A powerful, open-source agent inside Excel

If you use a “coding” agent to do research, write reports, or build things: you know they can do way more than write code. Pi for Excel puts some of that power inside your spreadsheets, where you can actually work with it interactively. No account needed: login with wherever you get your AI from.

Install it

Free & open source. View on GitHub

Why in Excel

Sees what you see

Excel is both your calculator and your interface. This gives your agent that same interface.

Pi for Excel reads the actual workbook: the structure, the formatting, the formulas, your current selection. It doesn't need an export and you can see it work in real time. It's working in the same place you are.

Built for real work

Multiple session tabs, conversation history, auto-context on every turn, any model you want. Built-in multi-provider web search and page fetch help you cross-check assumptions quickly.

Between saves, every edit gets an automatic checkpoint with one-click undo.

I pasted raw data in Sheet2. Clean it up, figure out what it is, and build me a summary.
What assumptions is this model making? Walk me through the logic. Cross-check with web search and the PDFs.
Fetch today's FX rates and update the currency column, then build an /fx extension to do that automatically.
Use tmux to ask Claude Code to build & open a webpage based on this file's analysis.
Your rules

Make it work exactly how you want

I have very specific opinions about how my spreadsheets are set up. You might too.

Set your format conventions once and they're baked into Pi's tools. Give it Skills and files. Set house rules for yourself or specific files — like AGENTS.md and CLAUDE.md, but for spreadsheets.

Rules dialog showing formatting conventions for all files, this workbook, and format settings
Example conventions
Number format #,##0.0_);(#,##0.0_);--_)
Cross-sheet links rgb(0, 128, 0)
Negative numbers (1,234.5) — red parentheses
Zero display --
Extensions

Ask it to extend itself

You can ask Pi for Excel to build its own extensions — sidebar widgets, sub-agents, live data feeds, specialist tools, SaaS integrations. Extensions can call LLMs, fetch HTTP data, persist storage, and register tools through the built-in bridge.

Examples coming soon — we're collecting real ones from actual use.

Installation
Three steps, no dev tools

Download one file, drop it in a folder, open Excel. If you have an agent like Claude Code or Pi handy, you can just ask it to do all of this for you.

1 Download the manifest

This small file tells Excel where to find Pi. It's the only thing you need to download.

manifest.prod.xml

2 Copy it to Excel's add-in folder

Open Terminal and paste this. It creates the folder if needed and copies the file.

$ mkdir -p ~/Library/Containers/com.microsoft.Excel/Data/Documents/wef && \
  cp ~/Downloads/manifest.prod.xml ~/Library/Containers/com.microsoft.Excel/Data/Documents/wef/
Saved it somewhere other than Downloads? Change ~/Downloads/ to wherever you put it.

3 Open Pi in Excel

  1. Quit Excel completely (⌘Q) and reopen it
  2. Go to Insert → My Add-ins
  3. Click Pi for Excel to open the sidebar
Heads up — Pi was built and tested on macOS. It should work on Windows (the underlying tech is cross-platform) but hasn't been extensively tested. Worth a try! If you hit issues, open a GitHub issue.

1 Download the manifest

Same file — a small config that tells Excel where to find Pi.

manifest.prod.xml

2 Upload it in Excel

  1. Open Excel
  2. Go to Insert → My Add-ins → Upload My Add-in…
  3. Select the manifest.prod.xml file you downloaded
Important: use Upload My Add-in… for this file — not Manage → XML Expansion Packs. That older Excel path can show misleading certificate errors for Office add-in manifests.

3 Open the sidebar

Click Open Pi in the ribbon.

Connect a provider
Use the models you already pay for

Works with your existing subscriptions, or with a plain API key.

Login with your subscription Recommended

If you already pay for Claude, Copilot, or another provider, you can log in directly — no API key needed. Some OAuth flows need a small local helper because Office webviews can block those endpoints via CORS.

Start the helper in Terminal (recommended if you already have Node.js): 

$ npx pi-for-excel-proxy

No Node.js? Use the installer script: 

$ curl -fsSL https://piforexcel.com/proxy | sh

Keep it running while you use Pi. In the sidebar: /settings → Proxy → enable, set URL to https://localhost:3003. Then run /login and sign in.

What does this do? It runs a tiny local CORS proxy on your machine so Excel can complete OAuth safely. No git clone or mkcert setup is required for hosted use. Your data still flows between your computer and your provider. The code is open source.

Paste an API key Simpler

If you have an API key, just paste it. No proxy needed. In the sidebar, type /login, expand a provider, paste your key, hit Save.