High GPU Usage from WindowServer on macOS Tahoe 26.1 with external Monitor

Hi everyone,

since updating to macOS Tahoe 26.1, I’ve been seeing very high GPU usage (50–80%) from the WindowServerprocess whenever my MacBook is connected to my Dell U2025QW (5K2K) monitor. This happens even when the system is idle. As a result, the MacBook heats up quickly and the fans ramp up during simple tasks.

If I disconnect the monitor, everything returns to normal. Before the update, the whole setup worked without any issues.

I tested this on two different machines:

• MacBook Pro 16” (M1 Pro)
• MacBook Pro 16” (M4 Pro)

Both show the exact same problem, so I can rule out a hardware defect.

Setup:

• Monitor: Dell U2025QW
• Resolution: 5K2K (“Looks like 3840 × 1620”)
• OS: macOS Tahoe 26.1

Is anyone else experiencing this?

Are there any known fixes or workarounds?

Thanks in advance for any help!