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codex - 💡(How to fix) Fix Windows app renders incorrectly with black bars until Windows dark theme is forced [2 comments, 2 participants]

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openai/codex#18356•Fetched 2026-04-18 05:55:21
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What version of the Codex App are you using (From “About Codex” dialog)?

26.415.1938.0

What subscription do you have?

Enterprise

What platform is your computer?

OS: Windows 10 IoT Enterprise LTSC 2021 - OS build: 19044

What issue are you seeing?

Summary

On Windows, the Codex desktop app rendered incorrectly with large black bars / black regions in the window. Reinstalling the app did not fix it.

The issue was resolved only after forcing Windows dark theme for apps and system UI.

What I tried

  1. Uninstalled and reinstalled the Codex desktop app from Microsoft Store.
  2. Disabled Windows transparency.
  3. Forced Windows light theme:
    • AppsUseLightTheme=1
    • SystemUsesLightTheme=1
  4. Restarted the app after each change.

None of the above fixed the rendering issue.

What fixed it

Forcing Windows dark theme fixed the rendering issue immediately after restarting the app:

  • AppsUseLightTheme=0
  • SystemUsesLightTheme=0

At the time this worked, Windows transparency was also disabled:

  • EnableTransparency=0

Notes

Before testing, AppsUseLightTheme and SystemUsesLightTheme were not explicitly present in the registry, so Windows was using its default/policy behavior rather than a forced light or dark value.

This may be a Windows-specific rendering/composition issue related to:

  • theme detection / fallback behavior
  • Electron/Chromium rendering under certain Windows theme states I cannot provide a guaranteed minimal repro yet, but the issue occurred in a state where:
  • Windows was not explicitly forced to dark mode
  • forcing light mode did not help
  • forcing dark mode did help

explicit AppsUseLightTheme / SystemUsesLightTheme values.

Actual behavior

The app rendered with black bars / incorrect black regions until dark mode was explicitly forced.

What steps can reproduce the bug?

Environment

  • Codex app version: 26.415.1938.0
  • OS: Windows 10 IoT Enterprise LTSC 2021
  • OS build: 19044
  • GPU/renderer context observed by the app: Microsoft Basic Render Driver

Symptoms

  • The Codex app window opened and was usable, but rendered with obvious black bars / black regions.
  • The issue persisted across uninstall/reinstall.
  • The issue appeared to be tied to Windows appearance/composition settings rather than app installation state.

What is the expected behavior?

Expected

The sidebars should be visable

Additional information

No response

extent analysis

TL;DR

Forcing Windows dark theme by setting AppsUseLightTheme=0 and SystemUsesLightTheme=0 in the registry may resolve the rendering issue with the Codex app on Windows 10 IoT Enterprise LTSC 2021.

Guidance

  • Verify that the issue is indeed related to the Windows theme by checking if the problem persists when switching between light and dark modes.
  • Try disabling Windows transparency by setting EnableTransparency=0 to see if it has any effect on the rendering issue.
  • Check the registry for any existing theme-related settings that might be overriding the default behavior.
  • Consider testing the app on a different Windows version or configuration to isolate the issue.

Example

No code snippet is provided as the issue seems to be related to Windows configuration and registry settings rather than code.

Notes

The issue may be specific to the Windows 10 IoT Enterprise LTSC 2021 version and the Microsoft Basic Render Driver. Further testing is needed to determine the root cause and to find a more permanent solution.

Recommendation

Apply the workaround by forcing Windows dark theme, as it has been reported to resolve the issue. This is a temporary solution until a more permanent fix can be found.

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codex - 💡(How to fix) Fix Windows app renders incorrectly with black bars until Windows dark theme is forced [2 comments, 2 participants]