Merge pull request #723 from trinh31201/bugfix/json-extraction-validation

micro-fix(graph): validate LLM JSON extraction to prevent empty/fabricated data

core/framework/graph/node.py

@@ -1348,7 +1348,9 @@ Expected output keys: {output_keys}
 LLM Response:
 {raw_response}
 
-Output ONLY the JSON object, nothing else."""
+Output ONLY the JSON object, nothing else.
+If no valid JSON object exists in the response, output exactly: {{"error": "NO_JSON_FOUND"}}
+Do NOT fabricate data or return empty objects."""
 
         try:
             result = cleaner_llm.complete(
@@ -1395,6 +1397,14 @@ Output ONLY the JSON object, nothing else."""
                 parsed = json.loads(cleaned)
             except json.JSONDecodeError:
                 parsed = json.loads(_fix_unescaped_newlines_in_json(cleaned))
+
+            # Validate LLM didn't return empty or fabricated data
+            if parsed.get("error") == "NO_JSON_FOUND":
+                raise ValueError("Cannot parse JSON from response")
+            if not parsed or parsed == {}:
+                raise ValueError("Cannot parse JSON from response")
+            if all(v is None for v in parsed.values()):
+                raise ValueError("Cannot parse JSON from response")
             logger.info("      ✓ LLM cleaned JSON output")
             return parsed