Cursor Agent Web, High CPU, Unresponsive

[Andri_Thorlacius]

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

1. UI to be responsive even if it is slow. Locking the UI thread is a very bad experience
2. 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

[condor (Condor (Tee))]

hi @Andri_Thorlacius and thank you for the detailed bug report.

Could you please check following so we can reproduce the issue:

• Does it still occur now?
• Could you mention your repo size, and how long the chat was in follow up prompts
• Please post the Background Agent request ID
• What actions did you do before it started hanging? (scrolling through long chat or reviewing many files?)