diff --git a/litellm/litellm_core_utils/litellm_logging.py b/litellm/litellm_core_utils/litellm_logging.py
index 3018f0c4d24..84bbbd87f91 100644
--- a/litellm/litellm_core_utils/litellm_logging.py
+++ b/litellm/litellm_core_utils/litellm_logging.py
@@ -5077,25 +5077,27 @@ class StandardLoggingPayloadSetup:
     def append_system_prompt_messages(kwargs: dict | None = None, messages: Any | None = None):
         """
         Append system prompt messages to the messages
-        """
-        if kwargs is not None:
-            if kwargs.get("system") is not None and isinstance(kwargs.get("system"), str):
-                if messages is None:
-                    return [{"role": "system", "content": kwargs.get("system")}]
-                elif isinstance(messages, list):
-                    if len(messages) == 0:
-                        return [{"role": "system", "content": kwargs.get("system")}]
-                    # check for duplicates
-                    if messages[0].get("role") == "system" and messages[0].get("content") == kwargs.get("system"):
-                        return messages
-                    messages = [{"role": "system", "content": kwargs.get("system")}] + messages
-                elif isinstance(messages, str):
-                    messages = [
-                        {"role": "system", "content": kwargs.get("system")},
-                        {"role": "user", "content": messages},
-                    ]
-                return messages
 
+        Anthropic's /v1/messages accepts ``system`` as a string or as a list of
+        content blocks; both shapes are logged.
+        """
+        if kwargs is None:
+            return messages
+        system: Final = kwargs.get("system")
+        if not isinstance(system, (str, list)) or (isinstance(system, list) and not system):
+            return messages
+        system_message: Final = {"role": "system", "content": system}
+        if messages is None:
+            return [system_message]
+        if isinstance(messages, list):
+            if len(messages) == 0:
+                return [system_message]
+            first: Final = messages[0]
+            if isinstance(first, dict) and first.get("role") == "system" and first.get("content") == system:
+                return messages
+            return [system_message, *messages]
+        if isinstance(messages, str):
+            return [system_message, {"role": "user", "content": messages}]
         return messages
 
     @staticmethod
diff --git a/tests/test_litellm/litellm_core_utils/test_litellm_logging.py b/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
index 0222e756ba1..d236893db13 100644
--- a/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
+++ b/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
@@ -2524,6 +2524,41 @@ def test_append_system_prompt_messages():
     assert result == messages
 
 
+def test_append_system_prompt_messages_content_blocks():
+    """
+    Anthropic /v1/messages accepts `system` as a list of content blocks; that shape must be logged
+    too, not silently dropped.
+    """
+    from litellm.litellm_core_utils.litellm_logging import StandardLoggingPayloadSetup
+
+    system_blocks = [
+        {
+            "type": "text",
+            "text": "You are a helpful assistant",
+            "cache_control": {"type": "ephemeral"},
+        }
+    ]
+    messages = [{"role": "user", "content": "Hello"}]
+
+    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
+        kwargs={"system": system_blocks}, messages=messages
+    )
+    assert result == [{"role": "system", "content": system_blocks}, *messages]
+
+    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
+        kwargs={"system": system_blocks}, messages=result
+    )
+    assert len(result) == 2
+
+    assert (
+        StandardLoggingPayloadSetup.append_system_prompt_messages(kwargs={"system": []}, messages=messages) == messages
+    )
+    assert StandardLoggingPayloadSetup.append_system_prompt_messages(kwargs={"system": ""}, messages=messages) == [
+        {"role": "system", "content": ""},
+        *messages,
+    ]
+
+
 @pytest.mark.asyncio
 async def test_async_success_handler_sets_standard_logging_object_for_pass_through_endpoints():
     """