[Windows] Auto-hidden taskbar cannot be revealed by mouse while ChatGPT Desktop is maximized

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

26.908.40834

What subscription do you have?

ChatGPT Plus

What platform is your computer?

Microsoft Windows NT 10.0.19045.0 x64

What issue are you seeing?

When the Windows taskbar is configured to auto-hide, it cannot be revealed by moving the mouse pointer to the bottom edge of the screen while the ChatGPT Desktop window is in the native maximized state.

The problem occurs specifically when ChatGPT Desktop is maximized.

The taskbar itself remains fully functional: pressing Ctrl+Esc causes it to appear immediately. Restoring the ChatGPT window to a non-maximized state also restores normal mouse edge-triggered taskbar behavior.

A manually resized ChatGPT window occupying almost the entire screen does not reproduce the issue. The problem appears to be specifically associated with the native maximized window state.

What steps can reproduce the bug?

1. In Windows, enable "Automatically hide the taskbar".
2. Open ChatGPT Desktop.
3. Maximize the ChatGPT window using the normal Windows maximize button.
4. Move the mouse pointer to the bottom edge of the screen.
5. The auto-hidden Windows taskbar does not appear.
6. Press Ctrl+Esc.
7. The taskbar appears immediately.
8. Restore the ChatGPT window to a non-maximized state.
9. Move the mouse pointer to the bottom edge again.
10. The taskbar now appears normally.

The issue is consistently reproducible when ChatGPT Desktop is maximized.

A manually resized window that occupies almost the full screen does not reproduce the problem; entering the native maximized state does.

What is the expected behavior?

A maximized ChatGPT Desktop window should not prevent Windows from revealing an auto-hidden taskbar when the mouse pointer reaches the bottom screen edge.

The Windows taskbar should behave in the same way whether the ChatGPT window is maximized or restored.

Additional information

This may be related to Windows misclassifying a maximized window using custom window chrome / a custom non-client area as a fullscreen application.

There are some particularly relevant precedents.

Electron previously had an issue with essentially the same observable behavior:

electron/electron#5990
"Maximized frameless window causes Windows' auto-hide task bar to not show"
https://github.com/electron/electron/issues/5990

It was later addressed by:

electron/electron#18321
"leave space for autohide taskbar for frameless maximized window"
https://github.com/electron/electron/pull/18321

Chromium also contains specific Windows handling for maximized windows and auto-hidden taskbars in HWNDMessageHandler. The relevant code explicitly discusses preventing Windows from treating the maximized window as a "fullscreen app":

https://chromium.googlesource.com/chromium/src/+/master/ui/views/win/hwnd_message_handler.cc

There is also a very recent and particularly similar Firefox issue:

Mozilla Bug 2064534
https://bugzilla.mozilla.org/show_bug.cgi?id=2064534

Firefox exhibited a very similar failure mode with maximized windows and an auto-hidden Windows taskbar. Reports for that bug also include the notable behavior that Ctrl+Esc can make the taskbar appear.

Mozilla's fix documents the Windows behavior explicitly:

"Windows may misdetect a maximized window with a custom non-client area as fullscreen"

The Firefox fix reasserts that the maximized custom-chrome window is not fullscreen after the relevant window state has been established, including additional Windows shell handling:

https://github.com/mozilla-firefox/firefox/commit/9349836256e5

I cannot determine whether ChatGPT Desktop has exactly the same root cause, but the reproduction pattern is strikingly similar:

• Only occurs in the native maximized state.
• Auto-hide mouse edge activation stops working.
• Ctrl+Esc still reveals the taskbar immediately.
• Restoring the window fixes the problem.

It may therefore be useful to check whether ChatGPT Desktop's custom titlebar / maximization path causes Windows fullscreen detection to change, or whether it bypasses or invalidates Chromium's existing auto-hide taskbar handling.

Related OpenAI issue:

#36594
"Windows taskbar with auto-hide overlaps the bottom of the Codex composer"
https://github.com/openai/codex/issues/36594

That issue appears related to maximized-window/taskbar handling, but its failure mode is different. In this case the auto-hidden taskbar cannot be revealed at all using the mouse while ChatGPT Desktop is maximized.

Start by tracing the desktop app's native maximization and custom-titlebar path, then compare its behavior with Chromium's ui/views/win/hwnd_message_handler.cc and the cited Electron and Firefox fixes. Reproduce the auto-hidden taskbar failure on Windows; done means mouse edge activation works while the app is natively maximized without breaking restored-window behavior.