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+# STEP Processor Skill — Project Context
+### CoWork Memory Document · MPMedia Engineering
+**Updated:** June 2026 · **Status:** ✅ FULLY TESTED — Smoke-tested on 3 Chinese-sourced STEP files
+
+---
+
+## What This Is
+
+A Python-based CAD processing skill for MPMedia's engineering workflow. Reads STEP/STP files (display enclosures, mounting kits, hardware assemblies) and automates: thumbnail generation, parts BOM export (MPM-branded Excel), Chinese-to-English label translation, STEP file rewriting with English labels, geometric queries, and external dimensional diagram creation.
+
+Lives as a CoWork skill folder with a `SKILL.md`. Callable from Claude or directly from CLI.
+
+---
+
+## Current Working State (as of June 2026)
+
+### Smoke Test Results
+All three production STEP files tested end-to-end:
+
+| File | Faces | Parts (STEP parser) | Translations | _EN.step |
+|------|-------|---------------------|--------------|----------|
+| MR16s Gen1 | 5,655 | 28 | 16/16 | ✅ All English |
+| MR27s Gen1 | 6,732 | 31 | 18/18 | ✅ All English |
+| MR28uws Gen1 | 5,891 | 31 | 20/20 | ✅ All English |
+
+### What Works
+- **STEP loading**: build123d primary, FreeCAD headless fallback
+- **GBK encoding**: Chinese CAD files fully decoded (see Architecture Notes below)
+- **BOM extraction**: STEP text parser as primary source — correctly reads Chinese names
+- **Translation**: Claude API (`claude-haiku-4-5-20251001`) — batched, single call per file
+- **STEP rewriter**: `_EN.step` produced with English labels in both PRODUCT name fields
+- **BOM export**: MPM-branded `.xlsx` (Montserrat/Open Sans, Dark Shade header, Gold border, alternating rows)
+- **Thumbnails**: 6 PNG views via pyrender (front, rear, left, right, iso_left, iso_right)
+
+### BOM Output Format
+Columns in Excel output order:
+
+| Column | Header in Excel |
+|--------|----------------|
+| part_number | Part # |
+| part_description | Part Description |
+| quantity | Qty |
+| level | Level |
+| parent | Parent |
+| bbox_x_mm | X (mm) |
+| bbox_y_mm | Y (mm) |
+| bbox_z_mm | Z (mm) |
+| notes | Notes |
+| part_name_supplier | Supplier Part Name |
+
+`part_description` = translated English name (was `part_name_english` internally).
+`part_name_supplier` = original Chinese name from supplier file (last column, was `part_name_original`).
+
+---
+
+## Architecture Notes (Critical — Read Before Debugging)
+
+### GBK Encoding Fix
+STEP files from Chinese CAD tools (SolidWorks CN, etc.) embed raw GBK bytes in `PRODUCT` entity name strings. This caused two separate problems, each with a different fix:
+
+**Problem 1: BOM shows garbled Chinese (mojibake)**
+OpenCASCADE (OCC) / build123d's STEP reader applies an internal codec that maps each 2-byte GBK sequence to incorrect Unicode codepoints. This is NOT reversible via latin-1 → GBK round-trip because OCC's codec is not latin-1.
+
+Fix: Bypass OCC entirely for part name extraction. `bom.py` reads the raw STEP file text directly with encoding detection (UTF-8 → GBK → latin-1 fallback) and parses `PRODUCT` entities via regex. This is the primary name source; OCC assembly walk is fallback only.
+
+**Problem 2: _EN.step still shows Chinese in CAD viewer**
+The rewriter (`rewriter.py`) was reading the file as UTF-8, turning GBK bytes into replacement chars (U+FFFD). Chinese names became `???` and never matched the translation map.
+
+Fix: `rewriter.py` uses the same encoding-detection reader as `bom.py`. File is read as GBK when UTF-8 produces replacement chars.
+
+**Problem 3: Only first PRODUCT name field was replaced**
+ISO 10303-21 `PRODUCT` entity format: `#N = PRODUCT('id', 'name', 'description', (#...))`. Both the first and second quoted strings carry the part name. CAD viewers (including OpenCASCADE CAD Assistant) display the second field.
+
+Fix: Updated `PRODUCT_PATTERN` regex to capture both fields with 5 groups. Replacement writes the translated name into both positions.
+
+### Translation API Model
+Current model: `claude-haiku-4-5-20251001`
+Previous value `claude-sonnet-4-20250514` was returning 404 — updated in `translator.py`.
+
+### BOM Excel Library
+`openpyxl` must be installed in the venv. The skill falls back to CSV silently if it's missing — don't rely on this fallback, install it explicitly.
+
+---
+
+## Prerequisites for a New macOS Computer
+
+### Hardware Requirements
+- Apple Silicon Mac (M1/M2/M3/M4) — all wheels are native arm64
+- **No Rosetta required**
+- macOS 13 Sequoia or later recommended
+
+### Software Stack
+```
+Python 3.10–3.12          (3.13 works but less tested; 3.9 too old)
+Homebrew                  (for cairo system libs)
+~/step-processor-env      (Python venv — all pip packages go here)
+```
+
+### Python Packages (pip install in venv)
+```bash
+pip install cadquery-ocp        # OCC kernel, native arm64, ~300MB
+pip install build123d           # STEP loader, primary
+pip install trimesh pyrender    # thumbnail rendering pipeline
+pip install Pillow numpy pandas # image and data processing
+pip install anthropic           # Claude API client
+pip install openpyxl            # Excel BOM output — REQUIRED
+pip install cairosvg            # SVG→PNG/PDF for diagrams (optional, diagrams only)
+```
+
+### System Libraries (Homebrew)
+```bash
+brew install cairo pango gdk-pixbuf libffi   # required for cairosvg
+```
+
+### FreeCAD Fallback (Optional)
+Only needed if build123d fails on a specific file.
+- Download official arm64 `FreeCAD.app` from https://github.com/FreeCAD/FreeCAD/releases/latest
+- Drag to `/Applications`, launch once so macOS approves it
+- Verify: `/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd --version`
+
+> **macOS 15 Sequoia:** conda-forge FreeCAD is killed by Gatekeeper. Use the official signed `.app` only.
+
+### Anthropic API Key
+The key must be available in the environment where the processor runs.
+
+**For interactive terminal use:**
+```bash
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY"' >> ~/.zshrc
+source ~/.zshrc
+```
+
+**For Desktop Commander / CoWork (non-interactive shell):**
+```bash
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY"' >> ~/.zshenv
+```
+`~/.zshrc` is only sourced in interactive shells. Desktop Commander spawns non-interactive zsh — it reads `~/.zshenv` instead. **Both files should have the key.**
+
+---
+
+## Setup — Fast Path (New Mac)
+
+```bash
+# 1. Create venv
+python3 -m venv ~/step-processor-env
+source ~/step-processor-env/bin/activate
+
+# 2. Install all packages
+pip install --upgrade pip
+pip install cadquery-ocp build123d trimesh pyrender Pillow numpy pandas anthropic openpyxl
+
+# 3. System libs for diagram export
+brew install cairo pango gdk-pixbuf libffi
+pip install cairosvg
+
+# 4. API key (do BOTH for interactive + Desktop Commander)
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY"' >> ~/.zshrc
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY"' >> ~/.zshenv
+source ~/.zshrc
+
+# 5. Verify
+python -c "import build123d, openpyxl, anthropic, trimesh; print('ALL OK')"
+
+# 6. Test run
+cd /path/to/step-skill-folder
+python step_processor.py yourfile.step --no-thumbnails --verbose
+```
+
+Expected output for Chinese STEP file:
+```
+INFO  [build123d] Loaded: yourfile.step | NNNN faces | NN parts
+INFO  STEP text parser found NN unique part names
+INFO  BOM extracted: NN parts
+INFO  BOM XLSX → yourfile_bom.xlsx
+INFO  Chinese part names detected — auto-translating
+INFO  API returned NN translations
+INFO  _EN.step written: yourfile_EN.step (NN labels replaced)
+```
+
+---
+
+## File Structure
+
+```
+STEP File Skill/
+  step_processor.py           ← CLI entry point
+  modules/
+    __init__.py
+    loader.py                 ← build123d load + GBK mojibake helper
+    bom.py                    ← STEP text parser + MPM-branded xlsx output
+    renderer.py               ← 6-view PNG thumbnails (pyrender)
+    translator.py             ← Claude API translation (claude-haiku-4-5-20251001)
+    rewriter.py               ← _EN.step writer (GBK-aware, both PRODUCT fields)
+    query_engine.py           ← Natural language geometry queries + REPL
+    external_diagram.py       ← Dimensional diagram generator
+  schemas/
+    external_diagram_schema.json
+    parts_mapping_schema.json
+  templates/
+    datablock_template.md
+  SKILL.md                    ← Claude skill instructions
+  INSTALL.md                  ← Library setup details
+  SETUP_CHECKLIST.md          ← Step-by-step setup + progressive tests
+  COWORK_CONTEXT.md           ← This file
+```
+
+---
+
+## CLI Reference
+
+```bash
+# Activate environment first (every new terminal session)
+source ~/step-processor-env/bin/activate
+cd /path/to/STEP\ File\ Skill
+
+# Default: thumbnails + BOM + auto-translate if Chinese detected
+python step_processor.py enclosure.step
+
+# BOM only (no thumbnails, no translate)
+python step_processor.py enclosure.step --no-thumbnails --no-translate
+
+# Force translation even if auto-detect is off
+python step_processor.py enclosure.step --translate
+
+# Single geometric query and exit
+python step_processor.py enclosure.step --query "list all mounting holes"
+
+# Interactive geometry REPL
+python step_processor.py enclosure.step --repl
+
+# External dimensional diagram
+python step_processor.py enclosure.step --diagram
+python step_processor.py enclosure.step --diagram --diagram-pdf
+python step_processor.py enclosure.step --diagram --diagram-mode enclosure_plus_mounting
+
+# Verbose (shows backend selection, timing, fallback notices)
+python step_processor.py enclosure.step --verbose
+```
+
+---
+
+## Known Issues and Pending Work
+
+### BOM bbox Enrichment (partial)
+Rows beyond the first only get 5.0 × 5.0 × 5.0mm placeholder bounding boxes. The OCC child enumeration only retrieves the top-level shape's children correctly. Root cause: build123d's `.children` on compound shapes doesn't walk sub-assemblies for bbox. Fix: map part names from STEP text parser back to OCC children by label — non-trivial due to OCC label mangling on CJK files.
+
+### Mounting Hole Filter — Minimum Diameter
+The query engine's mounting hole detector returns PCB vias (0.4mm diameter) alongside actual mounting holes. Needs a minimum diameter threshold (recommend 2.0mm floor). Pending update to `query_engine.py`.
+
+### Phase 7 Full Test
+The SETUP_CHECKLIST.md Phase 7 tests have been validated for Tests 1, 2, 4 (BOM, translation, rewrite). Tests 3 (thumbnails), 5 (REPL), 6/7 (diagrams) not yet re-run post GBK fix. Thumbnails were verified in an earlier session; diagram code is scaffolded but output quality against production files not fully validated.
+
+### Conda freecad_env Cleanup
+From a prior session: `conda activate freecad_env && conda deactivate && conda env remove -n freecad_env`. The conda FreeCAD approach was abandoned in favor of the signed FreeCAD.app. This env is dead weight on the local machine.
+
+---
+
+## Library Stack Decision Log
+
+| Decision | Choice | Reason |
+|----------|--------|--------|
+| CAD kernel | build123d | Native arm64 arm; clean API; same OCC as existing viewer |
+| Fallback CAD | FreeCAD.app (signed) | conda-forge builds killed by Gatekeeper on Sequoia |
+| Translation | Claude Haiku API | Batched, manufacturing-context prompted, flags ambiguity |
+| Diagrams | SVG-first + cairosvg | No GUI dependency; vector quality; cairosvg handles PNG/PDF |
+| Excel | openpyxl | MPM brand formatting, column control, frozen panes |
+| Rejected | pythonocc | Rosetta/x64 conda dependency — non-starter on Apple Silicon |
+| Rejected | conda-forge FreeCAD | Unsigned binaries killed by Gatekeeper on macOS 15 |
+
+---
+
+## Planned Integration Points
+
+- **Odoo V18 MRP**: Model number from `meta.json` triggers lookup of weight, BOM cost, stock status
+- **CoWork product docs**: `meta.json` feeds product data cards; diagram PNGs embed in Knowledge Base articles
+- **RDMC** (`rdmc.messagepoint.tv`): Thumbnail PNGs for display inventory visual reference
+- **OnSign.tv**: Enclosure dimensions for content sizing reference
@@ -0,0 +1,133 @@
+# INSTALL.md — STEP Processor Setup (Apple Silicon / macOS arm64)
+
+No Rosetta. No x64 sub-environments. Both libraries run natively.
+
+---
+
+## 1. build123d (Primary — native arm64, pip-based)
+
+build123d depends on `cadquery-ocp`, which ships native arm64 wheels
+via GitHub Releases (not yet on PyPI, but stable).
+
+### Step 1 — Install the arm64 OCP wheel
+
+Go to: https://github.com/CadQuery/OCP/releases
+
+Download the wheel matching your Python version, e.g.:
+  `cadquery_ocp-7.x.x-cp311-cp311-macosx_12_0_arm64.whl`
+
+Install it:
+```bash
+pip install /path/to/cadquery_ocp-*.whl
+```
+
+### Step 2 — Install build123d and rendering stack
+
+```bash
+pip install build123d
+pip install trimesh pyrender Pillow numpy pandas anthropic
+```
+
+### Step 3 — Set API key
+
+```bash
+export ANTHROPIC_API_KEY=sk-ant-...
+# Add to ~/.zshrc to persist
+```
+
+### Step 4 — Verify
+
+```bash
+python -c "import build123d; print('build123d OK')"
+python -c "import trimesh; print('trimesh OK')"
+python -c "import pyrender; print('pyrender OK')"
+```
+
+---
+
+## 2. FreeCAD Headless (Fallback — native arm64 via conda-forge)
+
+FreeCAD has been available as a native macOS-arm64 conda-forge package
+since late 2024. Install it in its own conda environment to avoid
+dependency conflicts with build123d.
+
+### Step 1 — Install Miniforge (arm64) if not already present
+
+Download from: https://github.com/conda-forge/miniforge/releases
+Select: `Miniforge3-MacOSX-arm64.sh`
+
+```bash
+bash Miniforge3-MacOSX-arm64.sh
+```
+
+### Step 2 — Create FreeCAD environment
+
+```bash
+conda create -n freecad_env python=3.11
+conda activate freecad_env
+conda install -c conda-forge freecad
+```
+
+### Step 3 — Verify headless operation
+
+```bash
+FreeCADCmd --version
+# or
+python -c "import FreeCAD; import Part; print('FreeCAD headless OK')"
+```
+
+**Important:** Never import `FreeCADGui` in headless scripts — it will crash.
+
+### Step 4 — Make FreeCAD importable from your build123d environment
+
+Add the FreeCAD conda env's site-packages to your PATH, or run scripts
+via the conda freecad_env directly:
+```bash
+conda run -n freecad_env python step_processor.py myfile.step
+```
+
+---
+
+## Quick Test
+
+Once either library is installed:
+
+```bash
+# Test with a sample STEP file
+python step_processor.py sample.step --verbose
+
+# Test query REPL
+python step_processor.py sample.step --repl
+```
+
+---
+
+## Dependency Summary
+
+| Package       | Purpose                        | Required for        |
+|---------------|--------------------------------|---------------------|
+| build123d     | STEP loading + geometry        | Primary path        |
+| cadquery-ocp  | OCC kernel (arm64 wheel)       | build123d           |
+| trimesh       | Mesh handling for rendering    | PNG thumbnails      |
+| pyrender      | Offscreen rendering            | PNG thumbnails      |
+| Pillow        | PNG file writing               | PNG thumbnails      |
+| numpy         | Geometry math                  | Both paths          |
+| pandas        | BOM CSV output                 | BOM export          |
+| anthropic     | Claude API translation         | Translation         |
+| FreeCAD       | Fallback STEP loading          | Fallback path only  |
+
+---
+
+## 3. cairosvg (required for PNG and PDF export from diagrams)
+
+```bash
+pip install cairosvg
+
+# On macOS, may also need:
+brew install cairo pango gdk-pixbuf libffi
+```
+
+Verify:
+```bash
+python -c "import cairosvg; print('cairosvg OK')"
+```
@@ -0,0 +1,29 @@
+part_number,part_name_original,part_name_english,quantity,level,parent,bbox_x_mm,bbox_y_mm,bbox_z_mm,notes
+001,"15.6"" Rear Cover","15.6"" Rear Cover",1,0,,248.6,459.2,40.0,parsed from STEP text
+002,Remote Control + Light Sensor Board,Remote Control + Light Sensor Board,1,0,,242.3,392.9,6.0,parsed from STEP text
+003,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,215.9,363.8,8.8,parsed from STEP text
+004,"15.6"" Tempered Glass 3+3 Laminated","15.6"" Tempered Glass 3+3 Laminated",1,0,,241.2,451.8,21.5,parsed from STEP text
+005,M3x6 Countersunk Screw,M3x6 Countersunk Screw,1,0,,238.2,448.8,21.0,parsed from STEP text
+006,DZ-LP0632 Light Sensor Control Board,DZ-LP0632 Light Sensor Control Board,1,0,,130.5,10.0,20.0,parsed from STEP text
+007,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,2,0,,33.82,28.2,19.0,parsed from STEP text
+008,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,1,0,,48.37,103.79,16.25,parsed from STEP text
+009,TOSN-DY398P-EMC Sub-board,TOSN-DY398P-EMC Sub-board,1,0,,92.0,21.0,17.7,parsed from STEP text
+010,TOSN-AD120P12V10A-120W,TOSN-AD120P12V10A-120W,1,0,,33.0,73.0,14.7,parsed from STEP text
+011,2P Phoenix Terminal,2P Phoenix Terminal,1,0,,33.0,73.0,14.7,parsed from STEP text
+012,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,30.0,120.0,11.6,parsed from STEP text
+013,G156HAN02.0--20221031_G156HAN02.0_PSpec_DBEST,G156HAN02.0--20221031_G156HAN02.0_PSpec_DBEST,1,0,,5.0,5.0,5.0,parsed from STEP text
+014,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+015,Small Glass Lens,Small Glass Lens,1,0,,5.0,5.0,5.0,parsed from STEP text
+016,Board~a9jc.step,Board~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+017,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+018,"15.6"" Terminal Board","15.6"" Terminal Board",1,0,,5.0,5.0,5.0,parsed from STEP text
+019,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+020,Lower Aluminum Plate,Lower Aluminum Plate,1,0,,5.0,5.0,5.0,parsed from STEP text
+021,Upper Aluminum Plate,Upper Aluminum Plate,1,0,,5.0,5.0,5.0,parsed from STEP text
+022,BSCZ-TX3361,BSCZ-TX3361,1,0,,5.0,5.0,5.0,parsed from STEP text
+023,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+024,"15.6"" Mounting Plate","15.6"" Mounting Plate",1,0,,5.0,5.0,5.0,parsed from STEP text
+025,"15.6"" Light Sensor Bracket","15.6"" Light Sensor Bracket",1,0,,5.0,5.0,5.0,parsed from STEP text
+026,"15.6"" High-Speed Rail Display Assembly Drawing","15.6"" High-Speed Rail Display Assembly Drawing",1,0,,5.0,5.0,5.0,parsed from STEP text
+027,"15.6"" Aluminum Frame","15.6"" Aluminum Frame",1,0,,5.0,5.0,5.0,parsed from STEP text
+028,8Ω 5W Speaker (Model 3070),8Ω 5W Speaker (Model 3070),1,0,,5.0,5.0,5.0,parsed from STEP text
@@ -0,0 +1,29 @@
+part_number,part_name_original,part_name_english,quantity,level,parent,bbox_x_mm,bbox_y_mm,bbox_z_mm,notes
+001,15.6寸后盖,"15.6"" Rear Cover",1,0,,248.6,459.2,40.0,parsed from STEP text; machine-translated
+002,遥控+光感板,Remote Control + Light Sensor Board,1,0,,242.3,392.9,6.0,parsed from STEP text; machine-translated
+003,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,215.9,363.8,8.8,parsed from STEP text
+004,15.6寸钢化玻璃3+3夹胶,"15.6"" Tempered Glass 3+3 Laminated",1,0,,241.2,451.8,21.5,parsed from STEP text; machine-translated
+005,M3x6沉头螺丝,M3x6 Countersunk Screw,1,0,,238.2,448.8,21.0,parsed from STEP text; machine-translated
+006,DZ-LP0632感光控制板,DZ-LP0632 Light Sensor Control Board,1,0,,130.5,10.0,20.0,parsed from STEP text; machine-translated
+007,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,2,0,,33.82,28.2,19.0,parsed from STEP text
+008,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,1,0,,48.37,103.79,16.25,parsed from STEP text
+009,TOSN-DY398P-EMC小板,TOSN-DY398P-EMC Sub-board,1,0,,92.0,21.0,17.7,parsed from STEP text; machine-translated
+010,TOSN-AD120P12V10A-120W,TOSN-AD120P12V10A-120W,1,0,,33.0,73.0,14.7,parsed from STEP text
+011,2P凤凰端子,2P Phoenix Terminal,1,0,,33.0,73.0,14.7,parsed from STEP text; machine-translated
+012,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,30.0,120.0,11.6,parsed from STEP text
+013,G156HAN02.0--20221031_G156HAN02.0_PSpec_DBEST,G156HAN02.0--20221031_G156HAN02.0_PSpec_DBEST,1,0,,5.0,5.0,5.0,parsed from STEP text
+014,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+015,小玻璃镜片,Small Glass Lens,1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+016,Board~a9jc.step,Board~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+017,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+018,15.6寸端子板,"15.6"" Terminal Board",1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+019,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+020,下铝板,Lower Aluminum Plate,1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+021,上铝板,Upper Aluminum Plate,1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+022,BSCZ-TX3361,BSCZ-TX3361,1,0,,5.0,5.0,5.0,parsed from STEP text
+023,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,1,0,,5.0,5.0,5.0,parsed from STEP text
+024,15.6寸安装板,"15.6"" Mounting Plate",1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+025,15.6寸光感支架,"15.6"" Light Sensor Bracket",1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+026,15.6寸高铁显示屏总装图,"15.6"" High-Speed Rail Display Assembly Drawing",1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+027,15.6寸铝框,"15.6"" Aluminum Frame",1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
+028,8欧5W喇叭（3070款）,8Ω 5W Speaker (Model 3070),1,0,,5.0,5.0,5.0,parsed from STEP text; machine-translated
@@ -0,0 +1,32 @@
+part_number,part_name_original,part_name_english,quantity,level,parent,bbox_x_mm,bbox_y_mm,bbox_z_mm,notes
+001,TOSN-DY398P-EMC小板,TOSN-DY398P-EMC Small PCB Board,1,0,,397.2,718.6,40.0,parsed from STEP text; machine-translated
+002,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,1,0,,390.9,652.3,6.0,parsed from STEP text
+003,光感支架,Light Sensor Bracket,1,0,,362.1,623.7,12.1,parsed from STEP text; machine-translated
+004,2P凤凰端子,2P Phoenix Connector Terminal,1,0,,389.8,711.2,23.1,parsed from STEP text; machine-translated
+005,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,1,0,,33.82,28.2,19.0,parsed from STEP text
+006,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,48.37,103.79,16.25,parsed from STEP text
+007,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,1,0,,110.0,49.0,8.6,parsed from STEP text
+008,DZ-LP6608 REV1.0,DZ-LP6608 REV1.0,1,0,,102.0,50.0,16.0,parsed from STEP text
+009,P270HVN03.0,P270HVN03.0,1,0,,386.0,483.0,22.6,parsed from STEP text
+010,Board~a9jc.step,Board~a9jc.step,1,0,,152.0,10.0,21.6,parsed from STEP text
+011,BSCZ-TX3361,BSCZ-TX3361,1,0,,33.0,73.0,14.7,parsed from STEP text
+012,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,2,0,,33.0,73.0,14.7,parsed from STEP text
+013,27寸高铁显示屏总装图,27-inch High-speed Rail Display Screen Assembly Drawing,1,0,,45.0,160.0,11.6,parsed from STEP text; machine-translated
+014,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,92.0,21.0,17.1,parsed from STEP text
+015,8欧5W喇叭（3070款）,8Ω 5W Speaker (Model 3070),1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+016,27寸屏压件1,27-inch Screen Clamp 1,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+017,27寸上铝板,27-inch Upper Aluminum Panel,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+018,小玻璃镜片,Small Glass Mirror Lens,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+019,钢化玻璃3+3夹胶,Tempered Glass 3+3 Laminated,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+020,27寸屏压件2,27-inch Screen Clamp 2,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+021,遥控+光感板,Remote Control + Light Sensor Board,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+022,屏压件,Screen Clamp,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+023,27寸下铝板,27-inch Lower Aluminum Panel,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+024,后盖,Rear Cover,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+025,安装板,Mounting Plate,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+026,M3x6沉头螺丝,M3x6 Countersunk Screw,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+027,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,6.0,6.0,5.0,parsed from STEP text
+028,端子板,Terminal Board,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+029,27寸铝框,27-inch Aluminum Frame,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+030,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,6.0,6.0,5.0,parsed from STEP text
+031,TOSN-AD120P12V10A-120W,TOSN-AD120P12V10A-120W,1,0,,6.0,6.0,5.0,parsed from STEP text
@@ -0,0 +1,32 @@
+part_number,part_name_original,part_name_english,quantity,level,parent,bbox_x_mm,bbox_y_mm,bbox_z_mm,notes
+001,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,J4~BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,2,0,,826.0,192.0,48.0,parsed from STEP text
+002,小玻璃镜片,Small Glass Lens,1,0,,39.85,185.7,9.0,parsed from STEP text; machine-translated
+003,8欧5W喇叭（3070款）,8Ω 5W Speaker (Model 3070),1,0,,39.85,185.7,9.0,parsed from STEP text; machine-translated
+004,TOSN-AD120P12V10A-120W,TOSN-AD120P12V10A-120W,1,0,,759.6,185.7,6.0,parsed from STEP text
+005,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07,1,0,,821.4,187.4,23.1,parsed from STEP text
+006,28寸屏压件,"28"" Screen Pressure Clip",1,0,,12.0,28.0,1.1,parsed from STEP text; machine-translated
+007,28寸端子板,"28"" Terminal Board",1,0,,618.0,183.6,24.1,parsed from STEP text; machine-translated
+008,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,3D_YZ-006-V3 HDMI TO 2SDI_2025-11-07.step,1,0,,12.3,65.0,14.0,parsed from STEP text
+009,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,21.0,92.0,19.2,parsed from STEP text
+010,TOSN-DY398P-EMC小板,TOSN-DY398P-EMC Subboard,1,0,,10.0,152.0,21.6,parsed from STEP text; machine-translated
+011,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,28.2,33.82,19.0,parsed from STEP text
+012,玻璃3+3,Glass 3+3,1,0,,103.79,48.37,16.25,parsed from STEP text; machine-translated
+013,BSCZ-TX3361,BSCZ-TX3361,1,0,,49.0,110.0,8.6,parsed from STEP text
+014,28寸后盖,"28"" Rear Cover",1,0,,102.0,50.0,16.0,parsed from STEP text; machine-translated
+015,28寸下铝板,"28"" Lower Aluminum Plate",1,0,,50.0,40.0,12.6,parsed from STEP text; machine-translated
+016,28寸高铁显示屏总装图,"28"" High-speed Rail Display Screen Assembly Drawing",1,0,,73.0,33.0,14.7,parsed from STEP text; machine-translated
+017,Board~a9jc.step,Board~a9jc.step,1,0,,73.0,33.0,14.7,parsed from STEP text
+018,jgj-hy0280HD03模组,jgj-hy0280HD03 Module,1,0,,95.0,42.0,8.5,parsed from STEP text; machine-translated
+019,遥控+光感板,Remote Control + Light Sensor Board,1,0,,59.0,79.0,39.2,parsed from STEP text; machine-translated
+020,2P凤凰端子,2P Phoenix Terminal,1,0,,29.0,21.0,29.7,parsed from STEP text; machine-translated
+021,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,BNC-1~BNC-TH_BNC-50KWYE~a9jc.step,1,0,,29.0,21.0,24.9,parsed from STEP text
+022,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,J7~XH4X1-2.54~CONN-TH_4P-P2.50_MEGASTAR_ZX-XH2.54-4PZZ~a9jc.step,1,0,,722.0,154.6,16.8,parsed from STEP text
+023,28寸恒流板,"28"" Constant Current Board",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+024,28寸条屏铝框,"28"" Strip Screen Aluminum Frame",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+025,28寸屏压件2,"28"" Screen Pressure Clip 2",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+026,M3x6沉头螺丝,M3x6 Countersunk Screw,1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+027,28寸上铝板,"28"" Upper Aluminum Plate",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+028,28寸屏压件1,"28"" Screen Pressure Clip 1",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+029,28寸光感支架,"28"" Light Sensor Bracket",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+030,28寸安装板,"28"" Mounting Plate",1,0,,6.0,6.0,5.0,parsed from STEP text; machine-translated
+031,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,J5~HDMI_A_F_SMD_19P~HDMI-SMD_HDMI-HX-19D~a9jc.step,1,0,,6.0,6.0,5.0,parsed from STEP text
@@ -0,0 +1,392 @@
+# STEP Processor — macOS Setup Checklist
+### Apple Silicon (Mac Studio M-series) · No Rosetta Required
+
+Work through this top to bottom. Each section has a ✅ verification command
+so you know it worked before moving on.
+
+---
+
+## PHASE 1 — Prerequisites
+
+### 1.1 — Confirm Python version
+
+```bash
+python3 --version
+```
+
+**You need Python 3.10, 3.11, or 3.12.**
+3.13 will work but is less tested. 3.9 is too old.
+
+If your version is wrong, install via Homebrew:
+```bash
+brew install python@3.11
+```
+Then use `python3.11` explicitly in all commands below.
+
+---
+
+### 1.2 — Confirm Homebrew is installed
+
+```bash
+brew --version
+```
+
+If missing:
+```bash
+/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+```
+
+---
+
+### 1.3 — Create a dedicated virtual environment
+
+Keep everything isolated from your system Python.
+Pick a folder — e.g. your CoWork dev directory.
+
+```bash
+python3 -m venv ~/step-processor-env
+source ~/step-processor-env/bin/activate
+```
+
+You should see `(step-processor-env)` in your terminal prompt.
+**All pip commands below assume this environment is active.**
+
+✅ Verify:
+```bash
+which python   # should point inside step-processor-env
+```
+
+---
+
+## PHASE 2 — Primary Library: build123d
+
+### 2.1 — Upgrade pip first
+
+```bash
+pip install --upgrade pip
+```
+
+---
+
+### 2.2 — Install cadquery-ocp (the OCC kernel, native arm64)
+
+This is now on PyPI directly — no manual wheel download needed.
+
+```bash
+pip install cadquery-ocp
+```
+
+This is a large download (~300MB). Let it run.
+
+✅ Verify:
+```bash
+python -c "import OCP; print('OCP kernel OK')"
+```
+
+---
+
+### 2.3 — Install build123d
+
+```bash
+pip install build123d
+```
+
+✅ Verify:
+```bash
+python -c "import build123d; print('build123d OK')"
+```
+
+---
+
+### 2.4 — Install the rendering stack
+
+```bash
+pip install trimesh pyrender Pillow numpy pandas anthropic openpyxl
+```
+
+> **Note:** `openpyxl` is required for Excel BOM output. If missing, the skill silently
+> falls back to CSV. Install it here to get MPM-branded `.xlsx` output.
+
+✅ Verify each:
+```bash
+python -c "import trimesh; print('trimesh OK')"
+python -c "import pyrender; print('pyrender OK')"
+python -c "import PIL; print('Pillow OK')"
+python -c "import pandas; print('pandas OK')"
+python -c "import anthropic; print('anthropic OK')"
+python -c "import openpyxl; print('openpyxl OK')"
+```
+
+---
+
+## PHASE 3 — Diagram Export: cairosvg
+
+Required for converting SVG diagrams to PNG and PDF.
+
+### 3.1 — Install system libraries via Homebrew
+
+```bash
+brew install cairo pango gdk-pixbuf libffi
+```
+
+### 3.2 — Install cairosvg
+
+```bash
+pip install cairosvg
+```
+
+✅ Verify:
+```bash
+python -c "import cairosvg; print('cairosvg OK')"
+```
+
+If you get a library not found error, run this and retry:
+```bash
+export PKG_CONFIG_PATH="/opt/homebrew/lib/pkgconfig"
+pip install cairosvg
+```
+
+---
+
+## PHASE 4 — Fallback Library: FreeCAD Headless
+
+Only needed if build123d fails on a specific file.
+
+> **macOS 15 Sequoia note:** The conda-forge FreeCAD package is killed silently
+> by Gatekeeper on Sequoia due to unsigned binaries. Use the official signed
+> FreeCAD.app instead (approach below). Conda approach will NOT work on Sequoia.
+
+### 4.1 — Install official FreeCAD.app (signed & notarized)
+
+Download the latest arm64 release from:
+```
+https://github.com/FreeCAD/FreeCAD/releases/latest
+```
+
+Open the .dmg and drag FreeCAD.app to /Applications as normal.
+Launch it once from /Applications so macOS registers the security approval.
+
+### 4.2 — Verify headless via app bundle
+
+The binary is `freecadcmd` (all lowercase) inside the bundle:
+
+```bash
+/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd --version
+# Should print: FreeCAD 1.x.x Revision: ...
+```
+
+✅ Verify Python import:
+```bash
+/Applications/FreeCAD.app/Contents/Resources/bin/python -c \
+  "import sys; sys.path.insert(0, '/Applications/FreeCAD.app/Contents/Resources/lib'); \
+   import FreeCAD; print('FreeCAD', FreeCAD.Version())"
+```
+
+**Key paths for loader.py:**
+- CLI binary: `/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd`
+- Python interpreter: `/Applications/FreeCAD.app/Contents/Resources/bin/python`
+- Module path (add to sys.path): `/Applications/FreeCAD.app/Contents/Resources/lib`
+
+The code invokes FreeCAD using the bundle's own Python — no conda env needed.
+
+---
+
+## PHASE 5 — API Key
+
+### 5.1 — Set your Anthropic API key
+
+```bash
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY-HERE"' >> ~/.zshrc
+echo 'export ANTHROPIC_API_KEY="sk-ant-YOUR-KEY-HERE"' >> ~/.zshenv
+source ~/.zshrc
+```
+
+> **Important:** Add the key to **both** `~/.zshrc` AND `~/.zshenv`.
+> `~/.zshrc` is only sourced in interactive terminal sessions.
+> `~/.zshenv` is sourced for all zsh invocations including Desktop Commander's
+> non-interactive shells — without it, translation will silently fail when
+> running via CoWork/Desktop Commander.
+
+✅ Verify:
+```bash
+echo $ANTHROPIC_API_KEY   # should print your key (or at least sk-ant-...)
+```
+
+---
+
+## PHASE 6 — Place the Skill Files
+
+### 6.1 — Copy the step-processor folder to your working location
+
+Recommended: somewhere in your CoWork project or a dedicated tools directory.
+
+```
+~/your-project/
+  step-processor/
+    step_processor.py
+    modules/
+      __init__.py
+      loader.py
+      bom.py
+      renderer.py
+      translator.py
+      rewriter.py
+      query_engine.py
+      external_diagram.py
+    schemas/
+      external_diagram_schema.json
+      parts_mapping_schema.json
+    templates/
+      datablock_template.md
+    SKILL.md
+    INSTALL.md
+```
+
+### 6.2 — Activate your environment before running
+
+```bash
+source ~/step-processor-env/bin/activate
+cd ~/your-project/step-processor
+```
+
+---
+
+## PHASE 7 — Test Run (do this when you have a STEP file ready)
+
+Work through these tests in order. Stop at the first failure and fix it
+before continuing.
+
+---
+
+### TEST 1 — Confirm the skill loads without errors
+
+```bash
+python step_processor.py --help
+```
+
+Expected: prints the CLI help/usage block with no ImportError or traceback.
+
+---
+
+### TEST 2 — Load a STEP file and extract BOM
+
+Replace `yourfile.step` with your actual file path.
+
+```bash
+python step_processor.py /path/to/yourfile.step --no-thumbnails --verbose
+```
+
+Expected output:
+```
+INFO  Loading: yourfile.step
+INFO  [build123d] Loaded: yourfile.step
+INFO  BOM extracted: N parts
+INFO  BOM XLSX → /path/to/yourfile_bom.xlsx
+```
+
+Open the `.xlsx` file to confirm part names look right.
+If you see Chinese characters in the `Supplier Part Name` column — that's expected and correct.
+The `Part Description` column will be populated with English in Test 4.
+If you see a CSV instead of xlsx, `openpyxl` is not installed — run `pip install openpyxl`.
+
+---
+
+### TEST 3 — Generate thumbnails
+
+```bash
+python step_processor.py /path/to/yourfile.step --no-bom --verbose
+```
+
+Expected: 6 PNG files appear next to the STEP file:
+`yourfile_front.png`, `yourfile_bottom.png`, `yourfile_left.png`,
+`yourfile_right.png`, `yourfile_iso_left.png`, `yourfile_iso_right.png`
+
+Open them in Preview to confirm they look like your enclosure from different angles.
+
+---
+
+### TEST 4 — Translation (requires API key)
+
+Only run this if the BOM from Test 2 has Chinese part names.
+
+```bash
+python step_processor.py /path/to/yourfile.step --no-thumbnails --translate --verbose
+```
+
+Expected: `part_name_english` column in the CSV is now populated with English names.
+A `yourfile_EN.step` should appear if Chinese labels were found in the STEP file itself.
+
+---
+
+### TEST 5 — Geometry query REPL
+
+```bash
+python step_processor.py /path/to/yourfile.step --no-thumbnails --no-bom --repl
+```
+
+At the `>` prompt, try:
+```
+> bounding box
+> list all holes
+> all parts
+> help
+> exit
+```
+
+Confirm the output tables look reasonable for your file.
+
+---
+
+### TEST 6 — External dimensional diagram
+
+```bash
+python step_processor.py /path/to/yourfile.step --diagram --verbose
+```
+
+Expected files next to the STEP:
+- `yourfile__external-diagram.svg`
+- `yourfile__external-diagram.png`
+- `yourfile__meta.json`
+
+Open the SVG in a browser (drag and drop into Safari or Chrome) to inspect the diagram.
+Open the PNG for the rasterized version.
+Open the JSON to confirm the metadata block populated correctly.
+
+---
+
+### TEST 7 — Diagram with PDF output
+
+```bash
+python step_processor.py /path/to/yourfile.step --diagram --diagram-pdf --verbose
+```
+
+Expected: adds `yourfile__external-diagram.pdf` to the outputs.
+Open in Preview to confirm it renders cleanly.
+
+---
+
+## Quick Reference — Re-activating After Restart
+
+Every time you open a new terminal session:
+```bash
+source ~/step-processor-env/bin/activate
+cd ~/your-project/step-processor
+export ANTHROPIC_API_KEY="sk-ant-..."   # only if not already in ~/.zshrc
+```
+
+---
+
+## Troubleshooting Quick Reference
+
+| Symptom | Fix |
+|---------|-----|
+| `ModuleNotFoundError: build123d` | `pip install build123d` (check env is activated) |
+| `ModuleNotFoundError: OCP` | `pip install cadquery-ocp` |
+| `ModuleNotFoundError: cairosvg` | `brew install cairo && pip install cairosvg` |
+| `pyrender` offscreen crash | Expected on some macOS setups — thumbnails will warn but diagram still generates |
+| BOM shows no parts / 1 part | Normal for single-body STEP files — the STEP text parser falls back to 1-row BOM |
+| Chinese labels not translated | Check `$ANTHROPIC_API_KEY` is set. If running via CoWork/Desktop Commander, add key to `~/.zshenv` not just `~/.zshrc` |
+| BOM output is CSV not xlsx | `openpyxl` not installed — `pip install openpyxl` with venv active |
+| `_EN.step` entity count mismatch warning | File has unusual STEP encoding — rewrite skipped, original untouched, BOM still correct |
+| FreeCAD fallback not working | Use signed FreeCAD.app — conda-forge is Gatekeeper-blocked on Sequoia. Path: `/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd` (all lowercase) |
+| Diagram SVG opens blank | Check `yourfile__meta.json` warnings array for geometry errors |
@@ -0,0 +1,430 @@
+# STEP File Processor Skill
+
+## Purpose
+This skill enables Claude to work with STEP/STP CAD files used in manufacturing.
+It provides:
+- PNG thumbnail extraction at 6 camera angles
+- Parts manifest / BOM export to CSV with automatic Chinese→English translation
+- Optional English-labeled STEP copy (source file never modified)
+- Natural language geometric query interface (holes, faces, dimensions, quantities)
+
+Designed for MPMedia's display enclosure and mounting kit product lines.
+
+---
+
+## When to invoke this skill
+
+Trigger on any of:
+- User provides a `.step` or `.stp` file path and asks to process, view, extract, or query it
+- User asks to "generate thumbnails" or "render views" of a STEP file
+- User asks to "extract BOM", "get parts list", or "show manifest" from a STEP file
+- User asks a geometric question about a STEP file: holes, faces, dimensions, quantities
+- User asks to "translate" a STEP file's part names
+- Claude Code context where a STEP file is present in the working directory
+
+**Read this entire SKILL.md before writing any code.**
+
+---
+
+## Library Stack
+
+### Primary: build123d
+- Modern OpenCASCADE Python wrapper; native Apple Silicon arm64 wheels
+- Clean, Pythonic API for STEP reading, assembly traversal, geometry queries
+- Offscreen PNG rendering via: build123d → export GLB/OBJ → trimesh → pyrender
+- Install: `pip install build123d trimesh pyrender pillow numpy pandas anthropic`
+- ARM64 OCP wheel required first — see INSTALL.md
+
+### Fallback: FreeCAD headless
+- Native macOS-arm64 build available via conda-forge (verified Nov 2024)
+- Used when build123d fails to load or render a specific file
+- Invoked via subprocess calling `FreeCADCmd` or by importing `FreeCAD` + `Part`
+- **Never import FreeCADGui** — headless only, GUI modules will crash
+- Install: `conda install -c conda-forge freecad` (arm64 native, no Rosetta)
+
+### Translation: Claude API (claude-sonnet-4-20250514)
+- Translates Chinese part names with manufacturing context awareness
+- e.g. 安装支架 → "Mounting Bracket" (not just "installation support")
+- Requires ANTHROPIC_API_KEY in environment
+
+### Supporting libraries (both tracks)
+- `Pillow` — PNG save/compose
+- `numpy` — geometry math
+- `pandas` — CSV/BOM output
+- `trimesh` + `pyrender` — GLB→PNG rendering fallback path
+
+---
+
+## File Structure
+
+```
+step-processor/
+  step_processor.py       ← CLI entry point + REPL
+  modules/
+    loader.py             ← STEP loading (build123d primary, FreeCAD fallback)
+    bom.py                ← Assembly tree traversal + BOM extraction
+    renderer.py           ← Offscreen PNG rendering (6 views)
+    translator.py         ← Claude API translation layer
+    rewriter.py           ← STEP label patcher (_EN copy only, never modifies source)
+    query_engine.py       ← Geometric query handler (holes, faces, dimensions)
+  INSTALL.md
+  SKILL.md
+```
+
+---
+
+## Dual-Track Fallback Pattern
+
+Every module must implement this pattern:
+
+```python
+def load_step(filepath):
+    try:
+        return _load_via_build123d(filepath)
+    except ImportError:
+        logger.warning("build123d not available — falling back to FreeCAD")
+        return _load_via_freecad(filepath)
+    except Exception as e:
+        logger.warning(f"build123d failed ({e}) — falling back to FreeCAD")
+        return _load_via_freecad(filepath)
+```
+
+Always log fallbacks at WARNING level so the user knows which path ran.
+
+FreeCAD fallback invocation pattern (subprocess, cleanest isolation):
+```python
+import subprocess, json, tempfile
+
+def _load_via_freecad(filepath):
+    script = f"""
+import FreeCAD, Part, json
+shape = Part.read("{filepath}")
+# extract data, write to temp JSON
+"""
+    result = subprocess.run(["FreeCADCmd", "--console", "-c", script], capture_output=True)
+    # parse result...
+```
+
+---
+
+## Camera Views
+
+Always produce these 6 views unless user specifies otherwise:
+
+| View Name  | Camera Direction          | File Suffix      |
+|------------|---------------------------|------------------|
+| Front      | +Y looking toward origin  | `_front.png`     |
+| Bottom     | -Z looking up             | `_bottom.png`    |
+| Left       | -X looking right          | `_left.png`      |
+| Right      | +X looking left           | `_right.png`     |
+| Iso Left   | +X+Y+Z (left-forward)     | `_iso_left.png`  |
+| Iso Right  | -X+Y+Z (right-forward)    | `_iso_right.png` |
+
+Default resolution: 1024×768. All PNGs saved to same folder as source STEP file.
+
+---
+
+## Output Naming Convention
+
+Given input: `/path/to/EnclosureA.step`
+
+| Output              | Path                              |
+|---------------------|-----------------------------------|
+| Thumbnails (×6)     | `/path/to/EnclosureA_front.png` etc. |
+| BOM CSV             | `/path/to/EnclosureA_bom.csv`    |
+| English STEP copy   | `/path/to/EnclosureA_EN.step`    |
+
+**Never overwrite or modify the source STEP file.**
+
+`_EN.step` is only created when Chinese labels are detected. If all labels are
+already ASCII/English, skip silently and note it in output.
+
+---
+
+## BOM CSV Schema
+
+```
+part_number, part_name_original, part_name_english, quantity, level, parent,
+bbox_x_mm, bbox_y_mm, bbox_z_mm, notes
+```
+
+- `level` = assembly depth (0 = root, 1 = direct children, etc.)
+- `parent` = part_name_english of parent assembly
+- `notes` = translator flags (e.g. "machine-translated", "ambiguous term")
+- Bounding boxes in millimeters, 2 decimal places
+- If no translation needed, `part_name_original` == `part_name_english`
+
+---
+
+## Translation Logic
+
+```
+bom.py extracts all part names
+  → translator.py checks each name for CJK unicode range (\u4e00-\u9fff)
+  → if any found: batch call Claude API with this system prompt:
+
+    "You are a mechanical engineering translator specializing in Chinese
+     manufacturing CAD files for display and enclosure products. Translate
+     the following part names from Chinese to English. Preserve technical
+     precision. Use standard hardware terminology. Output ONLY a JSON object
+     mapping original → translated, nothing else.
+     Example: {\"安装支架\": \"Mounting Bracket\", \"螺钉M4\": \"M4 Screw\"}"
+
+  → inject translations into BOM CSV
+  → if translation requested: produce _EN.step via rewriter.py
+```
+
+Flag uncertain translations in the `notes` column rather than silently guessing.
+
+---
+
+## STEP Label Rewriting (_EN copy)
+
+`rewriter.py` produces a translated copy — line-by-line, targeted replacement:
+
+1. Read source file line by line
+2. Identify lines containing `PRODUCT('`, `PRODUCT_DEFINITION_CONTEXT(` etc.
+3. Extract quoted name strings (first argument of PRODUCT entity)
+4. Replace CJK strings with translated equivalents from the translation map
+5. Write to `{filename}_EN.step`
+6. Validate: entity `#` count before == after. If mismatch → abort, warn, delete partial output
+
+**Do not use broad regex that could touch entity reference numbers (#123 etc.)**
+Target only the quoted string arguments of known STEP entity types.
+
+---
+
+## Geometric Query Engine
+
+`query_engine.py` handles natural language queries about loaded geometry.
+
+### Supported Query Types
+
+| Query pattern                    | What it extracts                                      |
+|----------------------------------|-------------------------------------------------------|
+| "list all mounting holes"        | Cylindrical faces, axis ⊥ to primary face, dia < 15mm|
+| "list all holes"                 | All cylindrical through-features                      |
+| "holes diameter [N]mm"           | Filter holes by diameter                              |
+| "tapped holes" / "threaded"      | Cylinders with helical features (if present in model) |
+| "face count"                     | Total face count by type (planar, cylindrical, etc.)  |
+| "bounding box"                   | Overall model extents in mm                           |
+| "part [name] dimensions"         | Bounding box of a specific named part                 |
+| "largest face"                   | Largest planar face area in mm²                       |
+| "wall thickness"                 | Min distance between opposing parallel faces          |
+| "all parts"                      | Full assembly listing with quantities                 |
+
+### Query Invocation
+
+**CLI (single query, exit after):**
+```bash
+python step_processor.py enclosure.step --query "list all mounting holes with diameter and depth"
+```
+
+**REPL (interactive, geometry stays loaded in memory between queries):**
+```bash
+python step_processor.py enclosure.step --repl
+> list mounting holes
+> bounding box
+> how many M4 holes
+> exit
+```
+
+### Query Output Format
+
+Always return a structured table:
+```
+MOUNTING HOLES — EnclosureA.step
+─────────────────────────────────────────────────────────────
+ #   Part Name          Diameter    Depth      Position (x,y,z)
+─────────────────────────────────────────────────────────────
+ 1   Front Panel        4.20 mm     8.00 mm    (12.50, 0.00, 45.20)
+ 2   Front Panel        4.20 mm     8.00 mm    (87.50, 0.00, 45.20)
+─────────────────────────────────────────────────────────────
+Total: 8 holes across 3 parts
+```
+
+---
+
+## CLI Reference
+
+```
+python step_processor.py <file.step> [options]
+
+Options:
+  --thumbnails          Generate 6 PNG views (default: on)
+  --no-thumbnails       Skip PNG generation
+  --bom                 Export BOM CSV (default: on)
+  --no-bom              Skip BOM export
+  --translate           Auto-translate Chinese labels in BOM + produce _EN.step
+  --no-translate        Skip translation even if Chinese labels detected
+  --query "..."         Run a single geometric query and exit
+  --repl                Enter interactive query REPL
+  --resolution WxH      Thumbnail resolution (default: 1024x768)
+  --views front,iso_left,iso_right  Comma-separated subset of views
+  --verbose             Show library selection, fallback notices, timing
+```
+
+**Default behavior (no flags):** `--thumbnails --bom` plus auto-detect translation.
+
+---
+
+## Error Handling
+
+| Condition                          | Behavior                                               |
+|------------------------------------|--------------------------------------------------------|
+| File not found                     | Exit with clear message, no partial output             |
+| Neither library available          | Exit with INSTALL.md reference                         |
+| build123d render fails             | Auto-fallback to FreeCAD path, log warning             |
+| Translation API unavailable        | Write BOM with original names only, note in output     |
+| STEP has no assembly structure     | Treat as single part, one-row BOM                      |
+| Chinese detected, no translate flag| Auto-translate by default (skip with --no-translate)   |
+| _EN.step entity count mismatch     | Abort rewrite, warn, delete partial file               |
+| FreeCAD headless GUI module import | Catch ImportError, skip that module, continue          |
+
+---
+
+## INSTALL.md Summary
+
+**build123d (primary — native arm64, no conda):**
+```bash
+# 1. Install the arm64 OCP wheel from CadQuery GitHub releases:
+#    https://github.com/CadQuery/OCP/releases — pick macosx_*_arm64.whl for your Python
+pip install path/to/cadquery_ocp-*.whl
+
+# 2. Install build123d and rendering stack
+pip install build123d trimesh pyrender pillow numpy pandas anthropic
+
+# 3. Set API key
+export ANTHROPIC_API_KEY=sk-ant-...
+```
+
+**FreeCAD (fallback — native arm64 via conda):**
+```bash
+# Install Miniforge arm64 if not already present:
+# https://github.com/conda-forge/miniforge/releases
+
+conda install -c conda-forge freecad
+# Verify headless works:
+FreeCADCmd --version
+```
+
+No Rosetta. No x64 sub-environment. Both libraries run natively on Apple Silicon.
+
+---
+
+## Notes for Claude
+
+- Default run = thumbnails + BOM + auto-translate if Chinese detected
+- When a user asks a geometry question, invoke query_engine — don't describe the STEP file from the BOM alone
+- Always confirm output file locations at end of run
+- If Chinese labels found, proactively note it and offer to show the translation map
+- In REPL mode, keep responses tight — it's a terminal session
+- When describing holes or geometry, lead with the table, not prose
+- If build123d fallback fires, tell the user which library ran
+
+---
+
+## Sub-skill: External Dimensional Diagram
+
+### Purpose
+Generates a standardized external dimensional diagram for installation planning,
+product reference, and non-CAD users. NOT a manufacturing drawing.
+Think: installation reference sheet with clean orthographic views + one ISO.
+
+### Terminology
+Use: "external dimensional diagram"
+Never use: shop drawing, manufacturing drawing, fabrication drawing
+
+### Entry point
+```python
+from modules.external_diagram import step_external_diagram
+
+meta = step_external_diagram(
+    path="enclosure.step",
+    mode="enclosure_only",              # or enclosure_plus_mounting, mounting_only
+    mapping_file="MR28UW_mapping.json", # optional
+    datablock_file="MR28UW.md",         # optional, auto-detected if omitted
+    options={
+        "style": "line_drawing",        # or "rendered" — auto if omitted
+        "pdf": True,                    # default False
+        "mounting_variant": "Wall Mount", # for enclosure_plus_mounting mode
+        "render_variants": True,        # generate diagram per mounting variant
+    }
+)
+```
+
+### Modes
+- `enclosure_only` — enclosure body only (default when no mapping file)
+- `enclosure_plus_mounting` — enclosure + selected mounting subassembly
+- `mounting_only` — mounting geometry only
+
+### Styles
+- `line_drawing` — pure SVG wireframe (MR28 reference style). Auto-selected for simple enclosures.
+- `rendered` — rendered ISO views composited with dimensioned orthographic line views
+  (MR16 reference style). Auto-selected for complex assemblies (>200 faces).
+
+### Layout auto-selection
+- `single_sheet` — default for most models
+- `multi_page` — auto-selected when any dimension > 1200mm or part count > 60
+
+### Outputs per run
+| File | Always? | Description |
+|------|---------|-------------|
+| `{stem}__external-diagram.svg` | Yes | Source SVG, always retained |
+| `{stem}__external-diagram.png` | Yes | PNG export via cairosvg |
+| `{stem}__external-diagram.pdf` | Optional (`--pdf` flag) | PDF via cairosvg |
+| `{stem}__meta.json` | Yes | Full metadata per schema |
+| Individual view PNGs | Rendered style only | front, side, rear, iso |
+| Variant diagrams | If `render_variants=True` | One set per mounting variant |
+
+### Dimensions shown
+Required: overall width, height, depth
+Auto-detected and shown when found:
+- Active area / screen aperture (with diagonal in mm and inches)
+- Mounting hole chain spacing (horizontal or vertical, auto-selected by readability)
+- VESA pattern if detected
+- Edge offsets to mounting geometry
+Units: metric primary (mm) with imperial in parentheses, smaller italic
+
+### Parts mapping file
+JSON file per product model — classifies parts as enclosure/mounting/internal/fastener.
+Drives show/hide logic per mode. Supports mounting variants.
+Schema: `schemas/parts_mapping_schema.json`
+Example: `schemas/parts_mapping_schema.json` → `examples` array
+
+### Datablock / title block
+Sourced from a `.md` file alongside the STEP file (auto-detected by matching stem name)
+or passed explicitly as `datablock_file`.
+Template: `templates/datablock_template.md`
+Edit the template to configure: model number, display name, revision, date, company,
+and any custom fields. Custom fields appear in the data block footer.
+
+### Metadata schema
+Full JSON schema: `schemas/external_diagram_schema.json`
+Designed for AI consumption, Odoo product data integration, search indexing,
+and CoWork documentation workflows. All geometry in mm.
+
+### CLI
+```bash
+# Basic — enclosure only, auto style
+python step_processor.py enclosure.step --diagram
+
+# With options
+python step_processor.py enclosure.step --diagram --diagram-mode enclosure_plus_mounting \
+  --diagram-style line_drawing --diagram-pdf \
+  --mapping mapping/MR28UW_mapping.json \
+  --datablock MR28UW.md
+
+# Render all mounting variants
+python step_processor.py enclosure.step --diagram --diagram-mode enclosure_plus_mounting \
+  --diagram-variants
+```
+
+### Notes for Claude
+- When a user says "generate a diagram", "make a dimensional sheet", or "create reference drawing" → invoke this sub-skill
+- Always confirm mode with user if unclear (enclosure_only vs with mounting)
+- If no mapping file exists, default to enclosure_only and note it
+- If multiple mounting variants detected in assembly tree, offer to render each
+- The meta.json output is the primary artifact for downstream AI/workflow consumption
+- cairosvg is required for PNG/PDF export: `pip install cairosvg`
+- Weight/mass fields in meta.json are reserved for future Odoo product data integration
@@ -0,0 +1 @@
+# step-processor modules package
@@ -0,0 +1,275 @@
+"""
+bom.py — BOM extraction from STEP assembly tree.
+
+Primary: build123d assembly traversal.
+Fallback: STEP ISO 10303-21 text parser for PRODUCT entities.
+Always produces a complete DataFrame; saved as MPM-branded Excel (.xlsx).
+"""
+import logging
+import math
+import re
+from collections import Counter
+from pathlib import Path
+
+import pandas as pd
+
+from .loader import StepModel
+
+logger = logging.getLogger("step_processor.bom")
+
+BOM_COLUMNS = [
+    "part_number", "part_name_original", "part_name_english",
+    "quantity", "level", "parent",
+    "bbox_x_mm", "bbox_y_mm", "bbox_z_mm", "notes"
+]
+
+# ── Excel output — MPM brand palette (hex, no #) ─────────────────────────────
+_MPM_DARK_SHADE     = "232022"   # header background + body text
+_MPM_LIGHT_SHADE    = "F5F1EC"   # header text
+_MPM_WARM_OFF_WHITE = "FAF7F2"   # alternating row tint
+_MPM_MIDDLE_GOLD    = "DCBB4F"   # accent border under header row
+
+# Column rename + reorder for stakeholder-facing Excel output.
+# Internal processing always uses BOM_COLUMNS names.
+_XLSX_RENAME = {
+    "part_name_english":  "part_description",
+    "part_name_original": "part_name_supplier",
+}
+_XLSX_ORDER = [
+    "part_number", "part_description", "quantity", "level", "parent",
+    "bbox_x_mm", "bbox_y_mm", "bbox_z_mm", "notes", "part_name_supplier",
+]
+_XLSX_HEADERS = {
+    "part_number":        "Part #",
+    "part_description":   "Part Description",
+    "quantity":           "Qty",
+    "level":              "Level",
+    "parent":             "Parent",
+    "bbox_x_mm":          "X (mm)",
+    "bbox_y_mm":          "Y (mm)",
+    "bbox_z_mm":          "Z (mm)",
+    "notes":              "Notes",
+    "part_name_supplier": "Supplier Part Name",
+}
+_XLSX_WIDTHS = {
+    "part_number": 12, "part_description": 40, "quantity": 8,
+    "level": 7, "parent": 22, "bbox_x_mm": 11, "bbox_y_mm": 11,
+    "bbox_z_mm": 11, "notes": 34, "part_name_supplier": 40,
+}
+
+
+def _safe(v):
+    """Convert NaN/None → None so openpyxl writes blank cells."""
+    if v is None:
+        return None
+    try:
+        if isinstance(v, float) and math.isnan(v):
+            return None
+    except Exception:
+        pass
+    return v
+
+
+def extract_bom(model: StepModel) -> pd.DataFrame:
+    """Extract BOM from a loaded StepModel. Returns DataFrame with BOM_COLUMNS.
+
+    Name-extraction strategy
+    ------------------------
+    The STEP text parser is always the primary source for part_name_original.
+    It reads raw bytes with GBK/UTF-8 encoding detection, correctly decoding
+    Chinese CAD part labels.
+
+    OCC's STEP reader (used by build123d) applies an internal codec that maps
+    each 2-byte GBK sequence to an incorrect Unicode codepoint — the resulting
+    strings cannot be recovered. We therefore never rely on child.label for
+    part names when the file may contain CJK characters.
+
+    OCC assembly walk (_bom_from_parts) is kept as a fallback only for files
+    where the text parser returns nothing (e.g., non-PRODUCT-entity STEP files).
+    """
+    rows = []
+
+    # Primary: STEP text parser — encoding-aware, correct for ASCII and CJK files
+    rows = _bom_from_step_text(model.path)
+
+    if not rows and model.backend == "build123d" and model.parts:
+        # Fallback: OCC assembly walk (CJK names will be garbled but structure intact)
+        logger.debug("STEP text parser empty — falling back to OCC assembly walk")
+        rows = _bom_from_parts(model.parts)
+
+    if not rows:
+        logger.info("No assembly structure — treating as single part")
+        stem = model.path.stem
+        rows = [{"part_number": "001", "part_name_original": stem,
+                 "part_name_english": stem, "quantity": 1, "level": 0,
+                 "parent": "", "bbox_x_mm": None, "bbox_y_mm": None,
+                 "bbox_z_mm": None, "notes": "single-body file"}]
+    df = pd.DataFrame(rows, columns=BOM_COLUMNS)
+    if model.backend == "build123d":
+        df = _enrich_bboxes(model, df)
+    logger.info(f"BOM extracted: {len(df)} parts")
+    return df
+
+
+def _bom_from_parts(parts: list) -> list:
+    name_counts = Counter(p["name"] for p in parts)
+    seen = set()
+    rows = []
+    for i, p in enumerate(parts):
+        name = p["name"]
+        if name in seen:
+            continue
+        seen.add(name)
+        rows.append({
+            "part_number": f"{len(rows)+1:03d}",
+            "part_name_original": name,
+            "part_name_english": name,
+            "quantity": name_counts[name],
+            "level": p.get("level", 0),
+            "parent": p.get("parent", ""),
+            "bbox_x_mm": None, "bbox_y_mm": None, "bbox_z_mm": None,
+            "notes": "",
+        })
+    return rows
+
+
+def _read_step_text(step_path: Path) -> str:
+    """Read STEP file text with CJK-aware encoding detection.
+
+    STEP files from Chinese manufacturers embed raw GBK bytes in name strings.
+    Strategy: try UTF-8 first (correct for modern files); if replacement chars
+    appear, retry as GBK (covers Chinese CAD exports); fall back to latin-1
+    which never fails (may contain mojibake, but at least it's readable).
+    """
+    for enc in ('utf-8', 'gbk'):
+        try:
+            text = step_path.read_text(encoding=enc)
+            if enc == 'utf-8' and '�' in text:
+                # Replacement chars detected — GBK bytes can't be UTF-8
+                continue
+            return text
+        except (UnicodeDecodeError, LookupError):
+            continue
+    return step_path.read_text(encoding='latin-1', errors='replace')
+
+
+def _bom_from_step_text(step_path: Path) -> list:
+    """Parse STEP ISO 10303-21 PRODUCT entities directly."""
+    try:
+        text = _read_step_text(step_path)
+    except Exception as e:
+        logger.warning(f"Could not read STEP text: {e}")
+        return []
+    pattern = re.compile(r"#\d+\s*=\s*PRODUCT\s*\(\s*'([^']*)'", re.IGNORECASE)
+    seen = {}
+    for match in pattern.finditer(text):
+        name = match.group(1).strip()
+        if not name or name.upper() in ("", "NONE"):
+            continue
+        if name in seen:
+            seen[name]["quantity"] += 1
+        else:
+            seen[name] = {
+                "part_number": f"{len(seen)+1:03d}",
+                "part_name_original": name, "part_name_english": name,
+                "quantity": 1, "level": 0, "parent": "",
+                "bbox_x_mm": None, "bbox_y_mm": None, "bbox_z_mm": None,
+                "notes": "parsed from STEP text",
+            }
+    rows = list(seen.values())
+    if rows:
+        logger.info(f"STEP text parser found {len(rows)} unique part names")
+    return rows
+
+
+def _enrich_bboxes(model: StepModel, df: pd.DataFrame) -> pd.DataFrame:
+    """Add bounding box dims per part from build123d. Best-effort."""
+    try:
+        bb = model.shape.bounding_box()
+        if len(df) == 1:
+            df.at[0, "bbox_x_mm"] = round(bb.size.X, 2)
+            df.at[0, "bbox_y_mm"] = round(bb.size.Y, 2)
+            df.at[0, "bbox_z_mm"] = round(bb.size.Z, 2)
+        else:
+            children = getattr(model.shape, "children", []) or []
+            for i, child in enumerate(children):
+                if i >= len(df):
+                    break
+                try:
+                    cb = child.bounding_box()
+                    df.at[i, "bbox_x_mm"] = round(cb.size.X, 2)
+                    df.at[i, "bbox_y_mm"] = round(cb.size.Y, 2)
+                    df.at[i, "bbox_z_mm"] = round(cb.size.Z, 2)
+                except Exception:
+                    pass
+    except Exception as e:
+        logger.debug(f"bbox enrichment skipped: {e}")
+    return df
+
+
+def save_bom_csv(df: pd.DataFrame, step_path: Path) -> Path:
+    """Write BOM DataFrame to CSV (legacy fallback)."""
+    out_path = step_path.parent / f"{step_path.stem}_bom.csv"
+    df.to_csv(out_path, index=False)
+    logger.info(f"BOM CSV → {out_path.name}")
+    return out_path
+
+
+def save_bom_xlsx(df: pd.DataFrame, step_path: Path) -> Path:
+    """Write BOM DataFrame to an MPM-branded Excel workbook.
+
+    Column changes vs internal schema (BOM_COLUMNS):
+      part_name_english  → Part Description  (column 2)
+      part_name_original → Supplier Part Name (last column)
+    Falls back to CSV if openpyxl is unavailable.
+    """
+    out_path = step_path.parent / f"{step_path.stem}_bom.xlsx"
+    try:
+        from openpyxl import Workbook
+        from openpyxl.styles import Alignment, Border, Font, PatternFill, Side
+        from openpyxl.utils import get_column_letter
+    except ImportError:
+        logger.warning("openpyxl not installed — falling back to CSV")
+        return save_bom_csv(df, step_path)
+
+    # Build display DataFrame
+    disp = df.rename(columns=_XLSX_RENAME).copy()
+    for col in _XLSX_ORDER:
+        if col not in disp.columns:
+            disp[col] = None
+    disp = disp[_XLSX_ORDER]
+
+    wb = Workbook()
+    ws = wb.active
+    ws.title = "Bill of Materials"
+
+    gold_border = Border(bottom=Side(style="medium", color=_MPM_MIDDLE_GOLD))
+    hdr_fill    = PatternFill("solid", fgColor=_MPM_DARK_SHADE)
+    hdr_font    = Font(name="Montserrat", bold=True, color=_MPM_LIGHT_SHADE, size=10)
+    hdr_align   = Alignment(horizontal="center", vertical="center", wrap_text=True)
+
+    # Header row
+    for c, col in enumerate(_XLSX_ORDER, 1):
+        cell = ws.cell(row=1, column=c, value=_XLSX_HEADERS.get(col, col))
+        cell.font      = hdr_font
+        cell.fill      = hdr_fill
+        cell.alignment = hdr_align
+        cell.border    = gold_border
+        ws.column_dimensions[get_column_letter(c)].width = _XLSX_WIDTHS.get(col, 15)
+    ws.row_dimensions[1].height = 28
+
+    # Data rows
+    body_font  = Font(name="Open Sans", size=10, color=_MPM_DARK_SHADE)
+    body_align = Alignment(horizontal="left", vertical="center")
+    for r, (_, row) in enumerate(disp.iterrows(), 2):
+        fill = PatternFill("solid", fgColor=_MPM_WARM_OFF_WHITE if r % 2 == 0 else "FFFFFF")
+        for c, col in enumerate(_XLSX_ORDER, 1):
+            cell = ws.cell(row=r, column=c, value=_safe(row[col]))
+            cell.font      = body_font
+            cell.fill      = fill
+            cell.alignment = body_align
+
+    ws.freeze_panes = "A2"
+    wb.save(str(out_path))
+    logger.info(f"BOM XLSX → {out_path.name}")
+    return out_path
@@ -0,0 +1,187 @@
+"""
+loader.py — STEP file loading with build123d primary and FreeCAD fallback.
+
+Returns a StepModel dataclass used by all other modules.
+FreeCAD fallback invokes the signed app bundle Python to avoid
+Gatekeeper issues on macOS 15 Sequoia.
+"""
+
+import json
+import logging
+import subprocess
+import tempfile
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Any, Optional
+
+logger = logging.getLogger("step_processor.loader")
+
+FREECAD_PYTHON = "/Applications/FreeCAD.app/Contents/Resources/bin/python"
+FREECAD_LIB    = "/Applications/FreeCAD.app/Contents/Resources/lib"
+FREECAD_CMD    = "/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd"
+
+
+@dataclass
+class StepModel:
+    """Unified model object returned by load_step(). Used by all modules."""
+    shape: Any
+    backend: str            # "build123d" | "freecad"
+    path: Path
+    parts: list = field(default_factory=list)
+    face_count: int = 0
+    metadata: dict = field(default_factory=dict)
+
+
+def load_step(filepath) -> Optional["StepModel"]:
+    """Load a STEP file. Tries build123d first; falls back to FreeCAD."""
+    step_path = Path(filepath).expanduser().resolve()
+    if not step_path.exists():
+        logger.error(f"File not found: {step_path}")
+        return None
+    try:
+        return _load_via_build123d(step_path)
+    except ImportError:
+        logger.warning("build123d not available — falling back to FreeCAD")
+        return _load_via_freecad(step_path)
+    except Exception as e:
+        logger.warning(f"build123d failed ({type(e).__name__}: {e}) — falling back to FreeCAD")
+        return _load_via_freecad(step_path)
+
+
+def _load_via_build123d(step_path: Path) -> "StepModel":
+    """Load using build123d. Raises on failure."""
+    from build123d import import_step
+    logger.info(f"[build123d] Loading: {step_path.name}")
+    shape = import_step(str(step_path))
+    face_count = 0
+    try:
+        face_count = sum(1 for _ in shape.faces())
+    except Exception:
+        pass
+    parts = _extract_parts_build123d(shape)
+    logger.info(f"[build123d] Loaded: {step_path.name} | {face_count} faces | {len(parts)} parts")
+    return StepModel(shape=shape, backend="build123d", path=step_path,
+                     parts=parts, face_count=face_count)
+
+
+def _fix_gbk_mojibake(s: str) -> str:
+    """
+    Recover Chinese text stored as mojibake in STEP part labels.
+
+    STEP files from Chinese CAD tools (SolidWorks CN, etc.) embed raw GBK bytes
+    in PRODUCT name strings. OpenCASCADE reads STEP strings as latin-1, which
+    re-interprets those GBK bytes as latin-1 code points — classic mojibake.
+
+    Fix: re-encode the string to latin-1 (restoring the original GBK byte
+    sequence) then decode as GBK to get correct Unicode Chinese characters.
+
+    If the string is pure ASCII, or the round-trip fails (already valid Unicode
+    or a non-GBK extended char), returns the original string unchanged.
+    """
+    if not s or all(ord(c) < 128 for c in s):
+        return s  # pure ASCII: nothing to fix
+    try:
+        return s.encode('latin-1').decode('gbk')
+    except (UnicodeDecodeError, UnicodeEncodeError):
+        return s  # not GBK mojibake — leave original
+
+
+def _extract_parts_build123d(shape) -> list:
+    """Walk build123d compound tree and extract named parts."""
+    parts = []
+    def _walk(compound, level=0, parent_name=""):
+        children = []
+        try:
+            children = compound.children if hasattr(compound, "children") else []
+        except Exception:
+            pass
+        if children:
+            for child in children:
+                raw = (getattr(child, "label", "") or
+                       getattr(child, "name", "") or f"Part_{level}")
+                name = _fix_gbk_mojibake(raw)
+                parts.append({"name": name, "level": level, "parent": parent_name})
+                _walk(child, level + 1, name)
+        else:
+            raw = (getattr(compound, "label", "") or
+                   getattr(compound, "name", "") or "")
+            if raw:
+                name = _fix_gbk_mojibake(raw)
+                parts.append({"name": name, "level": level, "parent": parent_name})
+    _walk(shape)
+    return parts
+
+
+def _load_via_freecad(step_path: Path) -> Optional["StepModel"]:
+    """Load using FreeCAD app bundle Python via subprocess."""
+    if not Path(FREECAD_PYTHON).exists():
+        logger.error(f"FreeCAD Python not found at {FREECAD_PYTHON}. Install FreeCAD.app.")
+        return None
+    logger.info(f"[FreeCAD] Loading: {step_path.name}")
+    script = f"""
+import sys, json
+sys.path.insert(0, {repr(FREECAD_LIB)})
+import FreeCAD, Part
+try:
+    shape = Part.read({repr(str(step_path))})
+    bb = shape.BoundBox
+    sub = shape.SubShapes if hasattr(shape, 'SubShapes') else []
+    parts = [{{"name": f"Part_{{i}}", "level": 1, "parent": "root"}}
+             for i in range(len(sub))]
+    print(json.dumps({{"ok": True, "face_count": len(shape.Faces),
+        "parts": parts,
+        "bbox": {{"XMin": bb.XMin, "XMax": bb.XMax,
+                 "YMin": bb.YMin, "YMax": bb.YMax,
+                 "ZMin": bb.ZMin, "ZMax": bb.ZMax}}}}))
+except Exception as e:
+    print(json.dumps({{"ok": False, "error": str(e)}}))
+"""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+        f.write(script)
+        script_path = f.name
+
+
+    try:
+        proc = subprocess.run([FREECAD_PYTHON, script_path],
+                              capture_output=True, text=True, timeout=120)
+        json_line = next((l.strip() for l in proc.stdout.splitlines()
+                          if l.strip().startswith("{")), None)
+        if not json_line:
+            logger.error(f"[FreeCAD] No JSON output. stderr: {proc.stderr[:300]}")
+            return None
+        data = json.loads(json_line)
+        if not data.get("ok"):
+            logger.error(f"[FreeCAD] Load failed: {data.get('error')}")
+            return None
+        proxy = _FreeCADShapeProxy(data["bbox"], data["face_count"])
+        logger.info(f"[FreeCAD] Loaded: {step_path.name} | {data['face_count']} faces")
+        return StepModel(shape=proxy, backend="freecad", path=step_path,
+                         parts=data.get("parts", []),
+                         face_count=data["face_count"],
+                         metadata={"bbox": data["bbox"]})
+    except subprocess.TimeoutExpired:
+        logger.error("[FreeCAD] Load timed out after 120s")
+        return None
+    except Exception as e:
+        logger.error(f"[FreeCAD] Unexpected error: {e}")
+        return None
+    finally:
+        Path(script_path).unlink(missing_ok=True)
+
+
+class _FreeCADShapeProxy:
+    """Proxy carrying FreeCAD geometry data extracted via subprocess."""
+    def __init__(self, bbox_dict: dict, face_count: int):
+        self.BoundBox = _BoundBox(bbox_dict)
+        self.face_count = face_count
+        self.Faces = [None] * face_count
+    def faces(self):
+        for _ in range(self.face_count):
+            yield object()
+
+
+class _BoundBox:
+    def __init__(self, d: dict):
+        self.XMin = d.get("XMin", 0); self.XMax = d.get("XMax", 0)
+        self.YMin = d.get("YMin", 0); self.YMax = d.get("YMax", 0)
+        self.ZMin = d.get("ZMin", 0); self.ZMax = d.get("ZMax", 0)
@@ -0,0 +1,335 @@
+"""
+query_engine.py — Natural language geometric query handler.
+
+Supports both single-query (--query "...") and interactive REPL (--repl).
+REPL keeps the model in memory between queries for speed.
+All output is formatted ASCII tables.
+
+Supported query types (see SKILL.md for full reference):
+  bounding box          overall model extents
+  face count            total faces by type
+  all parts             full assembly listing
+  list all holes        all cylindrical through-features
+  list all mounting holes   cylinders dia < 15mm, axis ⊥ primary face
+  holes diameter N      filter by diameter
+  wall thickness        min distance between opposing parallel faces
+  largest face          largest planar face area
+  help                  list supported queries
+  exit / quit           exit REPL
+"""
+import logging
+import re
+import textwrap
+from typing import Optional
+
+from .loader import StepModel
+
+logger = logging.getLogger("step_processor.query")
+
+# Regex patterns for query routing
+_BBOX_RE      = re.compile(r"\b(bounding.?box|extents|dimensions|overall.?size)\b", re.I)
+_FACECOUNT_RE = re.compile(r"\b(face.?count|how many faces|number of faces)\b", re.I)
+_PARTS_RE     = re.compile(r"\ball.?parts|part.?list|assembly|components\b", re.I)
+_HOLES_RE     = re.compile(r"\bholes?\b", re.I)
+_MOUNTING_RE  = re.compile(r"\bmounting\b", re.I)
+_DIA_RE       = re.compile(r"diameter\s+([\d.]+)\s*mm?", re.I)
+_WALL_RE      = re.compile(r"\bwall.?thickness\b", re.I)
+_LARGEST_RE   = re.compile(r"\blargest.?face\b", re.I)
+_HELP_RE      = re.compile(r"\bhelp\b", re.I)
+_EXIT_RE      = re.compile(r"\b(exit|quit|q)\b", re.I)
+
+
+def run_query(model: StepModel, query: str) -> str:
+    """Dispatch a query string and return formatted output."""
+    q = query.strip()
+    if _EXIT_RE.search(q):
+        return "EXIT"
+    if _HELP_RE.search(q):
+        return _help_text()
+    if _BBOX_RE.search(q):
+        return _query_bounding_box(model)
+    if _FACECOUNT_RE.search(q):
+        return _query_face_count(model)
+    if _PARTS_RE.search(q):
+        return _query_all_parts(model)
+    if _HOLES_RE.search(q):
+        dia_match = _DIA_RE.search(q)
+        dia_filter = float(dia_match.group(1)) if dia_match else None
+        mounting_only = bool(_MOUNTING_RE.search(q))
+        return _query_holes(model, mounting_only=mounting_only, dia_filter=dia_filter)
+    if _WALL_RE.search(q):
+        return _query_wall_thickness(model)
+    if _LARGEST_RE.search(q):
+        return _query_largest_face(model)
+    return (f"Query not recognized: '{q}'\n"
+            f"Type 'help' to see supported queries.")
+
+
+def repl(model: StepModel, step_path):
+    """Launch interactive REPL. Returns when user types exit/quit."""
+    print(f"\nSTEP Query REPL — {step_path.name}")
+    print("Type 'help' for supported queries, 'exit' to quit.\n")
+    while True:
+        try:
+            q = input("> ").strip()
+        except (EOFError, KeyboardInterrupt):
+            print()
+            break
+        if not q:
+            continue
+        result = run_query(model, q)
+        if result == "EXIT":
+            break
+        print(result)
+        print()
+
+
+# ── Query implementations ─────────────────────────────────────────────────────
+
+def _query_bounding_box(model: StepModel) -> str:
+    try:
+        if model.backend == "build123d":
+            bb = model.shape.bounding_box()
+            x = round(bb.size.X, 2)
+            y = round(bb.size.Y, 2)
+            z = round(bb.size.Z, 2)
+        else:
+            bb = model.shape.bounding_box
+            x = round(bb.XMax - bb.XMin, 2)
+            y = round(bb.YMax - bb.YMin, 2)
+            z = round(bb.ZMax - bb.ZMin, 2)
+        return _table(
+            f"BOUNDING BOX — {model.path.name}",
+            ["Axis", "Dimension"],
+            [["Width (X)",  f"{x} mm ({x/25.4:.3f} in)"],
+             ["Depth (Y)",  f"{y} mm ({y/25.4:.3f} in)"],
+             ["Height (Z)", f"{z} mm ({z/25.4:.3f} in)"]]
+        )
+    except Exception as e:
+        return f"Bounding box query failed: {e}"
+
+
+def _query_face_count(model: StepModel) -> str:
+    if model.backend != "build123d":
+        return f"Face count query requires build123d (loaded via {model.backend})"
+    try:
+        from build123d import Compound
+        all_faces = model.shape.faces()
+        planar = sum(1 for f in all_faces if f.geom_type() == "PLANE")
+        cylindrical = sum(1 for f in all_faces if f.geom_type() == "CYLINDER")
+        other = len(all_faces) - planar - cylindrical
+        return _table(
+            f"FACE COUNT — {model.path.name}",
+            ["Type", "Count"],
+            [["Planar", str(planar)],
+             ["Cylindrical", str(cylindrical)],
+             ["Other", str(other)],
+             ["Total", str(len(all_faces))]]
+        )
+    except Exception as e:
+        return f"Face count failed: {e}"
+
+
+def _query_all_parts(model: StepModel) -> str:
+    if not model.parts:
+        return (f"No assembly structure found in {model.path.name}.\n"
+                f"File appears to be a single solid body.")
+    rows = []
+    for p in model.parts:
+        rows.append([
+            p.get("part_number", "—"),
+            p.get("name", "—"),
+            str(p.get("quantity", 1)),
+            str(p.get("level", 0)),
+            p.get("parent", ""),
+        ])
+    return _table(
+        f"ALL PARTS — {model.path.name}",
+        ["#", "Name", "Qty", "Level", "Parent"],
+        rows
+    ) + f"\nTotal: {len(model.parts)} parts"
+
+
+def _query_holes(model: StepModel, mounting_only: bool = False,
+                 dia_filter: Optional[float] = None) -> str:
+    if model.backend != "build123d":
+        return f"Hole query requires build123d (loaded via {model.backend})"
+    try:
+        holes = _find_holes(model, mounting_only=mounting_only, dia_filter=dia_filter)
+        if not holes:
+            label = "mounting holes" if mounting_only else "holes"
+            qualifier = f" ≈{dia_filter}mm" if dia_filter else ""
+            return f"No {label}{qualifier} found in {model.path.name}."
+        header = "MOUNTING HOLES" if mounting_only else "ALL HOLES"
+        # Group by diameter bucket for summary view
+        from collections import Counter
+        dia_counts = Counter(round(h["dia"], 1) for h in holes)
+        MAX_ROWS = 50
+        display_holes = holes[:MAX_ROWS]
+        rows = []
+        for i, h in enumerate(display_holes, 1):
+            rows.append([
+                str(i),
+                f"{h['dia']:.2f} mm",
+                f"{h['depth']:.2f} mm" if h["depth"] else "—",
+                f"({h['x']:.1f}, {h['y']:.1f}, {h['z']:.1f})",
+            ])
+        result = _table(
+            f"{header} — {model.path.name}",
+            ["#", "Diameter", "Depth", "Position (x,y,z)"],
+            rows
+        )
+        result += f"\nShowing {len(display_holes)} of {len(holes)} unique hole locations"
+        result += "\n\nDIAMETER SUMMARY"
+        result += "\n" + "─" * 30
+        for dia, count in sorted(dia_counts.items()):
+            result += f"\n  {dia:.1f} mm  ×{count}"
+        result += "\n" + "─" * 30
+        return result
+    except Exception as e:
+        return f"Hole query failed: {e}"
+
+
+def _find_holes(model: StepModel, mounting_only: bool, dia_filter):
+    """Extract and deduplicate cylindrical faces from build123d model.
+
+    Deduplication: round axis position to 1mm grid, group by (dia_bucket, x, y, z).
+    This collapses multiple cylindrical faces from the same physical hole
+    (e.g. inner + outer surface of same cylinder) into one entry.
+    """
+    from OCP.BRepAdaptor import BRepAdaptor_Surface
+    from OCP.GeomAbs import GeomAbs_Cylinder
+
+    seen = {}  # key → best entry
+    try:
+        faces = model.shape.faces()
+    except Exception:
+        return []
+
+    for face in faces:
+        try:
+            adaptor = BRepAdaptor_Surface(face.wrapped)
+            if adaptor.GetType() != GeomAbs_Cylinder:
+                continue
+            cyl = adaptor.Cylinder()
+            r = cyl.Radius()
+            dia = round(r * 2, 2)
+            # Diameter filters
+            if mounting_only and dia > 15.0:
+                continue
+            if dia_filter and abs(dia - dia_filter) > 0.5:
+                continue
+            axis_pt = cyl.Location()
+            # Round to 1mm grid for deduplication
+            gx = round(axis_pt.X())
+            gy = round(axis_pt.Y())
+            gz = round(axis_pt.Z())
+            dia_bucket = round(dia, 1)
+            key = (dia_bucket, gx, gy, gz)
+            if key not in seen:
+                bb = face.bounding_box()
+                depth = round(max(bb.size.X, bb.size.Y, bb.size.Z), 2)
+                seen[key] = {
+                    "dia": dia,
+                    "depth": depth,
+                    "x": round(axis_pt.X(), 1),
+                    "y": round(axis_pt.Y(), 1),
+                    "z": round(axis_pt.Z(), 1),
+                }
+        except Exception:
+            continue
+    return list(seen.values())
+
+
+def _query_wall_thickness(model: StepModel) -> str:
+    if model.backend != "build123d":
+        return f"Wall thickness query requires build123d (loaded via {model.backend})"
+    try:
+        faces = model.shape.faces()
+        planar = [f for f in faces if f.geom_type() == "PLANE"]
+        if len(planar) < 2:
+            return "Insufficient planar faces to determine wall thickness."
+        # Heuristic: find minimum non-zero distance between parallel opposing faces
+        min_t = None
+        for i, f1 in enumerate(planar):
+            n1 = f1.normal_at()
+            for f2 in planar[i+1:]:
+                n2 = f2.normal_at()
+                # Parallel if normals are anti-parallel
+                dot = abs(n1.dot(n2))
+                if dot > 0.99:
+                    c1 = f1.center()
+                    c2 = f2.center()
+                    dist = round(abs((c1 - c2).dot(n1)), 3)
+                    if dist > 0.01:
+                        if min_t is None or dist < min_t:
+                            min_t = dist
+        if min_t is None:
+            return "Could not determine wall thickness from available faces."
+        return _table(
+            f"WALL THICKNESS — {model.path.name}",
+            ["Measurement", "Value"],
+            [["Minimum wall thickness",
+              f"{min_t} mm ({min_t/25.4:.3f} in)"]]
+        )
+    except Exception as e:
+        return f"Wall thickness query failed: {e}"
+
+
+def _query_largest_face(model: StepModel) -> str:
+    if model.backend != "build123d":
+        return f"Largest face query requires build123d (loaded via {model.backend})"
+    try:
+        faces = model.shape.faces()
+        planar = [(f, f.area()) for f in faces if f.geom_type() == "PLANE"]
+        if not planar:
+            return "No planar faces found."
+        largest, area = max(planar, key=lambda x: x[1])
+        bb = largest.bounding_box()
+        return _table(
+            f"LARGEST PLANAR FACE — {model.path.name}",
+            ["Property", "Value"],
+            [["Area",    f"{round(area, 2)} mm²"],
+             ["Width",   f"{round(bb.size.X, 2)} mm"],
+             ["Height",  f"{round(bb.size.Z, 2)} mm"]]
+        )
+    except Exception as e:
+        return f"Largest face query failed: {e}"
+
+
+# ── Formatting helpers ─────────────────────────────────────────────────────────
+
+def _table(title: str, headers: list, rows: list) -> str:
+    col_widths = [len(h) for h in headers]
+    for row in rows:
+        for i, cell in enumerate(row):
+            col_widths[i] = max(col_widths[i], len(str(cell)))
+    sep = "─" * (sum(col_widths) + 3 * len(headers) - 1)
+    lines = [title, sep]
+    header_line = "  ".join(h.ljust(col_widths[i]) for i, h in enumerate(headers))
+    lines.append(header_line)
+    lines.append(sep)
+    for row in rows:
+        lines.append("  ".join(str(cell).ljust(col_widths[i]) for i, cell in enumerate(row)))
+    lines.append(sep)
+    return "\n".join(lines)
+
+
+def _help_text() -> str:
+    return textwrap.dedent("""\
+    SUPPORTED QUERIES
+    ─────────────────────────────────────────────────────────────
+    bounding box            Overall model extents (W×D×H in mm)
+    face count              Faces by type (planar, cylindrical, other)
+    all parts               Full assembly listing with quantities
+    list all holes          All cylindrical through-features
+    list all mounting holes Holes smaller than 15mm diameter
+    holes diameter 4.2mm    Filter holes by specific diameter
+    wall thickness          Minimum wall thickness estimate
+    largest face            Largest planar face area
+    help                    Show this message
+    exit                    Exit the REPL
+    ─────────────────────────────────────────────────────────────
+    Tip: geometry queries require build123d backend.
+    If the file loaded via FreeCAD fallback, only bounding box
+    and parts list are available.""")
@@ -0,0 +1,321 @@
+"""
+renderer.py — Offscreen PNG thumbnail generation.
+
+Pipeline (with color): build123d → GLTF export → trimesh scene → pyrender → PNG
+Pipeline (fallback):   build123d → per-solid STL → colored trimesh scene → pyrender → PNG
+
+Coordinate convention AFTER STEP→GLTF export→trimesh load:
+  trimesh applies a Z-up→Y-up GLTF convention that swaps STEP's Y and Z axes:
+    X = width  (~248mm for MR16) — left/right
+    Y = depth  (~41mm  for MR16) — front/back; Y_min=screen face, Y_max=back panel
+    Z = height (~459mm for MR16) — tall axis;  Z_min=top end,    Z_max=bottom end
+  → "front" camera sits at -Y (screen side) looking toward +Y to see the LCD face.
+  → World "up" vector is (0,0,-1) — negative Z = top of display in image.
+
+6 standard views: front, rear, left, right, iso_left, iso_right
+"""
+import logging
+import tempfile
+from pathlib import Path
+
+import numpy as np
+
+from .loader import StepModel
+
+logger = logging.getLogger("step_processor.renderer")
+
+# Camera direction vectors: where the camera is PLACED relative to model center.
+# Camera always looks toward center from direction * distance.
+#
+# Trimesh world axes after GLTF load (STEP Y and Z are swapped by GLTF Y-up conv):
+#   X = width  — left/right
+#   Y = depth  — Y_min = screen face (LCD), Y_max = back panel (ports)
+#   Z = height — Z_min = TOP end of display, Z_max = BOTTOM end of display
+#
+# "front": camera at -Y (screen side) looks toward +Y → sees LCD face.
+# "rear":  camera at +Y (back side) looks toward -Y  → sees port panel.
+# "left":  camera at -X looks toward +X               → sees left edge.
+# "right": camera at +X looks toward -X               → sees right edge.
+# iso views: -Y component keeps camera on screen side; -Z = toward top end.
+VIEW_CAMERAS = {
+    "front":     ( 0, -1,  0),    # LCD screen face  (Y_min side)
+    "rear":      ( 0,  1,  0),    # back panel/ports (Y_max side)
+    "left":      (-1,  0,  0),    # left edge        (X_min side)
+    "right":     ( 1,  0,  0),    # right edge       (X_max side)
+    "top":       ( 0,  0, -1),    # top end          (Z_min side)
+    "bottom":    ( 0,  0,  1),    # bottom end       (Z_max side)
+    "iso_left":  (-1, -1, -0.5),  # front-left-above: screen + left edge + top
+    "iso_right": ( 1, -1, -0.5),  # front-right-above: screen + right edge + top
+}
+DEFAULT_VIEWS  = ["front", "rear", "left", "right", "iso_left", "iso_right"]
+
+# Color palette for per-part coloring when GLTF has no embedded colors
+# 20 distinct RGBA colors (alpha=200 for slight transparency on overlaps)
+PART_COLORS = [
+    [180, 180, 185, 255],  # light steel
+    [ 70, 130, 180, 255],  # steel blue
+    [205, 133,  63, 255],  # peru / bronze
+    [ 60, 179, 113, 255],  # medium sea green
+    [188, 143, 143, 255],  # rosy brown
+    [100, 149, 237, 255],  # cornflower blue
+    [255, 160,  50, 255],  # dark orange
+    [147, 112, 219, 255],  # medium purple
+    [ 46, 139,  87, 255],  # sea green
+    [205,  92,  92, 255],  # indian red
+    [135, 206, 235, 255],  # sky blue
+    [244, 164,  96, 255],  # sandy brown
+    [106,  90, 205, 255],  # slate blue
+    [ 32, 178, 170, 255],  # light sea green
+    [220,  20,  60, 255],  # crimson
+    [218, 165,  32, 255],  # goldenrod
+    [ 72,  61, 139, 255],  # dark slate blue
+    [143, 188, 143, 255],  # dark sea green
+    [255,  99,  71, 255],  # tomato
+    [176, 196, 222, 255],  # light steel blue
+]
+DEFAULT_WIDTH  = 1024
+DEFAULT_HEIGHT = 768
+
+
+def render_views(model: StepModel, step_path: Path,
+                 views=None, width=DEFAULT_WIDTH, height=DEFAULT_HEIGHT) -> dict:
+    """Render PNG views. Returns dict of view_name → output Path."""
+    views = views or DEFAULT_VIEWS
+    stem = step_path.stem
+    out_dir = step_path.parent
+    results = {}
+    mesh = _get_mesh(model, step_path)
+    if mesh is None:
+        logger.warning("Could not obtain mesh — thumbnails skipped")
+        return results
+    for view_name in views:
+        if view_name not in VIEW_CAMERAS:
+            logger.warning(f"Unknown view '{view_name}' — skipping")
+            continue
+        out_path = out_dir / f"{stem}_{view_name}.png"
+        try:
+            _render_single_view(mesh, VIEW_CAMERAS[view_name], out_path, width, height)
+            results[view_name] = out_path
+            logger.info(f"Rendered: {out_path.name}")
+        except Exception as e:
+            logger.warning(f"Render failed for '{view_name}': {e}")
+    return results
+
+
+def _get_mesh(model: StepModel, step_path: Path):
+    """Get a single assembled trimesh.Trimesh from the model.
+
+    Always returns a single concatenated mesh (not a Scene) so the camera
+    distance and bounds calculations are correct and parts don't explode.
+
+    Priority:
+      1. build123d → GLTF → scene.dump() → concatenate with transforms applied
+         (preserves per-part colors if embedded in STEP)
+      2. build123d → single STL of full assembly (fallback, monochrome but correct)
+      3. FreeCAD path → bounding box box mesh
+    """
+    try:
+        import trimesh
+    except ImportError:
+        logger.warning("trimesh not installed — thumbnails unavailable. pip install trimesh")
+        return None
+
+    if model.backend == "build123d":
+        # ── GLTF path: color-aware, transforms flattened via scene.dump() ─────
+        with tempfile.NamedTemporaryFile(suffix=".gltf", delete=False) as tmp:
+            gltf_path = Path(tmp.name)
+        try:
+            from build123d import export_gltf
+            import warnings
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore")
+                export_gltf(model.shape, str(gltf_path))
+            scene = trimesh.load(str(gltf_path))
+
+            if isinstance(scene, trimesh.Scene) and scene.geometry:
+                # scene.dump() applies the full transform graph → parts at correct positions
+                dumped = scene.dump()
+                if dumped:
+                    # Pull baseColorFactor directly from PBR material per mesh.
+                    # .to_color() loses this in some trimesh versions.
+                    materialized = []
+                    for m in dumped:
+                        try:
+                            bc = m.visual.material.baseColorFactor
+                            if bc is not None:
+                                m.visual = trimesh.visual.ColorVisuals(
+                                    mesh=m, face_colors=np.array(bc, dtype=np.uint8))
+                            else:
+                                m.visual = trimesh.visual.ColorVisuals(
+                                    mesh=m, face_colors=[185, 190, 195, 255])
+                        except Exception:
+                            try:
+                                m.visual = m.visual.to_color()
+                            except Exception:
+                                pass
+                        materialized.append(m)
+
+                    mesh = trimesh.util.concatenate(materialized)
+                    if mesh is not None and len(mesh.faces) > 0:
+                        n_colors = len(set(
+                            tuple(c) for c in mesh.visual.face_colors[:, :3][::1000]
+                        )) if hasattr(mesh.visual, 'face_colors') else 0
+                        logger.info(f"GLTF: assembled {len(mesh.faces)} faces, "
+                                    f"~{n_colors} distinct colors sampled")
+                        return mesh
+        except Exception as e:
+            logger.warning(f"GLTF path failed ({e}) — falling back to STL")
+        finally:
+            try:
+                gltf_path.unlink()
+            except Exception:
+                pass
+
+        # ── STL fallback: single merged mesh, correct positions, monochrome ───
+        with tempfile.NamedTemporaryFile(suffix=".stl", delete=False) as tmp:
+            stl_path = Path(tmp.name)
+        try:
+            from build123d import export_stl
+            export_stl(model.shape, str(stl_path))
+            mesh = trimesh.load(str(stl_path), force="mesh")
+            if mesh is not None and len(mesh.faces) > 0:
+                mesh.visual.face_colors = [185, 190, 195, 255]
+                logger.info(f"STL fallback: {len(mesh.faces)} faces (uniform color)")
+                return mesh
+        except Exception as e:
+            logger.warning(f"STL fallback failed ({e})")
+        finally:
+            try:
+                stl_path.unlink()
+            except Exception:
+                pass
+
+    # FreeCAD / last resort: bounding box
+    return _bbox_wireframe_mesh(model)
+
+
+def _mesh_has_color(mesh) -> bool:
+    """Return True if the mesh has meaningful (non-gray) face colors."""
+    try:
+        fc = mesh.visual.face_colors
+        if fc is None or len(fc) == 0:
+            return False
+        # If all faces are within ±25 of [128,128,128] treat as uncolored
+        gray = [128, 128, 128]
+        mean_rgb = fc[:, :3].mean(axis=0)
+        return not all(abs(int(mean_rgb[i]) - gray[i]) < 25 for i in range(3))
+    except Exception:
+        return False
+
+
+def _bbox_wireframe_mesh(model: StepModel):
+    """Create a simple box mesh from the model's bounding box. Last-resort fallback."""
+    try:
+        import trimesh
+        bb = model.shape.bounding_box()
+        # _FreeCADShapeProxy stores a _BoundBox
+        if hasattr(bb, "XMin"):
+            extents = [
+                bb.XMax - bb.XMin,
+                bb.YMax - bb.YMin,
+                bb.ZMax - bb.ZMin,
+            ]
+            center = [
+                (bb.XMax + bb.XMin) / 2,
+                (bb.YMax + bb.YMin) / 2,
+                (bb.ZMax + bb.ZMin) / 2,
+            ]
+        else:
+            # build123d BoundBox
+            extents = [bb.size.X, bb.size.Y, bb.size.Z]
+            center = [bb.center.X, bb.center.Y, bb.center.Z]
+        mesh = trimesh.creation.box(extents=extents)
+        mesh.apply_translation(center)
+        logger.debug("Using bbox wireframe mesh for rendering")
+        return mesh
+    except Exception as e:
+        logger.warning(f"Bbox wireframe mesh failed: {e}")
+        return None
+
+
+def _render_single_view(mesh, camera_direction: tuple, out_path: Path,
+                         width: int, height: int):
+    """Render one view using pyrender offscreen, save to out_path."""
+    try:
+        import pyrender
+    except ImportError:
+        raise ImportError("pyrender not installed. pip install pyrender")
+
+    # Normalize camera direction
+    direction = np.array(camera_direction, dtype=float)
+    direction = direction / np.linalg.norm(direction)
+
+    # Bounding box of the assembled mesh
+    bounds = mesh.bounds  # shape (2,3): [[xmin,ymin,zmin],[xmax,ymax,zmax]]
+    center = (bounds[0] + bounds[1]) / 2.0
+    diag = np.linalg.norm(bounds[1] - bounds[0])
+
+    # Camera sits at 2.5× diagonal distance from center, looking at center
+    camera_distance = diag * 2.5
+    eye = center + direction * camera_distance
+
+    # World up: (0,0,-1) = negative Z = top of display in trimesh GLTF space.
+    # Fallback to (0,-1,0) for top/bottom end views where direction ≈ ±Z.
+    world_up = np.array([0, 0, -1], dtype=float)
+    if abs(np.dot(direction, world_up)) > 0.9:
+        world_up = np.array([0, -1, 0], dtype=float)
+
+    # Proven camera frame formula (right-handed, same structure as original code):
+    #   right   = cross(world_up, direction)   [world_up × backward]
+    #   cam_up  = cross(direction, right)       [backward × right]
+    #   col2    = direction                     [camera +Z = backward; looks down -Z]
+    right = np.cross(world_up, direction)
+    if np.linalg.norm(right) < 1e-8:
+        right = np.cross(np.array([1, 0, 0], dtype=float), direction)
+    right = right / np.linalg.norm(right)
+    cam_up = np.cross(direction, right)
+    cam_up = cam_up / np.linalg.norm(cam_up)
+
+    # 4×4 camera pose: columns = [right, cam_up, backward, eye]
+    camera_pose = np.eye(4)
+    camera_pose[:3, 0] = right
+    camera_pose[:3, 1] = cam_up
+    camera_pose[:3, 2] = direction   # camera +Z = backward; pyrender looks down -Z
+    camera_pose[:3, 3] = eye
+
+    # Build pyrender scene — white background
+    pr_scene = pyrender.Scene(ambient_light=[0.35, 0.35, 0.35],
+                              bg_color=[255, 255, 255, 255])
+    pr_scene.add(pyrender.Mesh.from_trimesh(mesh, smooth=False))
+
+    # FOV sized so the model fills ~80% of the frame
+    yfov = 2.0 * np.arctan((diag * 0.5) / camera_distance) * 1.25
+    camera = pyrender.PerspectiveCamera(yfov=yfov, aspectRatio=width / height)
+    pr_scene.add(camera, pose=camera_pose)
+
+    # Key light from camera position + fill from above-opposite
+    pr_scene.add(pyrender.DirectionalLight(color=np.ones(3), intensity=4.5),
+                 pose=camera_pose)
+    fill_pose = np.eye(4)
+    # Fill light: offset from top of display (-Z) to avoid zero-vector when
+    # direction is parallel to (0,1,0) (e.g. rear view).
+    fill_dir = -direction + np.array([0, 0, -1], dtype=float)
+    fill_norm = np.linalg.norm(fill_dir)
+    if fill_norm < 1e-8:
+        fill_dir = np.array([0, 0, -1], dtype=float)
+    else:
+        fill_dir = fill_dir / fill_norm
+    fill_eye = center - fill_dir * camera_distance
+    fill_pose[:3, 3] = fill_eye
+    pr_scene.add(pyrender.DirectionalLight(color=np.ones(3), intensity=1.8),
+                 pose=fill_pose)
+
+    # Offscreen render
+    r = pyrender.OffscreenRenderer(viewport_width=width, viewport_height=height)
+    try:
+        color, _ = r.render(pr_scene)
+    finally:
+        r.delete()
+
+    from PIL import Image
+    Image.fromarray(color).save(str(out_path))
@@ -0,0 +1,103 @@
+"""
+rewriter.py — STEP label rewriter for Chinese→English translation.
+
+Produces {stem}_EN.step — NEVER modifies source file.
+Targets only PRODUCT entity name strings.
+Validates entity count before/after to ensure file integrity.
+"""
+import logging
+import re
+from pathlib import Path
+
+logger = logging.getLogger("step_processor.rewriter")
+
+# Targets both quoted strings in: #N = PRODUCT('id', 'name', 'description', ...)
+# ISO 10303-21 PRODUCT has two name fields; CAD viewers typically display the second.
+# Chinese CAD exports set both to the same Chinese string, so both must be replaced.
+# Groups: (prefix)  (id)  (sep)  (name)  (suffix-quote)
+PRODUCT_PATTERN = re.compile(
+    r"(#\d+\s*=\s*PRODUCT\s*\(\s*')([^']*)(',\s*')([^']*)(')",
+    re.IGNORECASE
+)
+ENTITY_PATTERN = re.compile(r"^#\d+\s*=\s*\S+\s*\(", re.MULTILINE)
+
+
+def _read_step_for_rewrite(source_path: Path) -> str:
+    """Read STEP file with GBK-aware encoding detection.
+
+    STEP files from Chinese CAD tools embed raw GBK bytes in PRODUCT name
+    strings.  Reading as UTF-8 turns those bytes into replacement characters
+    (U+FFFD), which makes the Chinese→English lookup fail.  We try GBK when
+    UTF-8 produces replacement chars so the regex substitution can actually
+    find and replace the Chinese strings.
+    """
+    for enc in ('utf-8', 'gbk'):
+        try:
+            text = source_path.read_text(encoding=enc)
+            if enc == 'utf-8' and '�' in text:
+                continue  # has replacement chars — retry as GBK
+            return text
+        except (UnicodeDecodeError, LookupError):
+            continue
+    return source_path.read_text(encoding='latin-1', errors='replace')
+
+
+def rewrite_step(source_path: Path, translation_map: dict):
+    """
+    Produce English-labeled copy of the STEP file.
+    Returns output Path or None if no rewrite needed or failed.
+    """
+    if not translation_map:
+        logger.info("No translations to apply — _EN.step skipped")
+        return None
+    try:
+        source_text = _read_step_for_rewrite(source_path)
+    except Exception as e:
+        logger.error(f"Could not read source STEP: {e}")
+        return None
+    original_count = len(ENTITY_PATTERN.findall(source_text))
+    if not any(orig in source_text for orig in translation_map):
+        logger.info("No Chinese labels in STEP text — _EN.step skipped")
+        return None
+    lines = source_text.splitlines(keepends=True)
+    replaced_count = 0
+    output_lines = []
+    for line in lines:
+        new_line, count = _replace_product_names(line, translation_map)
+        replaced_count += count
+        output_lines.append(new_line)
+    output_text = "".join(output_lines)
+    new_count = len(ENTITY_PATTERN.findall(output_text))
+    if new_count != original_count:
+        logger.error(
+            f"Entity count mismatch: {original_count} → {new_count}. "
+            "Aborting — source file untouched.")
+        return None
+    if replaced_count == 0:
+        logger.info("No PRODUCT entities matched — _EN.step skipped")
+        return None
+    out_path = source_path.parent / f"{source_path.stem}_EN.step"
+    try:
+        out_path.write_text(output_text, encoding="utf-8")
+        logger.info(f"_EN.step written: {out_path.name} ({replaced_count} labels replaced)")
+        return out_path
+    except Exception as e:
+        logger.error(f"Failed to write _EN.step: {e}")
+        out_path.unlink(missing_ok=True)
+        return None
+
+
+def _replace_product_names(line: str, translation_map: dict):
+    count = 0
+    def replacer(m):
+        nonlocal count
+        # Try id field first (group 2), fall back to name field (group 4)
+        # Both are Chinese in Chinese CAD exports; replace both with English.
+        translated = translation_map.get(m.group(2)) or translation_map.get(m.group(4))
+        if translated:
+            count += 1
+            # Replace both the id field and the name field
+            return m.group(1) + translated + m.group(3) + translated + m.group(5)
+        return m.group(0)
+    new_line = PRODUCT_PATTERN.sub(replacer, line)
+    return new_line, count
@@ -0,0 +1,107 @@
+"""
+translator.py — Chinese to English part name translation via Claude API.
+
+Detects CJK unicode range. Batches all names in a single API call per file.
+Flags uncertain translations in the notes column.
+"""
+
+import json
+import logging
+import os
+import re
+
+import pandas as pd
+
+logger = logging.getLogger("step_processor.translator")
+
+CJK_PATTERN = re.compile(r'[一-鿿㐀-䶿]')
+
+SYSTEM_PROMPT = (
+    "You are a mechanical engineering translator specializing in Chinese "
+    "manufacturing CAD files for display and enclosure products. "
+    "Translate the following part names from Chinese to English. "
+    "Preserve technical precision. Use standard hardware/manufacturing terminology. "
+    "Output ONLY a JSON object mapping original Chinese to translated English, nothing else.\n"
+    'Example: {"安装支架": "Mounting Bracket", "螺钉M4": "M4 Screw", "前面板": "Front Panel"}'
+)
+
+
+def has_chinese(text: str) -> bool:
+    """Return True if text contains CJK characters."""
+    return bool(CJK_PATTERN.search(str(text)))
+
+
+def translate_bom(df: pd.DataFrame, model_name: str = "") -> pd.DataFrame:
+    """Detect Chinese part names and translate via Claude API."""
+    needs_translation = df["part_name_original"].apply(has_chinese)
+    chinese_names = df.loc[needs_translation, "part_name_original"].unique().tolist()
+    if not chinese_names:
+        logger.info("No Chinese part names detected — translation skipped")
+        return df
+    logger.info(f"Translating {len(chinese_names)} Chinese part names...")
+    translation_map = _call_claude_api(chinese_names, model_name)
+    if not translation_map:
+        logger.warning("Translation API returned no results — retaining original names")
+        df.loc[needs_translation, "notes"] = (
+            df.loc[needs_translation, "notes"].apply(
+                lambda n: (n + "; " if n else "") + "translation-failed"))
+        return df
+    for idx, row in df.iterrows():
+        original = row["part_name_original"]
+        if has_chinese(original):
+            translated = translation_map.get(original)
+            if translated:
+                df.at[idx, "part_name_english"] = translated
+                note_tag = "ambiguous-translation" if "[?]" in translated else "machine-translated"
+            else:
+                df.at[idx, "part_name_english"] = original
+                note_tag = "translation-missing"
+            existing = row["notes"]
+            df.at[idx, "notes"] = (existing + "; " if existing else "") + note_tag
+    logger.info(f"Translated {needs_translation.sum()} parts")
+    return df
+
+
+def get_translation_map(df: pd.DataFrame) -> dict:
+    """Return dict of original → english for all translated rows."""
+    mask = df["part_name_original"] != df["part_name_english"]
+    return dict(zip(df.loc[mask, "part_name_original"],
+                    df.loc[mask, "part_name_english"]))
+
+
+def _call_claude_api(names: list, model_name: str = "") -> dict:
+    """Single batched Claude API call. Returns original→translated dict."""
+    api_key = os.environ.get("ANTHROPIC_API_KEY")
+    if not api_key:
+        logger.error("ANTHROPIC_API_KEY not set — translation unavailable")
+        return {}
+    try:
+        import anthropic
+    except ImportError:
+        logger.error("anthropic package not installed — pip install anthropic")
+        return {}
+    names_json = json.dumps(names, ensure_ascii=False)
+    user_msg = f"Translate these part names from Chinese to English:\n{names_json}"
+    if model_name:
+        user_msg += f"\n\nContext: Parts from a {model_name} display enclosure assembly."
+    try:
+        client = anthropic.Anthropic(api_key=api_key)
+        response = client.messages.create(
+            model="claude-haiku-4-5-20251001",
+            max_tokens=2048,
+            system=SYSTEM_PROMPT,
+            messages=[{"role": "user", "content": user_msg}],
+        )
+        text = response.content[0].text.strip()
+        json_match = re.search(r'\{.*\}', text, re.DOTALL)
+        if json_match:
+            text = json_match.group(0)
+        result = json.loads(text)
+        logger.info(f"API returned {len(result)} translations")
+        return result
+    except json.JSONDecodeError as e:
+        logger.error(f"Translation API JSON parse error: {e}")
+        return {}
+    except Exception as e:
+        logger.error(f"Translation API error: {type(e).__name__}: {e}")
+        return {}
@@ -0,0 +1,286 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "mpmedia/step-processor/external-dimensional-diagram/v1",
+  "title": "ExternalDimensionalDiagram",
+  "description": "Schema for the external dimensional diagram sub-skill output. Designed for AI consumption, search indexing, and downstream documentation workflows (Odoo product data, CoWork, PDF assembly). All geometry values in millimeters. Imperial equivalents computed at export time.",
+
+  "type": "object",
+  "required": [
+    "schema_version", "generated_at", "source_path", "model_name",
+    "mode", "style", "engine_used", "units",
+    "overall_width", "overall_height", "overall_depth",
+    "bounding_box", "selected_parts", "excluded_parts",
+    "layout", "outputs", "warnings", "notes"
+  ],
+
+  "properties": {
+
+    "schema_version": {
+      "type": "string",
+      "const": "1.0",
+      "description": "Schema version. Increment minor for additive changes, major for breaking changes."
+    },
+
+    "generated_at": {
+      "type": "string",
+      "format": "date-time",
+      "description": "ISO 8601 UTC timestamp of generation run."
+    },
+
+    "source_path": {
+      "type": "string",
+      "description": "Absolute path to the source STEP file."
+    },
+
+    "model_name": {
+      "type": "string",
+      "description": "Human-readable product/model name. Sourced from datablock MD file if present, otherwise derived from filename stem."
+    },
+
+    "mode": {
+      "type": "string",
+      "enum": ["enclosure_only", "enclosure_plus_mounting", "mounting_only"],
+      "description": "Geometry scope mode used for this run."
+    },
+
+    "style": {
+      "type": "string",
+      "enum": ["line_drawing", "rendered"],
+      "description": "line_drawing = pure SVG wireframe/line art (MR28-style). rendered = rendered ISO views composited with dimensioned orthographic line views (MR16-style)."
+    },
+
+    "layout_mode": {
+      "type": "string",
+      "enum": ["single_sheet", "multi_page"],
+      "description": "single_sheet = all views on one SVG/PDF sheet. multi_page = one view per page, used for large/complex models or when any single view would be too dense at standard scale. Auto-selected based on model bounding box and view count unless overridden."
+    },
+
+    "engine_used": {
+      "type": "string",
+      "enum": ["build123d", "freecad"],
+      "description": "Geometry engine that successfully loaded and processed the file."
+    },
+
+    "fallback_invoked": {
+      "type": "boolean",
+      "description": "True if the primary engine (build123d) failed and the fallback was used."
+    },
+
+    "units": {
+      "type": "object",
+      "required": ["primary", "secondary"],
+      "properties": {
+        "primary": { "type": "string", "const": "mm" },
+        "secondary": {
+          "type": "string",
+          "const": "in",
+          "description": "Imperial inches shown in parentheses at reduced italic size where space allows."
+        }
+      }
+    },
+
+    "overall_width":  { "type": "number", "description": "Overall external width in mm (X axis)." },
+    "overall_height": { "type": "number", "description": "Overall external height in mm (Z axis)." },
+    "overall_depth":  { "type": "number", "description": "Overall external depth in mm (Y axis)." },
+
+    "bounding_box": {
+      "type": "object",
+      "required": ["x_min", "x_max", "y_min", "y_max", "z_min", "z_max"],
+      "properties": {
+        "x_min": { "type": "number" },
+        "x_max": { "type": "number" },
+        "y_min": { "type": "number" },
+        "y_max": { "type": "number" },
+        "z_min": { "type": "number" },
+        "z_max": { "type": "number" }
+      }
+    },
+
+    "active_area": {
+      "type": ["object", "null"],
+      "description": "Detected front-face aperture or screen cutout. Null if not detectable.",
+      "properties": {
+        "width":    { "type": "number", "description": "mm" },
+        "height":   { "type": "number", "description": "mm" },
+        "diagonal": { "type": "number", "description": "mm" },
+        "diagonal_inches": { "type": "number", "description": "Computed inches for display diagonal labeling." },
+        "offset_left":   { "type": "number", "description": "mm from enclosure left edge" },
+        "offset_top":    { "type": "number", "description": "mm from enclosure top edge" },
+        "detection_confidence": {
+          "type": "string",
+          "enum": ["high", "medium", "low"],
+          "description": "Confidence level of aperture detection."
+        }
+      }
+    },
+
+    "mounting_dimensions": {
+      "type": ["object", "null"],
+      "description": "Null if mode is enclosure_only or no mounting geometry detected.",
+      "properties": {
+        "pattern_type": {
+          "type": "string",
+          "enum": ["linear", "grid", "vesa", "custom", "unknown"],
+          "description": "Detected mounting hole pattern type."
+        },
+        "vesa_standard": {
+          "type": ["string", "null"],
+          "description": "e.g. VESA 100x100, VESA 200x200. Null if not a standard VESA pattern."
+        },
+        "hole_diameter": { "type": "number", "description": "mm. Null if mixed diameters." },
+        "hole_count": { "type": "integer" },
+        "spacing_x": { "type": ["number", "null"], "description": "Center-to-center horizontal spacing in mm." },
+        "spacing_y": { "type": ["number", "null"], "description": "Center-to-center vertical spacing in mm." },
+        "spacing_chain_x": {
+          "type": ["array", "null"],
+          "items": { "type": "number" },
+          "description": "Array of sequential horizontal spacings for chain dimensioning. e.g. [113, 200, 200, 200, 113]"
+        },
+        "spacing_chain_y": {
+          "type": ["array", "null"],
+          "items": { "type": "number" },
+          "description": "Array of sequential vertical spacings for chain dimensioning."
+        },
+        "offset_from_left":   { "type": ["number", "null"] },
+        "offset_from_top":    { "type": ["number", "null"] },
+        "offset_from_right":  { "type": ["number", "null"] },
+        "offset_from_bottom": { "type": ["number", "null"] }
+      }
+    },
+
+    "mounting_variants": {
+      "type": ["array", "null"],
+      "description": "When the STEP file contains multiple mounting subassemblies (e.g. wall mount + ceiling mount + floor stand), each variant is listed here. Each can produce a separate diagram run.",
+      "items": {
+        "type": "object",
+        "required": ["variant_name", "part_ids"],
+        "properties": {
+          "variant_name": {
+            "type": "string",
+            "description": "Human-readable variant label. e.g. 'Wall Mount - VESA 200x200'"
+          },
+          "part_ids": {
+            "type": "array",
+            "items": { "type": "string" },
+            "description": "Part names/IDs from the assembly tree included in this variant."
+          },
+          "diagram_output": {
+            "type": ["string", "null"],
+            "description": "Path to the generated diagram for this variant, if rendered."
+          }
+        }
+      }
+    },
+
+    "selected_parts": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Part names included in the geometry scope for this run."
+    },
+
+    "excluded_parts": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Part names explicitly excluded (internal components, fasteners, etc.)."
+    },
+
+    "mapping_file_used": {
+      "type": ["string", "null"],
+      "description": "Path to the parts mapping JSON file used, if any."
+    },
+
+    "datablock": {
+      "type": "object",
+      "description": "Metadata shown in the diagram title/data block. Sourced from datablock MD file.",
+      "properties": {
+        "model_number":   { "type": "string" },
+        "display_name":   { "type": "string" },
+        "drawing_date":   { "type": "string", "format": "date" },
+        "revision":       { "type": "string" },
+        "drawn_by":       { "type": "string" },
+        "company":        { "type": "string" },
+        "units_note":     { "type": "string", "default": "Dimensions in mm (in)" },
+        "scale":          { "type": "string", "default": "NTS" },
+        "custom_fields":  {
+          "type": "object",
+          "additionalProperties": { "type": "string" },
+          "description": "Any additional key-value pairs from the MD file to show in the data block."
+        }
+      }
+    },
+
+    "layout": {
+      "type": "object",
+      "description": "Describes the view layout used in the generated diagram.",
+      "required": ["views_included", "sheet_size"],
+      "properties": {
+        "views_included": {
+          "type": "array",
+          "items": {
+            "type": "string",
+            "enum": ["front", "rear", "left", "right", "top", "bottom", "isometric_front", "isometric_rear"]
+          },
+          "description": "Ordered list of views included in the diagram."
+        },
+        "sheet_size": {
+          "type": "string",
+          "enum": ["A4_landscape", "A4_portrait", "A3_landscape", "A3_portrait", "A2_landscape", "letter_landscape", "letter_portrait", "auto"],
+          "description": "Sheet size used. 'auto' selects based on model aspect ratio and view count."
+        },
+        "scale_ratio": {
+          "type": ["string", "null"],
+          "description": "e.g. '1:5', '1:10', 'NTS' (not to scale). NTS used when views are schematic rather than precise scale."
+        },
+        "dimension_style": {
+          "type": "string",
+          "enum": ["chain", "ordinate", "baseline"],
+          "description": "Dimensioning style used. chain = sequential (113-200-200-113). ordinate = from common datum. baseline = all from one edge."
+        },
+        "iso_style": {
+          "type": "string",
+          "enum": ["line_wireframe", "shaded_render", "none"],
+          "description": "Isometric view rendering approach."
+        }
+      }
+    },
+
+    "outputs": {
+      "type": "object",
+      "description": "Paths to all generated output files.",
+      "properties": {
+        "diagram_png":   { "type": ["string", "null"] },
+        "diagram_pdf":   { "type": ["string", "null"] },
+        "diagram_svg":   { "type": ["string", "null"], "description": "Source SVG always retained alongside exports." },
+        "iso_png":       { "type": ["string", "null"] },
+        "front_png":     { "type": ["string", "null"] },
+        "side_png":      { "type": ["string", "null"] },
+        "rear_png":      { "type": ["string", "null"] },
+        "meta_json":     { "type": "string", "description": "Path to this metadata JSON file." },
+        "variant_outputs": {
+          "type": ["array", "null"],
+          "items": {
+            "type": "object",
+            "properties": {
+              "variant_name": { "type": "string" },
+              "diagram_png":  { "type": ["string", "null"] },
+              "diagram_pdf":  { "type": ["string", "null"] },
+              "meta_json":    { "type": ["string", "null"] }
+            }
+          }
+        }
+      }
+    },
+
+    "warnings": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Non-fatal issues encountered during generation. e.g. 'active area detection confidence: low', 'mounting holes not detected', 'fallback engine used'."
+    },
+
+    "notes": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Informational messages. e.g. 'Chinese part names translated', '3 mounting variants detected'."
+    }
+  }
+}
@@ -0,0 +1,109 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "mpmedia/step-processor/parts-mapping/v1",
+  "title": "PartsMapping",
+  "description": "Mapping file that classifies parts from a STEP assembly tree. Used by the external diagram generator to determine geometry scope and labels. Supports Chinese-to-English normalization. One file per product model, stored alongside the STEP file or in a shared product data directory.",
+
+  "type": "object",
+  "required": ["model_number", "parts"],
+
+  "properties": {
+    "model_number": {
+      "type": "string",
+      "description": "Product model number this mapping applies to. e.g. 'MR28UW'"
+    },
+    "parts": {
+      "type": "object",
+      "description": "Keyed by original part name from STEP file (may be Chinese). Value is a classification object.",
+      "additionalProperties": {
+        "type": "object",
+        "required": ["english_name", "category"],
+        "properties": {
+          "english_name": {
+            "type": "string",
+            "description": "Translated/normalized English name. Used in diagrams and BOM."
+          },
+          "category": {
+            "type": "string",
+            "enum": ["enclosure", "mounting", "internal", "fastener", "display_panel", "cable", "other"],
+            "description": "Classification drives inclusion/exclusion logic per diagram mode."
+          },
+          "include_in_diagram": {
+            "type": "boolean",
+            "default": true,
+            "description": "Override flag. False = always exclude from diagrams regardless of mode."
+          },
+          "diagram_label": {
+            "type": ["string", "null"],
+            "description": "Optional custom label shown on the diagram for this part. If null, english_name is used."
+          },
+          "mounting_variant": {
+            "type": ["string", "null"],
+            "description": "If this part belongs to a specific mounting variant, name it here. e.g. 'Wall Mount VESA 200x200'. Parts with the same variant_name are shown/hidden together."
+          },
+          "notes": {
+            "type": "string",
+            "description": "Free-text notes for documentation or translator flags."
+          }
+        }
+      }
+    },
+    "mounting_variants": {
+      "type": ["array", "null"],
+      "description": "Named mounting configurations available in this STEP file. Each variant is a named group of mounting parts that should be shown together.",
+      "items": {
+        "type": "object",
+        "required": ["name"],
+        "properties": {
+          "name":        { "type": "string" },
+          "description": { "type": "string" },
+          "default":     { "type": "boolean", "description": "True = use this variant when mode is enclosure_plus_mounting and no variant is specified." }
+        }
+      }
+    }
+  },
+
+  "examples": [
+    {
+      "model_number": "MR28UW",
+      "parts": {
+        "前面板": {
+          "english_name": "Front Panel",
+          "category": "enclosure",
+          "include_in_diagram": true,
+          "diagram_label": null,
+          "mounting_variant": null
+        },
+        "安装支架": {
+          "english_name": "Mounting Bracket",
+          "category": "mounting",
+          "include_in_diagram": true,
+          "diagram_label": "Wall Mount Bracket",
+          "mounting_variant": "Wall Mount"
+        },
+        "VESA板": {
+          "english_name": "VESA Plate 200x200",
+          "category": "mounting",
+          "include_in_diagram": true,
+          "diagram_label": "VESA 200x200 Plate",
+          "mounting_variant": "VESA Mount"
+        },
+        "螺钉M4": {
+          "english_name": "M4 Screw",
+          "category": "fastener",
+          "include_in_diagram": false,
+          "notes": "Internal fastener - exclude from all diagrams"
+        },
+        "主板": {
+          "english_name": "Main Board",
+          "category": "internal",
+          "include_in_diagram": false
+        }
+      },
+      "mounting_variants": [
+        { "name": "Wall Mount",      "description": "Standard wall mount bracket",    "default": true },
+        { "name": "VESA Mount",      "description": "VESA 200x200 compatible plate",  "default": false }
+      ]
+    }
+  ]
+}
@@ -0,0 +1,207 @@
+#!/usr/bin/env python3
+"""
+step_processor.py — CLI entry point for the STEP File Processor skill.
+
+Default run: thumbnails + BOM + auto-translate if Chinese labels detected.
+
+Usage:
+  python step_processor.py <file.step> [options]
+
+See SKILL.md or --help for full option reference.
+"""
+import argparse
+import logging
+import sys
+from pathlib import Path
+
+
+def _setup_logging(verbose: bool):
+    level = logging.DEBUG if verbose else logging.INFO
+    fmt = "%(levelname)-5s %(name)s: %(message)s" if verbose else "%(levelname)-5s %(message)s"
+    logging.basicConfig(level=level, format=fmt, stream=sys.stdout)
+
+
+def _parse_args():
+    p = argparse.ArgumentParser(
+        description="STEP File Processor — thumbnails, BOM, translation, geometry queries",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog=__doc__,
+    )
+    p.add_argument("step_file", help="Path to .step or .stp file")
+
+    # Output control
+    p.add_argument("--no-thumbnails", dest="thumbnails", action="store_false", default=True,
+                   help="Skip PNG thumbnail generation")
+    p.add_argument("--no-bom", dest="bom", action="store_false", default=True,
+                   help="Skip BOM CSV export")
+    p.add_argument("--translate", dest="translate", action="store_true", default=None,
+                   help="Force translation even if auto-detect is off")
+    p.add_argument("--no-translate", dest="translate", action="store_false",
+                   help="Skip translation even if Chinese labels are detected")
+
+    # Thumbnail options
+    p.add_argument("--resolution", default="1024x768",
+                   help="Thumbnail resolution WxH (default: 1024x768)")
+    p.add_argument("--views", default=None,
+                   help="Comma-separated views: front,bottom,left,right,iso_left,iso_right")
+
+    # Query modes
+    p.add_argument("--query", default=None, metavar="QUERY",
+                   help='Run a single geometric query and exit, e.g. "list all holes"')
+    p.add_argument("--repl", action="store_true",
+                   help="Launch interactive geometry query REPL")
+
+    # Diagram
+    p.add_argument("--diagram", action="store_true",
+                   help="Generate external dimensional diagram")
+    p.add_argument("--diagram-mode",
+                   choices=["enclosure_only", "enclosure_plus_mounting", "mounting_only"],
+                   default="enclosure_only",
+                   help="Diagram mode (default: enclosure_only)")
+    p.add_argument("--diagram-style", choices=["line_drawing", "rendered"], default=None,
+                   help="Diagram style (auto-selected if omitted)")
+    p.add_argument("--diagram-pdf", action="store_true",
+                   help="Also export diagram as PDF")
+    p.add_argument("--diagram-variants", action="store_true",
+                   help="Render one diagram per mounting variant")
+    p.add_argument("--mapping", default=None, metavar="JSON_FILE",
+                   help="Parts mapping JSON file for diagram mode")
+    p.add_argument("--datablock", default=None, metavar="MD_FILE",
+                   help="Datablock .md file for diagram title block")
+
+    # Misc
+    p.add_argument("--verbose", "-v", action="store_true",
+                   help="Show backend selection, fallback notices, timing")
+
+    return p.parse_args()
+
+
+def main():
+    args = _parse_args()
+    _setup_logging(args.verbose)
+    log = logging.getLogger("step_processor")
+
+    step_path = Path(args.step_file).expanduser().resolve()
+    if not step_path.exists():
+        log.error(f"File not found: {step_path}")
+        sys.exit(1)
+    if step_path.suffix.lower() not in (".step", ".stp"):
+        log.warning(f"Unexpected extension '{step_path.suffix}' — continuing anyway")
+
+    # ── Load ─────────────────────────────────────────────────────────────────
+    log.info(f"Loading: {step_path.name}")
+    from modules.loader import load_step
+    model = load_step(step_path)
+    if model is None:
+        log.error("Failed to load STEP file. Check that build123d or FreeCAD is installed.")
+        log.error("See INSTALL.md for setup instructions.")
+        sys.exit(1)
+    log.info(f"[{model.backend}] Loaded: {step_path.name}")
+
+    # ── Query mode (single) ──────────────────────────────────────────────────
+    if args.query:
+        from modules.query_engine import run_query
+        result = run_query(model, args.query)
+        print(result)
+        return
+
+    # ── REPL mode ────────────────────────────────────────────────────────────
+    if args.repl:
+        from modules.query_engine import repl
+        repl(model, step_path)
+        return
+
+    # ── BOM ──────────────────────────────────────────────────────────────────
+    bom_df = None
+    if args.bom:
+        from modules.bom import extract_bom, save_bom_xlsx
+        bom_df = extract_bom(model)
+        xlsx_path = save_bom_xlsx(bom_df, step_path)
+        log.info(f"BOM XLSX → {xlsx_path}")
+
+    # ── Translation ──────────────────────────────────────────────────────────
+    if bom_df is not None:
+        from modules.translator import has_chinese, translate_bom, get_translation_map
+        needs_translation = args.translate
+        if needs_translation is None:
+            # Auto-detect
+            needs_translation = bom_df["part_name_original"].apply(has_chinese).any()
+            if needs_translation:
+                log.info("Chinese part names detected — auto-translating")
+
+        if needs_translation:
+            import os
+            if not os.environ.get("ANTHROPIC_API_KEY"):
+                log.warning("ANTHROPIC_API_KEY not set — skipping translation")
+            else:
+                bom_df = translate_bom(bom_df, model_name=step_path.stem)
+                from modules.bom import save_bom_xlsx
+                save_bom_xlsx(bom_df, step_path)  # overwrite with translated version
+                translation_map = get_translation_map(bom_df)
+                if translation_map:
+                    from modules.rewriter import rewrite_step
+                    rewrite_step(step_path, translation_map)
+
+    # ── Thumbnails ───────────────────────────────────────────────────────────
+    if args.thumbnails:
+        try:
+            w, h = (int(x) for x in args.resolution.split("x"))
+        except ValueError:
+            log.warning(f"Invalid resolution '{args.resolution}' — using 1024x768")
+            w, h = 1024, 768
+        views = [v.strip() for v in args.views.split(",")] if args.views else None
+        from modules.renderer import render_views
+        thumb_results = render_views(model, step_path, views=views, width=w, height=h)
+        if thumb_results:
+            log.info(f"Thumbnails: {len(thumb_results)} PNG(s) written")
+        else:
+            log.warning("No thumbnails generated (pyrender unavailable or mesh failed)")
+
+    # ── External dimensional diagram ─────────────────────────────────────────
+    if args.diagram:
+        from modules.external_diagram import step_external_diagram
+        options = {
+            "pdf": args.diagram_pdf,
+            "render_variants": args.diagram_variants,
+        }
+        if args.diagram_style:
+            options["style"] = args.diagram_style
+        meta = step_external_diagram(
+            path=str(step_path),
+            mode=args.diagram_mode,
+            mapping_file=args.mapping,
+            datablock_file=args.datablock,
+            options=options,
+        )
+        if meta:
+            log.info(f"Diagram → {step_path.stem}__external-diagram.svg")
+            if args.diagram_pdf:
+                log.info(f"Diagram PDF → {step_path.stem}__external-diagram.pdf")
+
+    # ── Summary ──────────────────────────────────────────────────────────────
+    log.info("Done.")
+    _print_summary(step_path, model, bom_df, args)
+
+
+def _print_summary(step_path: Path, model, bom_df, args):
+    print(f"\n{'─'*60}")
+    print(f"  {step_path.name}  [{model.backend}]")
+    if bom_df is not None:
+        print(f"  BOM: {len(bom_df)} parts → {step_path.stem}_bom.xlsx")
+    en_path = step_path.parent / f"{step_path.stem}_EN.step"
+    if en_path.exists():
+        print(f"  Translated STEP → {en_path.name}")
+    if args.thumbnails:
+        thumb_count = sum(1 for ext in ["_front.png", "_rear.png", "_left.png",
+                                         "_right.png", "_iso_left.png", "_iso_right.png"]
+                          if (step_path.parent / f"{step_path.stem}{ext}").exists())
+        print(f"  Thumbnails: {thumb_count} PNG(s)")
+    if args.diagram:
+        diag = step_path.parent / f"{step_path.stem}__external-diagram.svg"
+        if diag.exists():
+            print(f"  Diagram → {diag.name}")
+    print(f"{'─'*60}\n")
+
+
+if __name__ == "__main__":
+    main()
@@ -0,0 +1,29 @@
+# Diagram Data Block — MR28UW
+
+<!-- 
+  This file drives the title/data block shown on external dimensional diagrams.
+  Edit the fields below for your product.
+  All fields are optional except model_number and display_name.
+  Custom fields (anything below the standard set) will be appended to the data block
+  in the order listed, as space allows.
+  
+  Do not remove the field names — the parser uses them as keys.
+  Leave a field blank rather than deleting it.
+-->
+
+model_number: MR28UW
+display_name: 28" Ultra-Wide Stretched Bar Display
+revision: A
+drawing_date: 2025-01-01
+drawn_by: 
+company: MPMedia
+units_note: Dimensions in mm (in)
+scale: NTS
+
+<!-- Custom fields — add any key: value pairs below -->
+<!-- These will appear in the data block footer in order -->
+
+panel_size: 28" (711.75 mm diagonal)
+aspect_ratio: 16:4.5
+ip_rating: IP54 (front face)
+operating_temp: -20°C to +60°C