diff --git a/backend/app/models.py b/backend/app/models.py
index 2389b4a532..345743917a 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -2,11 +2,14 @@
 
 from pydantic import EmailStr
 from sqlmodel import Field, Relationship, SQLModel
+from sqlalchemy import String
 
 
 # Shared properties
 class UserBase(SQLModel):
-    email: EmailStr = Field(unique=True, index=True, max_length=255)
+    email: EmailStr = Field(
+        unique=True, index=True, max_length=255, sa_type=String(255)
+    )
     is_active: bool = True
     is_superuser: bool = False
     full_name: str | None = Field(default=None, max_length=255)
@@ -18,20 +21,20 @@ class UserCreate(UserBase):
 
 
 class UserRegister(SQLModel):
-    email: EmailStr = Field(max_length=255)
+    email: str = Field(max_length=255)
     password: str = Field(min_length=8, max_length=40)
     full_name: str | None = Field(default=None, max_length=255)
 
 
 # Properties to receive via API on update, all are optional
 class UserUpdate(UserBase):
-    email: EmailStr | None = Field(default=None, max_length=255)  # type: ignore
+    email: str | None = Field(default=None, max_length=255)  # type: ignore
     password: str | None = Field(default=None, min_length=8, max_length=40)
 
 
 class UserUpdateMe(SQLModel):
     full_name: str | None = Field(default=None, max_length=255)
-    email: EmailStr | None = Field(default=None, max_length=255)
+    email: str | None = Field(default=None, max_length=255)
 
 
 class UpdatePassword(SQLModel):
@@ -43,7 +46,14 @@ class UpdatePassword(SQLModel):
 class User(UserBase, table=True):
     id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
     hashed_password: str
-    items: list["Item"] = Relationship(back_populates="owner", cascade_delete=True)
+    items: list["Item"] = Relationship(
+        back_populates="owner",
+        sa_relationship_kwargs={
+            "cascade": "all, delete-orphan",
+            "primaryjoin": "User.id == Item.owner_id",
+            "foreign_keys": "[Item.owner_id]",
+        },
+    )
 
 
 # Properties to return via API, id is always required
@@ -75,10 +85,15 @@ class ItemUpdate(ItemBase):
 # Database model, database table inferred from class name
 class Item(ItemBase, table=True):
     id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
-    owner_id: uuid.UUID = Field(
-        foreign_key="user.id", nullable=False, ondelete="CASCADE"
+    # Remove foreign_key constraint, but keep it indexed for performance
+    owner_id: uuid.UUID = Field(index=True, nullable=False)
+    owner: User | None = Relationship(
+        back_populates="items",
+        sa_relationship_kwargs={
+            "primaryjoin": "User.id == Item.owner_id",
+            "foreign_keys": "[Item.owner_id]",
+        },
     )
-    owner: User | None = Relationship(back_populates="items")
 
 
 # Properties to return via API, id is always required