Add Langfuse tracing via Langchain callback when generating answer

conversation/generate.py

@@ -8,6 +8,8 @@ from langchain_core.prompts import (
 )
 from langchain_core.runnables import RunnableParallel
 from langgraph.graph import MessagesState
+from langfuse import Langfuse, get_client
+from langfuse.langchain import CallbackHandler
 from pydantic import BaseModel
 
 from config import app_settings
@@ -19,6 +21,19 @@ llm = init_chat_model(
     model_provider="openai",
     api_key=app_settings.llm_api_key
 )
+ 
+# Initialize Langfuse client with constructor arguments
+Langfuse(
+    public_key=app_settings.langfuse_public_api_key,
+    secret_key=app_settings.langfuse_secret_api_key,
+    host=app_settings.langfuse_host
+)
+ 
+# Get the configured client instance
+langfuse = get_client()
+ 
+# Initialize the Langfuse handler
+langfuse_handler = CallbackHandler()
 
 
 # RAG answer synthesis prompt
@@ -82,5 +97,6 @@ def generate(state: MessagesState):
         "question": conversation_messages[-1].content,
         "chat_history": conversation_messages,
         "context": docs_content,
-    })
+    }, config={"callbacks": [langfuse_handler]})
+
     return {"messages": [response]}