kompas3d-mcp/CLAUDE.md

# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project goal

Build an **MCP (Model Context Protocol) server** that lets an LLM drive the CAD system **КОМПАС-3D** (ASCON). The server exposes КОМПАС operations (create/open documents, build 2D geometry, 3D parts and assemblies, read/write parameters, run macros) as MCP tools.

Authoritative references:
- **SDK knowledge base in this repo: `docs/Kompas3D_SDK/`** — clean Markdown, one article per COM interface, with YAML tags; search it with Grep/Read (see below). Committed to the repo (canonical), distilled from the КОМПАС SDK help. Prefer this over the web. For non-trivial lookups, delegate to the **`kompas-sdk-research`** skill (Sonnet subagent) to save context.
- Online SDK docs: https://help.ascon.ru/KOMPAS_SDK/22/ru-RU/index.html
- Local SDK install: `C:\Program Files\ASCON\KOMPAS-3D v24 Home\SDK`

## Navigating the SDK docs (`docs/Kompas3D_SDK/`)

`docs/Kompas3D_SDK/` is a structured MD knowledge base distilled from the 26 000-page Help&Manual WebHelp export. One article per COM interface/topic, split into `interfaces/`, `enums/`, `structures/`, `guides/` (+ `resources/` images), each with YAML frontmatter (`type`, `api`, `domain`, `tags`, `sources`); methods/properties are `## ` headings inside the interface article. **Search it directly — do not browse the raw HTML:**

- **Grep** over `docs/Kompas3D_SDK/` for an interface/method/property name or Russian keyword (method names are `## SetSideParam - …` headings, so the name lands you in the right article).
- **Read** the matching `*.md` — the interface article holds all its members, `Синтаксис Automation:`/`Синтаксис COM:` blocks (in code fences), parameters, notes.
- `docs/Kompas3D_SDK/index.md` — table of contents by category. Filter by frontmatter tags, e.g. `Grep "type: enum"` or `Grep "domain: \[.*3d"`.

The base is committed to the repo (canonical) — no regeneration step. It covers the **COM API7/API5** reference this project uses (interfaces named `iapplication_*`, `idocuments_*`, …). The cross-platform Qt/C++ **KsAPI** flavour (`ksapi_*`, non-COM binding) is intentionally **excluded** from the base — ignore unless explicitly working with KsAPI.

## Current state

**v1 + v2 + STEP/assembly + direct B-rep edit + structural model inspection implemented and working** (full sketch→feature→inspect→STEP round-trip + move_face + describe_model validated end-to-end). Stack:
**.NET 8 (`net8.0-windows`, x64), C#**, MCP via the official `ModelContextProtocol` SDK over **stdio**.
**71 MCP tools, 138 tests green (83 unit + 55 integration).** v2 added: sketch-on-face (by point and by index), revolve (boss/cut + sketch axis), fillet/chamfer (edge-by-point and by index), and Query tools `get_part_info` (МЦХ), `get_bounding_box`, `list_faces`, `list_edges`. After v2: `import_step`, `export_step` (`ConversionService`, `ConversionTools`), `list_components` (assembly traversal via `TopPart → IParts7`). `move_face` (`FaceEditService`, `EditTools`) — direct B-rep face editing. After move_face: **structural model inspection** — `describe_model`, `list_features`, `list_bodies`, `list_variables`, `describe_face`, `describe_edge`, `measure` (`ModelInspectionService`, `InspectionTools`). `describe_model` is the preferred first call over `model_snapshot` (no token cost for image context; gives feature tree, bodies, variables, topology summary, МЦХ). Package A «richer sketches»: 7 new sketch primitives — `sketch_add_arc`, `sketch_add_arc_3points`, `sketch_add_ellipse`, `sketch_add_polyline`, `sketch_add_polygon`, `sketch_add_spline`, `sketch_add_point`. `PartModeler` refactored into partial classes: `PartModeler.cs` (core), `PartModeler.Sketch.cs` (2D primitives), `PartModeler.Features.cs` (extrude/revolve/fillet/chamfer). Static `SketchGeometry` class in `Core/Modeling`. Package B «forming ops» complete: **`shell`** (оболочка, `o3d_shellOperation=43`) + **`rib`** (ребро жёсткости, `o3d_ribOperation=44`) + **`sweep`** (кинематическая операция, `o3d_baseEvolution=45`) + **`loft`** (по сечениям, `o3d_baseLoft=30`). Auxiliary geometry (start of package E): **`sketch_create_on_offset_plane`** (смещённая плоскость, `o3d_planeOffset=14`) — unlocked `loft`. Additional Edit tools: **`split_solid_by_plane`**, **`move_body`**, **`boolean_union`**. Package C «patterns & mirror» complete: **`linear_pattern`** (линейный массив, `o3d_meshCopy=35`) + **`circular_pattern`** (круговой массив, `o3d_circularCopy=36`) + **`mirror_operation`** (зеркальная копия операций, `o3d_mirrorOperation=48`) + **`mirror_body`** (зеркало тела, `o3d_mirrorAllOperation=49`). **`hole`** (`HoleService`, `FeatureTools`) — цилиндрическое отверстие (сквозное или глухое) через **API7** (`IModelContainer`/`IHole3D`/`IHoleDisposal`); первая формообразующая операция на API7 (прецедент ранее только у `move_face`). **`hole_counterbore`** — отверстие с цековкой (`ksHTCounterbore`, `ISpotfacingHoleParameters`). **`hole_countersink`** — отверстие с зенковкой (`ksHTCountersinking`, `ICountersinkHoleParameters`). **`hole_conic`** — коническое отверстие (`ksHTConic`, `IConicHoleParameters`: `ConicType=ksCNAngle`, `ConicAngle`); завершает набор типов отверстий. `HoleCore` рефакторен: принимает `ksHoleTypeEnum holeType` + `Action<IHole3D> configure` (настройка `HoleParameters` после установки `HoleType`, т.к. параметрический подынтерфейс недоступен до фиксации типа). Базовый `hole` = `ksHTBase` + `configure=null`. **`draft`** (уклон, `o3d_incline=42`) — наклон граней на угол относительно нейтральной координатной плоскости; реализован через **API5** `ksInclineDefinition` (операция называется Incline в API5, не Draft). Package D «parametrics» started: **`create_variable`**, **`set_variable`**, **`delete_variable`** (`VariableService`, `VariableTools`) — CRUD переменных модели через API5. `list_variables` исправлен (читает `ksPart.GetFeature().VariableCollection`, а не `ksPart.VariableCollection()`). **Ограничение:** переменная управляет геометрией только в параметрической модели (где размеры эскиза связаны с именем переменной); наши эскизы строятся литеральными координатами → `set_variable` хранит/вычисляет значение, но геометрию не меняет. Связь эскизных размеров с переменными (API2D) — не реализована. **Assembly class started:** **`assembly_add_component`** (`AssemblyService`, `AssemblyTools`, namespace `Kompas.Mcp.Core.Assemblies`) — первый инструмент класса СБОРКИ: вставка компонента (.m3d/.a3d) из файла в активную сборку с заданием положения origin (мм, мировая СК сборки); возвращает индекс и имя вставленного компонента.
See [`README.md`](README.md) and [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md); design decisions/caveats in
[`docs/OPEN_QUESTIONS.md`](docs/OPEN_QUESTIONS.md).

Principle: **MCP = translating SDK capabilities into general tools** (not task-specific). On top of MCP — skill **`.claude/skills/kompas-3d/`** with a methodology (playbooks, heuristics, validated in `usecases/`). Layout: `usecases/` (in .gitignore) is the proving ground; proven techniques are promoted to the skill.

Layout: `src/Kompas.Mcp.Core` (COM layer), `src/Kompas.Mcp.Host` (MCP stdio server + tools),
`tests/Kompas.Mcp.Tests` (unit + integration), `libs/kompas-interop/*.dll` (vendored КОМПАС interop
assemblies from SDK `Samples/Common`, referenced via `Directory.Build.props` → `KompasInteropDir`).

```powershell
dotnet build -c Release                          # build
dotnet test  --filter "Category=Unit"            # unit tests (no COM)
dotnet test  --filter "Category=Integration"     # integration (requires running КОМПАС)
dotnet run --project src/Kompas.Mcp.Host         # start the MCP server (stdio)
```

Key implementation facts (don't relearn):
- **All COM calls run on one dedicated STA thread** (`KompasDispatcher.InvokeAsync`); КОМПАС is single-instance STA. Services never touch COM off that thread.
- Connection goes through **API5** (`KOMPAS.Application.5` → `KompasObject`) then `ksGetApplication7()` → `IApplication`; the API5 root is needed for `ksPart` 3D-building and `ksDocument3D` snapshots.
- 3D is built via **API5 `ksPart`** (`NewEntity(o3d_sketch/o3d_bossExtrusion/o3d_bossRotated/o3d_fillet/o3d_chamfer/o3d_shellOperation=43/o3d_ribOperation=44/o3d_baseEvolution=45/...)`, `ksBossExtrusionDefinition`/`ksCutExtrusionDefinition`/`ksBossRotatedDefinition`/`ksFilletDefinition`/`ksChamferDefinition`/`ksShellDefinition`/`ksRibDefinition`/`ksBaseEvolutionDefinition`); cut-through holes use `dtBoth` + `etThroughAll`. API7 is used for app/documents.
- **Face/edge selection**: `ksPart.EntityCollection(o3d_face|o3d_edge)` → `SelectByPoint(x,y,z)` (world mm) filters to objects through the point, then `GetByIndex(0)`; or by stable index from `list_faces`/`list_edges`. `ksFaceDefinition.IsPlanar/IsCylinder/...` + `GetArea(ST_MIX_MM)` classify faces. `ksEdgeDefinition.IsLineSeg/IsCircle/IsArc/...` + `GetLength()` classify/measure edges. Sketch axis = line with system style **3** (осевая). Fillet/chamfer by edge index via `fillet_edge_index`/`chamfer_edge_index` (more reliable than by-point).
- **МЦХ / mass props**: use **API5 `ksPart.CalcMassInertiaProperties(ST_MIX_MM|ST_MIX_KG)`** → `ksMassInertiaParam` (`v`/`m`/`F`/`xc`/`yc`/`zc`), computed on demand. **Do NOT** use API7 `IMassInertiaParam7.Calculate()` — its `Actual` flag sticks after the first calc and won't refresh on API5 geometry changes (stale volume). Bounding box: `ksPart.GetGabarit(full:false, ...)`.
- **Snapshot**: `ksDocument3D.SaveAsToRasterFormat(file, ksRasterFormatParam)` renders to a temp file (the in-memory `resultArrayBytes` stays empty when a filename is given); read bytes back. Return to MCP via `ImageContentBlock.FromBytes(bytes, mime)` — **not** `Data = bytes` (Data holds base64 bytes). Use `model_snapshot` only for visually-spatial questions; **prefer `describe_model` first**.
- Logs go to **stderr** (stdout is the MCP channel). Integration tests reuse one КОМПАС via `KompasFixture`; artifacts land in gitignored `.scratch/`.
- **Structural model inspection** (`ModelInspectionService`, `InspectionTools`): `describe_model` — one-call structural "passport" (bounding box + МЦХ + bodies + topology summary + feature tree + variables); preferred over snapshot. `list_features` — feature tree with params (depth/radius/legs). `list_bodies` — list solid/surface bodies with face count. `list_variables` — model variables (name/expression/value, external/info flags); reads via `ksPart.GetFeature().VariableCollection` (all variables, including user-created) with fallback to `ksPart.VariableCollection()` (external-only — bug was fixed). `describe_face` — drill-down by index (type, area, normal, radius, edge count). `describe_edge` — drill-down by index (type, length, adjacent faces, vertices). `measure` — distance/angle between two objects (face|edge|vertex by index, unit `ST_MIX_MM`).
- **Variable management (package D start, `VariableService`, `VariableTools`)**: `create_variable(name, value, note?, external?)` — creates a model variable; `set_variable(name, expression)` — sets expression (constant `"30"` or formula `"width*2+5"`); `delete_variable(name)` — deletes (fails if dependents exist). **Key API facts (don't relearn):** variable creation MUST use `ksPart.GetFeature().VariableCollection` (property on root ksFeature) — NOT `ksPart.VariableCollection()` (returns external-only). Expression is the leading field; value is derived. Changes applied via `ksPart.RebuildModel()` (return checked); after rebuild the RCW variable is stale → re-read via fresh collection (`ReadValueFresh`). Dependent variables recalculate automatically. Deletion fails if dependents exist (RemoveVariable returns FALSE). **Geometry limitation:** variables control geometry only in a parametric model where sketch dimensions are linked to variable names; our sketches are built with literal coordinates → `set_variable` stores/computes the value but does NOT change geometry. Linking sketch dimensions to variables (parametric sketches via API2D) is not yet implemented.
- **Feature tree API** (don't relearn): read via API5 `ksPart.GetFeature()` → `(ksFeature).SubFeatureCollection(true,false)` → `ksFeatureCollection`. Cast `(ksFeature)part` does NOT work (RCW QI returns null) — must use `GetFeature()`. `ksFeature.type` returns only coarse `o3d_entity` and does NOT distinguish operations; precise type and params come from `ksFeature.GetObject()` → `ksEntity.GetDefinition()` and matching definition type (`ksBossExtrusionDefinition.GetSideParam`, `ksFilletDefinition.radius`, `ksChamferDefinition.GetChamferParam`, …). Node name ("Элемент выдавливания:1", "Скругление:1") is localized by КОМПАС itself.
- **STEP import/export, `list_components`, `move_face`, `split_solid_by_plane`, `move_body`, `boolean_union`, full inspection layer, richer sketch primitives (package A), `shell`, `rib`, `sweep`, `loft` (package B complete), `sketch_create_on_offset_plane` (package E start), `linear_pattern`, `circular_pattern`, `mirror_operation`, `mirror_body` (package C complete), `hole`, `hole_counterbore`, `hole_countersink`, `hole_conic` (all API7 via `HoleService`; `hole_conic` uses `ksHTConic`/`IConicHoleParameters`), `draft` (API5 `ksInclineDefinition`), `create_variable`/`set_variable`/`delete_variable` (package D start), `assembly_add_component` (API7, `AssemblyService`) are done.** Not yet done: parametric sketches — **investigated, unavailable via COM API** (`ksCDimWithVariable` cannot be constructed from external automation; see `docs/superpowers/specs/2026-05-27-parametric-sketch-findings.md`); 2D drawing; assembly mates/constraints; package E continuation (axis, angle plane). Known caveat: boss/cut direction on a selected face depends on face-normal orientation (`forward` may need flipping — agent picks via snapshot or `describe_face` normal). See `docs/OPEN_QUESTIONS.md` → «Ревью v2».
- **"STEP import without history"** detected structurally: `bodyCount > 0 && no formative features && features.Count <= bodyCount+1` (only origin + body). STEP with edits (move_face: "Смещённая плоскость", "Разрезать", "Переместить грани", "Булева операция") — that already has history.
- **Topology/measure API**: `ksFaceDefinition.EdgeCollection` / `GetCylinderParam` / `GetSurface().GetNormal` + `normalOrientation`; `ksEdgeDefinition.GetAdjacentFace(bool)` / `GetVertex(bool)` → `ksVertexDefinition.GetPoint`; bodies via `ksPart.BodyCollection()` → `ksBody` (`IsSolid` / `FaceCollection`); all variables via `ksPart.GetFeature().VariableCollection` → `ksVariable` (external-only: `ksPart.VariableCollection()` — do NOT use for reading all variables); measurements via `ksPart.GetMeasurer()` → `ksMeasurer` (`SetObject1/2`, `unit=ST_MIX_MM`, `Calc`, `distance`/`MinDistance`/`angle` in degrees / `IsAngleValid`).
- **STEP import COM pattern** (verified): `IApplication.get_Converter((object)(int)ksConverterFromSTEP=-3)` (pass format code, not DLL path) → `IConverter.ConverterParameters(cmd)` → set `IAdditionConvertParameters.Format=ksConverterFromSTEP` → `IKompasDocument3D1.ConvertFromAdditionFormat(path, prm)`. Export: `ConvertToAdditionFormat` with format codes for AP203/AP214/AP242. Param co-classes (AdditionConvertParameters etc.) are NOT CoCreatable — only via converter factories. Assembly traversal: `IKompasDocument3D.TopPart → IPart7.Parts (IParts7)`. Extract component: `prm.NeedCreateComponentsFiles=true` (writes .m3d files next to STEP) + `IPart7.OpenSourceDocument`.
- **Direct B-rep face editing (`move_face`)** (verified on top_spacer, 39.45→41.45 mm height): API7 face object retrieved via `IPart7.FindObjectsByPoint(x,y,z,true)` → cast to `KompasAPI7.IFace`; containers acquired at runtime via COM-QI: `(ISurfaceContainer)part`, `(IModelContainer)part`; `FaceMover` (SetFaces + Offset + Direction + Update) moves the face. distance>0 = outward (add material), <0 = inward. Works on both parametric and imported B-rep geometry. Full split-reposition workflow (SplitSolids/BodyRepositions) is driveable but not yet exposed as tools.
- **Shell operation (`shell`, package B)**: `ksShellDefinition` via `ksPart.NewEntity(o3d_shellOperation=43)`; `thickness` (mm) + `thinType` (bool: `true`=inward/`false`=outward; mapping: `thinType = !outward`) + `FaceArray()` (open faces, ≥1, by index from `list_faces`). Helper `SelectFaceByIndex` in `PartModeler.cs` (analogous to `SelectEdgeByIndex`, with range check). Validation: `thickness>0`, dedup via `Distinct`, range check before mutation. Transient RCWs in `ShellAsync`/`SelectFaceByIndex` are intentionally not released (consistent with Fillet/Chamfer pattern).
- **Rib operation (`rib`, package B)**: `ksRibDefinition` via `ksPart.NewEntity(o3d_ribOperation=44)`. Params: `sketchId`, `thickness` (mm), `side` (`left|right|up|down` → 0/1/2/3 via `SketchGeometry.RibSide()`), `symmetric` (bool), `angle` (°). `SetSketch(sketch)` → set `index=0`, `angle`, `side`; `SetThinParam(dtBoth, t/2, t/2)` when `symmetric=true`, else `SetThinParam(dtNormal, t, 0)`. Empirical: the rib contour must float in the gap (not touch the body at endpoints) — КОМПАС extends the web to the body automatically.
- **Sweep operation (`sweep`, package B)**: `ksBaseEvolutionDefinition` via `ksPart.NewEntity(o3d_baseEvolution=45)`. Params: `profileSketchId` (closed profile sketch), `pathSketchId` (open/closed path sketch on a different plane, typically perpendicular). `SetSketch(profile)` → `PathPartArray().Add(path)` → `sketchShiftType=0` → `SetThinParam(false)` → `Create()`. Validation: `profileSketchId != pathSketchId`. Profile and path must be on different (usually perpendicular) planes.
- **Offset plane (`sketch_create_on_offset_plane`, package E start)**: `OpenSketchOnOffsetPlaneAsync` in `PartModeler.Sketch.cs`. `ksPart.NewEntity(o3d_planeOffset=14)` → `ksPlaneOffsetDefinition` (`SetPlane(basePlane)` + `offset` mm + `direction`) → `Create()` → sketch on that plane. Used to place sketches at arbitrary heights — enables `loft` with parallel sections. `entity.Create()` result is checked (reliability fix applied to all `CreateSketchOn*` paths).
- **Loft operation (`loft`, package B)**: `ksBaseLoftDefinition` via `ksPart.NewEntity(o3d_baseLoft=30)`. Params: `sketchIds[]` (≥2 closed profile sketches on different parallel planes). `Sketchs().Add(each sketch)` → `SetLoftParam(closed=false, false, true)` → `SetThinParam(false)` → `Create()`. Requires parallel section sketches at different heights — use `sketch_create_on_offset_plane` for the non-base sections.
- **Patterns & mirror (package C)**: `linear_pattern` — `ksMeshCopyDefinition` via `ksPart.NewEntity(o3d_meshCopy=35)`; `SetAxis1(axis)` + `SetCopyParamAlongAxis(true,0,count,step,false)` + `count2=1` (disables 2nd direction → 1D linear); features added via `OperationArray()` (no Get). `circular_pattern` — `ksCircularCopyDefinition` via `NewEntity(o3d_circularCopy=36)`; `SetAxis(axis)`; properties set directly: `count1=1` (radial off), `count2=count` (ring), `step2=angle°` between neighbours, `factor2=false`, `inverce=reverse`; `GetOperationArray().Add(feature)`. `mirror_operation` — `ksMirrorCopyDefinition` via `NewEntity(o3d_mirrorOperation=48)`; `SetPlane(basePlane)` + `GetOperationArray().Add(feature)`. `mirror_body` — `ksMirrorCopyAllDefinition` via `NewEntity(o3d_mirrorAllOperation=49)`; `SetPlane(basePlane)`; `ChooseBodies()` does NOT cast to `ksChooseBodies` (returns null) and is not needed — `o3d_mirrorAllOperation` mirrors all bodies keeping the original (volume doubles). Source features retrieved by id from `_features` registry via new private `RequireFeature` helper (analogous to `RequireSketch`). New `src/Kompas.Mcp.Core/Modeling/CoordinateAxis.cs` — enum `CoordinateAxis {X,Y,Z}` + `CoordinateAxes.ToObj3dType/Parse` (→ `o3d_axisOX/OY/OZ = 71/72/73`), analogous to `BasePlane.cs`. `SketchGeometry.RequireMin(int value, int min, string paramName)` — validator for `count>=2`. Empirical: `count` includes the original instance (count=3 → 3 bodies); `count2=1` disables 2nd direction for linear; `step2` is angle° between neighbours for circular.
- **Hole operations (`hole`, `hole_counterbore`, `hole_countersink`, `hole_conic`)**: all implemented via **API7** (not API5 — `ksHoleDefinition` absent in interop). Service `src/Kompas.Mcp.Core/Modeling/HoleService.cs`. `HoleCore` helper is parameterised with `ksHoleTypeEnum holeType` + `Action<IHole3D> configure` callback (configure sets `HoleParameters` **after** `HoleType` is assigned, because the type-specific sub-interface — e.g. `ISpotfacingHoleParameters` — is not accessible until the type is fixed). Base `hole` = `ksHTBase` + `configure=null`. `hole_counterbore`: `ksHTCounterbore` + configure sets `(ISpotfacingHoleParameters)hole.HoleParameters` (`SpotfacingDiameter`, `SpotfacingDepth`); validates `spotDiameter>diameter` and `depth>spotDepth` for blind. `hole_countersink`: `ksHTCountersinking` + configure sets `(ICountersinkHoleParameters)hole.HoleParameters` (`CountersinkType=ksCTDiameterAngle`, `CountersinkDiameter`, `CountersinkAngle`); validates `sinkDiameter>diameter`, `0<sinkAngle<180`. `hole_conic`: `ksHTConic` + configure sets `(IConicHoleParameters)hole.HoleParameters` (`ConicType=ksCNAngle`, `ConicAngle`); validates `0<conicAngle<180`. All four share common placement logic (`IHoleDisposal`+`Points3D`, direction selection by volume delta, orphan rollback). None enters the `_features` API5 registry → no id returned.
- **Draft operation (`draft`)**: implemented via **API5** `ksInclineDefinition` (operation name in API5 is "Incline", not "Draft" — do NOT search for "Draft" in API5 docs). `ksPart.NewEntity(o3d_incline=42)` → `GetDefinition() as ksInclineDefinition` → `FaceArray()` (add faces by index via `SelectFaceByIndex`, range-checked before mutation) → `SetPlane(basePlane)` → `angle` (degrees) → `direction` → `Create()` → register in `_features`. Empirical: `direction=false`=expanding (outward, adds material), `direction=true`=tapering (inward) — **opposite to the SDK docs** → mapping in code: `def.direction = !outward`. Neutral plane set via `SetPlane(base coordinate plane)`. Angle validation: `RequireDraftAngle(0<angle<90, double.IsFinite)`. Returns feature id (registered in `_features` → patterns/mirror from package C apply). Note: `o3d_DraftFromEdges=644` / `IDraftFromEdges` is a different "draft from edge baseline" operation — not used here.
- **Assembly class (`assembly_add_component`, `AssemblyService`, `AssemblyTools`, namespace `Kompas.Mcp.Core.Assemblies`)**: first tool that *writes* into an assembly (previously assemblies were read-only via `list_components`). Workflow (API7): `IParts7.AddFromFile(path, ExternalFile=true, Redraw=true)` → `IPart7` → `part.Placement` (`IPlacement3D`) → `SetOrigin(x,y,z)` → `part.UpdatePlacement(true)` → `top.RebuildModel(true)`. Empirical: `UpdatePlacement` returns FALSE for a manually-positioned component (no mates) — this is NOT an error; `SetOrigin` applies the position, `RebuildModel(true)` makes it visible. Fixed (pinned-by-KOMPAS) first component moves correctly via `SetOrigin+RebuildModel` without unfixing. `RequireActiveAssembly` validates `doc.DocumentType == ksDocumentAssembly` BEFORE accessing `TopPart` (a part doc is also `IKompasDocument3D`). Rollback on failure: `RollbackInsertion` removes components beyond `beforeCount` via `IFeature7.Delete + RebuildModel`. Source file must be saved to disk (`document_save_as`) before insertion. Returns `AddedComponent { Index, Name }` (record in `Core/Assemblies/AddedComponent.cs`). Validation in `AssemblyValidation.cs`: `NormalizeComponentPath` (ensures .m3d/.a3d extension, normalises via `Path.GetFullPath`), `RequireFinitePosition`. DI: `AddSingleton<AssemblyService>()` in `Program.cs`.
- **Richer sketch primitives (package A, ksDocument2D API5 wrappers)**: `ksArcBy3Points` (3-point arc), `ksArcByAngle` (centre/radius/start-end angles in degrees, counterClockwise flag), `ksEllipse` via `ksEllipseParam` — struct obtained via `KompasObject.GetParamStruct(ko_EllipseParam=22)`; **property names are `A`/`B` (uppercase) in the interop**; `ksRegularPolygon` via `ksRegularPolygonParam` (`ko_RegularPolygonParam=92`) — `describe = !inscribed`; NURBS spline via `ksNurbs(order=4)` + `ksNurbsPoint` loop + `ksEndObj`; `ksPoint`. Param structs are released after use. `PartModeler` split into partial classes: `PartModeler.cs` (registry/helpers/NewParam<T>/reset), `PartModeler.Sketch.cs` (all 2D primitives), `PartModeler.Features.cs` (extrude/revolve/fillet/chamfer). Static `SketchGeometry` class (`Core/Modeling`) holds enum mappings (`ArcDirection`, `PolygonDescribe`) and validators (`RequirePositive`, `RequireVertexCount`, `RequirePoints`). Polyline/spline point lists use `record SketchPoint(X, Y)` with JSON names `x`/`y`.

## КОМПАС-3D API architecture (the critical context)

КОМПАС-3D is automated via a **COM Automation API**, Windows-only. КОМПАС-3D **must be installed and running/launchable** on the same machine — the MCP server is a COM client, not a standalone CAD engine. There are **two coexisting API generations**:

| | Entry point | Namespace (C#) | Style | Use when |
|---|---|---|---|---|
| **API5** (legacy) | `KompasObject` | `Kompas6API5` | procedural, flat | older features, 2D primitives, bootstrapping |
| **API7** (modern, preferred) | `IApplication` / `_Application` | `KompasAPI7` | OOP, interface-based | everything new — documents, 3D, parameters |

Constants live in separate libraries: `Kompas6Constants`, `Kompas6Constants3D` (C#), or `ksConstants.h` / `ksConstants3D.h` (C++).

### Connection pattern (verified from `Samples/CSharp.zip`)

1. Get the КОМПАС root object by COM ProgID. **Verified on this machine (v24 Home):**
   `KOMPAS.Application.7` and `KOMPAS.Application.5` are registered; `KOMPASLT.*` is **absent** —
   the Home edition uses the regular (non-LT) ProgIDs. Resolution order:
   - `KOMPAS.Application.7` — direct API7 `IApplication` (preferred)
   - `KOMPAS.Application.5` — API5 `KompasObject`, then `ksGetApplication7()`
   - `KOMPASLT.Application.5` — fallback for other installations
   - New instance: `Activator.CreateInstance(Type.GetTypeFromProgID(progId))`
   - Attach to a running instance: `Marshal.GetActiveObject(progId)`
2. If you entered via API5, obtain the modern application: `IApplication appl = (IApplication)kompas.ksGetApplication7();` (via `KOMPAS.Application.7` you already hold `IApplication`).
3. Set `appl.Visible = true` to show the КОМПАС window; drive documents via API7 interfaces (`IKompasDocument2D`, `IKompasDocument3D`, …).

> The SDK C# samples are mostly **КОМПАС plugin libraries** (DLLs loaded *into* КОМПАС as ActiveX, entry methods like `ExternalRunCommand`/`ExternalMenuItem`, registered via `[ComRegisterFunction]`). For an MCP server we want the **opposite direction**: a standalone *external automation client* that connects out-of-process via the ProgID pattern above. Read the samples for API usage, not for the plugin packaging/registration boilerplate.

## SDK layout (read-only reference, not part of this repo)

Under `C:\Program Files\ASCON\KOMPAS-3D v24 Home\SDK`:
- `lib\*.tlb` — COM type libraries to reference / generate interop from: `kAPI5.tlb`, `kAPI7.tlb`, `ksConstants.tlb`, `ksConstants3D.tlb`, `kAPI2D5COM.tlb`, `kAPI3D5COM.tlb`.
- `lib64\` — 64-bit import libs (`kAPI7.lib`, `kAPI5.lib`, …) and `.a` for C++/Builder.
- `Include\` — C++/Pascal headers (`Ks_TLB.h`, `kAPI2D5COM.h`, `LDefin2D.pas`, …).
- `KsAPI\` — the **KsAPI** (Qt/C++ cross-platform flavour): `Include\KsAPI.h`, `ksConstants*.h`, `Lib64\ksAPI.lib`, plus `Help\С чего начать.pdf` and a Linux/Debian 12 build guide.
- `Samples\` — zipped examples per language: `CSharp.zip`, `C++.zip`, `Pascal.zip`, `Basic.zip`. Inside `CSharp.zip`, the `Step1`…`Step12` and `Step2_API7_2D` / `Step2_API7_3D` projects are the progressive tutorial; `Gayka`, `SlideWrk`, `EventsAuto` are larger feature demos.
- `Help\KOMPAS_SDK_ru-RU.zip` and `KsAPI\Help\KsAPI_Help.zip` — offline copy of the docs.

To inspect a sample without unpacking the whole archive: `unzip -p "<path>\Samples\CSharp.zip" "Automation/Step2_API7_3D/Step2_API7_3D.cs"`. Note the `.cs` sample sources are **Windows-1251 encoded** (Cyrillic comments appear garbled in UTF-8 tools).

## Conventions / gotchas

- **Windows-only & 64-bit**: target x64 to match the installed КОМПАС; mixing bitness breaks COM activation. КОМПАС v24 Home is the installed edition — some full-edition API features may be unavailable.
- **Encoding**: SDK source samples are CP1251. New project files should be UTF-8.
- **COM lifetime**: release COM objects (`Marshal.ReleaseComObject`) / scope them; a leaked reference keeps the КОМПАС process alive.
- **API choice**: prefer API7 for new tool implementations; drop to API5 only for things API7 doesn't expose.