diff --git a/backend/app/api/v1/routes_clients.py b/backend/app/api/v1/routes_clients.py
index 5d04be8..788f239 100644
--- a/backend/app/api/v1/routes_clients.py
+++ b/backend/app/api/v1/routes_clients.py
@@ -64,15 +64,36 @@ async def _get_project_or_404(project_id: str, client_id: str, db: AsyncIOMotorD
 
 
 def _client_from_doc(doc: dict) -> Client:
-    return Client(**{**doc, "_id": str(doc["_id"])})
+    return Client(
+        id=str(doc["_id"]),
+        name=doc["name"],
+        slug=doc["slug"],
+        is_active=doc.get("is_active", True),
+        created_at=doc.get("created_at"),
+        updated_at=doc.get("updated_at"),
+    )
 
 
 def _team_from_doc(doc: dict) -> Team:
-    return Team(**{**doc, "_id": str(doc["_id"])})
+    return Team(
+        id=str(doc["_id"]),
+        name=doc["name"],
+        client_id=doc["client_id"],
+        member_user_ids=doc.get("member_user_ids", []),
+        created_at=doc.get("created_at"),
+        updated_at=doc.get("updated_at"),
+    )
 
 
 def _project_from_doc(doc: dict) -> Project:
-    return Project(**{**doc, "_id": str(doc["_id"])})
+    return Project(
+        id=str(doc["_id"]),
+        name=doc["name"],
+        client_id=doc["client_id"],
+        is_active=doc.get("is_active", True),
+        created_at=doc.get("created_at"),
+        updated_at=doc.get("updated_at"),
+    )
 
 
 # ---------------------------------------------------------------------------
diff --git a/backend/app/models/client.py b/backend/app/models/client.py
index 2cd98e6..f4a7659 100644
--- a/backend/app/models/client.py
+++ b/backend/app/models/client.py
@@ -2,7 +2,7 @@ from datetime import datetime
 from typing import Optional, Annotated
 
 from bson import ObjectId
-from pydantic import BaseModel, Field, BeforeValidator
+from pydantic import BaseModel, BeforeValidator
 
 
 def validate_object_id(v) -> str:
@@ -17,16 +17,13 @@ PyObjectId = Annotated[str, BeforeValidator(validate_object_id)]
 
 
 class Client(BaseModel):
-    id: Optional[PyObjectId] = Field(None, alias="_id")
+    id: Optional[str] = None
     name: str
-    slug: str  # lowercase, URL-safe identifier, unique
+    slug: str
     is_active: bool = True
     created_at: Optional[datetime] = None
     updated_at: Optional[datetime] = None
 
-    class Config:
-        populate_by_name = True
-
 
 class ClientCreate(BaseModel):
     name: str
@@ -40,16 +37,13 @@ class ClientUpdate(BaseModel):
 
 
 class Team(BaseModel):
-    id: Optional[PyObjectId] = Field(None, alias="_id")
+    id: Optional[str] = None
     name: str
     client_id: str
     member_user_ids: list[str] = []
     created_at: Optional[datetime] = None
     updated_at: Optional[datetime] = None
 
-    class Config:
-        populate_by_name = True
-
 
 class TeamCreate(BaseModel):
     name: str
@@ -60,16 +54,13 @@ class TeamUpdate(BaseModel):
 
 
 class Project(BaseModel):
-    id: Optional[PyObjectId] = Field(None, alias="_id")
+    id: Optional[str] = None
     name: str
     client_id: str
     is_active: bool = True
     created_at: Optional[datetime] = None
     updated_at: Optional[datetime] = None
 
-    class Config:
-        populate_by_name = True
-
 
 class ProjectCreate(BaseModel):
     name: str
diff --git a/frontend/src/hooks/useClients.ts b/frontend/src/hooks/useClients.ts
index 905239e..0d75fd4 100644
--- a/frontend/src/hooks/useClients.ts
+++ b/frontend/src/hooks/useClients.ts
@@ -97,7 +97,7 @@ export function usePMs(clientId: string) {
   return useQuery({
     queryKey: ['clients', clientId, 'pm'],
     queryFn: () => apiClient.listPMs(clientId),
-    enabled: !!clientId,
+    enabled: !!clientId && clientId !== 'undefined',
   });
 }
 
@@ -123,7 +123,7 @@ export function useTeams(clientId: string) {
   return useQuery({
     queryKey: ['clients', clientId, 'teams'],
     queryFn: () => apiClient.listTeams(clientId),
-    enabled: !!clientId,
+    enabled: !!clientId && clientId !== 'undefined',
   });
 }
 
@@ -176,7 +176,7 @@ export function useProjects(clientId: string) {
   return useQuery({
     queryKey: ['clients', clientId, 'projects'],
     queryFn: () => apiClient.listProjects(clientId),
-    enabled: !!clientId,
+    enabled: !!clientId && clientId !== 'undefined',
   });
 }