diff --git a/litellm/integrations/custom_logger.py b/litellm/integrations/custom_logger.py
index 41caf732db0..ba30447683b 100644
--- a/litellm/integrations/custom_logger.py
+++ b/litellm/integrations/custom_logger.py
@@ -927,6 +927,12 @@ class CustomLogger:  # https://docs.litellm.ai/docs/observability/custom_callbac
             if "messages" not in (excluded_fields or []) and standard_logging_object_copy.get("messages") is not None:
                 standard_logging_object_copy["messages"] = [Message(content=redacted_str).model_dump()]
 
+            if (
+                "system_prompt" not in (excluded_fields or [])
+                and standard_logging_object_copy.get("system_prompt") is not None
+            ):
+                standard_logging_object_copy["system_prompt"] = redacted_str
+
             if "response" not in (excluded_fields or []) and standard_logging_object_copy.get("response") is not None:
                 response: Final = standard_logging_object_copy["response"]
                 # Check if this is a ResponsesAPIResponse (has "output" field)
diff --git a/litellm/litellm_core_utils/litellm_logging.py b/litellm/litellm_core_utils/litellm_logging.py
index 3018f0c4d24..74653b4ec94 100644
--- a/litellm/litellm_core_utils/litellm_logging.py
+++ b/litellm/litellm_core_utils/litellm_logging.py
@@ -5074,29 +5074,17 @@ class StandardLoggingPayloadSetup:
         return start_time_float, end_time_float, completion_start_time_float
 
     @staticmethod
-    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
+    def get_system_prompt_from_kwargs(kwargs: dict | None = None) -> str | list | dict | None:
+        if kwargs is None:
+            return None
 
-        return messages
+        for key in ("system_instructions", "instructions", "system"):
+            value = kwargs.get(key)
+            if value is None:
+                continue
+            if isinstance(value, (str, list, dict)):
+                return value
+        return None
 
     @staticmethod
     def merge_litellm_metadata(litellm_params: Mapping[str, object]) -> dict:
@@ -6046,11 +6034,8 @@ def get_standard_logging_object_payload(
             model_id=_model_id,
             requester_ip_address=clean_metadata.get("requester_ip_address", None),
             user_agent=clean_metadata.get("user_agent", None),
-            messages=truncate_base64_in_messages(
-                StandardLoggingPayloadSetup.append_system_prompt_messages(
-                    kwargs=kwargs, messages=kwargs.get("messages")
-                )
-            ),
+            messages=truncate_base64_in_messages(kwargs.get("messages")),
+            system_prompt=StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(kwargs=kwargs),
             response=final_response_obj,
             model_parameters=ModelParamHelper.get_standard_logging_model_parameters(
                 kwargs.get("optional_params", None) or {}
diff --git a/litellm/litellm_core_utils/redact_messages.py b/litellm/litellm_core_utils/redact_messages.py
index 9402d465712..97afe6b329b 100644
--- a/litellm/litellm_core_utils/redact_messages.py
+++ b/litellm/litellm_core_utils/redact_messages.py
@@ -173,6 +173,9 @@ def _redact_standard_logging_object(model_call_details: dict):
     if standard_logging_object.get("messages") is not None:
         standard_logging_object["messages"] = [{"role": "user", "content": redacted_str}]
 
+    if standard_logging_object.get("system_prompt") is not None:
+        standard_logging_object["system_prompt"] = redacted_str
+
     response: Final = standard_logging_object.get("response")
     if response is not None:
         if isinstance(response, dict) and "output" in response:
diff --git a/litellm/types/utils.py b/litellm/types/utils.py
index 95429e899c9..7c7f871a0ab 100644
--- a/litellm/types/utils.py
+++ b/litellm/types/utils.py
@@ -3254,6 +3254,7 @@ class StandardLoggingPayload(TypedDict):
     requester_ip_address: str | None
     user_agent: str | None
     messages: str | list | dict | None
+    system_prompt: str | list | dict | None
     response: str | list | dict | None
     error_str: str | None
     error_information: StandardLoggingPayloadErrorInformation | None
diff --git a/tests/logging_callback_tests/test_standard_logging_payload_excluded_fields.py b/tests/logging_callback_tests/test_standard_logging_payload_excluded_fields.py
index d8c45d832ce..3a741e762b0 100644
--- a/tests/logging_callback_tests/test_standard_logging_payload_excluded_fields.py
+++ b/tests/logging_callback_tests/test_standard_logging_payload_excluded_fields.py
@@ -59,6 +59,7 @@ def create_sample_standard_logging_payload() -> Dict:
         "requester_ip_address": None,
         "user_agent": None,
         "messages": [{"role": "user", "content": "Hello, this is sensitive data!"}],
+        "system_prompt": [{"type": "text", "text": "sensitive system prompt"}],
         "response": {
             "choices": [{"message": {"content": "This is a sensitive response!"}}]
         },
@@ -223,6 +224,7 @@ class TestStandardLoggingPayloadExcludedFields:
         assert (
             result["standard_logging_object"]["messages"][0]["content"] == redacted_str
         )
+        assert result["standard_logging_object"]["system_prompt"] == redacted_str
         assert (
             result["standard_logging_object"]["response"]["choices"][0]["message"][
                 "content"
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..f3e08d3730f 100644
--- a/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
+++ b/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
@@ -2465,63 +2465,103 @@ def test_get_usage_as_dict():
     assert result == {"prompt_tokens": 0, "completion_tokens": 0, "total_tokens": 0}
 
 
-def test_append_system_prompt_messages():
-    """
-    Test append_system_prompt_messages prepends system message from kwargs to messages list.
-    """
+def test_get_system_prompt_from_kwargs():
     from litellm.litellm_core_utils.litellm_logging import StandardLoggingPayloadSetup
 
-    # Test case 1: system in kwargs with existing messages
-    kwargs = {"system": "You are a helpful assistant"}
-    messages = [{"role": "user", "content": "Hello"}]
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=kwargs, messages=messages
-    )
-    assert len(result) == 2
-    assert result[0] == {"role": "system", "content": "You are a helpful assistant"}
-    assert result[1] == {"role": "user", "content": "Hello"}
-
-    # Test case 2: system in kwargs with None messages
-    kwargs = {"system": "You are a helpful assistant"}
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=kwargs, messages=None
-    )
-    assert len(result) == 1
-    assert result[0] == {"role": "system", "content": "You are a helpful assistant"}
-
-    # Test case 3: system in kwargs with empty messages list
-    kwargs = {"system": "You are a helpful assistant"}
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=kwargs, messages=[]
-    )
-    assert len(result) == 1
-    assert result[0] == {"role": "system", "content": "You are a helpful assistant"}
-
-    # Test case 4: duplicate system message should not be added
-    kwargs = {"system": "You are a helpful assistant"}
-    messages = [
-        {"role": "system", "content": "You are a helpful assistant"},
-        {"role": "user", "content": "Hello"},
+    system_blocks = [
+        {"type": "text", "text": "SHAPE-SECRET", "cache_control": {"type": "ephemeral"}},
     ]
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=kwargs, messages=messages
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(
+        kwargs={"system": system_blocks, "messages": [{"role": "user", "content": "hi"}]}
     )
-    assert len(result) == 2
-    assert result[0] == {"role": "system", "content": "You are a helpful assistant"}
+    assert result == system_blocks
 
-    # Test case 5: no system in kwargs returns messages unchanged
-    kwargs = {}
-    messages = [{"role": "user", "content": "Hello"}]
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=kwargs, messages=messages
-    )
-    assert result == messages
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(kwargs={"system": "Be helpful"})
+    assert result == "Be helpful"
 
-    # Test case 6: None kwargs returns messages unchanged
-    result = StandardLoggingPayloadSetup.append_system_prompt_messages(
-        kwargs=None, messages=messages
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(kwargs={"instructions": "Follow policy"})
+    assert result == "Follow policy"
+
+    gemini_system = [{"role": "system", "content": "Be concise."}]
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(
+        kwargs={"system_instructions": gemini_system}
     )
-    assert result == messages
+    assert result == gemini_system
+
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(
+        kwargs={
+            "system_instructions": "From Gemini",
+            "instructions": "From Responses",
+            "system": "From Anthropic",
+        }
+    )
+    assert result == "From Gemini"
+
+    result = StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(
+        kwargs={"system_instructions": [], "instructions": "From Responses"}
+    )
+    assert result == []
+
+    assert StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(kwargs={}) is None
+    assert StandardLoggingPayloadSetup.get_system_prompt_from_kwargs(kwargs=None) is None
+
+
+def test_get_standard_logging_object_payload_keeps_system_prompt_separate_from_messages(logging_obj):
+    import datetime
+
+    from litellm.litellm_core_utils.litellm_logging import get_standard_logging_object_payload
+
+    user_messages = [{"role": "user", "content": "hello"}]
+    mock_response = {
+        "id": "msg_123",
+        "type": "message",
+        "role": "assistant",
+        "content": [{"type": "text", "text": "hi"}],
+        "model": "claude-sonnet-4-5",
+        "usage": {"input_tokens": 5, "output_tokens": 2},
+    }
+    now = datetime.datetime.now()
+
+    system_blocks = [
+        {"type": "text", "text": "SHAPE-SECRET", "cache_control": {"type": "ephemeral"}},
+    ]
+    list_kwargs = {
+        "model": "anthropic/claude-sonnet-4-5",
+        "system": system_blocks,
+        "messages": user_messages,
+        "litellm_params": {},
+    }
+    list_payload = get_standard_logging_object_payload(
+        kwargs=list_kwargs,
+        init_response_obj=mock_response,
+        start_time=now,
+        end_time=now,
+        logging_obj=logging_obj,
+        status="success",
+    )
+
+    assert list_payload is not None
+    assert list_payload["system_prompt"] == system_blocks
+    assert list_payload["messages"] == user_messages
+
+    string_kwargs = {
+        "model": "anthropic/claude-sonnet-4-5",
+        "system": "Be helpful",
+        "messages": user_messages,
+        "litellm_params": {},
+    }
+    string_payload = get_standard_logging_object_payload(
+        kwargs=string_kwargs,
+        init_response_obj=mock_response,
+        start_time=now,
+        end_time=now,
+        logging_obj=logging_obj,
+        status="success",
+    )
+
+    assert string_payload is not None
+    assert string_payload["system_prompt"] == "Be helpful"
+    assert string_payload["messages"] == user_messages
 
 
 @pytest.mark.asyncio
diff --git a/tests/test_litellm/litellm_core_utils/test_redact_messages.py b/tests/test_litellm/litellm_core_utils/test_redact_messages.py
index 3be0bae4120..c5599e4dd45 100644
--- a/tests/test_litellm/litellm_core_utils/test_redact_messages.py
+++ b/tests/test_litellm/litellm_core_utils/test_redact_messages.py
@@ -15,6 +15,7 @@ from litellm.integrations.custom_logger import CustomLogger
 from litellm.litellm_core_utils.redact_messages import (
     _redact_responses_api_output,
     perform_redaction,
+    redact_message_input_output_from_logging,
     redact_streaming_responses_for_custom_logger,
     should_redact_message_logging,
 )
@@ -182,6 +183,9 @@ class TestPerformRedaction:
             "input": "sensitive input",
             "standard_logging_object": {
                 "messages": [{"role": "user", "content": "sensitive input"}],
+                "system_prompt": [
+                    {"type": "text", "text": "SHAPE-SECRET", "cache_control": {"type": "ephemeral"}},
+                ],
                 "response": {
                     "output": [
                         {"text": "top-level text"},
@@ -208,6 +212,7 @@ class TestPerformRedaction:
         ]
         assert details["prompt"] == ""
         assert details["input"] == ""
+        assert details["standard_logging_object"]["system_prompt"] == "redacted-by-litellm"
 
         logged_response = details["standard_logging_object"]["response"]
         assert logged_response["usage"] == {"total_tokens": 1}
@@ -858,3 +863,47 @@ class TestRedactStreamingResponsesForCustomLogger:
 
         assert result_details is model_call_details
         assert response_obj.choices[0].message.content == "secret content"
+
+
+class TestSystemPromptRedaction:
+    REDACTED = "redacted-by-litellm"
+    SYSTEM_PROMPT = [{"type": "text", "text": "SHAPE-SECRET"}]
+
+    def _details_with_system_prompt(self, **extra):
+        details = {
+            "messages": [{"role": "user", "content": "hi"}],
+            "standard_logging_object": {
+                "messages": [{"role": "user", "content": "hi"}],
+                "system_prompt": self.SYSTEM_PROMPT,
+                "response": {"choices": [{"message": {"content": "secret"}}]},
+            },
+            "litellm_params": {"metadata": {}},
+        }
+        details.update(extra)
+        return details
+
+    def test_global_turn_off_message_logging_redacts_system_prompt(self):
+        litellm.turn_off_message_logging = True
+        details = self._details_with_system_prompt()
+
+        redact_message_input_output_from_logging(details, result=None)
+
+        assert details["standard_logging_object"]["system_prompt"] == self.REDACTED
+
+    def test_request_level_dynamic_param_redacts_system_prompt(self):
+        details = self._details_with_system_prompt(
+            standard_callback_dynamic_params={"turn_off_message_logging": True}
+        )
+
+        redact_message_input_output_from_logging(details, result=None)
+
+        assert details["standard_logging_object"]["system_prompt"] == self.REDACTED
+
+    def test_per_callback_turn_off_message_logging_redacts_system_prompt(self):
+        details = self._details_with_system_prompt()
+        logger = CustomLogger(turn_off_message_logging=True)
+
+        result = logger.redact_standard_logging_payload_from_model_call_details(details)
+
+        assert result["standard_logging_object"]["system_prompt"] == self.REDACTED
+        assert details["standard_logging_object"]["system_prompt"] == self.SYSTEM_PROMPT