From 4264079089a61ef90e09011fb8add37ead4af20e Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Thu, 8 Oct 2026 02:49:24 -0700
Subject: [PATCH 1/2] fix(responses): join function_call_output text parts with
 a newline in the chat-completions bridge

---
 .../litellm_completion_transformation/transformation.py   | 2 +-
 .../test_function_call_output_normalization.py            | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/litellm/responses/litellm_completion_transformation/transformation.py b/litellm/responses/litellm_completion_transformation/transformation.py
index b1dc6b3a98a..9bd8373f62a 100644
--- a/litellm/responses/litellm_completion_transformation/transformation.py
+++ b/litellm/responses/litellm_completion_transformation/transformation.py
@@ -1639,7 +1639,7 @@ class LiteLLMCompletionResponsesConfig:
                     # Ensure we include any accumulated text as text blocks too
                     return normalized_blocks
                 if text_acc:
-                    return "".join(text_acc)
+                    return "\n".join(text_acc)
                 try:
                     # last resort: keep something meaningful for providers that require a string
                     import json as _json
diff --git a/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py b/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
index 3af1ef51e3e..bbcba0d5312 100644
--- a/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
+++ b/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
@@ -11,14 +11,14 @@ from litellm.responses.litellm_completion_transformation.transformation import (
 )
 
 
-def test_function_call_output_list_input_text_is_converted_to_tool_string_content():
+def test_function_call_output_list_input_text_parts_reach_the_tool_message_on_separate_lines():
     out = LiteLLMCompletionResponsesConfig._transform_responses_api_tool_call_output_to_chat_completion_message(
         tool_call_output={
             "type": "function_call_output",
             "call_id": "call_1",
             "output": [
-                {"type": "input_text", "text": "hello"},
-                {"type": "input_text", "text": " world"},
+                {"type": "input_text", "text": "Paris: 22 degrees"},
+                {"type": "input_text", "text": "clear skies"},
             ],
         }
     )
@@ -27,7 +27,7 @@ def test_function_call_output_list_input_text_is_converted_to_tool_string_conten
     msg = out[0]
     assert msg["role"] == "tool"
     assert msg["tool_call_id"] == "call_1"
-    assert msg["content"] == "hello world"
+    assert msg["content"] == "Paris: 22 degrees\nclear skies"
 
 
 def test_function_call_output_string_passthrough():

From 574b96aefb8bbe35ed5c2c9d547ea6f564759639 Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Thu, 8 Oct 2026 04:09:36 -0700
Subject: [PATCH 2/2] test(responses): pin that a text part's leading
 whitespace survives the newline join

---
 .../test_function_call_output_normalization.py    | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py b/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
index bbcba0d5312..1a0b8d34ee0 100644
--- a/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
+++ b/tests/unit/responses/litellm_completion_transformation/test_function_call_output_normalization.py
@@ -30,6 +30,21 @@ def test_function_call_output_list_input_text_parts_reach_the_tool_message_on_se
     assert msg["content"] == "Paris: 22 degrees\nclear skies"
 
 
+def test_function_call_output_text_part_whitespace_survives_the_join():
+    out = LiteLLMCompletionResponsesConfig._transform_responses_api_tool_call_output_to_chat_completion_message(
+        tool_call_output={
+            "type": "function_call_output",
+            "call_id": "call_1",
+            "output": [
+                {"type": "input_text", "text": "hello"},
+                {"type": "input_text", "text": " world"},
+            ],
+        }
+    )
+
+    assert out[0]["content"] == "hello\n world"
+
+
 def test_function_call_output_string_passthrough():
     out = LiteLLMCompletionResponsesConfig._transform_responses_api_tool_call_output_to_chat_completion_message(
         tool_call_output={