/forgecad

name: forgecad
description: ForgeCAD model authoring, editing, debugging, and execution guidance for .forge.js, SVG-import, assembly, and CLI workflows. Use when building or modifying ForgeCAD geometry, structuring multi-file projects, validating scripts, or using ForgeCAD export/render tooling.
forgecad-public: true

ForgeCAD

Author or modify ForgeCAD models, sketches, assemblies, and CLI workflows. Prefer documented primitives, import rules, placement strategies, and CLI commands over inventing new APIs.

Workflow

1. Identify the artifact: `.forge.js`, SVG asset, or CLI/export task. 2. **If the model has any moving parts, load the `assembly` group and `{{SKILL_DIR}}/docs/guides/joint-design.md` upfront** — do not defer the kinematic structure to a refactor pass. 3. Load only the docs the task needs (see Source Map below). Start from the top group, add others as needed, and prefer these docs and recipes over ad-hoc repo examples. 4. If any two parts are intended to touch or mate in the final model, load `{{SKILL_DIR}}/docs/guides/positioning.md` immediately and default to connectors + `matchTo()`. 5. Default to a concrete first pass — easy iteration beats speculative design review. 6. If an existing model is broken, replace the weak structure rather than preserving bad architecture. 7. Validate with `forgecad run <file>` (add `--debug-imports` for import chain issues; pass `--backend manifold|occt|truck` when the backend matters). 8. For moving assemblies, return the `Assembly` directly so runtime controls re-solve the link/edge kinematics model instead of stacking viewport-only transforms. 9. Model the physical artifact, not an educational diagram. No explanatory labels, arrows, legends, or text plaques unless the user explicitly asks for a presentation or teaching view; product markings only where the real object would carry them. 10. Build the real closed CAD first. Never bake cutaways, sectioned shells, permanently exploded layouts, or hidden-parts views into the default model just to show internals — use viewer-only cut planes, `explodeView`, object hiding, transparency, or `inspect sections` after the artifact exists.

Import and Composition

• Always include the extension in relative imports: `require("./file.forge.js", { Param: value })` for model files, `require("./helpers.js")` for plain helper modules. Extensionless imports such as `require("./file")` do not resolve; ForgeCAD resolves project imports by exact path.
• ForgeCAD APIs are injected globals in `.forge.js` files. Use `bom()`, `box()`, `scene()`, `Shape`, etc. directly; never destructure those names from helpers (`const { bom } = require("./bom.js")`). Import helper files under a project-specific name such as `const bomHelpers = require("./bom.js")`.
• For static multi-part models, connectors + `matchTo()` are the default way to assemble touching parts.
• Top-level scripts can return `Assembly` or `SolvedAssembly` directly. Do not call `.toGroup()` just to render an assembly; use it only when you need `ShapeGroup` composition, transforms, or named-child lookup.
• `Import.svgSketch()` loads SVG files (file format loader, not a module import).
• `.placeReference('bottom', [0,0,0])` aligns any built-in anchor to a world coordinate; also works with custom `.withReferences()`.
• Plain `.js` modules hold shared helpers/constants (not model imports).

Source Map

Load groups top-to-bottom, stopping when you have what the task needs.

1. Core API (always read first)

Execution model, colors, coordinate system, primitives, booleans, patterns, imports, parameters, topology, edge queries.

• `{{SKILL_DIR}}/docs/API/core/concepts.md`
• `{{SKILL_DIR}}/docs/generated/runtime-names.md`
• `{{SKILL_DIR}}/docs/generated/core.md`

2. Static Assembly and Positioning (for any multi-part model)

Axis conventions, winding rules, and placement strategy. If parts should touch in the final model, read this group before writing placement code. Connectors + `matchTo()` are the default for mating interfaces; raw `translate()` and `rotate()` are for free offsets, not assembly contracts.

• `{{SKILL_DIR}}/docs/guides/coordinate-system.md`
• `{{SKILL_DIR}}/docs/guides/positioning.md`

3. Sketch APIs

2D construction, transforms, booleans, paths, on-face sketching, extrusion, anchors, text, regions.

• `{{SKILL_DIR}}/docs/generated/sketch.md`

4. Curves and Surfacing (for lofts, sweeps, splines)

Smooth curves, Hermite splines, lofted and swept solids. For straps, inlays, guards, brace members, vents, or physical bands that live on a carrier surface, use `Carrier` + `SurfaceBody` surface-member primitives before reaching for `variableSweep`, SDF sculpting, or manual boolean overlap recipes.

• `{{SKILL_DIR}}/docs/guides/surface-members.md`
• `{{SKILL_DIR}}/docs/generated/curves.md`

5. Assemblies and Mechanisms (for joints or kinematics)

Assembly graph, joint types, couplings, validation, and simulation export.

• `{{SKILL_DIR}}/docs/generated/assembly.md`

6. Sheet Metal (for bent parts, K-factor, flat patterns)

Bend operations, flat pattern unfolding, K-factor configuration.

• `{{SKILL_DIR}}/docs/generated/sheet-metal.md`

7. Output and Export (for STL/3MF/STEP, BOM, dimensions)

Mesh export, exact geometry export, bill of materials, dimension annotations.

• `{{SKILL_DIR}}/docs/generated/output.md`

8. Toolbox (fasteners and standard parts)

Parametric bolts, nuts, washers, standard hardware, gears, pipes, and structural profiles.

• `{{SKILL_DIR}}/docs/generated/lib.md`
• `{{SKILL_DIR}}/docs/generated/wood.md`

9. Runtime Viewport APIs (for cut planes, exploded views, hiding, and animation playback)

Viewer-only APIs such as cutPlane, explodeView, render labels, comparison references, and runtime display behavior.

• `{{SKILL_DIR}}/docs/generated/viewport.md`

10. Recipes and Debugging (for patterns and troubleshooting)

Modeling patterns, debugging tactics, copyable snippets.

• `