[Windows][Desktop 26.901.4073.0] Startup fails with 3221225477 / 0xC0000005 while standalone CLI and app-server work

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

26.901.4073.0

What subscription do you have?

ChatGPT Pro

What platform is your computer?

Microsoft Windows NT 10.0.22000.0 x64

What issue are you seeing?

ChatGPT / Codex Desktop consistently fails during startup.

The error dialog is:

ChatGPT failed to start.
(code=3221225477, signal=null).
Most recent error: Codex app-server websocket closed (code=3221225477)

3221225477 corresponds to 0xC0000005.

The UI sometimes appears for approximately 1–2 seconds before failing.

I reproduced the same failure in a completely new Windows user profile after installing ChatGPT/Codex there from scratch.

On that clean Windows profile, I was briefly able to start the ChatGPT sign-in flow. After successful browser authentication, the callback to localhost:1455/auth/callback returned ERR_CONNECTION_REFUSED because the Desktop application/local callback handler had already stopped.

Important control tests:

• Standalone Codex CLI works correctly:
  codex-cli 0.153.2

• Standalone app-server also starts successfully and remains running:
  codex.exe app-server --listen ws://127.0.0.1:8765

Therefore the standalone Codex CLI and app-server can both run successfully on this Windows installation. The failure appears specific to the Desktop application's startup/integration with its app-server.

Troubleshooting already performed with no change:

• Windows App Repair and Reset
• Complete uninstall/reinstall from Microsoft Store
• Complete uninstall/reinstall using the official direct MSIX
• Updated from 26.825.6671.0 to 26.901.4073.0
• Multiple Windows reboots
• Multiple VPN configurations
• Confirmed working system-level VPN via Windscribe WStunnel over TCP 443
• Microsoft Defender Firewall temporarily disabled for testing
• Completely new Windows user profile
• Confirmed approval_policy = "untrusted" is not present in .codex/config.toml
• Installed standalone Codex CLI
• Set CODEX_CLI_PATH to the working standalone executable

Logging diagnostics:

The expected Desktop log directory:

C:\Users\User\AppData\Local\Packages\OpenAI.Codex_2p2nqsd0c76g0\LocalCache\Local\Codex\Logs

is not created at all after reproducing the failure.

%USERPROFILE%.codex\logs does not exist.

%USERPROFILE%.codex.sandbox\sandbox.log does not exist.

The only .codex.sandbox logs present are old date-stamped files, with the newest from Aug 22, before this issue began.

C:\Users\User\AppData\Roaming\Codex\web\Codex\Crashpad\reports exists, but contains no crash dump files.

So this early startup failure currently generates neither current Desktop text logs nor a Crashpad dump.

What steps can reproduce the bug?

1. Start Windows normally.

2. Connect to a working system-level VPN (Windscribe WStunnel over TCP 443).

3. Launch ChatGPT / Codex Desktop 26.901.4073.0.

4. The UI may appear for approximately 1–2 seconds.

5. Desktop then fails with:

   ChatGPT failed to start.
   (code=3221225477, signal=null).
   Most recent error: Codex app-server websocket closed (code=3221225477)

6. Pressing "Check for Updates" reports that ChatGPT is up to date.

7. Relaunching reproduces the same failure.

The issue reproduces consistently.

It also reproduces in a completely new local Windows user profile with a clean ChatGPT/Codex installation.

What is the expected behavior?

ChatGPT / Codex Desktop should start normally, launch/connect to its local Codex app-server, and remain open.

The Desktop app should work on this machine because the standalone Codex CLI and standalone app-server both start and run successfully.

Additional information

This issue has also been reported to OpenAI Support and has been escalated to a support specialist.

Additional observations:

• ChatGPT/Codex Desktop reports that it is fully up to date.
• The failure persisted after upgrading from 26.825.6671.0 to 26.901.4073.0.
• The same failure reproduces in a completely new Windows user account with a clean ChatGPT/Codex installation.
• Standalone Codex CLI 0.153.2 works normally.
• Standalone codex.exe app-server --listen ws://127.0.0.1:8765 also starts successfully and remains running.
• Setting CODEX_CLI_PATH to the working standalone Codex executable did not resolve the Desktop failure.
• The Desktop app fails too early to generate its expected current text log directory or a Crashpad dump.
• Microsoft Defender Firewall was temporarily disabled during testing with no change.
• A working system-level VPN connection using Windscribe WStunnel over TCP 443 was confirmed, with no change to the Desktop failure.

The machine is currently running Windows 11 Pro 21H2 (build 22000.2538). I am aware this is an old Windows build, but because the standalone Codex CLI and standalone app-server both run successfully, the failure appears specific to the Desktop application's startup/integration layer.

OpenAI Support has been asked for an official verbose/debug logging procedure or diagnostic build because the normal Desktop logs and Crashpad reports are not being generated.

No source file or failing test is identified. Start by reproducing the Windows Desktop launch failure and compare it with the working codex.exe app-server --listen ws://127.0.0.1:8765 entry point; inspect the expected Desktop log path and Crashpad reports. Done means the Desktop app starts, connects to its local app-server, and remains open.