Jupyter Python Debugger Unreliable

[RavaszEmber]

Applies To

• Notebooks (.ipynb files)
• Interactive Window and/or Cell Scripts (.py files with #%% markers)

What happened?

I've been using the Jupyter extension for a while now and find it pretty useful. Today I wanted to debug a part of my code and when I run the debugger on a cell that takes <1s to run it hangs for over 2 minutes. When I try to pause it I get "Couldn't find a debug adapter descriptor for debug type "Python Kernel Debug Adapter" (Extension might have failed to activate)."

I reloaded my extensions, closed and reopened vs code, uninstalled Python and Jupyter extensions, closed, reopened and reinstalled. I checked that the python debugger works so ported the cell to a .py and the python debugger was able to run fine.

VS Code Version

Version: 1.100.3 (user setup) Commit: 258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3 Date: 2025-06-02T13:30:54.273Z Electron: 34.5.1 ElectronBuildId: 11369351 Chromium: 132.0.6834.210 Node.js: 20.19.0 V8: 13.2.152.41-electron.0 OS: Windows_NT x64 10.0.26100

Jupyter Extension Version

2025.4.1

Jupyter logs

Visual Studio Code (1.100.3, undefined, desktop)
Jupyter Extension Version: 2025.4.1.
Python Extension Version: 2025.6.1.
Pylance Extension Version: 2025.5.1.
Platform: win32 (x64).
Home = c:\Users\Benjamin
Temp Storage folder ~\AppData\Roaming\Code\User\globalStorage\ms-toolsai.jupyter\version-2025.4.1
Workspace folder ~\Desktop\OMSCS\Machine Learning\cs-7641-2025-summer-bmolnar3
05:54:18.630 [info] Starting Kernel (Python Path: ~\.conda\envs\ml\python.exe, Conda, 3.11.13) for '~\Desktop\OMSCS\Machine Learning\cs-7641-2025-summer-bmolnar3\supervised-learning\ml_classification_cancer.ipynb' (disableUI=true)
05:54:21.250 [info] Starting Kernel (Python Path: ~\.conda\envs\ml\python.exe, Conda, 3.11.13) for '~\Desktop\OMSCS\Machine Learning\cs-7641-2025-summer-bmolnar3\supervised-learning\ml_classification_bankruptcy.ipynb' (disableUI=true)
05:54:23.089 [info] Process Execution: ~\.conda\envs\ml\python.exe -c "import ipykernel; print(ipykernel.__version__); print("5dc3a68c-e34e-4080-9c3e-2a532b2ccb4d"); print(ipykernel.__file__)"
05:54:23.093 [info] Process Execution: ~\.conda\envs\ml\python.exe ~\.vscode\extensions\ms-toolsai.jupyter-2025.4.1-win32-x64\pythonFiles\vscode_datascience_helpers\kernel_interrupt_daemon.py --ppid 18040
    > cwd: ~\.vscode\extensions\ms-toolsai.jupyter-2025.4.1-win32-x64\pythonFiles\vscode_datascience_helpers
05:54:23.102 [info] Process Execution: ~\.conda\envs\ml\python.exe -m pip list
05:54:23.167 [info] Process Execution: ~\.conda\envs\ml\python.exe -m ipykernel_launcher --f=~\AppData\Roaming\jupyter\runtime\kernel-v305b31e2e19dec866b9fb5d56000368e4f3b5ec9b.json
    > cwd: ~\Desktop\OMSCS\Machine Learning\cs-7641-2025-summer-bmolnar3\supervised-learning
05:54:23.628 [info] Process Execution: ~\.conda\envs\ml\python.exe -c "import ipykernel; print(ipykernel.__version__); print("5dc3a68c-e34e-4080-9c3e-2a532b2ccb4d"); print(ipykernel.__file__)"
05:54:23.632 [info] Process Execution: ~\.conda\envs\ml\python.exe -m ipykernel_launcher --f=~\AppData\Roaming\jupyter\runtime\kernel-v3f2c4b26f70f8ca1cd54b32d8c7feb9e28ac1a9a0.json
    > cwd: ~\Desktop\OMSCS\Machine Learning\cs-7641-2025-summer-bmolnar3\supervised-learning
05:54:23.846 [info] Kernel successfully started
05:54:23.852 [info] Process Execution: ~\.conda\envs\ml\python.exe ~\.vscode\extensions\ms-toolsai.jupyter-2025.4.1-win32-x64\pythonFiles\printJupyterDataDir.py
05:54:24.302 [info] Kernel successfully started
05:54:24.431 [error] Widget Error: Failed to access CDN https://unpkg.com/ after 0 attempt(s), TypeError: Failed to fetch
05:54:24.838 [error] Widget Error: Failed to access CDN https://unpkg.com/ after 0 attempt(s), TypeError: Failed to fetch
05:54:26.170 [info] Starting debugging with mode 1
05:54:29.916 [info] Ending debug session 3e7b0da0-3f65-4f6d-b6cb-86dc405a52d2
05:54:31.052 [warn] Disposing old controller startUsingPythonInterpreter:'.jvsc74a57bd0d4e19dae4ecba9ebb19b195c35a80973efa3dc75a208c8ee2a8a83662785ea9d.c:\Users\bmolnar1\.conda\envs\rait_env\python.exe.c:\Users\bmolnar1\.conda\envs\rait_env\python.exe.-m#ipykernel_launcher' for view = 'jupyter-notebook'
05:54:31.052 [warn] Disposing old controller startUsingPythonInterpreter:'.jvsc74a57bd0d4e19dae4ecba9ebb19b195c35a80973efa3dc75a208c8ee2a8a83662785ea9d.c:\Users\bmolnar1\.conda\envs\rait_env\python.exe.c:\Users\bmolnar1\.conda\envs\rait_env\python.exe.-m#ipykernel_launcher (Interactive)' for view = 'interactive'
05:54:31.933 [info] Ending debug session 3e7b0da0-3f65-4f6d-b6cb-86dc405a52d2
05:54:31.933 [info] Ending debug session 3e7b0da0-3f65-4f6d-b6cb-86dc405a52d2
05:54:32.031 [info] Starting debugging with mode 1
05:54:32.510 [info] Ending debug session c12c8c1b-b1cf-40f7-a0f7-1d82da6f3493
05:54:34.521 [info] Ending debug session c12c8c1b-b1cf-40f7-a0f7-1d82da6f3493
05:54:34.521 [info] Ending debug session c12c8c1b-b1cf-40f7-a0f7-1d82da6f3493
05:54:36.975 [info] Starting debugging with mode 1
05:54:55.423 [info] Cannot start debugging. Already debugging this notebook document.
05:55:00.652 [error] Failed to disconnect debug session Error [CodeExpectedError]: custom request failed
    at vscode-file://vscode-app/c:/Users/<username>/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/workbench.desktop.main.js:1275:32346
05:55:00.652 [info] Ending debug session bf87e675-c5c3-4ed1-92ec-2774c5fcaeea
05:55:01.076 [info] Ending debug session bf87e675-c5c3-4ed1-92ec-2774c5fcaeea
05:55:01.076 [info] Ending debug session bf87e675-c5c3-4ed1-92ec-2774c5fcaeea

Coding Language and Runtime Version

Python 3.11.13

Language Extension Version (if applicable)

Python v2025.6.1

Anaconda Version (if applicable)

conda 24.11.3

Running Jupyter locally or remotely?

Local