[Windows 10] OpenAI.Codex 26.915.3509.0 fails at startup with “ChatGPT hit a snag”

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

New ChatGPT/Codex

What subscription do you have?

Plus

What platform is your computer?

Windows 10 (x64 and arm64) version 19045.7725

What issue are you seeing?

The new ChatGPT/Codex Windows application fails immediately during startup and displays:

ChatGPT hit a snag
Something went wrong. Restart ChatGPT to try again.

The error occurs before any sign-in screen, message composer, settings, or session becomes available.

ChatGPT Classic and ChatGPT on the web work correctly on the same computer, account, and network.

What steps can reproduce the bug?

Install OpenAI.Codex from the Microsoft Store.
Launch the application.
Wait for the application to initialize.

What is the expected behavior?

The application should open normally and display either the sign-in screen or main interface. If initialization fails, it should display a technical error code and create a diagnostic startup log.

Additional information

The application immediately displays “ChatGPT hit a snag” and cannot be used.

The failure occurs before sign-in and before the message composer loads. Consequently, it is impossible to use / to generate a session ID.

The following directory is never created:

%USERPROFILE%.codex.sandbox

Therefore, the documented sandbox.log file does not exist:

%USERPROFILE%.codex.sandbox\sandbox.log

Windows Reliability Monitor does not record an application crash, suggesting that the application handles the internal startup failure and displays its generic error screen.

Troubleshooting already completed:
Restarted the application and computer
Used Windows Repair and Reset
Completely uninstalled and reinstalled the application
Reinstalled through Microsoft Store and winget
Renamed .codex to force creation of a clean configuration
Tested the unelevated Windows sandbox configuration
Tried running the application as administrator
Tested a separate mobile hotspot
Confirmed Microsoft Edge WebView2 Runtime is installed
Ran DISM.exe /Online /Cleanup-Image /RestoreHealth
Ran sfc /scannow
Checked Windows Reliability Monitor
Confirmed ChatGPT Classic works on the same computer

No source file or test is named. Start by reproducing the Microsoft Store installation failure on Windows 10 and tracing the startup initialization path, using the reported absence of .codex/.sandbox and sandbox.log as diagnostics. Done means the app reaches sign-in or the main interface, or reports a technical error and creates a startup log.