Windows app sandbox hangs for every child process; packaged codex.exe returns Access is denied

Summary

In the Codex Windows app, every sandboxed shell command hangs without producing output. This affects both PowerShell and cmd.exe. The same commands complete normally when explicitly run outside the sandbox. A complete uninstall/reinstall did not resolve the issue because it restored the same app build.

Environment

• Codex Windows app: 26.707.3748.0
• Windows 11 Enterprise 10.0.26200 (build 26200), AMD64
• PowerShell 7.6.2
• Package status: Ok
• Package install: Microsoft Store/MSIX under C:\Program Files\WindowsApps

Minimal reproduction

1. Open a local repository in the Codex Windows app.
2. Run a sandboxed command such as:

``powershell
Write-Output 'sandbox-ok'
``

1. The command remains active indefinitely and produces no output.
2. Run a sandboxed non-PowerShell child process:

``powershell
cmd.exe /d /c "echo sandbox-cmd-ok"
``

1. It hangs identically with no output.
2. Run the first probe with explicit outside-sandbox/escalated execution. It completes successfully in a few seconds.

Additional diagnostic

Launching the helper installed with the app directly also fails:

C:\Program Files\WindowsApps\OpenAI.Codex_26.707.3748.0_x64__2p2nqsd0c76g0\app\resources\codex.exe
HELPER_LAUNCH_ERROR: ... Access is denied.

The app logs previously showed repeated child-process snapshot collection failures and stale Git snapshot messages. Node and npm work normally outside the Codex sandbox.

Expected behavior

Sandboxed child processes should start, stream output, and respect their configured timeout.

Actual behavior

Every sandboxed child process tested hangs without output until manually terminated. Outside-sandbox execution works normally.

Troubleshooting already performed

• Fully uninstalled and reinstalled the Codex Windows app.
• Confirmed the reinstalled package status is Ok.
• Confirmed the reinstall restored the same build, 26.707.3748.0.
• Isolated the problem from PowerShell by reproducing it with cmd.exe.
• Confirmed the repository, PowerShell, Node, and npm operate normally outside the sandbox.

A fix or a supported workaround for the packaged helper/sandbox launcher would be appreciated.