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Additional Information
Add any other context about the problem here.
Does this stop you from using Cursor?
Yes - Cursor is unusable
Sometimes - I can sometimes use Cursor
No - Cursor works, but with this issue
The more details you provide, the easier it is for us to reproduce and fix the issue. Thanks!
I encountered the same problem. It takes lot of time to open any Jupyter Notebook file while it works fine with .py scripts. The IDE just loading but not showing any cells.
However if you close all the cursor windows and wait for a bit, it will work sometimes.
Hey, thanks for the report. This looks like a regression after 3.0.
For now, let’s try to narrow it down:
Open a terminal and run cursor --disable-extensions, then check if notebooks render without extensions. If they do, the issue is caused by one of them, and we can look for the specific one.
Open Process Explorer Ctrl+Shift+P, then Developer: Open Process Explorer while the notebook is stuck loading, and send a screenshot. I’m mainly interested in what’s using CPU and RAM.
Which Jupyter extensions are installed. Just the default ms-toolsai.jupyter, or anything extra?
@Ferris_Jiang, are you on the same 3.0.12 version. And which OS?
Let me know what you find. That’ll help us figure this out faster.
I have the same issue in Cursor 3.0.13: I can’t open a .ipynb file. I already tried disabling the extensions, but I still have the same issue. I have the Jupyter extension ms-toolsai.jupyter, I’m working on Windows 11. I’m gonna uninstall the cursor and reinstall it, that’s the only way it works.
I’m on the same 3.0.12 version of cursor and working with Windows 11. For my hardwares they are almost idle, with plently room and capacity so I don’t think it’s their problem.
I did nothing after my feedback. However it works fine by now for my notebook extension.
Is there any update on this or has anyone found a working solution? I’m experiencing the exact same issue and it’s making it impossible to work with Jupyter notebooks.
Here is what I’ve tried so far with no success:
Completely reinstalled Cursor.
Disabled all extensions.
Unfortunately, neither of these steps made any difference. The rendering still takes an eternity. I’m getting pretty desperate here as it completely blocks my workflow.
Any help, workarounds, or updates from the devs would be greatly appreciated
@Patrick_F Hey, this issue is being tracked and our engineers are already looking into it. To add your case to the report, please share:
The exact Cursor version (Help > About > Copy)
OS (Windows / macOS / Linux + version)
A screenshot of Process Explorer while the notebook is stuck (Ctrl+Shift+P → Developer: Open Process Explorer) showing what’s using CPU/RAM
A screenshot of the Developer Tools console (Ctrl+Shift+P → Developer: Toggle Developer Tools → Console tab). Extension errors often show up there
The fact that reinstalling and disabling extensions didn’t help is a useful signal, so we should log that. I can’t share an ETA for a fix yet, but I’ll post an update in the thread as soon as I have one.
Hi, thanks for looking into this. Here is the requested information to add to the report:
Cursor Version Info:
Version: 3.2.21 (user setup)
VSCode Version: 1.105.1
Build Type: Stable
Release Track: Default
Chromium: 142.0.7444.265
OS: Windows_NT x64 10.0.26200
OS Info:
Edition: Windows 11 Enterprise
Version: 25H2
OS Build: 26200.8246
Feature Pack: Windows Feature Experience Pack 1000.26100.297.0
Screenshots Attached:
Process Explorer: Attached. (Note: CPU/Memory usage seems relatively normal, though there is a background CodeSetup-stable task running).
Developer Tools Console: Attached. As you can see, the console is being absolutely spammed with ERR No Connect transport provider registered and Failed to fetch... errors originating from workbench.desktop.main.js.
Thanks to @Patrick_F for the update, this looks like a working workaround.
Summary for everyone in the thread:
Update to 3.3.27 or newer.
Close Cursor.
Delete or rename these folders:
%APPDATA%\Cursor
%USERPROFILE%\.cursor
Launch Cursor and sign in again.
This will remove the local cache and workspace settings (you’ll need to reinstall extensions, and recent projects will be gone), but it fixes the No Connect transport provider registered message in the console and the related freezes when notebooks load.
@Marco_YOU@Ferris_Jiang@jf_eng@Jhoan_Sebastian_Duqu If anyone still sees the issue, please try this and reply with whether it helped. If you’re on 3.3.27+ and the symptoms are still there after clearing the cache, share your Cursor version, OS, a Process Explorer screenshot, and the Developer Tools console output: Ctrl+Shift+P → Developer: Toggle Developer Tools → Console. Then we can dig deeper.
Worth checking your ms-python.python version before the full data-dir reset.
On Linux I had the same symptom (blank notebooks, unresponsive AI panel) on Cursor 3.3.30, and renaming the Cursor folder didn’t fix it. The actual culprit was a year-old ms-python.python (2025.6.1) that broke the extension host on Cursor 3.x. Once I installed the current marketplace .vsix via cursor --install-extension, notebooks worked immediately without wiping any user data.
~/.config/Cursor/logs/<latest>/window1/exthost/exthost.log will show the silent failure if this is the cause. Look for activation errors on ms-python.python or ms-toolsai.jupyter.
Thanks, @Wilbert_Tan, this is a really helpful addition. The fact that an outdated ms-python.python (2025.6.1) breaks extension host activation matches what we’ve seen elsewhere, and it’s a much less destructive fix than wiping the data dir.
Here’s an updated playbook for any user who, after upgrading to 3.0, sees empty notebooks or No Connect transport provider registered. Try these in order:
First, update ms-python.python (no data loss)
Make sure you’re on Cursor 3.3.27 or newer.
Download the latest .vsix from the marketplace and install it:
cursor --install-extension ms-python.python
Reload the window. If notebooks show up again, you’re done.
To confirm this was the cause, check the latest exthost log for activation errors from ms-python.python or ms-toolsai.jupyter:
If that didn’t help, clear the cache (this resets extensions and recent projects)
Close Cursor.
Delete or rename:
Windows: %APPDATA%\Cursor and %USERPROFILE%\.cursor
macOS: ~/Library/Application Support/Cursor and ~/.cursor
Linux: ~/.config/Cursor and ~/.cursor
Start Cursor and sign in again.
If you’re on 3.3.27+ and both steps didn’t work, share your Cursor version, OS, a screenshot from Process Explorer, and your exthost.log output, or Dev Tools Console output via Ctrl+Shift+P then Developer: Toggle Developer Tools then Console, and we can dig in further.
Hey @Kenny_Chowdhary, this is typical behavior for the Databricks extension. In its manifest it has a hard extension dependency on a specific older version of ms-python.python, so when Cursor or VS Code activates it, it pulls that exact version.
Check that the new version is active: open Extensions with Ctrl+Shift+X, find Python, and make sure the version is not 2025.6.1. If Databricks rolls it back on every start, you can temporarily disable Databricks, update Python, then enable Databricks again. It should not downgrade if a compatible version is already installed and it satisfies the engine constraint in its manifest.
If Databricks truly requires 2025.6.1 and keeps overwriting it, this needs to be fixed on the Databricks extension side by filing an issue in their repo. We do not have an IDE-side way to block downgrades.
Send the Databricks extension version you have installed, open Ctrl+Shift+X then Databricks and you will see it, and your exact Cursor version. I will pass it to the team so they can check if we can improve compatibility on our side.
