diff --git a/backend/open_webui/models/users.py b/backend/open_webui/models/users.py
index 1eff4932d5..abbbe122ea 100644
--- a/backend/open_webui/models/users.py
+++ b/backend/open_webui/models/users.py
@@ -27,7 +27,6 @@ from sqlalchemy import (
     select,
     update,
 )
-from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.ext.asyncio import AsyncSession
 
 ####################
@@ -360,16 +359,10 @@ class UsersTable:
         sub: str,
         db: AsyncSession | None = None,
     ) -> UserModel | None:
-        """Look up a user by OAuth provider + subject claim (dialect-aware JSON filter)."""
+        """Look up a user by OAuth provider + subject claim."""
         async with get_async_db_context(db) as session:
-            dialect = session.bind.dialect.name
-            query = select(User)
-            if dialect == 'sqlite':
-                oauth_match = User.oauth.contains({provider: {'sub': sub}})
-                query = query.where(oauth_match)
-            elif dialect == 'postgresql':
-                oauth_match = User.oauth[provider].cast(JSONB)['sub'].astext == sub
-                query = query.where(oauth_match)
+            # Subscript, never contains(): on a JSON column contains() degrades to a substring LIKE.
+            query = select(User).where(User.oauth[provider]['sub'].as_string() == sub)
             row = (await session.execute(query)).scalars().first()
             return UserModel.model_validate(row) if row else None
 
@@ -379,16 +372,10 @@ class UsersTable:
         external_id: str,
         db: AsyncSession | None = None,
     ) -> UserModel | None:
-        """Look up a user by SCIM provider + external ID (dialect-aware JSON filter)."""
+        """Look up a user by SCIM provider + external ID."""
         async with get_async_db_context(db) as session:
-            dialect = session.bind.dialect.name
-            query = select(User)
-            if dialect == 'sqlite':
-                scim_match = User.scim.contains({provider: {'external_id': external_id}})
-                query = query.where(scim_match)
-            elif dialect == 'postgresql':
-                scim_match = User.scim[provider].cast(JSONB)['external_id'].astext == external_id
-                query = query.where(scim_match)
+            # Subscript, never contains(): on a JSON column contains() degrades to a substring LIKE.
+            query = select(User).where(User.scim[provider]['external_id'].as_string() == external_id)
             row = (await session.execute(query)).scalars().first()
             return UserModel.model_validate(row) if row else None