From c3f68a6d7eb7dc46a27f280d2ce5bc96388aeee9 Mon Sep 17 00:00:00 2001
From: Nuno Campos <nuno@langchain.dev>
Date: Wed, 29 May 2024 16:47:39 -0700
Subject: [PATCH] Use the last annotation as the reducer

---
 langgraph/graph/state.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/langgraph/graph/state.py b/langgraph/graph/state.py
index 450618958..9e7c00ced 100644
--- a/langgraph/graph/state.py
+++ b/langgraph/graph/state.py
@@ -466,7 +466,7 @@ def _get_channel(
 def _is_field_binop(typ: Type[Any]) -> Optional[BinaryOperatorAggregate]:
     if hasattr(typ, "__metadata__"):
         meta = typ.__metadata__
-        if len(meta) == 1 and callable(meta[0]):
+        if len(meta) > 1 and callable(meta[-1]):
             sig = signature(meta[0])
             params = list(sig.parameters.values())
             if len(params) == 2 and len(