With 128.7.0esr I'm still seeing this on macOS, but not anymore on linux X11 and windows (thank you!)
1) Open Thunderbird 128.7.0esr 2) Click on any message 3) Go offline and wait for CPU to idle 4) Move mouse up and down above list so that messages highlight, without clicking on anything macOS 14.4.1: CPU jumps to 100% Ubuntu 24.04.1 (X11): CPU remains <10% Windows 10 Pro 22H2: CPU remains <10% Changing settings for gfx.webrender.force-disabled and gfx.webrender.software made no difference on macOS. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1959747 Title: [upstream] Very high CPU and slow responsiveness in Thunderbird 91-102 To manage notifications about this bug go to: https://bugs.launchpad.net/thunderbird/+bug/1959747/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs