Typed Domain Grounding
A statically typed Kotlin DSL plus compiler and validation feedback gives LLMs a ground truth to work against — the same principle that makes kUML reliable, applied to engineering data.
Kotlin DSL · ISO 10303 · AP242 · CAD · Engineering
Engineering that compiles.
One typed source. STEP-native models. Readable for humans and AI.
kSTEP is the first AI-first, code-first, STEP-native engineering modeling DSL for Kotlin/JVM. It brings Typed Domain Grounding — the architecture proven in kUML — to physical engineering: a statically typed DSL plus compiler feedback that gives humans and LLMs a reliable ground truth, from product structure to geometry.
Bracket.kstep.kts
// product-structure.kstep.kts — shortened excerpt of the playground example
val appCtx = applicationContext { application = "configuration control" }.getOrThrow()
val prodCtx =
productContext {
name = "engineering"
frameOfReference = appCtx
disciplineType = "mechanical"
}.getOrThrow()
val housing =
product("HSG-100") {
name = "Housing"
description = "Enclosure housing"
frameOfReference = setOf(prodCtx)
}.getOrThrow()
// ... product definitions, nextAssemblyUsageOccurrence, stepFile { } -> STEP Part 21Shortened excerpt of the playground example — pre-release v0.3.0 (JVM-only CLI zip without native bridges), geometry only in a local build.
Code-first. AI-first. STEP-native.
Today's CAD world offers GUI suites with proprietary formats — or code-first scripting without real AI integration. kSTEP is the deliberate third way.
STEP-native, not proprietary
kSTEP speaks ISO 10303 directly — AP242, Part 21 export, product structure and beyond. No binary vendor formats, no lossy conversion.
A proven geometry kernel
Geometry builds on OpenCascade (OCCT), accessed via JNI on the desktop first — with a WASM path already open for a later browser playground, from the same codebase. Several foundation pieces already work end to end: real B-Rep solids (boxes, extrusions, fillets, chamfers, cylinders, holes, revolve, union/difference/intersection) with a parametric feature history, a sketch DSL with PlaneGCS constraints and geometric edge selectors, geometry and placed assemblies in a single STEP file, `kstep import` to read STEP files with geometry back, glTF/GLB export, and an interactive desktop viewer (orbit, pan, zoom, per-part material colors, smooth shading on curved surfaces). Since v0.3.0 it also has persistent naming of generated edges, undo/redo, mirror, scale and shell, face and vertex selection, and colours and layers in STEP export and import; PMI, pocket or hole from a face, draft and thickening are still ahead. Geometry needs a system OpenCascade and a self-build; the release zip contains no native bridges.
AI-first, not AI bolted on
LLM agents are a first-class user of the DSL — named parameters everywhere, validation loops, and an MCP server that already exposes the DSL as tool-calling tools, mirroring what kUML already ships.
Type safety as a feature
CadQuery and Build123d are Python — no static types, no compiler feedback. Kotlin's type system is kSTEP's deliberate differentiator, not an accident of language preference.
Open source, license-clean
Apache 2.0 for kSTEP's own code, dynamically linked against LGPL OCCT and PlaneGCS. Cleared deliberately during Discovery — no GPL traps.
Follow the build.
The repository is real, the milestones are public, and every step lands in the open.
kSTEP on GitHub