feat: full Langfuse tracing A-Z with @observe + get_client() v3.11 API

backend/agent/controller.py

@@ -13,11 +13,10 @@ import uuid
 from fastapi import BackgroundTasks
 from langchain_core.messages import AIMessage, HumanMessage
 from langchain_core.runnables import RunnableConfig
-from langfuse import Langfuse, propagate_attributes
+from langfuse import get_client as get_langfuse, observe, propagate_attributes
 
 from common.cache import redis_cache
 from common.conversation_manager import get_conversation_manager
-from common.langfuse_client import get_callback_handler
 from config import DEFAULT_MODEL, REDIS_CACHE_TURN_ON
 
 from .controller_helpers import (
@@ -32,7 +31,7 @@ from .streaming_callback import ProductIDStreamingCallback
 
 logger = logging.getLogger(__name__)
 
-
+@observe(name="chat-request")
 async def chat_controller(
     query: str,
     identity_key: str,
@@ -113,8 +112,27 @@ async def chat_controller(
     }
 
     run_id = str(uuid.uuid4())
-    trace_id = Langfuse.create_trace_id()
-    langfuse_handler = get_callback_handler()
+    session_id = f"{identity_key}-{run_id[:8]}"
+
+    # Set Langfuse trace metadata (nests under @observe parent)
+    langfuse = get_langfuse()
+    langfuse.update_current_trace(
+        user_id=identity_key,
+        session_id=session_id,
+        tags=["chatbot", "user:authenticated" if is_authenticated else "user:anonymous"],
+        metadata={
+            "device_id": device_id,
+            "customer_id": identity_key if is_authenticated else None,
+            "model": model_name,
+        },
+    )
+
+    # Get handler from context → nested under same trace as @observe
+    try:
+        langfuse_handler = langfuse.get_current_langchain_handler()
+    except Exception:
+        langfuse_handler = None
+        logger.warning("⚠️ Could not get Langfuse langchain handler")
 
     streaming_callback = ProductIDStreamingCallback()
 
@@ -123,21 +141,15 @@ async def chat_controller(
             "user_id": identity_key,
             "transient_images": images or [],
             "run_id": run_id,
-            "trace_id": trace_id,
         },
         run_id=run_id,
         metadata={
-            "trace_id": trace_id,
-            "session_id": f"{identity_key}-{run_id[:8]}",
+            "session_id": session_id,
             "device_id": device_id,
-            "customer_id": identity_key if is_authenticated else None,
-            "langfuse_tags": ["chatbot", "user:authenticated" if is_authenticated else "user:anonymous"],
         },
         callbacks=[langfuse_handler, streaming_callback] if langfuse_handler else [streaming_callback],
     )
 
-    session_id = f"{identity_key}-{run_id[:8]}"
-
     logger.info("🌊 Starting LLM streaming...")
 
     event_count = 0
@@ -166,7 +178,6 @@ async def chat_controller(
 
     early_response = False
 
-    with propagate_attributes(user_id=identity_key, session_id=session_id):
     stream_task = asyncio.create_task(consume_events())
 
     if return_user_insight:
@@ -297,7 +308,7 @@ async def chat_controller(
             stream_task=stream_task,
             streaming_callback=streaming_callback,
             identity_key=identity_key,
-            trace_id=trace_id,
+            trace_id=langfuse.get_current_trace_id() if langfuse else run_id,
         )
 
     # ====================== BUILD RESPONSE ======================

backend/agent/tools/data_retrieval_tool.py

@@ -159,8 +159,10 @@ async def _execute_single_search(
                 (first_p.get("description_text") or "")[:100],
             )
 
-        from langfuse import langfuse_context
-        langfuse_context.update_current_observation(
+        from langfuse import get_client as get_langfuse
+        try:
+            lf = get_langfuse()
+            lf.update_current_observation(
                 input={
                     "description": item.description[:200] if item.description else None,
                     "product_name": item.product_name,
@@ -175,6 +177,8 @@ async def _execute_single_search(
                     "db_ms": round(db_time, 2),
                 },
             )
+        except Exception:
+            pass  # Don't break if Langfuse not available
 
         return format_product_results(products), {"fallback_used": False}
     except Exception as e: