From b68f9211c2ee7de2c21f75a501aba47db4f71995 Mon Sep 17 00:00:00 2001
From: Nuno Campos <nuno@langchain.dev>
Date: Wed, 4 Sep 2024 12:13:38 -0700
Subject: [PATCH] Run branch.reader in bg thread

---
 libs/langgraph/langgraph/graph/graph.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libs/langgraph/langgraph/graph/graph.py b/libs/langgraph/langgraph/graph/graph.py
index 41175c170..21868bf7c 100644
--- a/libs/langgraph/langgraph/graph/graph.py
+++ b/libs/langgraph/langgraph/graph/graph.py
@@ -1,3 +1,4 @@
+import asyncio
 import logging
 from collections import defaultdict
 from typing import (
@@ -97,7 +98,7 @@ class Branch(NamedTuple):
         writer: Callable[[list[str], RunnableConfig], Optional[Runnable]],
     ) -> Runnable:
         if reader:
-            value = reader(config)
+            value = await asyncio.to_thread(reader, config)
             # passthrough additional keys from node to branch
             # only doable when using dict states
             if isinstance(value, dict) and isinstance(input, dict):