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Codex Issues / #29427

codex-windows-sandbox-setup.exe Application Error

Open 💬 4 comments Opened Jun 22, 2026 by tmc101
💡 Likely answer: A maintainer (github-actions[bot], contributor) responded on this thread — see the highlighted reply below.

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

Version 26.616.51431 • Released 20 Jun 2026

What subscription do you have?

Plus

What platform is your computer?

Microsoft Windows NT 10.0.26100.0 x64

What issue are you seeing?

When I start the Codex Application it prompts me to 'Install the required sandbox update':

<img width="780" height="182" alt="Image" src="https://github.com/user-attachments/assets/8edc012a-9fe4-4fdf-903f-df290a74d9fd" />

When I click on update it requests admin permission. I enter credentials with Admin permission.

It then errors with:

<img width="439" height="245" alt="Image" src="https://github.com/user-attachments/assets/187cf902-5569-4027-8913-9d29708baad9" />

The Codex app now reports:

<img width="743" height="94" alt="Image" src="https://github.com/user-attachments/assets/142ea572-2b8e-4ae2-9bfc-08e34cc174f3" />

Retries do not work.

What steps can reproduce the bug?

  1. Launch the Codex on on Windows 11.
  2. Click the button to update the sandbox.

What is the expected behavior?

The codex-windows-sandbox-setup.exe does not error.

Additional information

_No response_

View original on GitHub ↗

4 Comments

github-actions[bot] contributor · 2 months ago

Potential duplicates detected. Please review them and close your issue if it is a duplicate.

  • #29418
  • #29200
  • #29115
  • #29127
  • #29089

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xfire0111 · 2 months ago

Same issue on Codex 26.623.5546.0, Windows 11 Home 10.0.26200.

Smart App Control is enabled:
VerifiedAndReputablePolicyState = 1

codex-windows-sandbox-setup.exe fails with:
0xc0000142

sandbox.log repeatedly shows:
sandbox setup required: sandbox setup marker missing or incompatible

Issue started after runtime aec6b7c6fcdfb66a appeared on 2026-06-28 13:38.

Helper path:
~user\AppData\Local\OpenAI\Codex\bin\aec6b7c6fcdfb66a\codex-windows-sandbox-setup.exe

Helper SHA256:

2FD812AC28D942461640B7251BF566A7960433253274119CDC9709CF25FDA5E7

I attached a local diagnostic summary.

cooltzy · 1 month ago

the same problem，

Levyks · 1 month ago

I was struggling with the same issue and was able to fix it with the help of (lol) claude using ProcMon

Basically, in the UAC prompt, I was using different credentials from the user I was currently logged in (company policy, my user does not have admin rights)

The thing is, this admin user's SID was never had the ChatGPT AppX register registered, and this was causing the error

I had to log in to the admin user, install ChatGPT there, open it at least once (no need to log in, just literally open and close the app), log back in into my main account, and it started working there