How do I fix the white line glitch on my Mac after the Tahoe 26.2 update?

Why does my wallpaper look blurry on macOS Tahoe 26.2 and how can I stop it?

Users who updated to macOS Tahoe 26.2 report distinct visual artifacts. These issues manifest primarily as a white line along the display bezel and unexpected wallpaper resolution drops. Data collected from community forums indicates these bugs affect Apple Silicon models, including the M1 MacBook Air, M2 MacBook Air, and 16-inch MacBook Pro. The absence of these artifacts in screenshots suggests a software-level rendering error rather than hardware failure.

Issue 1: The Top Bezel White Line Artifact

A faint, translucent line appears at the absolute top edge of the display. Some users observe this line extending down the side bezels. This artifact typically becomes visible when the cursor hovers over the Dock.

Since the line does not appear in standard screenshots, the issue likely resides in the final display output layer rather than the logical framebuffer. This points to a conflict within the operating system’s graphical interface rendering engine.

Strategic Workaround

You can eliminate this artifact by altering the menu bar transparency settings. This forces the OS to render a solid container, overriding the glitch.

1. Navigate to System Settings.
2. Select Control Center (or Desktop & Dock depending on specific build configuration).
3. Locate the Menu Bar options.
4. Change “Automatically hide and show the menu bar” to Never.
5. Ensure “Show menu bar background” is enabled.

Note: This creates a permanent, opaque bar at the top of your screen. While effective, it disables the transparent aesthetic of the new design language.

Issue 2: Wallpaper Resolution Degradation

The second prevalent issue involves desktop wallpapers appearing blurry, resembling a 480p low-resolution image. This visual degradation occurs randomly but links strongly to the use of “Spaces” (virtual desktops).

Technical Observations

• Screenshot behavior: The blur is invisible in screenshots, confirming the source image file remains intact while the display rendering fails.
• Trigger: Assigning the exact same wallpaper file to multiple different Spaces often triggers the blur.
• Temporary Reset: Toggling “Liquid Glass” settings restores clarity momentarily before the blur returns.

Troubleshooting Steps

To maintain image sharpness, you must disrupt the rendering conflict caused by identical backgrounds.

1. Open System Settings > Wallpaper.
2. Assign a unique wallpaper to each active Space.
3. Avoid reusing the same image file across different virtual desktops.

Root Cause Analysis: The Liquid Glass Engine

These anomalies suggest instability within the “Liquid Glass” design framework introduced in Tahoe. This UI layer relies on complex translucency and light-reactive elements. The white line likely results from a miscalculation in the edge-masking algorithm, while the wallpaper blur indicates a memory management error when caching background assets for Mission Control.

Professional Recommendation

Apple has not released an official patch statement. However, the prevalence of reports suggests a fix is imminent in version 26.3.

Immediate Action Required

Do not attempt hardware repairs. This is strictly a software defect. Submit a detailed log to Apple to expedite the patch cycle:

1. Open Spotlight (Cmd + Space).
2. Type Feedback Assistant.
3. File a report under macOS > Graphics & Display.