Windows Codex app causes mouse stutter during startup and task switching without CPU/Disk saturation

Summary

On Windows 11, launching the Codex desktop app and switching/opening tasks causes visible system mouse stutter. The issue persists after a clean Windows 11 reinstall and after multiple local mitigations. It is severe enough to affect normal PC operation during Codex startup.

Environment

• OS: Windows 11, clean reinstall
• Codex package: OpenAI.Codex_26.707.9981.0_x64__2p2nqsd0c76g0
• Codex version: 26.707.9981.0
• WebView2 Runtime: 150.0.4078.65
• GPU: NVIDIA GeForce RTX 4060 Ti
• NVIDIA driver: 32.0.16.1074, driver date 2026-07-02
• Mouse: wired HID mouse, SteelSeries device HID\VID_1038&PID_1361&MI_00&COL01

Symptoms

• Mouse stutters during Codex startup, originally for roughly 30 seconds.
• Mouse also stutters when opening/switching Codex tasks, especially tasks that have not been opened recently.
• The behavior occurs only after starting Codex/projects; normal system use before opening Codex does not show the same stutter.
• Reinstalling Windows 11 did not resolve the issue.

Reproduction

1. Close Codex completely.
2. Start Codex desktop app.
3. Observe mouse movement during startup and while the task list/task UI loads.
4. Open or switch to a Codex task.
5. Observe additional mouse stutter.

Diagnostics already performed

The following tests did not resolve the issue:

• Clean Windows 11 reinstall.
• Closing ToDesk.
• Closing QQ Music and SteelSeries background apps.
• Moving the wired mouse to another rear USB port.
• Lowering SteelSeries mouse polling rate from 800Hz to 125Hz.
• Disabling Todesk Virtual Display Adapter and retesting, then re-enabling it.
• Windows app Repair for Codex.
• GPU preference changes: power saving vs high performance.
• Disabling Windows windowed game optimizations.
• Launching with GPU rendering disabled.
• Deleting WebView/Chromium shader caches (GrShaderCache, ShaderCache, GPUPersistentCache).

Local profile/cache observations

Moving the Codex WebView profile temporarily improved the issue, but the stutter returned after Codex regenerated the local profile/cache.

Observed profile sizes:

• New profile shortly after reset: ~65 MB
• New profile after Codex startup/use: ~121 MB
• Old profile backup: ~131 MB

The growth was mainly in Chromium/WebView component/cache directories such as:

• component_crx_cache
• WasmTtsEngine
• WidevineCdm
• Default
• GrShaderCache

This suggests clearing local profile/cache is only a temporary mitigation.

WPR/WPA/xperf evidence

A Windows Performance Recorder trace was captured during a reproduced stutter:

• Trace duration: 169 seconds
• Events: ~27.5 million
• Lost events: 0
• ETL size: ~2.72 GB

The trace is available if maintainers want it, but I am not attaching it publicly because ETL traces can include local paths/process metadata.

High-level analysis with WPA/xperf:

• No sustained CPU, disk, or memory saturation.
• During the 70s-100s peak window, the system still had ~75% Idle CPU.
• During the 120s-125s UI-delay window, the system still had ~78% Idle CPU.
• Main contributors in the peak windows included ChatGPT.exe, codex.exe, dwm.exe, and WebView-related activity, but none saturated the system.
• uidelay captured a foreground ChatGPT.exe message-check delay of 218 ms on Chrome_RenderWidgetHostHWND / Chrome_WidgetWin_1.
• DPC/ISR activity showed USB/NVIDIA/DirectX-related modules active, but no single driver-level stall clearly explains a 30-second user-visible stutter.

Codex logs

Codex desktop logs during startup/task use showed repeated frontend/UI related messages, including many occurrences of:

ResizeObserver loop completed with undelivered notifications.

Startup logs also showed relatively slow initialization calls in some runs, for example:

plugin/list durationMs=1898
plugin/list durationMs=4393

There were also repeated browser/sidebar lifecycle warnings around task/window ownership, but no clear system-level crash or display driver reset was found in Windows Event Viewer.

Expected behavior

Starting Codex and switching tasks should not cause system-level mouse stutter when CPU, disk, and memory are not saturated.

Actual behavior

Codex startup/task switching causes visible mouse stutter even on a clean Windows 11 install, and the issue returns after local profile/cache regeneration.

Notes

This appears more consistent with Codex desktop frontend/WebView rendering or initialization behavior than with a general Windows, USB port, mouse polling rate, GPU preference, or old local profile issue.