GitHub Codespaces (browser) freezes after opening Codex sidebar

What version of the Codex App are you using (From “About Codex” dialog)?

Latest codex codespace release

What subscription do you have?

ChatGPT Plus subscription

What platform is your computer?

Windows laptop

What issue are you seeing?

The OpenAI Codex VS Code extension appears to freeze the browser-based GitHub Codespaces editor.

A newly created Codespace opens and functions normally. After installing the Codex extension and selecting the Codex activity bar icon, the browser freezes and the Codespace becomes unusable.

After this occurs, reopening the same Codespace only displays a white page.

The issue reproduces consistently.

What steps can reproduce the bug?

Steps to Reproduce
Create a brand-new GitHub Codespace.
Open it in the browser (github.dev).
Confirm the editor loads normally.
Install the official OpenAI Codex extension.
Click the Codex icon in the Activity Bar.
Expected Behaviour

The Codex sidebar should open normally.

Actual Behaviour

The browser freezes immediately.

Afterwards:

the Codespace can no longer be opened
reopening only shows a white page
deleting the Codespace and creating another works until Codex is installed again
Troubleshooting Performed
Tested multiple repositories.
Tested a completely new repository.
Deleted and recreated Codespaces.
Disabled Settings Sync.
Tested multiple browsers.
Tested an Incognito/InPrivate session.
Verified that https://vscode.dev loads normally.
Opened a fresh Codespace in Incognito with no extensions installed.
The fresh Codespace worked normally until the Codex extension was installed.
Installing the Codex extension and opening the Codex sidebar immediately reproduced the freeze.
Additional Notes

The problem appears to be triggered specifically by opening the Codex sidebar inside browser-hosted GitHub Codespaces.

The behaviour is fully reproducible on my system.

What is the expected behavior?

_No response_

Additional information

_No response_