I was trying to get a coding agent to fix a few notebook cells, and it asked me to copy-paste snippets just so it could figure out which ones I meant. It worked, but it felt like a step backward. I knew exactly which cells I meant, but I had no direct way to point to them.

Usually, we point agents to notebook cells indirectly: the cell that loads the dataset, the cell that does the groupby and filtering, and so on. It works, but it is not a great way to address a cell. Insert a cell, delete one, or reorder the notebook, and positional references change. Descriptions can also be ambiguous when several cells look similar.

Then I noticed something interesting while watching the agent work: it was already using the cell’s id to find the cells I was talking about. The agent had a precise identifier for the cell. I did not.

That got me thinking: why can’t we use the same language?

With cell ID I should be able to say:

Fix cell e66c99c5. The groupby looks wrong.

Short, precise, and directly useful to both sides.

The id that’s already there

Since nbformat 4.5, Jupyter notebook cells have an id:

{
  "cell_type": "code",
  "id": "e66c99c5",
  "metadata": {},
  "source": [
    "df = load_dataset(path)\n",
    "df.head()"
  ]
}

The id gives the cell an identity independent of its position in the notebook.

So the information was already there. The agent could see it. I just could not easily see or copy it from VS Code.

That’s what led me to build Notebook Cell Id.

Notebook Cell Id

Notebook Cell Id is a small VS Code extension that shows each notebook cell’s nbformat id directly in the cell’s status bar.

A notebook in VS Code with each cell’s nbformat id shown in its status bar; the badge of one cell is highlighted

Each cell gets a small badge such as:

⧉ #5 e66c99c5

Click it and the id is copied.

There are also Command Palette commands:

  • Notebook: Copy Cell Id → e66c99c5
  • Notebook: Copy Cell Id with Notebook Path → article_mat/v2_nb/step_3.ipynb cell e66c99c5

Copying the id was only half the loop, though. The other half is going back the other way: the agent hands you a cell id, and you need to land on that exact cell.

Find Cell by Id

That’s the newest addition: Notebook: Find Cell by Id. Run it, paste in an id, and VS Code selects and scrolls to that cell.

It’s bound to Ctrl+Alt+F (Cmd+Alt+F on macOS) while a notebook is focused - Ctrl+F was left alone since VS Code already uses it for the built-in text find widget. It’s also one click away as a button in the notebook’s top toolbar, right next to +Code / +Markdown:

The notebook toolbar with a highlighted “Find Cell by Id” button between “Clear All Outputs” and “Outline”

So the id now works both ways. The agent tells me e66c99c5 is the problem cell, and I jump straight to it - no scrolling, no “which one is that again.”

The source is available on GitHub under the MIT license.

One caveat: cells only carry ids in nbformat 4.5 and newer - older notebooks show no badges until we re-save them.

Install Notebook Cell Id

Sometimes the information we need is already there ;)