diff --git a/board_config.zen b/board_config.zen
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+++ b/board_config.zen
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+# Copper constraints - all clearances and widths for copper features
+Copper = record(
+    minimum_clearance=field(float | None, None),  # Minimum clearance between copper features
+    minimum_track_width=field(float | None, None),  # Minimum track width
+    minimum_connection_width=field(float | None, None),  # Minimum connection width (KiCad: m_MinConn)
+    minimum_annular_width=field(float | None, None),  # Minimum annular ring width for vias
+    minimum_via_diameter=field(float | None, None),  # Minimum via diameter
+    copper_to_hole_clearance=field(float | None, None),  # Clearance from copper to holes
+    copper_to_edge_clearance=field(float | None, None),  # Clearance from copper to board edge
+)
+
+# Hole constraints - drill sizes and clearances
+Holes = record(
+    minimum_through_hole=field(float | None, None),  # Minimum through hole diameter
+    hole_to_hole_clearance=field(float | None, None),  # Minimum clearance between holes
+)
+
+# Micro via constraints - specialized via rules
+Uvias = record(
+    minimum_uvia_diameter=field(float | None, None),  # Minimum micro via diameter
+    minimum_uvia_hole=field(float | None, None),  # Minimum micro via hole diameter
+)
+
+# Silkscreen constraints - text and graphics rules
+Silkscreen = record(
+    minimum_item_clearance=field(float | None, None),  # Minimum clearance for silkscreen items
+    minimum_text_height=field(float | None, None),  # Minimum text height
+    # Note: minimum_text_thickness is complex in KiCad API, not supported yet
+)
+
+# All design rule constraints grouped together
+Constraints = record(
+    copper=field(Copper | None, None),
+    holes=field(Holes | None, None),
+    uvias=field(Uvias | None, None),
+    silkscreen=field(Silkscreen | None, None),
+)
+
+# Via dimensions for pre-defined sizes
+ViaDimension = record(
+    diameter=field(float | None, None),  # Via diameter in mm
+    drill=field(float | None, None),  # Via drill size in mm
+)
+
+# NOTE: Differential pair dimensions are not supported due to missing SWIG template
+# in KiCad Python API. The following would be needed in board.i:
+# %template(DIFF_PAIR_DIMENSION_Vector) std::vector<DIFF_PAIR_DIMENSION>;
+#
+# DiffPairDimension = record(
+#     width=float,                      # Track width in mm
+#     gap=float,                        # Gap between tracks in mm
+#     via_gap=float,                    # Gap for vias in mm
+# )
+
+# Pre-defined sizes that appear in KiCad GUI dropdowns
+PredefinedSizes = record(
+    track_widths=field(list | None, None),  # List of track widths in mm (e.g. [0.1, 0.15, 0.2])
+    via_dimensions=field(list | None, None),  # List of ViaDimension objects
+    # diff_pair_dimensions=list,     # Not supported - missing KiCad SWIG template
+)
+
+# Netclass definition for PCB routing rules
+NetClass = record(
+    name=field(str | None, None),  # Netclass name
+    clearance=field(float | None, None),  # Clearance in mm
+    track_width=field(float | None, None),  # Track width in mm
+    via_diameter=field(float | None, None),  # Via diameter in mm
+    via_drill=field(float | None, None),  # Via drill/hole in mm
+    microvia_diameter=field(float | None, None),  # Microvia diameter in mm
+    microvia_drill=field(float | None, None),  # Microvia drill/hole in mm
+    diff_pair_width=field(float | None, None),  # Differential pair width in mm
+    diff_pair_gap=field(float | None, None),  # Differential pair gap in mm
+    diff_pair_via_gap=field(float | None, None),  # Differential pair via gap in mm
+    priority=field(int | None, None),  # Priority for netclass resolution (higher = higher priority)
+    color=field(str | None, None),  # PCB color (hex like "#FF0000" or CSS name)
+)
+
+# Design rules container
+DesignRules = record(
+    constraints=field(Constraints | None, None),
+    predefined_sizes=field(PredefinedSizes | None, None),
+    netclasses=field(list | None, None),  # List of NetClass objects
+)
+
+# Material definition for stackup layers
+Material = record(
+    name=field(str | None, None),  # Material name
+    vendor=field(str | None, None),  # Optional vendor
+    relative_permittivity=field(float | None, None),  # Epsilon R (dielectric constant)
+    loss_tangent=field(float | None, None),  # Loss tangent
+    reference_frequency=field(float | None, None),  # Optional frequency in Hz
+)
+
+# Copper layer definition for stackup
+CopperLayer = record(
+    thickness=field(float | None, None),  # Thickness in mm
+    role=field(str | None, None),  # "signal", "power", "mixed"
+)
+
+# Dielectric layer definition for stackup
+DielectricLayer = record(
+    thickness=field(float | None, None),  # Thickness in mm
+    material=field(str | None, None),  # Material name (ref to materials list)
+    form=field(str | None, None),  # "core" or "prepreg"
+)
+
+# Board stackup configuration
+Stackup = record(
+    materials=field(list[Material] | None, None),  # List of Material objects
+    silk_screen_color=field(str | None, None),  # Hex color like "#44805BFF"
+    solder_mask_color=field(str | None, None),  # Hex color like "#191919E6"
+    thickness=field(float | None, None),  # Total thickness in mm
+    symmetric=field(bool | None, None),  # Assert symmetric stackup (default: True)
+    layers=field(list[CopperLayer | DielectricLayer] | None, None),  # Ordered list of stackup layers
+    copper_finish=field(str | None, None),  # Surface finish: "ENIG", "HAL SnPb", "HAL lead-free"
+)
+
+# Complete board configuration
+BoardConfig = record(
+    design_rules=field(DesignRules | None, None),
+    stackup=field(Stackup | None, None),  # Board stackup configuration
+    num_user_layers=field(int, 4),  # Number of User.N layers (User.1, User.2, etc.)
+)
+
+
+def deep_merge(base, override):
+    """Deep merge two records, with override values taking precedence.
+
+    For records: recursively merges fields
+    For lists: override replaces base entirely
+    For primitives: override value used if not None
+    """
+
+    if override == None:
+        return base
+    if base == None:
+        return override
+
+    # Handle list types - override replaces entirely
+    if type(base) == "list":
+        return override if type(override) == "list" else base
+
+    # Check if both are records by checking if they have getattr/type
+    base_type = type(base)
+    override_type = type(override)
+
+    # Only merge if both are record types (not primitive types)
+    if base_type == "record" and override_type == "record":
+        merged = {}
+
+        # Get all field names from both records
+        base_fields = dir(base)
+        override_fields = dir(override)
+        all_fields = set(base_fields + override_fields)
+
+        for field in all_fields:
+            if field.startswith("_"):  # Skip private fields
+                continue
+
+            base_val = getattr(base, field, None) if field in base_fields else None
+            override_val = getattr(override, field, None) if field in override_fields else None
+
+            if override_val != None:
+                if base_val != None and type(base_val) != "list":
+                    # Recursively merge if both exist and not lists
+                    merged[field] = deep_merge(base_val, override_val)
+                else:
+                    # Use override value (including for lists)
+                    merged[field] = override_val
+            elif base_val != None:
+                # Keep base value when override is None but base has a value
+
+                merged[field] = base_val
+            else:
+                # Both are None, keep None
+                merged[field] = None
+
+        # Extract record type from string representation
+        base_str = str(base)
+        if base_str.startswith("record["):
+            type_name = base_str.split("[")[1].split("]")[0]
+            if type_name == "BoardConfig":
+                return BoardConfig(**merged)
+            elif type_name == "DesignRules":
+                return DesignRules(**merged)
+            elif type_name == "Constraints":
+                return Constraints(**merged)
+            elif type_name == "PredefinedSizes":
+                return PredefinedSizes(**merged)
+            elif type_name == "Copper":
+                return Copper(**merged)
+            elif type_name == "Holes":
+                return Holes(**merged)
+            elif type_name == "Uvias":
+                return Uvias(**merged)
+            elif type_name == "Silkscreen":
+                return Silkscreen(**merged)
+            elif type_name == "ViaDimension":
+                return ViaDimension(**merged)
+            elif type_name == "NetClass":
+                return NetClass(**merged)
+
+            elif type_name == "Stackup":
+                return Stackup(**merged)
+            elif type_name == "Material":
+                return Material(**merged)
+            elif type_name == "CopperLayer":
+                return CopperLayer(**merged)
+            elif type_name == "DielectricLayer":
+                return DielectricLayer(**merged)
+            else:
+                error("Unknown record type for merge: " + type_name)
+        else:
+            error("Unable to determine record type from: " + base_str)
+
+    # Not records, override wins
+    return override
+
+
+def merge_configs(*configs: BoardConfig) -> BoardConfig:
+    """Merge multiple BoardConfig objects, with later configs taking precedence.
+
+    Args:
+        *configs: Variable number of BoardConfig objects to merge
+
+    Returns:
+        BoardConfig: Merged configuration with later configs overriding earlier ones
+    """
+    if not configs:
+        return BoardConfig()
+
+    result = configs[0]
+    for config in configs[1:]:
+        result = deep_merge(result, config)
+
+    return result
+
+
+def Board(
+    name: str,
+    config: BoardConfig,
+    layout_path: str,
+    layout_hints: list | None = None,
+    default: bool = False,
+):
+    builtin.add_board_config(
+        name=name,
+        default=default,
+        config=config,
+    )
+    add_property("layout_path", Path(layout_path, allow_not_exist=True))
+    if layout_hints:
+        add_property("layout_hints", layout_hints)
+
+
+# Standard Base Configurations
+
+# Common materials that can be reused across board configurations
+
+# Standard PCB Materials
+FR4_CORE = Material(
+    name="FR4-Core",
+    relative_permittivity=4.6,
+    loss_tangent=0.025,  # Typical for standard FR4 core
+)
+
+BASE_PREPREG = Material(
+    name="Prepreg",
+    relative_permittivity=4.4,
+    loss_tangent=0.025,  # Standard prepreg material
+)
+
+# Common stackup configurations
+
+# Base 4-layer stackup (1.6mm, 1oz outer/0.5oz inner)
+BASE_4L_STACKUP = Stackup(
+    materials=[FR4_CORE, BASE_PREPREG],
+    thickness=1.6,
+    symmetric=True,
+    copper_finish="HAL SnPb",
+    silk_screen_color="White",
+    solder_mask_color="Black",
+    layers=[
+        CopperLayer(thickness=0.035, role="mixed"),  # Top layer (1oz)
+        DielectricLayer(thickness=0.21040, material="Prepreg", form="prepreg"),
+        CopperLayer(thickness=0.0152, role="power"),  # Inner L2 (0.5oz)
+        DielectricLayer(thickness=1.065, material="FR4-Core", form="core"),
+        CopperLayer(thickness=0.0152, role="power"),  # Inner L3 (0.5oz)
+        DielectricLayer(thickness=0.21040, material="Prepreg", form="prepreg"),
+        CopperLayer(thickness=0.035, role="mixed"),  # Bottom layer (1oz)
+    ],
+)
+
+# Common constraint sets for different fabrication capabilities
+
+# Base PCB Constraints (1oz copper)
+BASE_CONSTRAINTS = Constraints(
+    copper=Copper(
+        minimum_clearance=0.09,  # Min spacing between copper features (1oz)
+        minimum_track_width=0.09,  # Min track width (1oz)
+        minimum_via_diameter=0.25,  # Min via diameter (0.25mm)
+        copper_to_hole_clearance=0.2,  # Inner layer via hole to copper clearance
+        copper_to_edge_clearance=0.3,  # Reasonable edge clearance
+    ),
+    holes=Holes(
+        minimum_through_hole=0.15,  # Min via hole size
+        hole_to_hole_clearance=0.2,  # Via hole-to-hole spacing
+    ),
+    uvias=Uvias(
+        minimum_uvia_diameter=0.15,  # Micro via diameter (if supported)
+        minimum_uvia_hole=0.1,  # Micro via hole (if supported)
+    ),
+    silkscreen=Silkscreen(
+        minimum_item_clearance=0.1,  # Reasonable silkscreen clearance
+        minimum_text_height=0.8,  # Reasonable minimum text height
+    ),
+)
+
+# Heavy Copper Constraints (2oz copper)
+HEAVY_COPPER_CONSTRAINTS = Constraints(
+    copper=Copper(
+        minimum_clearance=0.2,  # Min spacing (2oz copper)
+        minimum_track_width=0.16,  # Min track width (2oz copper)
+        minimum_via_diameter=0.25,  # Same via diameter
+        copper_to_hole_clearance=0.2,  # Same hole clearance
+        copper_to_edge_clearance=0.3,  # Same edge clearance
+    ),
+    holes=Holes(
+        minimum_through_hole=0.15,  # Same hole size
+        hole_to_hole_clearance=0.2,  # Same hole spacing
+    ),
+    uvias=Uvias(
+        minimum_uvia_diameter=0.15,
+        minimum_uvia_hole=0.1,
+    ),
+    silkscreen=Silkscreen(
+        minimum_item_clearance=0.1,
+        minimum_text_height=0.8,
+    ),
+)
+
+# Common netclass definitions
+
+# Default netclass for general-purpose PCB manufacturing
+DEFAULT_NETCLASS = NetClass(
+    name="Default",
+    clearance=0.15,  # Conservative clearance (different nets)
+    track_width=0.15,  # Safe track width for most manufacturers
+    via_diameter=0.4,  # Standard via size
+    via_drill=0.2,  # Standard drill size
+    diff_pair_width=0.2,  # Reasonable diff pair width
+    diff_pair_gap=0.2,  # Reasonable diff pair gap
+)
+
+# Common predefined sizes for design tool dropdowns
+
+# Base predefined sizes for common PCB design
+BASE_PREDEFINED_SIZES = PredefinedSizes(
+    track_widths=[
+        0.1,  # Safe minimum
+        0.2,  # Standard signals
+        0.4,  # Power traces
+        0.8,  # Heavy power
+    ],
+    via_dimensions=[
+        ViaDimension(diameter=0.35, drill=0.2),  # Small via
+        ViaDimension(diameter=0.4, drill=0.25),  # Standard via
+        ViaDimension(diameter=0.45, drill=0.3),  # Large via
+    ],
+)
+
+# Base board configurations that can be extended
+
+# Complete base 4-layer board configuration (1oz outer, 0.5oz inner, base constraints)
+BASE_4L = BoardConfig(
+    design_rules=DesignRules(
+        constraints=BASE_CONSTRAINTS,
+        predefined_sizes=BASE_PREDEFINED_SIZES,
+        netclasses=[DEFAULT_NETCLASS],
+    ),
+    stackup=BASE_4L_STACKUP,
+)