OpenTakeoff

The measurement engine for building plans—built so an AI agent can drive it, and so an estimator wants to.

A takeoff is the act of measuring quantities off a construction drawing. OpenTakeoff does it two ways over one engine: 47 MCP tools for an agent, and a browser canvas for a person. Agents and people share the takeoff document and quantity calculations. Each sheet carries its calibration; measurements carry geometry, method and authorship. Recalibration updates quantities together, incompatible imports report scale conflicts, and agent measurements carry an explicit review status. See the Phase 1 test guide.

For agents · Try the canvas · The engine's contract · For the person at the canvas · The data layer · Research · Fork it · Contribute

The two manuals: agent manual · user manual

Read this in: 日本語 · 한국어 · 简体中文

Watch it: an autonomous agent runs a takeoff, live, no cuts (2:47) · hospital finish plan → report in about a minute (1:14) · canvas walkthrough (1:10) · One-Click Area (0:51)

One-Click Area is temporarily gated. The flood engine is being re-validated against a wider plan corpus. Until that finishes the One-Click tool is off the canvas rail (O reports the gate) and the one_click / detect_rooms MCP verbs are not registered (a default build ships 45 tools). Trace rooms with Area (A) in the canvas and measure_polygon over MCP; every other tool, sweep and derivation is unchanged. A build lifts the gate with VITE_ONE_CLICK=1 (canvas) / OPENTAKEOFF_ONE_CLICK=1 (server). Sections and videos below that show One-Click describe the engine as it returns — see docs/design/ONE_CLICK_GATE.md.

Start here

Windows, macOS, Linux — all of it

OpenTakeoff is a client-only browser app, so the canvas runs the same on Windows, macOS, ChromeOS and Linux in any current Chrome, Edge, Firefox or Safari. Nothing installs, nothing uploads, and no feature is gated on an operating system.

• Shortcuts are platform-aware. The app labels modifiers for the keyboard in front of you — Ctrl / Alt / Shift on Windows and Linux, ⌘ / ⌥ / ⇧ on a Mac — and the handlers have always treated ⌘ and Ctrl as the same key. Press ? in the canvas for the current list.
• The MCP server is tested on Windows. npx -y opentakeoff-mcp runs on Windows, macOS and Linux, and CI runs the full MCP suite — typecheck, tests, build and the packaged smoke test — on windows-latest as well as ubuntu-latest on every change.
• Optional extras. The bundled capture server is stdlib Python 3 and runs anywhere Python does — on Windows invoke it with python capture\capture_server.py selftest (or the py launcher) rather than python3. Neither it nor the optional server/ AI sandbox is needed to use the canvas.
• Locked-down enterprise fleets (MSIX packaging, Windows Sandbox, Intune silent deploy) are tracked in #226 and not yet built.

What this is

Measuring quantities off a plan is the input to every construction bid—how much floor, how much wall, how many fixtures, at what scale, on which sheet. It happens thousands of times a day. Until OpenTakeoff there was no open-source takeoff engine at all, web-based or otherwise, and nothing an autonomous agent could call.

OpenTakeoff is that engine, with two front ends over identical geometry:

• A stdio MCP server—npx -y opentakeoff-mcp, 45 tools, on the official MCP registry. An agent opens a plan, reads the title block, sets the scale, floods the rooms, checks its own work on a rendered overlay, and hands back a marked-up planset PDF.
• A browser canvas—no backend, no account, no upload. An estimator drags in a plan set and traces it, using One-Click room detection, CAD hatches, roll-goods seam layout, a materials buy list, and exports.

Neither is a wrapper around the other. The MCP server imports web/src/lib/{oneclick,sheets,geometry,totals} directly, so a shape committed by an agent is field-identical to one committed by a hand at the canvas—same flood mask, same corner snap, same waste math, same refusal messages.

Provenance is the load-bearing part. Every shape records the scale it was measured at, the method that produced it (vector flood, raster trace, hand-drawn, agent-proposed), whether a human corrected it, and the machine's original boundary frozen beside the correction. Downstream, that's an audit trail a PM can read. Upstream, it's a labeled (geometry → finish) pair—the training signal takeoff models have never had at scale. That second use is not a side effect; see the data layer.

Recently shipped

• Stitched sheets—a floor split across a match line becomes one working surface; a room that crosses the seam traces as one shape, One-Click included (#161)
• PDF layer roles—CAD-exported sheets state what their ink is, so One-Click reads the layer tree instead of inferring boundaries from hatch, with a Layers panel on the canvas and scored corpus IoU (#85)
• The sheet graph—an agent asks "what finish is in room 134, and how do you know" and gets the schedule row with a citation per cell, across continuation sheets, rotated headers, and multi-building keys: sheet_graph / resolve_tag / find_schedule (#87)
• Roll goods—opt a condition into broadloom or sheet material and the engine figures the seams: lanes, multi-roll splits, cuts drawn to scale over their rooms in cutting order, a to-scale roll diagram with drag-to-reorder, and order footage beside the measured quantities (#136)
• Transitions, at the canvas—⟂ Transitions… in the Takeoffs panel derives the line where two finishes meet from rooms you already measured; derive_transitions does the same over MCP. Flood-traced rooms don't share edges, so what's actually there is proximity in two flavors that mean different things: finishes changing inside one open space commit as a butt joint, while rooms parallel across a partition come back withheld as questions—the transition is a threshold in a doorway, and nothing in a trace record says where the doorway is. Committing 34 LF of threshold because two rooms share 34 LF of wall would be a wrong bid with a machine's confidence behind it (#202)
• symbol_sweep—every instance of a repeated symbol from one marqueed example, crossing scales only by a stated ratio, never a searched one
• mark_verdict / delete_verdict—an agent signs its own work as a graphite AGENT diamond; only a human hand mints the green APPROVED seal
• One-Click accuracy wave—face extraction and gap tolerance from [RFC #60](https://github.com/Kentucky-ai/ope