In-app Browser fails to start on Windows 11 with CreateProcessAsUserW failed: 5

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

26.609.41114

What subscription do you have?

ChatGPT Plus

What platform is your computer?

Microsoft Windows NT 10.0.22631.0 x64

What issue are you seeing?

Microsoft Windows NT 10.0.22631.0 x64The in-app Browser plugin in the official Codex desktop app on Windows 11 suddenly stopped working around June 12, 2026.

Before that, the in-app browser was working normally. Since then, any attempt to connect to the in-app browser fails at the browser control channel / browser control process startup step.

Visible error:

Windows sandbox startup failed: CreateProcessAsUserW failed: 5

I submitted in-app feedback from the affected Codex session.

Feedback ID:
019ebe88-6d1b-7022-8e55-d98c535cd79a

What I have tried:

• Uninstalled and reinstalled the official Codex desktop app from Microsoft Store
• Confirmed the Browser plugin files exist
• Tried connecting to the in-app browser multiple times
• Tried retrying/resetting the browser control session
• The same Windows sandbox / permission error still occurs

I also verified that the Browser plugin files exist by successfully reading:

C:\Users\wang.codex\plugins\cache\openai-bundled\browser\26.609.41114\skills\control-in-app-browser\SKILL.md

So the Browser plugin itself appears to be installed. However, when Codex tries to actually connect to the in-app browser, it fails while starting the browser control process. Retrying produces the same result, so this does not look like a temporary startup failure, webpage issue, or network issue.

Environment:

• App: Official Codex desktop app from Microsoft Store
• OS: Windows 11
• User profile path: C:\Users\wang
• Browser plugin path: C:\Users\wang.codex\plugins\cache\openai-bundled\browser\26.609.41114
• Error: Windows sandbox startup failed: CreateProcessAsUserW failed: 5

Could you please check whether there is a known issue with the Windows sandbox or in-app browser control process around the June 12 timeframe? Also, please let me know how I can reset or repair the Codex Windows sandbox / browser control environment.

What steps can reproduce the bug?

1. Open the official Codex desktop app on Windows 11.
2. Start a Codex session.
3. Ask Codex to use the in-app Browser plugin or connect to the in-app browser.
4. Codex attempts to connect to the browser control channel.
5. The connection fails while starting the browser control process.
6. Retrying the browser connection produces the same Windows sandbox error.

What is the expected behavior?

The in-app browser should start successfully, connect to the browser control channel, and allow Codex to open and control browser pages normally.

Additional information

_No response_