diff --git a/backend/app/schemas/device_type.py b/backend/app/schemas/device_type.py
new file mode 100644
index 00000000..8d2b70a2
--- /dev/null
+++ b/backend/app/schemas/device_type.py
@@ -0,0 +1,38 @@
+"""Pydantic schemas for device types."""
+from datetime import datetime
+from typing import Optional
+from uuid import UUID
+
+from pydantic import BaseModel, Field
+
+
+class DeviceTypeCreate(BaseModel):
+    slug: str = Field(min_length=1, max_length=50, pattern=r"^[a-z0-9\-]+$")
+    label: str = Field(min_length=1, max_length=100)
+    category: str = Field(
+        min_length=1, max_length=50,
+        pattern=r"^(network|compute|storage|cloud|endpoint|infrastructure|security)$",
+    )
+    sort_order: int = Field(default=0, ge=0)
+
+
+class DeviceTypeUpdate(BaseModel):
+    label: str | None = Field(default=None, min_length=1, max_length=100)
+    category: str | None = Field(
+        default=None, min_length=1, max_length=50,
+        pattern=r"^(network|compute|storage|cloud|endpoint|infrastructure|security)$",
+    )
+    sort_order: int | None = Field(default=None, ge=0)
+
+
+class DeviceTypeResponse(BaseModel):
+    id: UUID
+    slug: str
+    label: str
+    category: str
+    is_system: bool
+    team_id: UUID | None = None
+    sort_order: int
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
diff --git a/backend/app/schemas/network_diagram.py b/backend/app/schemas/network_diagram.py
new file mode 100644
index 00000000..2b25356a
--- /dev/null
+++ b/backend/app/schemas/network_diagram.py
@@ -0,0 +1,130 @@
+"""Pydantic schemas for network diagrams."""
+from datetime import datetime
+from typing import Optional
+from uuid import UUID
+
+from pydantic import BaseModel, Field
+
+
+class DeviceProperties(BaseModel):
+    hostname: str | None = None
+    ip: str | None = None
+    subnet: str | None = None
+    vendor: str | None = None
+    model: str | None = None
+    role: str | None = None
+    vlan: str | None = None
+    notes: str | None = None
+    status: str = Field(default="unknown", pattern=r"^(unknown|online|offline|degraded)$")
+
+
+class DiagramNode(BaseModel):
+    id: str
+    type: str
+    label: str
+    position: dict
+    properties: DeviceProperties = Field(default_factory=DeviceProperties)
+
+
+class DiagramEdge(BaseModel):
+    id: str
+    source: str
+    target: str
+    label: str | None = None
+    connectionType: str = "ethernet"
+    speed: str | None = None
+    notes: str | None = None
+
+
+class NetworkDiagramCreate(BaseModel):
+    name: str = Field(min_length=1, max_length=255)
+    client_name: str | None = None
+    asset_name: str | None = None
+    description: str | None = None
+    nodes: list[DiagramNode] = Field(default_factory=list)
+    edges: list[DiagramEdge] = Field(default_factory=list)
+
+
+class NetworkDiagramUpdate(BaseModel):
+    name: str | None = Field(default=None, min_length=1, max_length=255)
+    client_name: str | None = None
+    asset_name: str | None = None
+    description: str | None = None
+    nodes: list[DiagramNode] | None = None
+    edges: list[DiagramEdge] | None = None
+
+
+class NetworkDiagramResponse(BaseModel):
+    id: UUID
+    team_id: UUID
+    name: str
+    client_name: str | None = None
+    asset_name: str | None = None
+    description: str | None = None
+    nodes: list[DiagramNode] = Field(default_factory=list)
+    edges: list[DiagramEdge] = Field(default_factory=list)
+    thumbnail_url: str | None = None
+    is_archived: bool = False
+    created_by: UUID | None = None
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class NetworkDiagramListItem(BaseModel):
+    id: UUID
+    name: str
+    client_name: str | None = None
+    description: str | None = None
+    node_count: int = 0
+    created_by: UUID | None = None
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class ExistingBounds(BaseModel):
+    minX: float
+    maxX: float
+    minY: float
+    maxY: float
+
+
+class AIGenerateRequest(BaseModel):
+    description: str = Field(min_length=1, max_length=5000)
+    client_name: str | None = None
+    mode: str = Field(default="replace", pattern=r"^(replace|merge)$")
+    existingBounds: ExistingBounds | None = None
+
+
+class AIGenerateResponse(BaseModel):
+    nodes: list[DiagramNode]
+    edges: list[DiagramEdge]
+    suggestedName: str | None = None
+    notes: str | None = None
+
+
+class DiagramImportRequest(BaseModel):
+    schemaVersion: int = Field(ge=1, le=1)
+    name: str = Field(min_length=1, max_length=255)
+    client_name: str | None = None
+    description: str | None = None
+    nodes: list[DiagramNode] = Field(default_factory=list)
+    edges: list[DiagramEdge] = Field(default_factory=list)
+
+
+class DiagramImportResponse(BaseModel):
+    diagram: NetworkDiagramResponse
+    warnings: list[str] = Field(default_factory=list)
+
+
+class DiagramExportResponse(BaseModel):
+    schemaVersion: int = 1
+    name: str
+    client_name: str | None = None
+    description: str | None = None
+    nodes: list[DiagramNode]
+    edges: list[DiagramEdge]
+    exportedAt: str