Troubleshooting

"Could not connect to the Bridge"

(Dev loop.) Live isn't open, the Bridge isn't installed, or it's on a different port.

• Confirm Live is open and the Bridge is listed under Settings → Extensions (run ableton-ext install-bridge and drag the .ablx in if not).
• Just installed it? Reopen Live so the extension activates.
• Override the URL: ableton-ext run my_ext.py --bridge ws://127.0.0.1:17890.

A built .ablx installs but the menu doesn't appear

The packaged extension spawns a short-lived WASM runtime on activation; give it a second after install, and reopen Live if needed. Check Live's log for a [pyodide] line. Make sure your extension file guards app.run() under if __name__ == "__main__": — the build runs it as the entry point.

A call hangs, then times out

Almost always a mutation outside a transaction in custom low-level code — data-model writes only commit inside one. Use the high-level model (which handles this) or wrap writes in with app.transaction():.

"Failed to insert device"

Usually device ordering, not a bug: a MIDI track can hold only one instrument, and audio effects must come after the instrument. Insert at a valid index, or onto a fresh track. Also check the device name matches Live's exact built-in name (e.g. "Reverb", "Audio Effect Rack").

"API version mismatch"

Your Python SDK and the host expect different API versions. Update both to a matching pair.

Still stuck?

Open an issue with the Python output (and, if you're running from source, the Bridge terminal — it logs every call as -> method / <- ok/ERROR) on GitHub.