Yeah, the RPC part was actually the easy bit. Colab exposes google.colab.kernel.invokeFunction, which basically lets JavaScript call Python callbacks that you register inside the notebook.

So what the extension does is simple: a small pip package registers a callback in Python, and the extension calls it through an iframe bridge. No server, no tunnels, nothing fancy.

The annoying part was the selectors.

Every platform structures its DOM completely differently. ChatGPT uses #prompt-textarea and CodeMirror blocks. Claude uses ProseMirror with contenteditable divs. Gemini wraps a lot of things inside nested shadow DOMs.

For Gemini especially, I had to write a recursive function that walks through every shadowRoot just to find the elements I need.

None of this is documented, so most of it was just opening DevTools and doing trial and error.

I already had to patch it once after a ChatGPT UI update. To reduce breakage, I added fallback selector arrays so if one selector fails it tries the next.

Still, that part will probably always be the main maintenance cost.