Interchangeable marimo markdown format for Slidev + marimo edit

[lucharo]

Vision

Create a single markdown format that works as:

1. A marimo notebook (marimo edit notebook.md)
2. A Slidev presentation (slidev notebook.md)

Current State

Marimo has nb.md format using code fences with {.marimo} class:

import marimo as mo

Slidev uses marimo-live code fences or <MarimoCell> components to reference cells.

Proposed Format

Extend marimo's nb.md format with:

1. Slide separators (---) that marimo ignores but Slidev uses
2. Cell naming via attributes or comments
3. <MarimoCell> references between slides

Example:

---
title: My Notebook/Presentation
marimo-version: 0.19.7
---

\`\`\`python {.marimo name="imports"}
import marimo as mo
import altair as alt
\`\`\`

\`\`\`python {.marimo name="slider"}
slider = mo.ui.slider(1, 100)
slider
\`\`\`

---

# Slide 1: Interactive Demo

<MarimoCell cell="slider" />

---

# Slide 2: Results

<MarimoCell cell="chart" />

How It Would Work

For marimo edit notebook.md

• Marimo reads code fences with {.marimo}, ignores --- and <MarimoCell>
• Runs as normal reactive notebook

For slidev notebook.md

• Slidev addon:
  1. Starts marimo kernel in headless mode (background process)
  2. Renders slides with <MarimoCell> components
  3. Components fetch output from running kernel

Benefits

• Single source of truth
• Full IDE support for Python code
• Works offline in either mode
• No code duplication between notebook and slides