Milton

A Microsoft Excel Add-In for Bring-Your-Own-Model (BYOM) agentic spreadsheet interactions.

Development

pnpm dev
pnpm start

pnpm dev starts the Office app's Vite HTTPS dev server on a worktree-derived local port. pnpm start generates and sideloads a worktree-specific Excel manifest so multiple Codex worktrees can be debugged side by side.

For the first agent-chat milestone, create a shared local dev env once:

pnpm dev:env-init

This creates ~/.config/milton/office-dev.env. Values in that file are loaded by pnpm dev, pnpm start, and pnpm validate from every worktree.

The env file should contain:

DEBUG_OPENAI_API_KEY=sk-...
DEBUG_OPENAI_MODEL=gpt-5-mini

You can still create apps/office/.env.local inside one worktree for a worktree-specific override.

The task pane calls OpenAI directly from the browser runtime. This is a local development path only because DEBUG_OPENAI_API_KEY is exposed to the task pane.

Stop a sideloaded debug session with:

pnpm stop

Project layout

apps/
  office/
    commands/          Office command function page
    manifests/         Office manifests
    public/assets/     Static icon and logo assets served by Vite
    taskpanes/excel/   Excel task pane app
    vite.config.ts     Office app build config
docs/
packages/
  office-host/         Typed Office host integrations
  office-runtime/      OfficeJS code execution runtime and agent tool
  pi-agent-core/       Vendored Pi agent package, with a browser entrypoint for Milton
  pi-ai/               Vendored Pi model/provider abstraction package
  ui/                  Shared React UI

The source local Excel manifest is apps/office/manifests/excel.local.xml. Development sideloading uses generated manifests under apps/office/.generated/.

Checks

pnpm build
pnpm validate

Dependency notes

pnpm-workspace.yaml patches office-addin-dev-settings with semver because that package currently imports it at runtime without declaring it as a dependency.