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Sommelier, or AI-CDL

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I’ve built an Excel Addin1 that allows an agent of your choice to work hand in hand with you on a spreadsheet, while you’re working on it. You can do it with Copilot, but this way you can choose your agent2, so you can go with a self hosted one for privacy, or one that has access to data that you might not want to share directly with Microsoft.

How does it work

You copy a prompt (or you install a skill on your agent) that shares with your agent an address to which they can open a communication channel. That address is on a server to which the addin will connect as well, so that messages can be exchanged between the two. Also, it will share tools with your agent so that it can read and edit the spreadsheet you’re working on.

Messages are e2e encrypted, so the server cannot read them, so even if you don’t trust the code on my server (and you shouldn’t!) you can trust what you see on the client (and you can even check on the repository)

How to use it

I should publish the Addin to the Microsoft marketplace, but for the moment it can only be used via (sideload)[https://learn.microsoft.com/en-us/office/dev/add-ins/testing/sideload-office-add-ins-for-testing]. Install the addin via the manifest provided on the website, and follow the instructions.

Why

I have a pi instance that harnesses the mighty power of a (as of 2026-09-20) qwen3.8-flash-next instance on my homelab, and has access to some personal data. I wanted to be able to build an Excel spreadsheet and use that data, so I built a prototype of this project on my own. Then I asked codex to rebuild it from scratch, by keeping the core logic but strengthening it.

  1. I’ve spent way more time than I expected, or wanted, working on Excel Addins. For all the lucky ones that do not know them, they are a way to augment your Excel experience using JAVASCRIPT: you can load an HTML page in a sidepanel (yes, there is a browser somewhere here), interact directly with the spreadsheet using JS in the sidepanel, and publish new functions defined in JS that the user can implement.

    It’s pretty cool, if you don’t have to make it work and debug it across several different OSs, Excel versions, access limits in a financial institution. I’m kidding: it’s Excel, it’s not cool, but people for whatever reason love it. ↩︎

  2. I’ve used it with opencode, pi, and codex, but I guess that by whatever day it is you’re reading this the harness you’ll be using will be something completely different. ↩︎