to Agent mode. Safe and powerful.
2. Drop to Chat mode when brainstorming.
3. Reserve Full Access for sandbox repos.
4. Always review diffs. Don’t apply blindly.
5. Scope API keys. Treat them like production secrets.

Think of Codex like a teammate. You wouldn’t merge code without review—don’t skip that step here.

Real-world workflow examples

Refactoring a slow function

1. Highlight the function.
2. Ask Codex: “Find the bottleneck and suggest a minimal fix.”
3. Preview the diff.
4. Run npm test locally.
5. Accept the patch if all passes.

Adding a unit test

1. In Chat mode, ask: “Write a Jest test for utils/slugify.ts.”
2. Switch to Agent mode.
3. Apply the proposed test file.
4. Run npm run test.

Handling CI failures

1. In Agent mode, run: “Fix the failing CI pipeline.”
2. Codex proposes edits.
3. Review → validate → merge.

Troubleshooting common issues

• Sign-in loop: Log out, clear VS Code auth cache, retry.
• Permission prompts every time: Check approval mode. Switch from Chat to Agent.
• Windows quirks: Use WSL for best support. Native Windows is still experimental.
• Proxy/firewall errors: Configure http.proxy in VS Code settings.

If all else fails, reinstall the extension and reset settings.

Security hygiene

• Never paste secrets into prompts.
• Prefer environment variables for credentials.
• Limit scopes when authenticating with API keys.
• Treat “Full Access” like root privileges.

Where this fits in your stack

Codex isn’t replacing your judgment. It’s speeding up repetitive dev tasks while keeping you in control. The VS Code extension works best when combined with:

• Codex CLI for repo-wide operations
• Cloud delegation for heavy lifting
• Git workflows for safe reviews

By connecting these pieces, you create a seamless AI-powered workflow inside the tools you already use. For a full breakdown of how Codex unifies terminal, editor, and cloud, see the complete integration guide. To understand trust levels, read the approval modes guide. For heavier tasks, compare local vs cloud workflows.

Conclusion

The Codex VS Code extension is more than a sidebar—it’s an embedded teammate. Installed in minutes, it lets you:

• Stay in your editor
• Run real coding tasks
• Review and approve diffs
• Scale to cloud when needed

If you’re serious about improving dev velocity in 2025, start here. Install the extension, choose safe defaults, and experiment with real tasks. The productivity gain is immediate.