Title: High CPU usage by WindowServer during Twitch playback on M4 Pro (macOS 26 Tahoe)
Description: After upgrading to macOS 26 (Tahoe), I’ve noticed that Twitch playback in both Safari and Microsoft Edge causes WindowServer to consume 40–50% CPU on a MacBook Pro with the M4 Pro chip. This results in noticeable fan noise and reduced battery life, even when only one 1080p stream is active. This behavior was not present in the previous version of macOS.
Steps to reproduce:
- Open Twitch in Safari or Edge.
- Play any live stream at 720p or 1080p.
- Observe Activity Monitor – WindowServer process hits 45%+ CPU consistently.
Expected: Hardware video decoding and efficient GPU-based composition should prevent CPU overload.
Actual: WindowServer consumes high CPU, fans activate
Hardware: MacBook Pro 14” (M4 Pro, 2025), macOS 26.0 (Tahoe)