fix

agent.py

@@ -147,10 +147,21 @@ def build_graph(provider: str = "huggingface"):
         print("\n--- Assistant Node ---")
         print("Incoming messages to assistant:")
         for msg in state["messages"]:
-            msg.pretty_print() #
+            msg.pretty_print() 
+
+        # Defensive check
+        if not state["messages"]:
+            raise ValueError("No messages provided to the assistant.")
+
+        # Must contain at least one HumanMessage (Claude requirement)
+        if not any(isinstance(msg, HumanMessage) for msg in state["messages"]):
+            raise ValueError("Claude requires at least one HumanMessage in the input.")
+
+        response = llm_with_tools.invoke(state["messages"])
+        return {"messages": state["messages"] + [response]}
         
-        """Assistant node"""
-        return {"messages": [llm_with_tools.invoke(state["messages"])]}
+        # """Assistant node"""
+        # return {"messages": [llm_with_tools.invoke(state["messages"])]}
     
     # def retriever(state: MessagesState):
     #     """Retriever node"""

app.py

@@ -37,8 +37,8 @@ except Exception as e:
 
 def run_langgraph_agent(user_input: str):
     graph = build_graph()
-    result = graph.invoke({"input": user_input})
-    return result["output"] if "output" in result else result
+    result = graph.invoke({"messages": [HumanMessage(content=user_input)]})
+    return result["messages"][-1].content if "messages" in result else result
 
 
 demo = gr.Interface(

requirements.txt

@@ -3,6 +3,7 @@ gradio
 langchain
 langchain-community
 langchain-core
+langchain-anthropic
 langchain-google-genai
 langchain-huggingface
 langchain-groq