fix: type casting

backend/config.py

@@ -680,9 +680,11 @@ Question:
 SEARCH_QUERY_PROMPT_LENGTH_THRESHOLD = PersistentConfig(
     "SEARCH_QUERY_PROMPT_LENGTH_THRESHOLD",
     "task.search.prompt_length_threshold",
-    os.environ.get(
-        "SEARCH_QUERY_PROMPT_LENGTH_THRESHOLD",
-        100,
+    int(
+        os.environ.get(
+            "SEARCH_QUERY_PROMPT_LENGTH_THRESHOLD",
+            100,
+        )
     ),
 )