From 19ff81e74f51ab3857eaf933f947f5a891127428 Mon Sep 17 00:00:00 2001
From: Nuno Campos <nuno@langchain.dev>
Date: Wed, 7 Feb 2024 15:46:13 -0800
Subject: [PATCH] Fix stream events/log with some kinds of non addable output
 (#17205)

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---
 libs/core/langchain_core/tracers/log_stream.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libs/core/langchain_core/tracers/log_stream.py b/libs/core/langchain_core/tracers/log_stream.py
index c6b8da943a..db56626451 100644
--- a/libs/core/langchain_core/tracers/log_stream.py
+++ b/libs/core/langchain_core/tracers/log_stream.py
@@ -572,6 +572,7 @@ async def _astream_log_implementation(
                     try:
                         final_output = final_output + chunk  # type: ignore
                     except TypeError:
+                        prev_final_output = None
                         final_output = chunk
                 patches: List[Dict[str, Any]] = []
                 if with_streamed_output_list: