From 6396cc03f729c334589c86089160a484bec30edf Mon Sep 17 00:00:00 2001
From: Daniel Cadenas <dcadenas@gmail.com>
Date: Thu, 6 Aug 2026 17:50:42 -0300
Subject: [PATCH] fix(core): merge mixed system message content

---
 .../prompt_templates/factory.py               | 16 ++++++-
 tests/llm_translation/test_optional_params.py | 47 +++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/litellm/litellm_core_utils/prompt_templates/factory.py b/litellm/litellm_core_utils/prompt_templates/factory.py
index 3a1a426eaa9..e238727c19e 100644
--- a/litellm/litellm_core_utils/prompt_templates/factory.py
+++ b/litellm/litellm_core_utils/prompt_templates/factory.py
@@ -18,6 +18,7 @@ from litellm import verbose_logger
 from litellm._uuid import uuid
 from litellm.litellm_core_utils.url_utils import async_safe_get, safe_get
 from litellm.llms.custom_httpx.http_handler import HTTPHandler, get_async_httpx_client
+from litellm.types.completion import ChatCompletionContentPartTextParam
 from litellm.types.files import get_file_extension_from_mime_type
 from litellm.types.llms.anthropic import *
 from litellm.types.llms.bedrock import CachePointBlock
@@ -107,7 +108,20 @@ def map_system_message_pt(messages: list) -> list:
                 next_role = next_m["role"]
                 if next_role == "user" or next_role == "assistant":  # Next message is a user or assistant message
                     # Merge system prompt into the next message
-                    next_m["content"] = m["content"] + " " + next_m["content"]
+                    system_content = m["content"]
+                    next_content = next_m["content"]
+                    if isinstance(system_content, list):
+                        next_m["content"] = tuple(system_content) + (
+                            tuple(next_content)
+                            if isinstance(next_content, list)
+                            else (ChatCompletionContentPartTextParam(type="text", text=next_content),)
+                        )
+                    elif isinstance(next_content, list):
+                        next_m["content"] = (
+                            ChatCompletionContentPartTextParam(type="text", text=system_content),
+                        ) + tuple(next_content)
+                    else:
+                        next_m["content"] = system_content + " " + next_content
                 elif next_role == "system":  # Next message is a system message
                     # Append a user message instead of the system message
                     new_message = {"role": "user", "content": m["content"]}
diff --git a/tests/llm_translation/test_optional_params.py b/tests/llm_translation/test_optional_params.py
index 9ebdb4b7e97..707caca2d10 100644
--- a/tests/llm_translation/test_optional_params.py
+++ b/tests/llm_translation/test_optional_params.py
@@ -55,6 +55,53 @@ def test_supports_system_message():
     assert isinstance(response, litellm.ModelResponse)
 
 
+@pytest.mark.parametrize(
+    "system_content,user_content,expected_content",
+    [
+        (
+            [{"type": "text", "text": "Follow these instructions."}],
+            [{"type": "text", "text": "Hello there!"}],
+            (
+                {"type": "text", "text": "Follow these instructions."},
+                {"type": "text", "text": "Hello there!"},
+            ),
+        ),
+        (
+            [{"type": "text", "text": "Follow these instructions."}],
+            "Hello there!",
+            (
+                {"type": "text", "text": "Follow these instructions."},
+                {"type": "text", "text": "Hello there!"},
+            ),
+        ),
+        (
+            "Follow these instructions.",
+            [{"type": "text", "text": "Hello there!"}],
+            (
+                {"type": "text", "text": "Follow these instructions."},
+                {"type": "text", "text": "Hello there!"},
+            ),
+        ),
+        (
+            "Follow these instructions.",
+            "Hello there!",
+            "Follow these instructions. Hello there!",
+        ),
+    ],
+)
+def test_map_system_message_with_mixed_content_types(
+    system_content, user_content, expected_content
+):
+    messages = [
+        {"role": "system", "content": system_content},
+        {"role": "user", "content": user_content},
+    ]
+
+    new_messages = map_system_message_pt(messages=messages)
+
+    assert new_messages == [{"role": "user", "content": expected_content}]
+
+
 @pytest.mark.parametrize(
     "stop_sequence, expected_count", [("\n", 0), (["\n"], 0), (["finish_reason"], 1)]
 )