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Aug 23, 2026 · product · in progress

SolidBrief

Conversational CAD for 3D printing. Describe a part or a small printable product in plain language, and SolidBrief asks what it needs to know, builds checked CAD in an isolated worker, and hands back STEP, STL and a 3D preview with a receipt of what was verified.

role Everything — product, CAD pipeline, backend, frontend, and evaluation

  • Python
  • FastAPI
  • CadQuery
  • SQLite
  • Docker
  • React
  • TypeScript
  • Three.js
  • Vite

Case study

Contents
  1. 00Top
  2. 01Highlights
  3. 02From prompt to part
  4. 03Checked, and honest about what checked means
  5. 04Composition
  6. 05Where it stands

SolidBrief is a showcase of an AI tool built to be useful rather than impressive: you describe what you want to print, and it produces geometry you can inspect, edit and trust as far as its checks go, and no further. It's aimed at 3D printing today and, possibly, at engineers who need a quick industrial part tomorrow.

Highlights

  • Turns a chat message into versioned single parts, a reviewed two-piece enclosure, or a guided printable system of up to four parts plus preview-only reference geometry.
  • Asks one focused question at a time while the brief is underspecified, then proposes an outline of parts to review and refine. No CAD is built until you choose to build it.
  • Uses reviewed parametric templates for common parts (an L-bracket, a spacer bushing, a mounting plate, the enclosure) and retained, ordinary CadQuery source for everything else, so even the free-form path stays inspectable and editable.
  • Builds and inspects every part in an isolated Docker worker, then exports STEP, STL and a GLB preview, each revision with a receipt of its lineage, worker and artifact hashes.
  • Measured by a live-model evaluation suite of eleven conversations and 38 turns, run through the product's own public interface; the model that authors a part never grades it.

From prompt to part

The first version, Cadgen, proved the core idea: prompt to structured parameters to a CadQuery template to STEP and GLB, with editable dimensions instead of opaque generated code. Templates keep generation predictable and make smaller models viable. SolidBrief keeps that route as the default for recognized parts and adds a second one for geometry no template covers: custom CadQuery source the model writes and you can read. When a follow-up asks for something a template can't do, SolidBrief says so and asks before continuing as custom source, rather than quietly bending the template.

Checked, and honest about what checked means

A green revision means the exported file passed SolidBrief's stated checks: it builds, it's a single valid solid where it should be, the STEP reopens, the composition's static requirements hold. It is not a manufacturing approval or a professional engineering review, and the product says so. The line between measured facts about the geometry and design intent nobody has verified is written down, because a CAD tool that overclaims is worse than one that underclaims.

Composition

Small printable products are rarely one part. A composition manifest owns stable part and instance identities, which parts are manufactured and which are only reference, fixed placements, and the interaction requirements between them. Each part is built and inspected on its own before the assembly is put together and checked as a whole. Edits scoped to one component, reuse of unchanged parts and durable design decisions are the next slices; hinges, motion and general multi-body solving are deliberately out of scope for now.

Where it stands

The current slice covers text to versioned single-solid geometry, the four reviewed templates, custom source for uncommon geometry, the two-piece enclosure, and guided printable systems with STL delivery, packaged as a local application. Unit-aware 3MF export and component-scoped edits are next on the roadmap.