I’m experiencing extremely high CPU and memory usage when using Cursor, and it’s making my machine almost unusable.
Issue Details
• Multiple Cursor Helper (Plugin): extension-host (user) processes are each consuming around 4GB of memory
• Several of them are running simultaneously
• CPU usage stays near 100% across many extension-host processes
• System idle is 0% and fans are constantly running
• Memory pressure increases significantly
From Activity Monitor:
• 8–10 extension-host processes each using ~4GB RAM
• Total memory usage by Cursor-related processes exceeds 30GB
• CPU usage per extension-host ~97–99%
Questions
• Is this expected behavior?
• Could this be related to a specific plugin?
• Is there a way to limit extension-host processes or memory usage?
• Are there known issues with memory leaks?
Please let me know if logs or additional diagnostics would help. I’m happy to provide them.
Thanks in advance
Steps to Reproduce
This happens even when I’m not actively running heavy tasks.
Then open the command palette with CMD + Shift + P and run “Developer: Open Extension Monitor”
This will show CPU and memory per extension. Please share a screenshot of the results
Also try:
CMD + Shift + P > “Developer: Open Process Explorer” to match PIDs to specific processes and see what each extension-host is tied to
Quick test: start Cursor from a terminal with cursor --disable-extensions and see if the issue still happens. If it goes away, a specific extension is the cause.
A few questions:
How many Cursor windows do you usually keep open? Each window has its own extension-host process, so multiple windows could explain the count.
Which extensions do you have installed? A list would help.
How big is your project, like file count and approximate size?
The team is aware of extension host performance issues and is tracking them.
Thanks for the guidance! Here’s the information you requested:
Number of Windows: Currently, I’m working with just 1 Cursor window open, and my project is relatively small (19 files, ~560 KB - a Cloudflare Workers tutorial). However, I typically keep 2-3 windows open during my regular workflow. When I do open additional windows for other tasks, I close them once they’re no longer needed.
The Issue: Even though I’m diligent about closing windows, I’ve noticed that the extension-host processes don’t seem to decrease. They appear to accumulate and persist as lingering processes rather than being properly cleaned up when windows are closed. This is my main concern—it feels like the processes are stacking up over time.
Extensions List: I ran cursor --list-extensions and here’s the output:
I’m happy to run the Extension Monitor and Process Explorer as you suggested and share the results. Would that help identify which extensions might be causing the issue?
At the moment, my system currently has enough resources to handle this, but if the issue gets worse, I’ll attach an updated Activity Monitor screenshot for you to review.
Hey, thanks for the screenshot. I can see the issue. In Extension Host 44653, <ext-host-runtime> is using 100% CPU.
You’ve got 4 third‑party AI extensions running together with Cursor’s built‑in AI: Claude Code, Cline, CodeRabbit, and OpenAI ChatGPT. It’s most likely one of those. They can conflict and eat up resources.
Please try this:
Disable all four AI extensions, restart Cursor, and check if it gets better.
If it’s still bad, disable any language extensions you don’t need for this project (Java, C++, Python/Jupyter, Flutter/Dart).
A more drastic check: run cursor --disable-extensions in a terminal to confirm it’s extension-related.
About the “stuck” processes after you close windows, the team is aware. Quick question: does fully quitting Cursor (CMD+Q) remove them, or do they stay even after that?
Before pressing Cmd + Q, Cursor was using around 20GB of memory. However, when I fully quit the app with Cmd + Q, all processes terminated normally.
I disabled all third-party AI extensions (Claude Code, Cline, CodeRabbit, and OpenAI ChatGPT), then restarted Cursor. After relaunching, I immediately opened the Extension Monitor and captured the attached screenshot. This is the current state right after startup.
Great data, thanks for going through all the steps.
Good news: the root cause of the extreme 30 GB and 97 to 99% CPU situation is clear. It was four third party AI extensions (Claude Code, Cline, CodeRabbit, ChatGPT) running at the same time together with Cursor’s built in AI. Disabling them dropped usage from 30 GB to about 1,5 GB. That’s the fix.
A quick note about Extension Monitor: the “% Ext Host” column showing 100% for <ext-host-runtime> is not CPU usage. It means that component accounts for 100% of the activity inside that specific extension host, which is expected when no other extensions are loaded in that host. Your actual CPU usage is about 8% (the “% CPU” columns), which is normal.
Comparison of the two screenshots:
With extensions (AI off): about 1,45 GB total across 3 hosts
With --disable-extensions: about 1,24 GB total across 3 hosts
The difference is about 200 MB, which is your non AI extensions, and that’s normal. Both setups look healthy for Cursor’s baseline state.
A couple recommendations for the future:
Don’t stack multiple AI coding extensions on top of Cursor’s built in AI. If you want to use one of them (like Claude Code), disable the others. Running all four at once was the main reason things got out of control.
You have a lot of language extensions installed (Java, C++, Python or Jupyter, Flutter or Dart, Go, C#), and they load even for a small Cloudflare Workers project. You might want to use VS Code Profiles (Profiles in Visual Studio Code) so only the relevant extensions are active for each project type.
About processes piling up when closing windows: Cmd+Q fully clears everything, as you confirmed. The team knows that closing individual windows doesn’t always shut down processes correctly.
Let me know if everything stays stable with the AI extensions disabled.
