# Architecture

## Bootstrap flow

```
FreeCAD startup
  └─ src/Mod/Create/Init.py
       └─ addon_loader.load_addons(gui=False)
            ├─ scan_addons("mods/")         — find package.xml manifests
            ├─ parse_manifest()             — extract <kindred> extensions
            ├─ validate_manifest()          — check min/max_create_version
            ├─ resolve_load_order()         — topological sort by <dependency>
            └─ for each addon in order:
                 ├─ add addon dir to sys.path
                 ├─ exec(Init.py)
                 └─ register in AddonRegistry (FreeCAD.KindredAddons)

  └─ src/Mod/Create/InitGui.py
       ├─ addon_loader.load_addons(gui=True)
       │    └─ for each addon in order:
       │         └─ exec(InitGui.py)
       │              ├─ sdk (priority 0):    logs "SDK loaded"
       │              ├─ ztools (priority 50): schedules deferred _register() (2000ms)
       │              │    ├─ imports ZTools commands
       │              │    ├─ installs _ZToolsManipulator (global)
       │              │    └─ injects commands into editing contexts
       │              └─ silo (priority 60):  registers SiloWorkbench
       │                   └─ schedules deferred Silo overlay registration (2500ms)
       ├─ EditingContextResolver singleton created (MainWindow constructor)
       │    ├─ registers built-in contexts (PartDesign, Sketcher, Assembly, Spreadsheet)
       │    ├─ connects to signalInEdit/signalResetEdit/signalActiveDocument/signalActivateView
       │    └─ BreadcrumbToolBar connected to contextChanged signal
       └─ Deferred setup (QTimer):
            ├─  500ms: _register_kc_format()        → .kc file format
            ├─ 1500ms: _register_silo_origin()      → registers Silo FileOrigin
            ├─ 2000ms: _setup_silo_auth_panel()     → "Database Auth" dock
            ├─ 2000ms: ZTools _register()            → commands + manipulator
            ├─ 2500ms: Silo overlay registration     → "Silo Origin" toolbar overlay
            ├─ 3000ms: _check_silo_first_start()    → settings prompt
            ├─ 4000ms: _setup_silo_activity_panel() → "Database Activity" dock
            └─ 10000ms: _check_for_updates()        → update checker (Gitea API)
```

### Addon lifecycle

Each addon in `mods/` provides a `package.xml` manifest with a `<kindred>` extension block:

```xml
<kindred>
    <min_create_version>0.1.0</min_create_version>
    <load_priority>50</load_priority>
    <pure_python>true</pure_python>
    <dependencies>
        <dependency>sdk</dependency>
    </dependencies>
</kindred>
```

The loader (`addon_loader.py`) processes addons in this order:

1. **Scan** — find all `mods/*/package.xml` files
2. **Parse** — extract `<kindred>` metadata (version bounds, priority, dependencies)
3. **Validate** — reject addons incompatible with the current Create version
4. **Resolve** — topological sort by `<dependency>` declarations, breaking ties by `<load_priority>`
5. **Load** — execute `Init.py` (console) then `InitGui.py` (GUI) for each addon
6. **Register** — populate `FreeCAD.KindredAddons` registry with addon state

Current load order: **sdk** (0) → **ztools** (50) → **silo** (60)

## Key source layout

```
src/Mod/Create/              Kindred Create module
  ├── Init.py                Console bootstrap — loads addons via manifest-driven loader
  ├── InitGui.py             GUI bootstrap — loads addons, Silo integration, update checker
  ├── addon_loader.py        Manifest-driven addon loader with dependency resolution
  ├── kc_format.py           .kc file format round-trip preservation
  ├── version.py.in          CMake template → version.py (build-time)
  ├── update_checker.py      Checks Gitea releases API for updates
  ├── CreateGlobal.h         C++ export macros (CreateExport, CreateGuiExport)
  ├── App/                   C++ App library (CreateApp.so)
  │   ├── AppCreate.cpp      Module entry point — PyMOD_INIT_FUNC(CreateApp)
  │   └── AppCreatePy.cpp    Python module object (Py::ExtensionModule)
  └── Gui/                   C++ Gui library (CreateGui.so)
      ├── AppCreateGui.cpp   Module entry point — PyMOD_INIT_FUNC(CreateGui)
      └── AppCreateGuiPy.cpp Python module object (Py::ExtensionModule)

mods/sdk/                    [dir] Kindred addon SDK — stable API contract
  ├── package.xml            Manifest (priority 0, no dependencies)
  ├── kindred_sdk/
  │   ├── __init__.py        Public API re-exports
  │   ├── context.py         Editing context wrappers (register_context, register_overlay, ...)
  │   ├── theme.py           YAML-driven palette system (get_theme_tokens, load_palette, Palette)
  │   ├── origin.py          FileOrigin registration (register_origin, unregister_origin)
  │   ├── dock.py            Deferred dock panel helper (register_dock_panel)
  │   ├── compat.py          Version detection (create_version, freecad_version)
  │   └── palettes/
  │       └── catppuccin-mocha.yaml   26 colors + 14 semantic roles
  └── Init.py / InitGui.py   Minimal log messages

mods/ztools/                 [submodule] command provider (not a workbench)
  ├── package.xml            Manifest (priority 50, depends on sdk)
  ├── ztools/InitGui.py      Deferred command registration + _ZToolsManipulator
  ├── ztools/ztools/
  │   ├── commands/          Datum, pattern, pocket, assembly, spreadsheet
  │   ├── datums/core.py     Datum creation via Part::AttachExtension
  │   └── resources/         Icons (SDK theme tokens), theme utilities
  └── CatppuccinMocha/       Theme preference pack (QSS)

mods/silo/                   [submodule → silo-mod.git] FreeCAD workbench
  ├── freecad/package.xml    Manifest (priority 60, depends on sdk)
  ├── silo-client/           [submodule → silo-client.git] shared API client
  │   └── silo_client/       SiloClient, SiloSettings, CATEGORY_NAMES
  └── freecad/               FreeCAD workbench (Python)
      ├── InitGui.py         SiloWorkbench + overlay registration (via SDK)
      ├── silo_commands.py   Commands + FreeCADSiloSettings adapter
      └── silo_origin.py     FileOrigin backend for Silo (via SDK)

src/Gui/EditingContext.h/.cpp        EditingContextResolver singleton + context registry
src/Gui/BreadcrumbToolBar.h/.cpp     Color-coded breadcrumb toolbar (Catppuccin Mocha)
src/Gui/FileOrigin.h/.cpp           FileOrigin base class + LocalFileOrigin
src/Gui/CommandOrigin.cpp            Origin_Commit/Pull/Push/Info/BOM commands
src/Gui/OriginManager.h/.cpp        Origin lifecycle management
src/Gui/OriginSelectorWidget.h/.cpp  UI for origin selection

src/Gui/Stylesheets/         QSS themes and SVG assets
src/Gui/PreferencePacks/     KindredCreate preference pack (cfg + build-time QSS)
```

See [INTEGRATION_PLAN.md](INTEGRATION_PLAN.md) for architecture layers and phase status.