Delving deep into novel ways to extend Excel and make it more accessible. Perhaps different approach to copilot in that AI is only used during authoring, the yielded output being a standalone artifact.

The result is https://xllify.com

It embeds Luau which tames the very old school C SDK. This means that the same code can run as native add-ins on Windows (XLL) and the more modern-but-far-slower web engine, thanks to WASM. Luau is safe and fast.

The exact same bytecode runs in both styles of add-in. You get the performance of native with no extra work. Many approaches for writing custom functions are unacceptably slow, particularly when their inputs come from fast moving realtime data feeds.

I know Luau is perhaps a left-field choice. However, coupled with a coding assistant and bringing that lightweight conversational dev experience right into Excel (xllify Assistant is an add-in itself) this is perhaps less of a barrier.