I had the same issue (at least it seemed the same), however it is possible to work around it if you are using the Python extension in conjunction with Remote Debugging.

You can ignore the extension's activation failure if that is your primary use, since VSCode is still able to debug remotely using Python Remote Attach.


After some more work on this, I found that updating the Python Extension to the pre-release version cleared up the various errors that came with the recent updates.

Answer from Zachary Barnett on Stack Overflow
🌐
GitHub
github.com › microsoft › vscode-python › issues › 18109
Extension Activation failed · Issue #18109 · microsoft/vscode-python
December 3, 2021 - " Extension activation failed, run the 'developer: Toggle Developer Tools' command for more information. ( I'm not sure how to do that, I tried to input this in the terminal. However, I got an error.
Author   sherxyar
🌐
Reddit
reddit.com › r/vscode › jupyter extension activation failed can't run any notebook cells. helpp
r/vscode on Reddit: Jupyter Extension Activation Failed Can't Run Any Notebook Cells. HELPP
October 9, 2025 -

Hey everyone,

I'm running into a persistent issue with the Jupyter extension in VS Code and I'm hoping someone can point me in the right direction.

I'm trying to run a simple Python cell in a .ipynb notebook, but I can't execute anything because the Jupyter extension fails to start. As you can see in the screenshot, I keep getting the error notification: Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information.

What I've Tried So Far:

  • Reinstalling: I have completely uninstalled and reinstalled the Jupyter extension (and its related dependencies like the Python extension) multiple times.

  • Restarts: I have closed and reopened VS Code, and even restarted my computer.

  • New Environments: I've created fresh virtual environments (using venv) and installed ipykernel within them, but the issue persists no matter which interpreter I select.

  • Different Files: This happens with any notebook file, even a brand new one with a single print() statement.

I feel like I'm missing something obvious, but I can't figure out what

🌐
GitHub
github.com › continuedev › continue › issues › 3009
Extension is not activating(Visual Studio Code) · Issue #3009 · continuedev/continue
November 20, 2024 - 2024-11-20 21:54:01.212 [info] Extension host with pid 7500 started 2024-11-20 21:54:01.330 [info] ExtensionService#_doActivateExtension vscode.git-base, startup: true, activationEvent: '*', root cause: vscode.git 2024-11-20 21:54:01.343 [info] ExtensionService#_doActivateExtension vscode.emmet, startup: false, activationEvent: 'onLanguage' 2024-11-20 21:54:01.437 [info] ExtensionService#_doActivateExtension vscode.git, startup: true, activationEvent: '*' 2024-11-20 21:54:01.655 [info] ExtensionService#_doActivateExtension vscode.github, startup: true, activationEvent: '*' 2024-11-20 21:54:01.
Author   MaheshBhushan
🌐
Arch Linux Forums
bbs.archlinux.org › viewtopic.php
[SOLVED] VS Code, after upgrading: Python extension fails to load...? / Applications & Desktop Environments / Arch Linux Forums
UPDATE: I found https://github.com/microsoft/vscode-python/issues/15445 and now understand that I should use the CONSOLE-stuff from Help > Toggle Developer Tools. This reveals: *** Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information.
Find elsewhere
🌐
GitHub
github.com › microsoft › vscode-python › issues › 25489
VSCode-Python Extension Activation Failed · Issue #25489 · microsoft/vscode-python
September 28, 2025 - SCode/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:114:13345) at Vb.l (file:///c:/MyPrograms/Tools/VSCode/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:114:12801) 2025-09-29 00:26:16.851 [info] Experiment 'pythonSurveyNotification' is active 2025-09-29 00:26:16.851 [error] extension activation failed Error: command 'python.viewOutput' already exists at ey.registerCommand (file:///c:/MyPrograms/Tools/VSCode/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:114:40314) at Object.registerCommand (file:///c:/MyPrograms/Tools/VSCode/resources/app/ou
Author   duytrung
🌐
Visual Studio Code
code.visualstudio.com › api › references › activation-events
Activation Events | Visual Studio Code Extension API
November 3, 2021 - Here is a list of all available Activation Events: ... We also provide a reference of all fields in the package.json extension manifest.
🌐
ServiceNow Community
servicenow.com › community › developer-forum › vs-code-extension-error-activating-extension-servicenow-now › m-p › 2693127
Re: VS Code Extension Error Activating extension ServiceNow.now-vscode failed: Cannot find module ke
December 11, 2023 - I started getting the error after VScode updated to its September release. Once I installed the August 2023 version the extension started working again.
Top answer
1 of 3
19

I had this same issue and finally got it fixed!


If you are on an Linux and are using an Arch-based distro with AUR support, simply install the code-features package using:

yay -S code-features

or any AUR helper of your choosing.


On other operating systems, you should do the following:

Open your VSCode's product.json. I do not know where this file is on your operating system, so please do some research.

Look for the following line:

"extensionAllowedProposedApi": [ ...

Add the following entry to that array:

"ms-toolsai.jupyter": ["notebookConcatTextDocument", 
    "notebookControllerKind", "notebookDebugOptions", "notebookDeprecated", 
    "notebookEditor", "notebookEditorDecorationType", "notebookEditorEdit", 
    "notebookMessaging", "notebookMime", "notebookCellExecutionState", 
    "portsAttributes", "textDocumentNotebook", "quickPickSortByLabel"]

For example, if the line was originally:

"extensionAllowedProposedApi": [ "extension1", "extension2" ]

Then change it to:

"extensionAllowedProposedApi": [ "extension1", "extension2", 
    "ms-toolsai.jupyter": ["notebookConcatTextDocument", 
    "notebookControllerKind", "notebookDebugOptions", "notebookDeprecated", 
    "notebookEditor", "notebookEditorDecorationType", "notebookEditorEdit", 
    "notebookMessaging", "notebookMime", "notebookCellExecutionState", 
    "portsAttributes", "textDocumentNotebook", "quickPickSortByLabel"] ]

Note that with the second method, you will need to edit product.json every time you update VSCode.

2 of 3
6

Just ran into this today (I'm on MacOS for my work computer). In my case, upgrading to the pre-release version of the Jupyter extension (v2022.5.1001281006) solved it right away.

If you're not an experienced programmer/software engineer, as is the case for me, I suggest trying to upgrade (or roll back) either VS code or the plugin itself before going with your own dev code for the plugin, as with @CAG2 pt2 answer. (Personally, I had trouble finding a 'product.json' file; perhaps you need an insider's build of VS code for that kind of thing [edit]: https://code.visualstudio.com/api/advanced-topics/using-proposed-api, in which case I think you'd be editing 'package.json').

🌐
GitHub
github.com › microsoft › vscode › issues › 174376
Jupyter extension activation fails · Issue #174376 · microsoft/vscode
February 14, 2023 - Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned. notificationsAlerts.ts:42 Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information.
Author   mlangiu
🌐
GitHub
github.com › microsoft › vscode-jupyter › issues › 17036
Extension Activation Failed · Issue #17036 · microsoft/vscode-jupyter
October 9, 2025 - Extension activation failed message upon opening / restarting VS code. Console logs below: """log.ts:460 ERR Extension 'ms-toolsai.jupyter' wants API proposal 'notebookCellExecutionState' but that proposal DOES NOT EXIST. Likely, the proposal has been finalized (check 'vscode.d.ts') or was abandoned.
Author   mbosseme
🌐
GitHub
github.com › microsoft › vscode-python › issues › 6863
Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information. · Issue #6863 · microsoft/vscode-python
August 6, 2019 - Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information.#6863 ... bugIssue identified by VS Code Team member as probable bugIssue identified by VS Code Team member as probable bug ... After vscode got its python insider's daily update(today), it cannot load the extension and displays what the title shows above.
Author   AeneasZhu
🌐
GitHub
github.com › microsoft › vscode-python › issues › 20456
Extension activation failed under latest insiders build · Issue #20456 · microsoft/vscode-python
January 4, 2023 - A few hours ago VSC was updated to the latest insiders build and upon restart the Python extension fails to load with the following error message being shown in the Developer Tools console: Activating extension 'ms-python.python' failed: this.a.sendEventData is not a function.
Author   ghylander
🌐
GitHub
github.com › microsoft › vscode › issues › 188049
Extension Manager fails to load (some) extensions; stuck on "Activating Extensions" · Issue #188049 · microsoft/vscode
July 17, 2023 - Every time I try to do either of the two steps in 3., the status bar shows "Activating Extensions..." for a few seconds, otherwise nothing happens. Similarly, my own extension (which hasn't changed in weeks, see https://github.com/slatex/sTeX-IDE) stopped working, similarly failing to activate.
Author   Jazzpirate
🌐
Reddit
reddit.com › r/vscode › linux - jupyter extension activation failed
r/vscode on Reddit: Linux - Jupyter Extension activation failed
January 30, 2022 -

I'm trying to open and execute some ipynb files in Code on Arch Linux. Installed Python and Jupyter extensions.

Whenever I try to run code in the ipnyb file, I get this nagging error message for the Jupyter extension saying

Extension activation failed, run the 'Developer: Toggle Developer Tools' command for more information.

I tried switching the interpreter to the default Python 3.10.2 and also the Python 3.9.x installation in the Anaconda custom environment, but still no luck. Any idea how to fix this?