revert langserve upgrade and change api

app/main.py

@@ -399,10 +399,11 @@ add_routes(
 
 add_routes(
     app,
-    RunnableLambda(lambda d: flexible_handler(d).result),  # returns just the string
+    RunnableLambda(lambda d: flexible_handler(d).result),
     path="/chatfed",
-    config={"enable_streaming": True, "exclude_run_metadata": True},
-    output_type=str                                      
+    output_type=str,           # <-- still needed so /invoke returns a string
+    enable_streaming=True,     # <-- old API
+    include_run_metadata=False # <-- old API; same effect as exclude_run_metadata=True
 )
 
 # ChatUI-compatible streaming route (yields tokens via SSE)

requirements.txt

@@ -14,8 +14,7 @@ langgraph>=0.2.0
 langchain-core>=0.2.0
 Pillow>=9.0.0
 fastapi>=0.100.0
-langserve[all]==0.0.46
-# langserve[all]>=0.0.30
+langserve[all]>=0.0.30
 uvicorn[standard]>=0.23.0
 typing_extensions>=4.5.0
 python-multipart>=0.0.6