Show HN: Sommelier, an Excel Addin for your agent

Sommelier (there is a nice wordplay on Excel and pairing) is an Excel Addin + relay server that lets your agent work hand in hand with you while you're working on an Excel spreadsheet. It's heavily inspired by the excellent marimo pair.

It's useful when you either don't want to use Microsoft Copilot, want to use a local model + harness for security reason, or want to use an agent that already has access to personal data.

I've tested it with some harnesses (pi, opencode, codex) but I guess that it should work on many others.

Not having a Microsoft developer account, I've yet to publish it to the marketplace, but it's sideloadable.

While the first prototype was written by me, I've only kept the core and let an LLM rewrite the code.