Windows Codex blank screen caused by config.toml filled entirely with NUL bytes; reinstall does not recover

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

26.903.894.0

What subscription do you have?

Pro

What platform is your computer?

No response

What issue are you seeing?

.Codex on Windows opened as a completely blank white window and was unusable.

The application processes were running normally in Task Manager. When maximizing/restoring the window, the normal Codex UI sometimes appeared for only a fraction of a second before returning to a white screen.

Rebooting Windows, signing out/in, checking VPN/proxy/Secure DNS, clearing site data/cookies, uninstalling Codex, and reinstalling the latest version did not resolve the issue.

I later installed Codex CLI. The CLI reported:

Error loading config.toml:
C:\Users<username>.codex\config.toml:1:2701
key with no value, expected '='

I inspected config.toml and found:

• File size: 2700 bytes
• Last modified: 2026-09-07 09:24:03 local time
• All 2700 bytes were 0x00 (NUL)

After backing up and renaming only this corrupted config.toml file, Codex CLI immediately started normally.

I then launched the Windows desktop app again. It also immediately displayed normally instead of the blank white screen.

My existing Codex projects/history were still intact.

A normal uninstall/reinstall did not resolve the problem because the corrupted config.toml remained under the user's .codex directory.

What steps can reproduce the bug?

I do not know what originally caused config.toml to become corrupted, so I cannot provide a reliable procedure for reproducing the corruption itself.

The observed failure condition was:

1. A config.toml existed at:
   C:\Users<username>.codex\config.toml

2. The file size was exactly 2700 bytes.

3. All bytes in the file were 0x00 (NUL).

4. Launch the Codex Windows desktop app.

5. Codex processes start, but the application window remains completely white.

6. Uninstall and reinstall the Codex desktop app.

7. Launch Codex again.

8. The blank white screen remains because the corrupted config.toml is preserved.

Recovery procedure:

1. Back up config.toml.

2. Rename the corrupted config.toml so it is no longer used as the active configuration.

3. Launch Codex CLI.
   The CLI starts normally.

4. Launch the Windows desktop app.
   The GUI also starts normally.

5. Existing Codex projects/history remain intact.

What is the expected behavior?

If config.toml cannot be parsed or is corrupted, the Windows desktop application should not fail with only a blank white window.

It should instead:

• display a clear configuration error,
• offer to regenerate/reset the corrupted configuration, or
• safely fall back to a default configuration.

Reinstall/troubleshooting guidance should also account for corrupted files under the user's .codex directory, because a normal uninstall/reinstall did not remove or repair this file.

Additional information

I preserved:

• the corrupted config.toml
• a backup copy
• screenshots of the CLI parse error
• file size and last-modified timestamp
• a Format-Hex dump confirming that all 2700 bytes were 0x00
• screenshots showing successful recovery after renaming config.toml

I can provide these if useful.

I am not claiming that Codex itself caused config.toml to become corrupted. I can only confirm that the corrupted file existed, caused Codex CLI to fail parsing it, and that renaming it immediately restored both Codex CLI and the Windows desktop GUI.

No source files or tests are named. Start by locating config.toml parsing in the Rust CLI and Windows desktop app, then reproduce the failure with an all-NUL configuration file. Done means the app avoids a blank window and provides a clear error, recovery option, or safe default when configuration parsing fails.