Update LangGraphAgent to use ChatTogether model instead of ChatOpenRouter

agent.py

@@ -1,6 +1,6 @@
 import os
 from typing import Optional
-
+from langchain_together import ChatTogether
 from langgraph.graph import StateGraph, START, END, MessagesState
 from langchain_core.messages import HumanMessage, AIMessage, SystemMessage
 from langchain_google_genai import ChatGoogleGenerativeAI
@@ -77,8 +77,10 @@ class LangGraphAgent:
             # model = ChatGoogleGenerativeAI(
             #     model="gemma-3-27b-it",
             # )
-            model = ChatOpenRouter(
-                model="z-ai/glm-4.5-air:free",
+            model = ChatTogether(
+                model="openai/gpt-oss-20b",
+                api_key=os.getenv("TOGETHER_API_KEY"),
+
             )
             if model is None and ChatOpenAI is not None:
                 model = ChatOpenAI(