diff --git a/backend/app/api/deps.py b/backend/app/api/deps.py
index 43810c38..fd946e31 100644
--- a/backend/app/api/deps.py
+++ b/backend/app/api/deps.py
@@ -121,6 +121,9 @@ def get_current_user_org_project(
             organization_id = api_key_record.organization_id
             project_id = api_key_record.project_id
 
+    else:
+        raise HTTPException(status_code=401, detail="Invalid API Key")
+
     return UserProjectOrg(
         **current_user.model_dump(),
         organization_id=organization_id,
diff --git a/backend/app/api/routes/threads.py b/backend/app/api/routes/threads.py
index e0e77fc2..90fe0415 100644
--- a/backend/app/api/routes/threads.py
+++ b/backend/app/api/routes/threads.py
@@ -9,9 +9,9 @@
 from typing import Optional
 from langfuse.decorators import observe, langfuse_context
 
-from app.api.deps import get_current_user_org, get_db
+from app.api.deps import get_current_user_org, get_db, get_current_user_org_project
 from app.core import logging, settings
-from app.models import UserOrganization, OpenAIThreadCreate
+from app.models import UserOrganization, OpenAIThreadCreate, UserProjectOrg
 from app.crud import upsert_thread_result, get_thread_result
 from app.utils import APIResponse
 from app.crud.credentials import get_provider_credential
@@ -372,7 +372,7 @@ async def start_thread(
     request: StartThreadRequest,
     background_tasks: BackgroundTasks,
     db: Session = Depends(get_db),
-    _current_user: UserOrganization = Depends(get_current_user_org),
+    _current_user: UserProjectOrg = Depends(get_current_user_org_project),
 ):
     """
     Create a new OpenAI thread for the given question and start polling in the background.
@@ -383,7 +383,7 @@ async def start_thread(
         session=db,
         org_id=_current_user.organization_id,
         provider="openai",
-        project_id=request.get("project_id"),
+        project_id=_current_user.project_id,
     )
 
     # Configure OpenAI client