Qubes has become incredibly sluggish since I updated dom0 today. What happened? Is there a solution?

:police_car_light: Strange things observed today.

What does this sluggishness manifest as for you? Did it happen immediately or only after a reboot? Are you on stable, security-testing or testing repos?

It’s extremely slow—it’s become sluggish, like an old computer. It looks like dom0 is using an excessive amount of CPU. The slowdown started right after I updated dom0 and rebooted. I believe I’m using the stable version; I haven’t made any changes since installation, so it’s still on the default se…

Could you check which process is using this much CPU? htop or btop are good commands to do that.

it’s Xorg , qubes-guid and xfwm4

I noticed this too. It appears that when fcitx5 is launched on a VM with gui-agent-linux v4.3.19 installed, it hangs. So, when I reverted it to the previous version, it now works properly: sudo dnf install qubes-gui-agent-4.3.18 It seems the debian repositories don’t have packages for previous ve…

@kzlz I believe you should make an issue on the issue tracker for this.

I think you’re right; the VM doesn’t become incredibly slow if I use a template without fcitx. However, since I only use Kicksecure and Whonix templates, I’m not really sure how to revert to the previous version.

Do you see the high cpu usage in dom0 or in the appvms / qubes? Also as you mentioned xfwm4. Is everyone who experiences this running xfce? Anyone running KDE or something else?

I pushed a fix here: Limit XEmbed size normalization to 1x1 clients by besendorf · Pull Request #265 · QubesOS/qubes-gui-agent-linux · GitHub

Qubes became extremely sluggish after a dom0 update

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Martin32 August 18, 2026, 9:30pm 13

Does anyone know how to fix this