open-excel

Open-source AI-powered Excel add-in with tool-calling agent loop.

Overview

An Excel add-in (React/Vite/TypeScript/Office.js) that provides an AI-powered taskpane with:

• routed taskpane shell
• gated boot flow
• local provider configuration
• tool-calling workbook agent loop
• Office.js workbook adapter

The LLM backend uses any OpenAI-compatible endpoint via LiteLLM.

Stack

• Vite
• React
• TypeScript
• React Router
• Zustand
• Office.js
• LiteLLM via OpenAI-compatible /chat/completions

Implemented tools

• get_sheets_metadata
• get_cell_ranges
• set_cell_range
• clear_cell_range
• get_range_image
• execute_office_js

Not implemented yet

• bootstrap / claims merge
• MCP
• conductor
• PowerPoint / Word surfaces
• telemetry and analytics
• chart OOXML extraction

Development

bun install
bun run certs:install
bun run dev

Default LiteLLM taskpane endpoint:

• /api/litellm/v1

Default LiteLLM upstream:

• http://127.0.0.1:4000

Environment variables:

• LITELLM_UPSTREAM_URL
• VITE_LITELLM_BASE_URL
• VITE_LITELLM_MODEL
• VITE_LITELLM_API_KEY

The Vite dev server proxies /api/litellm/* to LITELLM_UPSTREAM_URL, so the Excel taskpane can stay on HTTPS while talking to a local HTTP LiteLLM process.

Default model alias:

• claude-opus-4.6

Build

bun run build

E2E Flow

The only supported E2E path is the real Excel Online taskpane opened from More options -> Open Excel.

Detailed workflow notes live in:

• docs/e2e-workflow.md

Office sideload

An Excel add-in manifest is included:

• manifest.xml

Expected dev URL:

• https://localhost:5173

Notes:

• The Vite dev server uses office-addin-dev-certs for trusted localhost HTTPS certificates.
• The included icons are placeholders only.
• Run bun run manifest:validate before sideloading.
• Use bun run office:web:start to start the dev server and launch Excel on the web sideload flow with the official debugging toolchain.
• In Excel Online, reopen the taskpane from More options -> Open Excel when multiple add-ins are present.