[Windows desktop] 80% zoom causes flashing while typing and floods renderer with ResizeObserver errors

What version of the Codex App are you using?

Codex Desktop 26.814.5167.0.

What platform is your computer?

• Windows 10, build 19045.7663
• x64
• Codex app zoom: 80%

What issue are you seeing?

At 80% zoom, the Codex Desktop window visibly flashes/blinks, especially while typing in the composer. During stronger episodes the UI can also pause or show the Windows "not responding" prompt.

The blinking appears to be a renderer layout/repaint loop rather than a display-driver reset. During the observed interval:

• the active desktop log accumulated 512 instances of ResizeObserver loop completed with undelivered notifications;
• the count rose from 118 to 512 while the user and Codex were actively exchanging/typing messages;
• every sampled event identified the primary renderer as focused and visible;
• no contemporaneous Windows Display, DWM, WHEA, GPU-reset, compositor-crash, or renderer-crash event was found.

Steps to reproduce

1. Open Codex Desktop on Windows.
2. Set the app zoom to 80%.
3. Open a task and focus the message composer.
4. Type continuously for several sentences. The effect may be easier to trigger while a response or another task is updating.
5. Observe the main Codex window flashing/blinking or briefly stalling.
6. Inspect the current Codex Desktop log for bursts of the ResizeObserver error below.

A controlled 80%-versus-100% A/B test was not performed during this incident, so 80% is the reliably observed configuration rather than a proven exclusive trigger.

Expected behavior

Typing and background task updates should not cause the composer or conversation view to oscillate in size, repaint visibly, or block input at any supported zoom level.

Actual behavior

The focused primary window repeatedly flashes while the composer is being edited. The renderer log is flooded with layout-loop errors during the same period.

Sanitized log excerpt

2026-08-19T05:53:07.872Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true
2026-08-19T05:53:09.503Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true
2026-08-19T05:53:10.347Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true
2026-08-19T05:53:15.502Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true
2026-08-19T05:53:22.871Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true
2026-08-19T05:53:25.622Z error [electron-message-handler] [desktop-notifications][global-error] ResizeObserver loop completed with undelivered notifications. rendererWindowAppearance=primary rendererWindowFocused=true rendererWindowVisible=true

Observed range in this log:

first occurrence: 2026-08-19T04:38:47.453Z
last sampled occurrence: 2026-08-19T05:53:25.622Z
total occurrences: 512

Related issues

• #11901 — broader UI flickering while Codex is working
• #23245 — vertical conversation-output jitter on macOS
• #22333 — UI twitch/reflow during refresh

This report is specifically for Windows Desktop at 80% zoom, with composer activity and a directly correlated ResizeObserver error storm.

Start by reproducing the Windows Desktop behavior at 80% zoom while typing in the composer and monitor the current Codex Desktop renderer log for ResizeObserver error bursts. Compare the observed behavior at supported zoom levels; done means typing and background task updates no longer cause visible flashing, layout oscillation, input stalls, or a ResizeObserver error storm.