@diatechai/cad — the headless viewport

An AI agent connects to Diatech CAD by pasting one URL into its custom-connector settings, and without this package every step of every render happens on our server: the compile, the booleans and the picture. Only the first of those is ours to do. The editor has run the rest in the browser for a long time — that code is not the CAD kernel, and this package is that same code on the command line.

DIATECH_URL=https://cad.diatech.ai DIATECH_TOKEN=… \
  npx -y @diatechai/cad@latest render design.ds --view hero --out render.png

Call the diascript_setup MCP tool for the URL and a token; it is the only place they come from, and it prints this exact line.

What runs where

The server parses, resolves and evaluates the design — the kernel, the stone packing, the report — over the editor's own compile socket (/api/compile, your token in the Authorization header). It answers with what it answers the editor's viewport with: meshes, and recipes naming geometry to build locally — a mesh Boolean arrives as its ordered steps over lossless operand meshes. An expensive Boolean it needs mid-compile it asks this machine for, and checks what comes back. This package then does what the browser does.

| | server | here | |---|---|---| | parse → resolve → kernel | ● | | | B-Rep → triangles | ● | | | metal weight, stone table | ● | | | mesh Booleans (drills, cutters, unions) | | ● | | instancing, grouping | | ● | | shading and the PNG | | ● |

The Booleans are manifold-3d — the same WASM build and release the editor and the server load, run by the editor's own module rather than a re-implementation. One that fails fails the render; it is never drawn as its overlapping operands. Nothing here can build CAD geometry from a design; it draws triangles the server sent.

Commands

cad render <file.ds> [--view hero] [--out render.png] [--size 512] [--server]
cad report <file.ds> [--server]

--view takes hero, front, right, top or iso, and repeats: several angles cost one compile, one download and one composition between them, so ask for them together.

report prints the metal weight, the stone table and the overall size — the numbers a picture cannot carry, in the summary diascript_render returns (bounds_mm.size, metal, stones, and warnings apart from errors). A render is auto-framed, so a 17 mm ring and a 170 mm one make the same image and only the bounding box catches it. It is a separate compile on purpose: the render build defers exactly the cuts this package performs, so a weight taken from it would be the weight of the uncut body. The Booleans a report needs are the ones a render just computed and kept, so it reads "authority": "client_mesh".

--server has the server compute every Boolean itself — an authoritative report, or a render of what the server carves. It is also the answer when a Boolean fails on this machine, whether the server asked for it or the render composes it: the command prints the failure and says to rerun with --server, and never does so on its own.

The cache

Every node the server sends carries a content hash, and each render lists the hashes this machine already holds. The server then sends only what changed — after an edit that is usually one node. Each Boolean's result is kept too, so an unchanged one is not recomputed and a report can name it instead of resending its operands. The files live in $DIATECH_CACHE_DIR, or ~/.cache/diatech-cad, and the directory is bounded; deleting it costs one slower render. Only keys in the shapes the server mints ever become filenames; a write lands whole or not at all, and a file that does not decode is deleted and fetched or computed again.

Refusals and retries

A refused compile prints {"ok": false, "error", "message", …} and exits 1, whether the server refused the connection (401 sign-in, 403 subscription, 409 seat) or ended it. When every compile slot of the account is busy (429) the command waits out Retry-After and reconnects for up to a minute first. It retries nothing else. A server that never answers the upgrade (30 s), or goes silent mid-compile (300 s without a frame or a ping), is a network error.

Limits

A local render is a preview: auto-framed, flat-shaded, screen tessellation. Metal reflects the viewer's light tent; stones stay on a separate, faceted light. Manufacturing files are server exports. If the server does not speak this package's compile protocol (dscad.compile.v1), the socket does not open, and if it answers with a payload protocol this package does not know, it refuses rather than drawing geometry it may read wrongly — upgrade with npx -y @diatechai/cad@latest, or fall back to the diascript_render MCP tool.