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Regression: ipykernel 6.30.0 breaks VSCode debugging #1412
Description
Dear developer community,
Using ipykernel 6.30.0 starting a debug session in VSCode doesn't hit any breakpoints (and doesn't execute anything)
I started the debug session like this:
After a painful debugging session I discovered that downgrading ipykernel to the version 6.29.5 fixed the issue.
I'm using VSCode Version: 1.102.2
and the Jupyter Extension from Microsoft (ms-toolsai.jupyter) Version: 2025.6.0
My operating system: macOS Sequoia Version 15.5
Reproduction steps:
In a fresh folder
python -m venv .venv
source .venv/bin/activate
pip install jupyterlab
<start debugging session in an arbitrary .ipynb file using ".venv/bin/python" as the kernel>
<observe no breakpoints being hit>
I tested with python3.11 and python3.13
If you cannot reproduce the bug I'm happy to provide additional environment information.
Best regards,
Robin
Activity
ianthomas23 commentedon Aug 1, 2025
This is probably a question for VSCode.
dkharrat commentedon Aug 1, 2025
Downgrading ipykernel to 6.29.5 works. So it looks like 6.30.0 introduced a regression?
ianthomas23 commentedon Aug 1, 2025
Or VSCode implements special handling that has not been updated to cope with ipykernel 6.30.0. This happens on many releases of
matplotlib,ipympl, etc.brichet commentedon Aug 1, 2025
Looks like it also affects Jupyterlab jupyterlab/jupyterlab#17739
ianthomas23 commentedon Aug 4, 2025
I've confirmed this is a bug in
ipykernel 6.30.0. I recommend pinning toipykernel < 6.30until I've fixed it and made a new release.ianthomas23 commentedon Aug 4, 2025
This is fixed by #1416 and has been released as
ipykernel 6.30.1.