# 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, dispatch the **`kompas-sdk-research`** subagent (Haiku) 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

**Status:** v1 + v2 + STEP/assembly + direct B-rep edit + structural inspection + 2D drawings — 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**. **83 MCP tools, 331 tests green (201 unit + 130 integration).**

Where to look (single source of truth — do **not** duplicate these lists here):
- **Full tool catalog** (by group, all 83) → [`README.md`](README.md) §«Инструменты».
- **Roadmap / what's already done** → [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) §10.
- **Backlog / what's left** → [`docs/TODO.md`](docs/TODO.md) (canonical; top of «2D-ЧЕРТЁЖ» = next priority. Associative diametral/radial→circle binding (`associate` flag), sheet format (`drawing_set_sheet_format`), leaders (`drawing_add_leader`) done — next: bases, tolerances, arc/angular/rough binding; plus extra mate types, package E continuation).
- **Design decisions / caveats** → [`docs/OPEN_QUESTIONS.md`](docs/OPEN_QUESTIONS.md). Known caveat («Ревью v2»): boss/cut direction on a selected face depends on face-normal orientation — `forward` may need flipping; the agent picks via snapshot or `describe_face` normal.
- **Verified COM call-chains & gotchas** → «Key implementation facts» below + memory files (`kompas-*-api*.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. A separate skill **`.claude/skills/kompas-fdm-design/`** is a DFM methodology layer for FDM/FFF 3D-printing (overhang rules, wall thickness, teardrop holes, fits/clearances, orientation for strength, elephant foot, bosses/inserts/snap-fits) with a lightweight geometry audit using existing inspection tools; it works on top of `kompas-3d` (the build layer) and exports via `export_step` — no slicer integration.

**Delegation subagents** (`.claude/agents/`, dispatched via the `Agent` tool to keep heavy work off Opus's context — system prompt lives in the agent definition, so pass only the variable part as the prompt):
- **`kompas-sdk-research`** (model: **Haiku**, read-only — `Glob`/`Grep`/`Read`): finds an interface/method/enum/constant signature in the `docs/Kompas3D_SDK/` MD knowledge base and returns a compressed summary. Dispatch it for any non-trivial SDK lookup instead of grepping the help yourself; a wrong answer is cheap — Opus re-verifies against `libs/kompas-interop/*.dll` by reflection.
- **`docs-maintainer`** (model: **Sonnet**, `Read`/`Edit`/`Write`/`Glob`/`Grep`): syncs `README.md`/`CLAUDE.md`/`docs/ARCHITECTURE.md`/`docs/OPEN_QUESTIONS.md`/`docs/presentation.html` with code changes from a change summary you provide. Dispatch it for doc updates instead of editing docs by hand. (Both were skills before — converted to native subagents; the model split reflects task type: bounded retrieval → Haiku, judgement-heavy editing → Sonnet.)

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**: API5 (`KOMPAS.Application.5` → `KompasObject`) then `ksGetApplication7()` → `IApplication`; the API5 root is needed for `ksPart` 3D-building and `ksDocument3D` snapshots. API7 is used for app/documents, holes, assemblies, drawings, direct B-rep edit.
- **3D via API5 `ksPart`**: `NewEntity(o3d_*)` + matching definition; always check `entity.Create()` return. Entity codes: `o3d_sketch`/`o3d_bossExtrusion`/`o3d_cutExtrusion`/`o3d_bossRotated`/`o3d_fillet`/`o3d_chamfer`, `o3d_shellOperation=43`, `o3d_ribOperation=44`, `o3d_baseEvolution=45` (sweep), `o3d_baseLoft=30`, `o3d_planeOffset=14`, `o3d_meshCopy=35` (linear pattern), `o3d_circularCopy=36`, `o3d_mirrorOperation=48`, `o3d_mirrorAllOperation=49`, `o3d_incline=42` (draft), axes `o3d_axisOX/OY/OZ=71/72/73`. Definitions: `ksBossExtrusionDefinition`/`ksCutExtrusionDefinition`/`ksBossRotatedDefinition`/`ksFilletDefinition`/`ksChamferDefinition`/`ksShellDefinition`/`ksRibDefinition`/`ksBaseEvolutionDefinition`/`ksBaseLoftDefinition`/`ksPlaneOffsetDefinition`/`ksMeshCopyDefinition`/`ksCircularCopyDefinition`/`ksMirrorCopyDefinition`/`ksMirrorCopyAllDefinition`/`ksInclineDefinition`. Cut-through holes use `dtBoth` + `etThroughAll`.
- **Face/edge selection**: `ksPart.EntityCollection(o3d_face|o3d_edge)` → `SelectByPoint(x,y,z)` (world mm) → `GetByIndex(0)`; or by stable index from `list_faces`/`list_edges` (helpers `SelectFaceByIndex`/`SelectEdgeByIndex`, range-checked before mutation; by-index more reliable than by-point). Classify: `ksFaceDefinition.IsPlanar/IsCylinder/…` + `GetArea(ST_MIX_MM)`; `ksEdgeDefinition.IsLineSeg/IsCircle/IsArc/…` + `GetLength()`. Sketch axis = line with system style **3** (осевая).
- **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** (structural «passport» — bbox + МЦХ + bodies + topology + feature tree + variables, no image token cost).
- Logs go to **stderr** (stdout is the MCP channel). Integration tests reuse one КОМПАС via `KompasFixture`; artifacts land in gitignored `.scratch/`. All integration test classes inherit `IntegrationTestBase` (`IAsyncLifetime`) → `DocumentService.CloseAllAsync` after each test (prevents tab accumulation).
- **Feature tree API**: 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()` + the matching definition (`ksBossExtrusionDefinition.GetSideParam`, `ksFilletDefinition.radius`, `ksChamferDefinition.GetChamferParam`, …). Node names ("Элемент выдавливания:1") are localized by КОМПАС. Features registered by id in `_features` support patterns/mirror; helpers `RequireSketch`/`RequireFeature`.
- **Variables (API5)**: create/read via `ksPart.GetFeature().VariableCollection` (property on root ksFeature) — **NOT** `ksPart.VariableCollection()` (returns external-only). Expression is the leading field; value is derived. Apply via `ksPart.RebuildModel()` (check return); after rebuild the RCW variable is stale → re-read via a fresh collection (`ReadValueFresh`). Dependents recalculate automatically; deletion fails if dependents exist (`RemoveVariable` returns FALSE). **Geometry limitation:** variables drive geometry only in a parametric model (sketch dims linked to variable names); our sketches use literal coords → `set_variable` stores/computes the value but does NOT move geometry. Parametric sketches **unavailable via COM** (`ksCDimWithVariable` not constructible from external automation — see `docs/superpowers/specs/2026-05-27-parametric-sketch-findings.md`; do not retry without new info).
- **Topology / measure API**: `ksFaceDefinition.EdgeCollection` / `GetCylinderParam` / `GetSurface().GetNormal` + `normalOrientation`; `ksEdgeDefinition.GetAdjacentFace(bool)` / `GetVertex(bool)` → `ksVertexDefinition.GetPoint`; bodies via `ksPart.BodyCollection()` → `ksBody` (`IsSolid` / `FaceCollection`); measurements via `ksPart.GetMeasurer()` → `ksMeasurer` (`SetObject1/2`, `unit=ST_MIX_MM`, `Calc`, `distance`/`MinDistance`/`angle` in degrees / `IsAngleValid`).
- **"STEP import without history"** detected structurally: `bodyCount > 0 && no formative features && features.Count <= bodyCount+1` (only origin + body). STEP with edits ("Смещённая плоскость" / "Разрезать" / "Переместить грани" / "Булева операция") already has history.
- **STEP import/export COM pattern** (verified): `IApplication.get_Converter((object)(int)ksConverterFromSTEP=-3)` (pass format code, not DLL path) → `IConverter.ConverterParameters(cmd)` → `IAdditionConvertParameters.Format=ksConverterFromSTEP` → `IKompasDocument3D1.ConvertFromAdditionFormat(path, prm)`. Export: `ConvertToAdditionFormat` (format codes AP203/AP214/AP242). Param co-classes (AdditionConvertParameters etc.) are NOT CoCreatable — only via converter factories. Assembly traversal (`list_components`): `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): API7 face via `IPart7.FindObjectsByPoint(x,y,z,true)` → cast to `KompasAPI7.IFace`; containers via runtime COM-QI `(ISurfaceContainer)part`, `(IModelContainer)part`; `FaceMover` (SetFaces + Offset + Direction + Update) moves the face. distance>0 = outward (add material), <0 = inward. Works on parametric and imported B-rep. Full split-reposition workflow (SplitSolids/BodyRepositions) is driveable; only partly exposed as tools (`split_solid_by_plane`, `move_body`, `boolean_union`).
- **Forming ops (API5 definitions)**:
  - `shell` (`ksShellDefinition`, o3d_shellOperation=43): `thickness` + `thinType` (bool, `= !outward`) + `FaceArray()` (open faces ≥1 by index). Transient RCWs intentionally not released (consistent with Fillet/Chamfer).
  - `rib` (`ksRibDefinition`, =44): `SetSketch(sketch)` → `index=0`, `angle`, `side` (`left|right|up|down` → 0/1/2/3 via `SketchGeometry.RibSide()`); `SetThinParam(dtBoth, t/2, t/2)` if symmetric, else `(dtNormal, t, 0)`. Empirical: the rib contour must float in the gap (not touch the body) — КОМПАС extends the web automatically.
  - `sweep` (`ksBaseEvolutionDefinition`, =45): `SetSketch(profile)` → `PathPartArray().Add(path)` → `sketchShiftType=0` → `SetThinParam(false)` → `Create()`. Profile & path on different (usually ⟂) planes; `profileSketchId != pathSketchId`.
  - `loft` (`ksBaseLoftDefinition`, =30): `Sketchs().Add(each)` → `SetLoftParam(false,false,true)` → `SetThinParam(false)`. ≥2 closed sections on parallel planes — use `sketch_create_on_offset_plane` for non-base sections.
  - offset plane (`sketch_create_on_offset_plane`, `ksPlaneOffsetDefinition`, o3d_planeOffset=14): `SetPlane(base)` + `offset` mm + `direction` → `Create()` → sketch on it (`OpenSketchOnOffsetPlaneAsync`).
  - `draft` (`ksInclineDefinition`, o3d_incline=42 — API5 calls the op **Incline**, NOT Draft): `FaceArray()` (by index) + `SetPlane(neutral base plane)` + `angle` (degrees) + `direction`. **Empirical, opposite to SDK docs:** `direction=false`=expanding/outward (adds material), `true`=tapering/inward → code maps `def.direction = !outward`. Validate `0<angle<90`. (`o3d_DraftFromEdges=644` / `IDraftFromEdges` is a different op — not used.)
- **Patterns & mirror (API5)**: `linear_pattern` (`ksMeshCopyDefinition`, =35): `SetAxis1(axis)` + `SetCopyParamAlongAxis(true,0,count,step,false)` + `count2=1` (disables 2nd direction → 1D); features via `OperationArray()`. `circular_pattern` (`ksCircularCopyDefinition`, =36): `SetAxis(axis)`; `count1=1` (radial off), `count2=count` (ring), `step2=angle°` between neighbours, `factor2=false`, `inverce=reverse`; `GetOperationArray().Add(feature)`. `mirror_operation` (`ksMirrorCopyDefinition`, =48): `SetPlane(base)` + `GetOperationArray().Add(feature)`. `mirror_body` (`ksMirrorCopyAllDefinition`, =49): `SetPlane(base)`; `ChooseBodies()` casts to null in interop and is NOT needed — mirrors all bodies keeping the original (volume doubles). Empirical: `count` includes the original instance (count=3 → 3 instances). Axes: `CoordinateAxis{X,Y,Z}` → `o3d_axisOX/OY/OZ` (`Core/Modeling/CoordinateAxis.cs`, analogous to `BasePlane.cs`).
- **Hole ops (API7 only — `ksHoleDefinition` absent in API5 interop; `HoleService`)**: `HoleCore(ksHoleTypeEnum holeType, Action<IHole3D> configure)` — `configure` sets `HoleParameters` **after** `HoleType` is assigned (the type-specific sub-interface is inaccessible until the type is fixed). Placement shared: `IModelContainer`/`IHole3D`/`IHoleDisposal` + `Points3D`, direction chosen by volume delta, orphan rollback. None registered in `_features` → no id returned. `hole`=`ksHTBase`, configure=null. `hole_counterbore`=`ksHTCounterbore` + `(ISpotfacingHoleParameters)` (`SpotfacingDiameter`/`SpotfacingDepth`). `hole_countersink`=`ksHTCountersinking` + `(ICountersinkHoleParameters)` (`CountersinkType=ksCTDiameterAngle`, `CountersinkDiameter`/`Angle`). `hole_conic`=`ksHTConic` + `(IConicHoleParameters)` (`ConicType=ksCNAngle`, `ConicAngle`).
- **Assembly (API7, `AssemblyService`, namespace `Kompas.Mcp.Core.Assemblies`)**: `assembly_add_component` — `IParts7.AddFromFile(path, ExternalFile=true, Redraw=true)` → `IPart7.Placement` (`IPlacement3D`) → `SetOrigin(x,y,z)` (mm, assembly world CS) → `UpdatePlacement(true)` → `top.RebuildModel(true)`. **Empirical:** `UpdatePlacement` returns FALSE for a manually-positioned component (no mates) — NOT an error. Validate `DocumentType==ksDocumentAssembly` before touching `TopPart`; rollback via `IFeature7.Delete` + `RebuildModel`. `assembly_add_mate` — `top.MateConstraints` (`IMateConstraints3D`) → `Add(MateConstraintType)` → `BaseObject1/2` (faces via `top.FindObjectsByPoint(x,y,z,FirstLevel=false)`) → `ParamValue` (distance) → `Update()` → `RebuildModel(true)`; check `mate.Valid` (false → rollback `mate.Owner.Delete`). Types `coincidence`(mc_Coincidence=0) / `distance`(mc_Distance=5, value>0) verified live; `parallel`/`perpendicular`/`concentric`/`angle`/`tangency` — future.
- **Drawing (API7, `DrawingService`, namespace `Kompas.Mcp.Core.Drawings`)** — entry via `IKompasDocument2D`; requires an active drawing doc (`DocumentType==ksDocumentDrawing`). All coords are **view-local** (mm) unless noted. Model file must be saved before placing views.
  - `drawing_create_standard_views`: `doc2d.ViewsAndLayersManager.Views.AddStandartViews(path, "#Спереди", projTypes, x, y, scale, dx=20, dy=20)` where `projTypes=object[]{1,3,5}` (Front/Up/Left as SAFEARRAY VT_I4). Success: `created==3`; content check: sum of new views' `IView.ObjectCount` > 0 else rollback `IView.Delete`. Returns `ViewNumbers` (the `IView.Number` values — address views by these when placing annotations).
  - `drawing_fill_title_block`: `doc2d.LayoutSheets.ItemByNumber[1].Stamp` (`IStamp`) → `stamp.Text[columnId].Str = text` (indexed property; `IText.Str` overwrites, no Clear needed) → `stamp.Update()`. Fields→columns (`ksStampEnum`): Name=1, Designation=2, Material=3. Non-transactional (all cells → single `Update`).
  - **Dimensions go into `(ISymbols2DContainer)view`, NOT the sheet, and are NOT counted in `IView.ObjectCount`** (that counts geometry in `IDrawingContainer`) — verify placement via the container's `*.Count`. Common flow: `Add()` → set coords → `AutoNominalValue=true` → `Update()` → check `Valid` → read `((IDimensionText)dim).NominalValue`; rollback `dim.Delete()` on FALSE/invalid/zero. Leader/angle in **radians** (`DimensionAngles.ToRadians`). Free placement = set coords directly; **associative** (diametral/radial only) = set `BaseObject` to a projected circle → value read from geometry (see below).
    - linear (`ILineDimension`): `X1,Y1,X2,Y2` (extension pts) + `X3,Y3` (dim line) + `Orientation` (`DimensionOrientation{Horizontal,Vertical,Parallel}` → `ksLinDParallel=0`/`Horizontal=1`/`Vertical=2`; parallel needs no explicit Angle).
    - diametral (`IDiametralDimension`): `Xc,Yc,Radius` + `Angle`; `NominalValue` = 2·Radius.
    - radial (`IRadialDimension`): `Xc,Yc,Radius` + `Angle`, `DimensionType=true`; **`NominalValue` = Radius, NOT diameter** — contrary to SDK docs, confirmed by spike.
    - **associative** diametral/radial (`associate=true` flag): instead of coords, find a projected circle in `(IDrawingContainer)view.Circles` by center+radius key (`CircularObjectMatch.SelectMatchIndex`, tol 1 mm; throws on none/ambiguous; concentric disambiguated by radius), set `dim.BaseObject = circle` (`_Circle` implements `IDrawingObject`) → `NominalValue` read from geometry. `RequireViewContainers` gives both QIs; free path stays on `RequireSymbols2DContainer`. Arc/angular/rough binding — not yet (own spike needed; `ILineDimension` has no `BaseObject`).
    - angular (`IAngleDimension`, `AngleDimensions.Add(ksDrADimension=10)`): vertex `Xc,Yc` + side pts `X1,Y1`/`X2,Y2` + arc-position `X3,Y3` (positions the arc only, does NOT pick the angle); measured angle chosen by `DimensionType` = `AngleDimensionType{Min,Max,More}` (on rays 0°/45° → min=45°/max=135° supplement/more=315° reflex). `NominalValue` in degrees.
  - `drawing_add_rough` (`Roughs.Add()`/`IRough`: `BranchX0/Y0`, `Angle`) + `(IRoughParams)rough` QI: `SignType` = `RoughSignType{NoProcessing,DeleteMaterial,WithoutDeleteMaterial}`, value (Ra/Rz) = `RoughParamText.Str`.
  - `drawing_add_text` — **text lives in `IDrawingContainer`, NOT `ISymbols2DContainer`, and NOT in `IView.ObjectCount`**: `(IDrawingContainer)view.DrawingTexts.Add()`/`IDrawingText` (`X/Y/Angle`) + `(IText)dt.Str` = text; count via `DrawingTexts.Count`. Do NOT set `Height` (that's block height, not font).
  - `drawing_set_technical_requirements` — **document-level**: `(IDrawingDocument)doc.TechnicalDemand`/`ITechnicalDemand`: `td.Text.Str = text` → `td.Update()` (`IsCreated` False→True on first set; overwrites; `\n` multiline).
  - `DrawingAnnotationResult{Value(read-back), ViewNumber}` is the shared result for rough/text.
  - `drawing_add_leader` — `ISymbols2DContainer.Leaders.Add(ksDrLeader)` → `IBaseLeader`. **КРИТИЧЕСКИЙ ПОРЯДОК (спайк):** новая выноска имеет 0 ответвлений → `(IBranchs)bl.AddBranchByPoint(0,x,y)` (остриё) ДО `SetBranchTextPosition(textX,textY)`/`Update`, иначе КОМПАС падает `RPC_E_SERVERFAULT`. Текст — `(ILeader)bl.TextOnShelf.Str`; `ShelfDirection` (enum `ShelfDirection{Auto,Right,Left,Up,Down}`, Auto = не задавать). `AddBranchByPoint`/`SetBranchTextPosition` возвращают bool — проверять. Результат — общий `DrawingAnnotationResult`.
  - `drawing_set_sheet_format` — `RequireLayoutSheet(n).Format` (`ISheetFormat`): `Format`=`ksDocumentFormatEnum` (`PaperFormat{A0..A5,User}`+`PaperFormats.Parse/ToKompas/FromKompas`), standard → set `VerticalOrientation=!landscape` (W/H auto-computed from enum+orientation, e.g. A3 landscape→420×297); **User → set `FormatWidth/Height` only, КОМПАС auto-derives `VerticalOrientation` from W/H and ignores the flag, never swaps W/H (spike)** → `sheet.Update()`. New drawing defaults A4 portrait. `ValidateFormatDimensions`: User needs W/H>0, standard forbids W/H (must be 0).
- **Richer sketch primitives (API5 `ksDocument2D` wrappers)**: `ksArcBy3Points`; `ksArcByAngle` (centre/radius/start-end angles in degrees + counterClockwise flag); `ksEllipse` via `ksEllipseParam` (`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 released after use. `PartModeler` is partial: `.cs` (registry/helpers/`NewParam<T>`/reset), `.Sketch.cs` (2D primitives), `.Features.cs` (extrude/revolve/fillet/chamfer). Static `SketchGeometry` (`Core/Modeling`) holds enum maps + validators (`RequirePositive`, `RequireVertexCount`, `RequirePoints`, `RequireMin`). Point lists use `record SketchPoint(X, Y)` (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.