Children of Jupyter: What Core Should Steal Back - Max Klein, Independent

Children of Jupyter: What Core Should Steal Back - Max Klein, Independent Jupyter's 2011 kernel design has aged well: Colab, VS Code, Deepnote, and even ChatGPT's Python tool all run Jupyter kernels today. The notebook itself, though, still runs on the same linear REPL as in 2011, and hidden state remains its most famous complaint. A generation of descendants (Observable, Pluto, marimo, Hex, Livebook, Deepnote) has spent a decade shipping fixes for these problems. It is past time for Jupyter core to steal from its children, but first it needs a survey of what they built. This talk maps the significant new notebook features and illustrates them with demos: - Reactive execution that ends hidden state - The environment packaged inside the notebook file - Cells that are SQL queries, live inputs, or forms that write code - Notebooks laid out as canvases and graphs - Notebooks as apps, as scheduled jobs, and as agent scratchpads I'll close by arguing that opt-in reactive execution is the feature to steal first. Every implementation so far, including the ipyflow work presented at JupyterCon 2025, is tied to a single language. I'll share my in-progress design and prototype for adding reactivity to the kernel protocol, so that any kernel can implement it.