diff --git a/periscope/src/backend/periscopex/models.py b/periscope/src/backend/periscopex/models.py
new file mode 100644
index 0000000..bc0d90c
--- /dev/null
+++ b/periscope/src/backend/periscopex/models.py
@@ -0,0 +1,534 @@
+"""Periscope schematic and layout data contracts.
+
+Public types used by graph build, review, and PCB exam. Layout primitives are
+distinct types: pad (component pin land), via (drill, never a pin), segment
+(track), zone (pour/keepout). Do not coerce one into another.
+"""
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import Annotated, Any, Literal
+
+from pydantic import BaseModel, Discriminator, Field, Tag, field_validator, model_validator
+
+
+class Pin(BaseModel):
+    number: int | str
+    name: str
+    description: str | None = None
+    functions: list[str] | None = None
+
+
+class PackageInfo(BaseModel):
+    base_family: str
+    package: str
+    pin_count: int
+    description: str | None = None
+
+
+class AbsMaxRating(BaseModel):
+    parameter: str
+    min: float | None = None
+    max: float | None = None
+    unit: str
+    source_page: int
+
+
+class Rule(BaseModel):
+    rule_id: str | None = None  # {MPN}-{001}
+    description: str
+    source_page: int
+
+
+def _check_subtype(v: object) -> str | None:
+    """Shared pre-validator for component_subtype fields."""
+    if v is None or v == "":
+        return None
+    from backend.periscopex.taxonomy import validate_subtype
+    return validate_subtype(str(v))
+
+
+class InternalFeatures(BaseModel):
+    """Block-diagram extras: ESD clamps, on-die pull-ups, analog switches."""
+    esd_clamp_pins: list[str] = []
+    pullup_pins: list[str] = []
+    analog_switch: list[str] = []
+
+
+class ComponentConstraints(BaseModel):
+    mpn: str
+    model_version: str = "1.0.0"  # semver; bumped on prune (patch) or skill update (minor)
+    component_subtype: str | None = None  # dotted taxonomy path, e.g. "ic.ldo", "ic.mcu"
+    package_info: PackageInfo | None = None
+    pintable: list[Pin]
+    absolute_maximum_ratings: list[AbsMaxRating]
+    rules: list[Rule]
+    internal_features: InternalFeatures | None = None
+    layout_rules: list[dict] = []
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+    def pin_by_number(self, number: int | str) -> Pin | None:
+        """Look up a pin by its number."""
+        for p in self.pintable:
+            if str(p.number) == str(number):
+                return p
+        return None
+
+
+# ---------------------------------------------------------------------------
+# Design graph models
+# ---------------------------------------------------------------------------
+
+
+class NetType(str, Enum):
+    POWER = "power"
+    GROUND = "ground"
+    SIGNAL = "signal"
+    UNKNOWN = "unknown"
+
+
+class ComponentType(str, Enum):
+    RESISTOR = "resistor"
+    CAPACITOR = "capacitor"
+    INDUCTOR = "inductor"
+    IC = "ic"
+    CONNECTOR = "connector"
+    CRYSTAL = "crystal"
+    DISCRETE = "discrete"
+    TRANSFORMER = "transformer"
+    FUSE = "fuse"
+    SWITCH = "switch"
+    TEST_POINT = "test_point"
+    FIDUCIAL = "fiducial"
+    MECHANICAL = "mechanical"
+    UNKNOWN = "unknown"
+
+
+# ---------------------------------------------------------------------------
+# Component specs taxonomy — type-specific, standardised-unit models
+# ---------------------------------------------------------------------------
+
+
+class ResistorSpecs(BaseModel):
+    """Standardised resistor parameters. Value always in ohms."""
+    specs_type: Literal["resistor"] = "resistor"
+    component_subtype: str | None = None  # e.g. "passive.resistor"
+    value_ohms: float
+    value_formatted: str
+    tolerance: str | None = None  # "±1%" or "±0.5ohm"
+    package: str | None = None
+    power_rating_w: str | None = None
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+
+class CapacitorSpecs(BaseModel):
+    """Standardised capacitor parameters. Value always in farads."""
+    specs_type: Literal["capacitor"] = "capacitor"
+    component_subtype: str | None = None  # e.g. "passive.capacitor.ceramic"
+    value_farads: float
+    value_formatted: str
+    tolerance: str | None = None  # "±10%" or "±0.25pF"
+    package: str | None = None
+    voltage_rating_v: str | None = None
+    dielectric: str | None = None
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+
+class InductorSpecs(BaseModel):
+    """Standardised inductor / ferrite-bead parameters."""
+    specs_type: Literal["inductor"] = "inductor"
+    component_subtype: str | None = None  # e.g. "passive.inductor" or "passive.ferrite_bead"
+    value_henries: float | None = None
+    value_formatted: str
+    tolerance: str | None = None  # "±5%" or "±0.1uH"
+    package: str | None = None
+    current_rating_a: str | None = None
+    dcr_ohms: float | None = None
+    impedance_ohm: float | None = None  # ferrite beads: Z at test frequency
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+    @model_validator(mode="after")
+    def _require_primary_value(self) -> InductorSpecs:
+        if self.component_subtype == "passive.ferrite_bead":
+            if self.impedance_ohm is None:
+                raise ValueError("ferrite bead requires impedance_ohm")
+            return self
+        if self.value_henries is None:
+            raise ValueError("inductor requires value_henries")
+        return self
+
+
+class SimpleComponentSpecs(BaseModel):
+    """Specs for discrete/simple components. Schema defined in taxonomy JSON."""
+    specs_type: str  # taxonomy type: "discrete", "connector", "crystal", etc.
+    component_subtype: str | None = None
+    values: dict[str, float | str | None] = {}
+    pintable: list[Pin] = []
+    package_info: PackageInfo | None = None
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+    def pin_by_number(self, number: int | str) -> Pin | None:
+        """Look up a pin by its number."""
+        for p in self.pintable:
+            if str(p.number) == str(number):
+                return p
+        return None
+
+
+def _specs_tag(v: Any) -> str:
+    """Route to the correct specs model based on specs_type."""
+    st = v.get("specs_type") if isinstance(v, dict) else v.specs_type
+    return st if st in ("resistor", "capacitor", "inductor") else "simple"
+
+
+ComponentSpecs = Annotated[
+    Annotated[ResistorSpecs, Tag("resistor")]
+    | Annotated[CapacitorSpecs, Tag("capacitor")]
+    | Annotated[InductorSpecs, Tag("inductor")]
+    | Annotated[SimpleComponentSpecs, Tag("simple")],
+    Discriminator(_specs_tag),
+]
+
+
+class ComponentModel(BaseModel):
+    """Persisted specs file — one per MPN in component-models/."""
+    mpn: str
+    specs: ComponentSpecs
+
+
+# ---------------------------------------------------------------------------
+# Design graph models
+# ---------------------------------------------------------------------------
+
+
+class PinConnection(BaseModel):
+    """A pin on a component that participates in a net."""
+    component_ref: str
+    pin_number: str
+    pin_name: str | None = None  # enriched from datasheet pintable
+
+
+class Net(BaseModel):
+    """An electrical net with mutable type/voltage for agent refinement."""
+    name: str
+    net_type: NetType = NetType.UNKNOWN
+    voltage: float | None = None
+    pins: list[PinConnection] = []
+
+
+class Component(BaseModel):
+    """A placed component in the design graph (topology only)."""
+    reference: str
+    value: str
+    footprint: str
+    component_type: ComponentType = ComponentType.UNKNOWN
+    component_subtype: str | None = None  # dotted taxonomy path, e.g. "ic.ldo", "ic.mcu"
+    mpn: str | None = None
+    pins: dict[str, str] = {}  # pin_number -> net_name
+    specs: ComponentSpecs | None = None
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+
+class CadIndexEntry(BaseModel):
+    """KiCad symbol identity for plugin pan-and-zoom."""
+    uuid: str = ""
+    sheet: str = ""
+
+
+class DesignGraph(BaseModel):
+    """
+    Bipartite design graph: Components <-> Nets.
+
+    Traversal paths:
+      component.pins[pin_num] -> net_name -> graph.nets[net_name].pins -> other components
+      net.pins[i].component_ref -> graph.components[ref] -> its other pins/nets
+    """
+    components: dict[str, Component] = {}
+    nets: dict[str, Net] = {}
+    # KiCad property table vs uploaded BOM (empty on PADS/EDIF).
+    bom_fields: dict[str, dict] = {}
+    schematic_fields: dict[str, dict] = {}
+    cad_index: dict[str, CadIndexEntry] = {}
+
+    # -- Traversal helpers --------------------------------------------------
+
+    def components_on_net(self, net_name: str) -> list[str]:
+        """All component refs connected to a net."""
+        net = self.nets.get(net_name)
+        if not net:
+            return []
+        return list({pc.component_ref for pc in net.pins})
+
+    def nets_of_component(self, ref: str) -> list[str]:
+        """All net names a component touches."""
+        comp = self.components.get(ref)
+        if not comp:
+            return []
+        return list(set(comp.pins.values()))
+
+    def neighbors(self, ref: str) -> dict[str, list[str]]:
+        """Components sharing a net with *ref*, grouped by net name."""
+        result: dict[str, list[str]] = {}
+        for net_name in self.nets_of_component(ref):
+            others = [r for r in self.components_on_net(net_name) if r != ref]
+            if others:
+                result[net_name] = others
+        return result
+
+    def components_by_type(self, comp_type: ComponentType) -> list[str]:
+        """All refs matching a component type."""
+        return [r for r, c in self.components.items() if c.component_type == comp_type]
+
+    def power_nets(self) -> list[Net]:
+        """All power and ground nets."""
+        return [n for n in self.nets.values() if n.net_type in (NetType.POWER, NetType.GROUND)]
+
+    def capacitors_on_net(self, net_name: str) -> list[str]:
+        """Capacitor refs connected to a net (useful for decoupling checks)."""
+        return [
+            r for r in self.components_on_net(net_name)
+            if (c := self.components.get(r)) is not None
+            and c.component_type == ComponentType.CAPACITOR
+        ]
+
+    def components_by_subtype(self, prefix: str) -> list[str]:
+        """All refs whose component_subtype starts with *prefix*.
+
+        Examples:
+            components_by_subtype("ic.power")       -> all power ICs
+            components_by_subtype("passive.capacitor") -> all capacitors
+            components_by_subtype("passive")          -> all passives
+        """
+        prefix_dot = prefix if prefix.endswith(".") else prefix + "."
+        return [
+            r for r, c in self.components.items()
+            if c.component_subtype and (
+                c.component_subtype == prefix
+                or c.component_subtype.startswith(prefix_dot)
+            )
+        ]
+
+    def pin_net(self, ref: str, pin_number: str) -> str | None:
+        """Net name for a specific pin on a component."""
+        comp = self.components.get(ref)
+        if not comp:
+            return None
+        return comp.pins.get(pin_number)
+
+
+# ---------------------------------------------------------------------------
+# Validation report models
+# ---------------------------------------------------------------------------
+
+
+class Finding(BaseModel):
+    """A single review finding — an issue found during direct datasheet review."""
+    finding_id: str | None = None
+    designator: str
+    mpn: str = ""
+    aspect: str | None = None       # "power_supply", "clock", etc. (for complex ICs)
+    finding: str                     # What was observed in the actual circuit
+    why: str = ""                    # Why it matters — from the datasheet
+    source_page: int | None = None   # Datasheet page (null for deterministic checks)
+    source_quote: str = ""           # Verbatim datasheet text supporting the finding (for PDF highlight)
+    source_designator: str | None = None  # Designator whose datasheet source_page/source_quote refer to; None = this finding's own `designator`. Set when the evidence came from a connected component's datasheet excerpt (get_datasheet_excerpt), so the viewer opens the right PDF at the right page.
+    status: Literal["ERROR", "WARNING", "INFO"]
+    recommendation: str = ""
+    reference: str = ""
+    source: str | None = None        # None/"review" = LLM; "pin_mux_check"/"led_current_check"/"supply_decoupling_check"/… = deterministic
+    net: str | None = None          # net name for CAD telemetry / SI filters
+    pins: list[str] = []           # e.g. ["U3.54"] for pan-and-zoom
+    rule_id: str | None = None       # deterministic id, e.g. PE-MUX-001
+    cad_sheet: str | None = None     # schematic sheet filename for plugin sync
+    cad_uuid: str | None = None      # KiCad symbol/pin uuid
+    variant: str | None = None      # DNP / ECO / assembly variant
+    # Finding engine (docs/motore-finding.md) — optional for legacy JSON.
+    facts: str = ""
+    requirement: str = ""
+    inference: str = ""
+    provenance: Literal["MANDATORY", "RECOMMENDED", "TYPICAL", "EXAMPLE"] | None = None
+    finding_class: Literal["RULE", "RISK", "REVIEW", "INFO"] | None = None
+    confidence: float | None = None
+    evidence_status: Literal["SUFFICIENT", "INSUFFICIENT"] | None = None
+    calculation: str = ""
+    assumptions: list[str] = []
+    action: str = ""
+    decision_id: str | None = None
+    suppressed: bool = False
+
+
+class ValidationReport(BaseModel):
+    """Full validation output."""
+    project: str
+    timestamp: str
+    findings: list[Finding]
+    summary: dict[str, int]
+    coverage: dict[str, list[str]] = {}  # designator -> areas checked and found OK
+    review_errors: dict[str, str] = {}   # designator -> error message for ICs whose review raised
+    not_reviewed: list[dict] = []        # [{"designator","reason"}] — ICs skipped (e.g. no datasheet PDF)
+
+
+class FindingComment(BaseModel):
+    """A comment on a finding, stored outside the ValidationReport model."""
+    comment_id: str
+    finding_id: str
+    user_id: str
+    user_name: str
+    text: str
+    mentions: list[str] = []
+    created_at: str
+
+
+# ---------------------------------------------------------------------------
+# Passive component pattern models
+# ---------------------------------------------------------------------------
+
+
+class PassiveFieldDef(BaseModel):
+    """One named field in a passive component part number."""
+    name: str
+    position: int
+    length: int
+    description: str
+    lookup: dict[str, str] = {}
+
+
+class ValueDecoder(BaseModel):
+    """How to decode the value field (resistance/capacitance) into a number.
+
+    letter_multipliers maps characters to power-of-10 exponents (int) or the
+    special string ``"decimal_point"`` for R-notation (e.g. 4R7 = 4.7 ohms).
+    """
+    type: str  # "eia3_pf" | "eia4_ohm_conditional"
+    base_unit: str  # "pF" | "ohm"
+    output_unit: str  # "F" | "ohm"
+    letter_multipliers: dict[str, int | str] = {}
+    zero_code: str | None = None
+    conditional_on: dict | None = None
+
+
+class PassivePattern(BaseModel):
+    """Regex pattern + field decoders for a passive component family."""
+    manufacturer: str
+    series: str
+    component_type: ComponentType
+    component_subtype: str | None = None  # dotted taxonomy path, e.g. "passive.capacitor.ceramic"
+    description: str
+    regex: str
+    fields: list[PassiveFieldDef]
+    value_decoder: ValueDecoder
+    example_mpns: list[str] = []
+    datasheet_key: str | None = None  # library storage key for shared datasheet PDF
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+
+
+class ResolvedPassive(BaseModel):
+    """Result of resolving a BOM MPN against a stored pattern."""
+    mpn: str
+    references: list[str]
+    component_type: ComponentType
+    component_subtype: str | None = None  # dotted taxonomy path, e.g. "passive.resistor"
+
+    _validate_subtype = field_validator("component_subtype", mode="before")(
+        staticmethod(_check_subtype)
+    )
+    manufacturer: str
+    series: str
+    value: float
+    value_formatted: str
+    tolerance: str | None = None
+    package: str | None = None
+    voltage_rating: str | None = None
+    power_rating: str | None = None
+    dielectric: str | None = None
+    raw_fields: dict[str, str] = {}
+
+
+class LayoutPad(BaseModel):
+    """Component pin land. Not a via, track, or zone."""
+    number: str
+    x: float
+    y: float
+    net: str = ""
+    pinfunction: str = ""
+
+
+class LayoutFootprint(BaseModel):
+    reference: str
+    footprint: str = ""
+    x: float
+    y: float
+    layer: str = ""
+    pads: list[LayoutPad] = []
+    courtyard: list[tuple[float, float]] = []
+
+
+class LayoutSegment(BaseModel):
+    """Copper track segment. Not a pad, via, or zone."""
+    start: tuple[float, float]
+    end: tuple[float, float]
+    width: float = 0.0
+    layer: str = ""
+    net: str = ""
+
+
+class LayoutVia(BaseModel):
+    """Board or footprint via. Has drill; has no pin number."""
+    x: float
+    y: float
+    net: str = ""
+    drill: float | None = None
+
+
+class LayoutDielectric(BaseModel):
+    name: str
+    er: float
+    height_mm: float
+
+
+class LayoutStackup(BaseModel):
+    copper_layers: list[str]
+    dielectrics: list[LayoutDielectric]
+    copper_thickness_mm: float | None = None
+
+
+class LayoutZone(BaseModel):
+    """Copper pour or keepout outline. Not a track or via."""
+    net: str
+    layer: str
+    outlines: list[list[tuple[float, float]]] = []
+    keepout: bool = False
+    name: str = ""
+
+
+class LayoutGraph(BaseModel):
+    """Parsed `.kicad_pcb` geometry. Optional; schema validation does not require it."""
+    nets: dict[str, int] = {}
+    footprints: dict[str, LayoutFootprint] = {}
+    segments: list[LayoutSegment] = []
+    vias: list[LayoutVia] = []
+    stackup: LayoutStackup | None = None
+    zones: list[LayoutZone] = []
+
diff --git a/tests/test_periscope_models_rewrite.py b/tests/test_periscope_models_rewrite.py
new file mode 100644
index 0000000..7f84fb6
--- /dev/null
+++ b/tests/test_periscope_models_rewrite.py
@@ -0,0 +1,44 @@
+"""Periscope models load from src; layout primitives stay disjoint."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import backend.periscopex.models as models
+from backend.periscopex.models import (
+    LayoutPad,
+    LayoutSegment,
+    LayoutVia,
+    LayoutZone,
+)
+
+
+def test_models_module_is_src():
+    path = Path(models.__file__).resolve()
+    assert path.parts[-5:] == ("periscope", "src", "backend", "periscopex", "models.py")
+    text = path.read_text(encoding="utf-8")
+    assert "Native Periscope overlay" not in text
+    assert "pad (component pin land)" in text
+
+
+def test_pad_via_track_zone_are_distinct_types():
+    pad = LayoutPad(number="1", x=0.0, y=0.0, net="GND")
+    via = LayoutVia(x=0.0, y=0.0, net="GND", drill=0.3)
+    track = LayoutSegment(start=(0.0, 0.0), end=(1.0, 0.0), net="GND")
+    zone = LayoutZone(net="GND", layer="F.Cu")
+    kinds = {type(pad), type(via), type(track), type(zone)}
+    assert len(kinds) == 4
+    assert not hasattr(via, "number")
+    assert hasattr(pad, "number")
+    assert not hasattr(track, "drill")
+    assert not hasattr(zone, "drill")
+    assert pad.model_dump() != via.model_dump()
+
+
+def test_via_is_not_a_pad_even_on_same_net_and_xy():
+    """Negative: same net and coordinates do not make a via a pad."""
+    pad = LayoutPad(number="2", x=1.0, y=2.0, net="3V3")
+    via = LayoutVia(x=1.0, y=2.0, net="3V3", drill=0.2)
+    assert type(via) is not type(pad)
+    assert "number" not in type(via).model_fields
+    assert "number" in type(pad).model_fields