Fix: pass system prompt via SystemMessage instead of state_modifier

state_modifier not supported in installed LangGraph version.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -8,6 +8,7 @@ from langchain_community.tools import DuckDuckGoSearchRun, WikipediaQueryRun
 from langchain_community.utilities import WikipediaAPIWrapper
 from langchain_experimental.tools import PythonREPLTool
 from langchain.tools import tool
+from langchain_core.messages import SystemMessage, HumanMessage
 
 # --- Constants ---
 DEFAULT_API_URL = "https://agents-course-unit4-scoring.hf.space"
@@ -48,14 +49,14 @@ class BasicAgent:
             PythonREPLTool(),
             fetch_task_file,
         ]
-        self.agent = create_react_agent(llm, tools, state_modifier=SYSTEM_PROMPT)
+        self.agent = create_react_agent(llm, tools)
         print("BasicAgent initialized with LangGraph + Groq (llama-3.1-70b-versatile).")
 
     def __call__(self, question: str, task_id: str = "") -> str:
         full_question = f"[Task ID: {task_id}]\n\n{question}" if task_id else question
         print(f"Running agent on task {task_id}: {question[:80]}...")
         result = self.agent.invoke(
-            {"messages": [("user", full_question)]},
+            {"messages": [SystemMessage(content=SYSTEM_PROMPT), HumanMessage(content=full_question)]},
             {"recursion_limit": 50},
         )
         raw_answer = result["messages"][-1].content