Windows setup fails with `helper_failed` and no UAC prompt

Windows setup fails with helper_failed and no UAC prompt

Codex Windows helper_failed Bug Report.md

Environment

• OS: Windows 11 Home China, 25H2
• OS Build: 26200
• Architecture: x64
• Codex Desktop version: 26.908.9136.0
• Package: OpenAI.Codex_26.908.9136.0_x64__2p2nqsd0c76g0

Problem

Codex Windows setup fails with helper_failed.

Clicking Retry Windows setup does not trigger a UAC elevation prompt.

Troubleshooting performed

• Windows account is an Administrator.

• CPU virtualization is enabled.

• OpenAI.Codex AppX package reports:

  • Status: Ok
  • SignatureKind: Store

• The bundled helper exists at:
  ...\app\resources\codex-windows-sandbox-setup.exe

• Authenticode signature of the helper is Valid, signed by OpenAI OpCo, LLC.

• Running the helper directly from an elevated PowerShell results in:
  Access Denied

• The helper file reports Encrypted / Application Protected.

• Codex services/AppX installation appear otherwise normal.

Expected behavior

Clicking Retry Windows setup should successfully run the required Windows sandbox setup helper and complete the setup, including the necessary UAC elevation.

Actual behavior

The setup fails with helper_failed, and no UAC prompt appears.

Please investigate whether the Windows AppX/MSIX protection or the sandbox setup helper is preventing the helper from launching/elevating correctly.

Start with the attached bug report and the Windows setup path that launches app/resources/codex-windows-sandbox-setup.exe when Retry Windows setup is selected. Reproduce the helper_failed result on the reported Windows environment and inspect why the helper returns Access Denied without a UAC prompt. Done means the helper launches with the required elevation and Windows sandbox setup completes successfully.