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: 53 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

Protocol work: Takeoff Protocol draft and compatibility status—formalizing existing records; current takeoff behavior is unchanged.

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 53 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.

The Premium workspace offers compact controls, searchable actions and sheets, personal panel arrangements, adjustable surfaces and larger sheet previews. It is the default when this browser has no saved layout choice; Classic layout remains available. See the workspace design and research.

Sheet navigation releases closed PDFs and embedded fonts from the tile workers; see the 30-flip rendering check. Beyond the PDFs in open tabs, at most four idle PDFs stay loaded (two on a phone or tablet, or a browser that reports 4 GB of memory or less), least recently used out first; see the 12-PDF check.

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 sharing geometry and quantity modules:

• Review cleanup—agents can edit annotation text with undo while preserving geometry and review; RFI-linked notes require browser review. Scope warnings distinguish numeric edge residue from real small overlaps.
• A stdio MCP server—npx -y opentakeoff-mcp, 53 tools, on the official MCP registry. An agent opens a plan, reads the title block, sets the scale, traces the rooms to their wall faces (the flood engine stays gated), 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 shared web modules, so quantity math and takeoff records are compatible. Browser and MCP room-detection paths currently differ; shared code does not guarantee identical boundaries on every plan. One-Click remains gated while that boundary is re-validated.

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. This includes agent shapes drawn with manual measurement tools; the actor and drawing method are separate fields. 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

• Tracing rules an agent actually reads—the room-boundary conventions an estimator uses (innermost wall face, door openings crossed on the wall centerline, columns and chases wrapped, never a hatch edge or a door leaf, a tight overlay check per ring) now ship inside the server: takeoff://wiki/workflows, the initialize instructions and the measure_polygon description. On a task with no conventions in it, one unprompted run went from 0 of 6 rooms with door notches to 6 of 6 (#423, MCP 0.9.84)
• A plan set with reference rings, and blind runs against it—three public floor plans (a VA healthcare finish plan, a VA clinic floor plan, a city public-domain ADU) with estimator-trace references, a scorer profile for concave rooms and finish splits, and published blind agent runs with frozen exports, scores and overlays. The runs found defects in the references first; the references are v2 and still unreviewed by a