diff --git a/.architecture-rules/api.yaml b/.architecture-rules/api.yaml
index 023b59de..a141988d 100644
--- a/.architecture-rules/api.yaml
+++ b/.architecture-rules/api.yaml
@@ -56,6 +56,54 @@ api_endpoint_rules:
       def get_data(): ...
 
   - id: "API-002"
+    name: "No Pydantic imports in API endpoint files"
+    severity: "error"
+    description: |
+      API endpoint files must NOT import Pydantic directly (BaseModel, Field, etc.).
+      All Pydantic schemas must be defined in models/schema/*.py and imported from there.
+
+      WHY THIS MATTERS:
+      - Separation of concerns: API handles HTTP, schemas handle data structure
+      - Discoverability: All schemas in one place for easy review
+      - Reusability: Schemas can be shared across endpoints
+      - Prevents inline schema definitions that violate API-001
+
+      WRONG:
+        from pydantic import BaseModel, Field
+        class MyRequest(BaseModel):  # Inline schema
+            name: str
+
+      RIGHT:
+        # In models/schema/my_feature.py
+        from pydantic import BaseModel
+        class MyRequest(BaseModel):
+            name: str
+
+        # In app/api/v1/admin/my_feature.py
+        from models.schema.my_feature import MyRequest
+    pattern:
+      file_pattern: "app/api/v1/**/*.py"
+      anti_patterns:
+        - "from pydantic import"
+        - "from pydantic.main import"
+    example_good: |
+      # In app/api/v1/admin/vendors.py
+      from models.schema.vendor import (
+          LetzshopExportRequest,
+          LetzshopExportResponse,
+      )
+
+      @router.post("/export", response_model=LetzshopExportResponse)
+      def export_products(request: LetzshopExportRequest):
+          ...
+    example_bad: |
+      # In app/api/v1/admin/vendors.py
+      from pydantic import BaseModel  # WRONG: Don't import pydantic here
+
+      class LetzshopExportRequest(BaseModel):  # WRONG: Define in models/schema/
+          include_inactive: bool = False
+
+  - id: "API-003"
     name: "Endpoint must NOT contain business logic"
     severity: "error"
     description: |
@@ -76,7 +124,7 @@ api_endpoint_rules:
         - "db.delete("
         - "db.query("
 
-  - id: "API-003"
+  - id: "API-004"
     name: "Endpoint must NOT raise ANY exceptions directly"
     severity: "error"
     description: |
@@ -116,7 +164,7 @@ api_endpoint_rules:
       exceptions:
         - "app/exceptions/handler.py"
 
-  - id: "API-004"
+  - id: "API-005"
     name: "Endpoint must have proper authentication/authorization"
     severity: "warning"
     description: |
@@ -128,7 +176,7 @@ api_endpoint_rules:
 
       Public endpoint markers (place on line before or after decorator):
       - # public - Descriptive marker for intentionally unauthenticated endpoints
-      - # noqa: API-004 - Standard noqa style to suppress warning
+      - # noqa: API-005 - Standard noqa style to suppress warning
 
       Example:
         # public - Stripe webhook receives external callbacks
@@ -143,9 +191,9 @@ api_endpoint_rules:
         - "*/auth.py"
       public_markers:
         - "# public"
-        - "# noqa: api-004"
+        - "# noqa: api-005"
 
-  - id: "API-005"
+  - id: "API-006"
     name: "Multi-tenant endpoints must scope queries to vendor_id"
     severity: "error"
     description: |
diff --git a/app/api/v1/admin/vendor_products.py b/app/api/v1/admin/vendor_products.py
index c8a4abc6..2a2bb4c1 100644
--- a/app/api/v1/admin/vendor_products.py
+++ b/app/api/v1/admin/vendor_products.py
@@ -6,162 +6,35 @@ Provides management of vendor-specific product catalogs:
 - Browse products in vendor catalogs
 - View product details with override info
 - Remove products from catalog
+
+Architecture Notes:
+- All Pydantic schemas are defined in models/schema/vendor_product.py
+- Business logic is delegated to vendor_product_service
 """
 
 import logging
 
 from fastapi import APIRouter, Depends, Query
-from pydantic import BaseModel
 from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_admin_api
 from app.core.database import get_db
 from app.services.vendor_product_service import vendor_product_service
 from models.database.user import User
+from models.schema.vendor_product import (
+    CatalogVendor,
+    CatalogVendorsResponse,
+    RemoveProductResponse,
+    VendorProductDetail,
+    VendorProductListItem,
+    VendorProductListResponse,
+    VendorProductStats,
+)
 
 router = APIRouter(prefix="/vendor-products")
 logger = logging.getLogger(__name__)
 
 
-# ============================================================================
-# Pydantic Models
-# ============================================================================
-
-
-class VendorProductListItem(BaseModel):
-    """Product item for vendor catalog list view."""
-
-    id: int
-    vendor_id: int
-    vendor_name: str | None = None
-    vendor_code: str | None = None
-    marketplace_product_id: int
-    vendor_sku: str | None = None
-    title: str | None = None
-    brand: str | None = None
-    effective_price: float | None = None
-    effective_currency: str | None = None
-    is_active: bool | None = None
-    is_featured: bool | None = None
-    is_digital: bool | None = None
-    image_url: str | None = None
-    source_marketplace: str | None = None
-    source_vendor: str | None = None
-    created_at: str | None = None
-    updated_at: str | None = None
-
-    class Config:
-        from_attributes = True
-
-
-class VendorProductListResponse(BaseModel):
-    """Paginated vendor product list response."""
-
-    products: list[VendorProductListItem]
-    total: int
-    skip: int
-    limit: int
-
-
-class VendorProductStats(BaseModel):
-    """Vendor product statistics."""
-
-    total: int
-    active: int
-    inactive: int
-    featured: int
-    digital: int
-    physical: int
-    by_vendor: dict[str, int]
-
-
-class CatalogVendor(BaseModel):
-    """Vendor with products in catalog."""
-
-    id: int
-    name: str
-    vendor_code: str
-
-
-class CatalogVendorsResponse(BaseModel):
-    """Response for catalog vendors list."""
-
-    vendors: list[CatalogVendor]
-
-
-class VendorProductDetail(BaseModel):
-    """Detailed vendor product information."""
-
-    id: int
-    vendor_id: int
-    vendor_name: str | None = None
-    vendor_code: str | None = None
-    marketplace_product_id: int
-    vendor_sku: str | None = None
-    # Override info from get_override_info()
-    price: float | None = None
-    price_overridden: bool | None = None
-    price_source: float | None = None
-    sale_price: float | None = None
-    sale_price_overridden: bool | None = None
-    sale_price_source: float | None = None
-    currency: str | None = None
-    currency_overridden: bool | None = None
-    currency_source: str | None = None
-    brand: str | None = None
-    brand_overridden: bool | None = None
-    brand_source: str | None = None
-    condition: str | None = None
-    condition_overridden: bool | None = None
-    condition_source: str | None = None
-    availability: str | None = None
-    availability_overridden: bool | None = None
-    availability_source: str | None = None
-    primary_image_url: str | None = None
-    primary_image_url_overridden: bool | None = None
-    primary_image_url_source: str | None = None
-    is_digital: bool | None = None
-    product_type: str | None = None
-    # Vendor-specific fields
-    is_featured: bool | None = None
-    is_active: bool | None = None
-    display_order: int | None = None
-    min_quantity: int | None = None
-    max_quantity: int | None = None
-    # Supplier tracking
-    supplier: str | None = None
-    supplier_product_id: str | None = None
-    cost: float | None = None  # What vendor pays to acquire product
-    margin_percent: float | None = None
-    # Tax/profit info
-    tax_rate_percent: int | None = None
-    net_price: float | None = None
-    vat_amount: float | None = None
-    profit: float | None = None
-    profit_margin_percent: float | None = None
-    # Digital fulfillment
-    download_url: str | None = None
-    license_type: str | None = None
-    fulfillment_email_template: str | None = None
-    # Source info
-    source_marketplace: str | None = None
-    source_vendor: str | None = None
-    source_gtin: str | None = None
-    source_sku: str | None = None
-    # Translations
-    marketplace_translations: dict | None = None
-    vendor_translations: dict | None = None
-    # Timestamps
-    created_at: str | None = None
-    updated_at: str | None = None
-
-
-class RemoveProductResponse(BaseModel):
-    """Response from product removal."""
-
-    message: str
-
-
 # ============================================================================
 # Endpoints
 # ============================================================================
diff --git a/models/schema/vendor_product.py b/models/schema/vendor_product.py
new file mode 100644
index 00000000..4d120a6e
--- /dev/null
+++ b/models/schema/vendor_product.py
@@ -0,0 +1,145 @@
+# models/schema/vendor_product.py
+"""
+Pydantic schemas for vendor product catalog operations.
+
+Used by admin vendor product endpoints for:
+- Product listing and filtering
+- Product statistics
+- Product detail views
+- Catalog vendor listings
+"""
+
+from pydantic import BaseModel, ConfigDict
+
+
+class VendorProductListItem(BaseModel):
+    """Product item for vendor catalog list view."""
+
+    model_config = ConfigDict(from_attributes=True)
+
+    id: int
+    vendor_id: int
+    vendor_name: str | None = None
+    vendor_code: str | None = None
+    marketplace_product_id: int
+    vendor_sku: str | None = None
+    title: str | None = None
+    brand: str | None = None
+    effective_price: float | None = None
+    effective_currency: str | None = None
+    is_active: bool | None = None
+    is_featured: bool | None = None
+    is_digital: bool | None = None
+    image_url: str | None = None
+    source_marketplace: str | None = None
+    source_vendor: str | None = None
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class VendorProductListResponse(BaseModel):
+    """Paginated vendor product list response."""
+
+    products: list[VendorProductListItem]
+    total: int
+    skip: int
+    limit: int
+
+
+class VendorProductStats(BaseModel):
+    """Vendor product statistics."""
+
+    total: int
+    active: int
+    inactive: int
+    featured: int
+    digital: int
+    physical: int
+    by_vendor: dict[str, int]
+
+
+class CatalogVendor(BaseModel):
+    """Vendor with products in catalog."""
+
+    id: int
+    name: str
+    vendor_code: str
+
+
+class CatalogVendorsResponse(BaseModel):
+    """Response for catalog vendors list."""
+
+    vendors: list[CatalogVendor]
+
+
+class VendorProductDetail(BaseModel):
+    """Detailed vendor product information."""
+
+    id: int
+    vendor_id: int
+    vendor_name: str | None = None
+    vendor_code: str | None = None
+    marketplace_product_id: int
+    vendor_sku: str | None = None
+    # Override info from get_override_info()
+    price: float | None = None
+    price_overridden: bool | None = None
+    price_source: float | None = None
+    sale_price: float | None = None
+    sale_price_overridden: bool | None = None
+    sale_price_source: float | None = None
+    currency: str | None = None
+    currency_overridden: bool | None = None
+    currency_source: str | None = None
+    brand: str | None = None
+    brand_overridden: bool | None = None
+    brand_source: str | None = None
+    condition: str | None = None
+    condition_overridden: bool | None = None
+    condition_source: str | None = None
+    availability: str | None = None
+    availability_overridden: bool | None = None
+    availability_source: str | None = None
+    primary_image_url: str | None = None
+    primary_image_url_overridden: bool | None = None
+    primary_image_url_source: str | None = None
+    is_digital: bool | None = None
+    product_type: str | None = None
+    # Vendor-specific fields
+    is_featured: bool | None = None
+    is_active: bool | None = None
+    display_order: int | None = None
+    min_quantity: int | None = None
+    max_quantity: int | None = None
+    # Supplier tracking
+    supplier: str | None = None
+    supplier_product_id: str | None = None
+    cost: float | None = None  # What vendor pays to acquire product
+    margin_percent: float | None = None
+    # Tax/profit info
+    tax_rate_percent: int | None = None
+    net_price: float | None = None
+    vat_amount: float | None = None
+    profit: float | None = None
+    profit_margin_percent: float | None = None
+    # Digital fulfillment
+    download_url: str | None = None
+    license_type: str | None = None
+    fulfillment_email_template: str | None = None
+    # Source info
+    source_marketplace: str | None = None
+    source_vendor: str | None = None
+    source_gtin: str | None = None
+    source_sku: str | None = None
+    # Translations
+    marketplace_translations: dict | None = None
+    vendor_translations: dict | None = None
+    # Timestamps
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class RemoveProductResponse(BaseModel):
+    """Response from product removal."""
+
+    message: str