Where does the bug appear (feature/product)?
Background Agent (GitHub, Slack, Web, Linear)
Describe the Bug
When ever I use the web UI for the agent with a complex request suddenly the web UI starts ■■■■■■■ my CPU to 100% and that chat is pretty much un usable because it is so unresponsive.
Takes 10-120 sec from an input click to affect the state on the screen
I have got a beefy new computer so that should not be a problem.
It looks like my CPU is only at 100% while the tab is open, navigating away drops the CPU usage down.
Navigating back to the tab causes the CPU to go straight to 100% again and stay there.
That chat history is pretty much unusable in that state.
Steps to Reproduce
I have been having this issue to a varying degree with changes I am creating using the webUI.
I belive it is tied to either chat history lengt or the size of the change?
Might be related to the repository I am working on. It is qutie big?
Expected Behavior
I would like the
- UI to be responsive even if it is slow. Locking the UI thread is a very bad experience
- My CPU not to be stuck at 100% if I
Screenshots / Screen Recordings
Operating System
Linux
Current Cursor Version (Menu → About Cursor → Copy)
Cursor web interface on the 31st of oct 2025
For AI issues: which model did you use?
Sonnet 4.5,
But it doesn’t matter as the web UI thread is the issue.
Additional Information
CPU: Intel Core Ultra 5 245K x14
Ram: 64GB
GPU: Nvidia 5060
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36
Does this stop you from using Cursor
Sometimes - I can sometimes use Cursor