diff --git a/mealie/db/models/_model_base.py b/mealie/db/models/_model_base.py
index 00da8ece6..db409b66e 100644
--- a/mealie/db/models/_model_base.py
+++ b/mealie/db/models/_model_base.py
@@ -1,6 +1,6 @@
 import string
 from datetime import datetime
-from typing import Annotated, ClassVar
+from typing import Annotated, ClassVar, get_origin
 
 from sqlalchemy import Integer
 from sqlalchemy.orm import DeclarativeBase, Mapped, declared_attr, mapped_column, synonym
@@ -19,9 +19,17 @@ class PrivateColumn[T]:
     """
     Drop-in replacement for `Mapped[]` that marks a column as private.
     Private columns cannot be used in query filter expressions.
+
+    Only valid on scalar column fields. Using it on a relationship type (e.g. `list[Model]`)
+    will raise a `TypeError` at class definition time.
     """
 
     def __class_getitem__(cls, item: type) -> type:
+        if get_origin(item) is list or item is list:
+            raise TypeError(
+                f"PrivateColumn cannot be used on relationship fields (got {item!r}). "
+                "Annotate the related model's scalar column directly instead."
+            )
         return Mapped[Annotated[item, mapped_column(info={"private": True})]]
 
 
diff --git a/tests/unit_tests/repository_tests/test_query_filter_builder.py b/tests/unit_tests/repository_tests/test_query_filter_builder.py
index 0f60d86bd..09799049e 100644
--- a/tests/unit_tests/repository_tests/test_query_filter_builder.py
+++ b/tests/unit_tests/repository_tests/test_query_filter_builder.py
@@ -1,6 +1,7 @@
 import pytest
 import sqlalchemy as sa
 
+from mealie.db.models._model_base import PrivateColumn
 from mealie.db.models.recipe.recipe import RecipeModel
 from mealie.db.models.users.users import LongLiveToken, User
 from mealie.services.query_filter.builder import (
@@ -87,6 +88,12 @@ def test_query_filter_builder_json_uses_raw_value():
 # ---------------------------------------------------------------------------
 
 
+def test_private_column_rejects_list_type():
+    """PrivateColumn[list[X]] must raise TypeError at definition time to prevent misuse on relationships."""
+    with pytest.raises(TypeError, match="relationship"):
+        PrivateColumn[list[User]]
+
+
 def test_private_field_user_password_raises():
     """Filtering on User.password (PrivateColumn) should raise ValueError."""
     with pytest.raises(ValueError, match="private field"):