Visual border and rendering lag around Start Menu in Windows 11 ARM on macOS 26 / Parallels 26.1.1

After updating to macOS 26.0 (Tahoe) and Parallels Desktop 26.1.1, I've started noticing a strange border / halo effect around the Windows 11 ARM Start Menu when it's opened.
Sometimes, when I open the Start Menu, it appears slightly shifted or misaligned for about a second, then it repositions itself correctly. The border looks like a semi-transparent frame surrounding the menu (see attached screenshot).
This issue didn't exist on earlier versions of macOS or Parallels -- it started appearing only after updating both the host and Parallels to the latest versions.
Setup details:

• MacBook Pro M4 Max
  macOS 26.0
• Parallels Desktop 26.1.1
• Windows 11 ARM (fully updated)
• Mode: happens both in Windowed and Coherence modes

Tried so far:

• Reinstalling Parallels Tools
  Checking graphics settings (auto vs Metal)
• Restarting Windows / macOS
• Switching display modes

None of these changed the behavior.
Has anyone else experienced this border / glow issue with the Start Menu in Windows 11 ARM?
Any known workaround or fix (e.g., boot flags like video.metal=0, or disabling specific macOS window effects)?
Thanks in advance!

 

The issue isn't with the underlining host system (hardware/software) ... it's with Parallels software, specifically coherence mode.

 

Yes, same problem since Windows Update KB5066835, 10/14/2025.

 

I have the same problem after the KB5066835 update. It has actually gotten much worse, as the border is now almost 1 cm wide and sometimes displays elements from Windows. As long as a Windows window is located below the Start menu, it's still okay, but if it's a Mac window, it looks terrible.

 

Also happens when you click on the power/shutdown option under the start menu ... Windows background takes over, corrupting the view. Same thing happens to Windows notification alerts. Sometimes the border/background is either grey or full-on/parts of the Windows set background image.

 

Here are a few screenshots before and after the update (KB5066835) and with Windows in the background.
It appears as if the Coherence window has a fixed width (see custom layout).

 

Still not fixed. I've contacted support twice -- they act like they don't understand what the issue is.
"Send a screenshot, try uninstalling the KB" -- yeah, the one that can't be uninstalled because the build is newer.
The product is turning into crap..

 

Same here. Apparently, they don't test Cohrence Mode themselves, otherwise they would see it immediately and not constantly ask for some 9-digit Report-ID.

I have now solved the problem using "Windhawk" and the "Windows 11 Start Menu Styler" mod. Here I have added an (additional entry) in the settings:

Target: StartDocked.StartSizingFramePanel > Windows.UI.Xaml.Controls.Border
Style: Background:=<AcrylicBrush TintColor="{ThemeResource CardStrokeColorDefaultSolid}" FallbackColor="{ThemeResource CardStrokeColorDefaultSolid}" TintOpacity="1" TintLuminosityOpacity="1" Opacity="1"/>

Now the border is at least the color of the theme and no longer the Windows desktop background.
Maybe Parallels will release an update at some point...

PS: With the "Resource Redirect" mod, I also changed the color of the ugly yellow folders in Explorer.