The Jupyter notebook bug that only crashes for other people

Cell 0 uses df . Cell 1 defines df . Notebook works for you because your kernel ran the cells in some other order and the variable's still in memory. You commit. Someone clones the repo, hits Restart and Run All, dies on cell 0. Standard Python linters can't catch this. ruff, flake8, mypy operate on one source file at a time. A notebook is N cells whose execution order in your kernel may have nothing to do with their order on disk. The bug isn't inside any single cell. It's in the relationship b