exp: proof of concept for VSCode debug server

[dmadisetti]

📝 Summary

This PR adds a Debug Adapter Protocol (DAP) server to marimo, enabling debugging capabilities through VS Code and other DAP-compatible debuggers.

Usage

The debug server automatically starts when running marimo edit and listens on a dynamically assigned port. VS Code can connect using:

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python Debugger: Remote Attach",
            "type": "debugpy",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 5678
            },
            "pathMappings": [
                {
                    "localRoot": "${workspaceFolder}",
                    "remoteRoot": "."
                }
            ]
        }
    ]
}

Current Status

✅ Working:

• VS Code can connect to the debug server
• Initialize handshake completes successfully
• Message parsing and response generation works

🔄 Next Steps:

• Integrate with marimo's cell execution system
• Implement actual breakpoint functionality
• Add cell-specific debugging features

Alternative Solution

This PR implements Solution 1 (DAP protocol). There's also Solution 2 which uses debugpy out of the box by temporarily disabling marimo's stack trace rewriting feature. While easier to implement, Solution 2 has limitations:

• Users step through marimo internals instead of cells
• Can't be used with edit server
• Relies on environment detection
• More brittle solution

Solution 1 provides the true "native" debugging experience but requires more development time to implement full DAP protocol features.

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Name	Status	Preview	Comments	Updated (UTC)
marimo-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 7, 2025 2:22am