marimo-screenshot

name	marimo-screenshot
description	Capture rendered marimo notebook output as a screenshot for analysis

Marimo Screenshot

Capture a marimo notebook's rendered output (charts, tables, markdown) as a PNG screenshot that Claude can view and analyze.

Usage

When the user wants you to see notebook output, or when you need to analyze charts/visualizations in a marimo notebook.

Workflow

1. Start the notebook in run mode (executes cells, serves rendered output):

   uv run marimo run notebooks/<notebook>.py --port 2719 --headless &
   

2. Wait for server to start:

   sleep 10
   

3. Take screenshot with JS render time (Altair/Vega charts need ~15s):

   npx playwright screenshot --wait-for-timeout 15000 --full-page \
     "http://localhost:2719" /tmp/marimo_output.png
   

4. Read the screenshot using the Read tool:

   Read /tmp/marimo_output.png
   

5. Kill the server when done:

   pkill -f "marimo run.*2719"
   

Key Details

• Use marimo run (not edit) - this executes cells and renders output
• --headless runs server-only without opening a browser
• --wait-for-timeout 15000 gives charts time to render via JavaScript
• --full-page captures the entire scrollable notebook
• Port 2719 avoids conflict with the user's edit server on 2718

Troubleshooting

Charts not appearing:

• Cells must return their output (e.g., mo.vstack([chart]) as the last expression)
• If inside if/else, ensure all branches return a value

Blank screenshot:

• Increase --wait-for-timeout to 20000 or more
• Check that the notebook runs without errors: uv run marimo run notebook.py

Port in use:

• Kill existing process: pkill -f "marimo run.*2719"
• Or use a different port