Give the agent the spreadsheet, not a chat box beside it.

The engine is IronCalc, a full spreadsheet engine compiled to WebAssembly and running in your browser. The agent's tools run there too, against the same document you're editing. Ask it to build something and watch the cursor move and the cells fill in.

See how it works

Early, single-player, and more experiment than product. The parts we built around the engine are open source.

pricing.sheet

Plan

Seats

MRR

Free

Pro

=B3*29

Scale

$792

YouAgentC3 ← =B3*29

Watch the agent work

The grid and engine below are the real thing, running in your browser right now. A recorded script drives the same tools the live agent uses — no account, no inference. When it finishes, the sheet is yours to edit.

revenue-modelRecorded · no sign-in

Loading engine…

Agent

A recorded session — the agent builds a model in the grid to the left.

Why not just add AI to a spreadsheet?

Most attempts bolt a chat panel onto a grid, or wire the model in from outside over MCP. The hard part isn't the transport, it's what the model gets back: it reads one range, writes another, and to see what the write did, it reads again. On a sheet full of formulas, that round-trip is most of the work.

So the tools are built around what the agent gets back.

A structure-aware read: Instead of a cell-by-cell dump, the agent gets a compact sketch — regions, headers, types, fills — enough to see the layout of a sheet without reading every cell.
A delta echo on every write: Every write comes back with what it changed on that sheet, recalculated formulas included, so the agent usually doesn't have to read back after an edit.
Range-level verbs: Fill, sort, and format each take a whole region in one call, instead of a loop of single-cell edits that fan out into round-trips.

How it works

The engine runs in your browser

IronCalc handles formulas, dynamic arrays, undo, styles, and number formats, all client-side. The server never parses a spreadsheet — it stores the engine's own bytes and hands them back.

The agent’s tools run there too

Chat runs on Claude, hosted or on your own API key — but the tool calls the model makes execute in your browser, against the same document you're editing.

You watch it happen

The agent focuses a range, switches to the sheet it's working on, writes, and the changed cells pulse. Your cursor is blue, the agent's is violet, so you can always tell whose cursor is whose.

What it isn’t, yet

It's an early proof of an idea, and we use it ourselves.

Single-player. No realtime collaboration yet — one client edits a workbook at a time.
One owner per workbook. No sharing, no roles, no view links. A workbook is reachable by its owner or by nobody.
No xlsx import yet. CSV import, xlsx export, and a Google Sheets bridge work today; xlsx import doesn't yet.
Some engine features aren’t wired up. Frozen panes, merged cells, and borders exist in the engine but aren't wired into the UI yet.

What we built is open source

The engine is IronCalc, an open-source project we build on but didn't write. Our parts — the server daemon, the agent's tool definitions, and the sync protocol — live in sheetkit. This app is the UI on top.

View sheetkit