diff --git a/api/app/models/file_metadata_model.py b/api/app/models/file_metadata_model.py
index baf9bd97..28e87367 100644
--- a/api/app/models/file_metadata_model.py
+++ b/api/app/models/file_metadata_model.py
@@ -35,7 +35,7 @@ class FileMetadata(Base):
 
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4, index=True)
     tenant_id = Column(UUID(as_uuid=True), nullable=False, index=True, comment="Tenant ID")
-    workspace_id = Column(UUID(as_uuid=True), nullable=False, index=True, comment="Workspace ID")
+    workspace_id = Column(UUID(as_uuid=True), nullable=True, index=True, comment="Workspace ID")
     file_key = Column(String(512), nullable=False, unique=True, index=True, comment="Storage file key")
     file_name = Column(String(255), nullable=False, comment="Original file name")
     file_ext = Column(String(32), nullable=False, comment="File extension")
diff --git a/api/app/services/file_storage_service.py b/api/app/services/file_storage_service.py
index 672e1cff..bb9f1894 100644
--- a/api/app/services/file_storage_service.py
+++ b/api/app/services/file_storage_service.py
@@ -26,7 +26,7 @@ logger = get_business_logger()
 
 def generate_file_key(
     tenant_id: uuid.UUID,
-    workspace_id: uuid.UUID,
+    workspace_id: uuid.UUID | None,
     file_id: uuid.UUID,
     file_ext: str,
 ) -> str:
@@ -56,8 +56,9 @@ def generate_file_key(
     # Ensure file_ext starts with a dot
     if file_ext and not file_ext.startswith('.'):
         file_ext = f'.{file_ext}'
-    
-    return f"{tenant_id}/{workspace_id}/{file_id}{file_ext}"
+    if workspace_id:
+        return f"{tenant_id}/{workspace_id}/{file_id}{file_ext}"
+    return f"{tenant_id}/{file_id}{file_ext}"
 
 
 class FileStorageService:
@@ -96,7 +97,7 @@ class FileStorageService:
     async def upload_file(
         self,
         tenant_id: uuid.UUID,
-        workspace_id: uuid.UUID,
+        workspace_id: uuid.UUID | None,
         file_id: uuid.UUID,
         file_ext: str,
         content: bytes,