jcollab

MCP server (stdio) that lets Claude read, edit and run cells in live JupyterLab notebooks through the shared Yjs document, so open browser tabs update immediately and cells look exactly as if the user had run them.

• Discovery, no setup: finds all running Jupyter servers of the user via ~/.local/share/jupyter/runtime/jpserver-*.json (pid alive + /api/status probe). Tools take instance (port, root:port or root dir name); optional if only one runs.
• Verified writes: every mutating tool reads the file back and reports persisted; duplicate cell ids (client/server Yjs version skew) are detected and explained.
• Execution fidelity: [*] busy state, streamed outputs, kernel execution count, metadata.execution timings (jupyterlab-execute-time). run_code is silent (store_history=False), consumes no execution count.
• Tools: list_instances, list_notebooks, read_notebook, read_cell (images), insert_cell, insert_cell_at_start, edit_cell, change_cell_type, delete_cell, move_cell, split_cell, merge_cells, get_metadata, set_metadata (cell/notebook), run_cell, run_cells, run_code, clear_outputs, inspect_variables, kernel_status, interrupt_kernel, restart_kernel, sync_health, user_focus, point_at, find_mentions, add_comment.

Install

From PyPI:

pip install jcollab
claude mcp add --scope user jcollab -- jcollab

From source:

python3 -m venv .venv && .venv/bin/pip install .
claude mcp add --scope user jcollab -- $PWD/.venv/bin/jcollab

Lab extension jcollab-scroll (scrolls the user's notebook to the cell point_at targets) is part of the package. Install it into the interpreter of jupyter-lab with pip install --no-deps jcollab, then restart JupyterLab. Source and built output: labext/.

Requires a JupyterLab with jupyter-collaboration. Keep jupyter-ydoc of this package on the same major version as the server's (pinned >=3,<4; see sync_health).

Tests

tests/integration.py [instance] expects a throwaway JupyterLab (token-less) whose root contains spike.ipynb.