diff --git a/litellm/llms/sap/chat/handler.py b/litellm/llms/sap/chat/handler.py
index 67504d99b89..88b22d565f7 100755
--- a/litellm/llms/sap/chat/handler.py
+++ b/litellm/llms/sap/chat/handler.py
@@ -32,16 +32,6 @@ def _now_ts() -> int:
     return int(time.time())
 
 
-def normalize_reasoning_content(raw: dict[str, object]) -> dict[str, object]:
-    """Transform reasoning_content from SAP Orchestration format [{"content": ..., "signature": ...}] to Optional[str] and a thinking_blocks list."""
-    choices: Final[list[object]] = list(raw.get("choices") or [])
-    normalized_choices: Final[dict[str, object]] = [
-        normalize_choice(choice) for choice in choices if isinstance(choice, dict)
-    ]
-    normalized_result: Final[dict[str, object]] = {**raw, "choices": normalized_choices}
-    return normalized_result
-
-
 def normalize_choice(choice: dict[str, object]) -> dict[str, object]:
     """Normalize a single choice dict (message or delta shape) in isolation."""
     for key in ("message", "delta"):
@@ -67,6 +57,40 @@ def normalize_choice(choice: dict[str, object]) -> dict[str, object]:
     return choice
 
 
+def normalize_reasoning_content(raw: dict[str, object]) -> dict[str, object]:
+    """Transform reasoning_content from SAP Orchestration format [{"content": ..., "signature": ...}] to Optional[str] and a thinking_blocks list."""
+    choices: Final[list[object]] = list(raw.get("choices") or [])
+    normalized_choices: Final[dict[str, object]] = [
+        normalize_choice(choice) for choice in choices if isinstance(choice, dict)
+    ]
+    normalized_result: Final[dict[str, object]] = {**raw, "choices": normalized_choices}
+    return normalized_result
+
+
+def denormalize_reasoning_content(message: dict[str, object]) -> dict[str, object]:
+    """Inverse of normalize_reasoning_content: rebuild list[ReasoningBlock] from thinking_blocks.
+
+    LiteLLM normalizes SAP's reasoning_content list into a str + thinking_blocks before
+    returning a ModelResponse. When that response is replayed as a history message the dict
+    must be converted back to the SAP shape before SAPAssistantMessage validation.
+    """
+    if message.get("role") != "assistant":
+        return message
+    thinking_blocks = message.get("thinking_blocks")
+    if not isinstance(thinking_blocks, list):
+        return message
+    reasoning_content: Final = [
+        {"content": block.get("thinking") or "", "signature": block.get("signature")}
+        for block in thinking_blocks
+        if isinstance(block, dict)
+    ]
+    return {
+        k: v
+        for k, v in message.items()
+        if k not in ("thinking_blocks", "reasoning_content")
+    } | {"reasoning_content": reasoning_content}
+
+
 def _is_terminal_chunk(chunk: OpenAIChatCompletionChunk) -> bool:
     """OpenAI-shaped chunk is terminal if any choice has a non-None finish_reason."""
     try:
diff --git a/litellm/llms/sap/chat/transformation.py b/litellm/llms/sap/chat/transformation.py
index 06e6b1535c6..6a70e2a8824 100755
--- a/litellm/llms/sap/chat/transformation.py
+++ b/litellm/llms/sap/chat/transformation.py
@@ -29,6 +29,7 @@ from .handler import (
     GenAIHubOrchestrationError,
     SAPStreamIterator,
     normalize_reasoning_content,
+    denormalize_reasoning_content,
 )
 from .models import (
     ChatCompletionTool,
@@ -104,8 +105,9 @@ def _messages_to_sap_template(messages: list[AllMessageValues]) -> list:
     template: Final = []
     for message in messages:
         folded_message = _fold_message_cache_control(message)
-        message_role_class = _message_role_mapping(str(folded_message["role"]))
-        validated_message = validate_dict(folded_message, message_role_class)
+        denormalized_message = denormalize_reasoning_content(folded_message)
+        message_role_class = _message_role_mapping(str(denormalized_message["role"]))
+        validated_message = validate_dict(denormalized_message, message_role_class)
         template.append(validated_message)
     return template
 
diff --git a/tests/unit/llms/sap/chat/test_sap_transformation.py b/tests/unit/llms/sap/chat/test_sap_transformation.py
index e9c87ae8048..22e360b8532 100644
--- a/tests/unit/llms/sap/chat/test_sap_transformation.py
+++ b/tests/unit/llms/sap/chat/test_sap_transformation.py
@@ -1141,4 +1141,74 @@ class TestMessagesToSapTemplateReasoningContent:
         assistant_msg = result[1]
         assert assistant_msg["reasoning_content"] == [
             {"content": "Simple arithmetic.", "signature": "sig1"}
-        ]
\ No newline at end of file
+        ]
+
+    def test_litellm_normalized_assistant_message_round_trips_signature(self):
+        """After a non-streaming SAP call, the ModelResponse has reasoning_content: str
+        and thinking_blocks: list (LiteLLM native format). Replaying it as a history
+        message must not raise and must preserve the signature.
+        """
+        from litellm.llms.sap.chat.transformation import _messages_to_sap_template
+
+        signature = "EtwHCkABGAIqQKNbQn0Uz=="
+        messages = [
+            {"role": "user", "content": "Translate it."},
+            {
+                "role": "assistant",
+                "content": "The text is Lorem Ipsum.",
+                "reasoning_content": "Lorem ipsum is pseudo-Latin...",
+                "thinking_blocks": [
+                    {"type": "thinking", "thinking": "Lorem ipsum is pseudo-Latin...", "signature": signature}
+                ],
+            },
+            {"role": "user", "content": "Summarise it."},
+        ]
+
+        result = _messages_to_sap_template(messages)
+        assistant = next(m for m in result if m.get("role") == "assistant")
+
+        reasoning = assistant.get("reasoning_content")
+        assert isinstance(reasoning, list)
+        assert any(block.get("signature") == signature for block in reasoning)
+
+    def test_streaming_assembled_assistant_message_round_trips_signature(self):
+        """After a streaming SAP call, normalize_reasoning_content runs on every chunk.
+        The assembled assistant message has the same LiteLLM-native shape as the
+        non-streaming case. Verify the signature survives the round-trip.
+        """
+        from litellm.llms.sap.chat.handler import normalize_reasoning_content
+        from litellm.llms.sap.chat.transformation import _messages_to_sap_template
+
+        signature = "EtwHCkABGAIqQKNbQn0Uz=="
+        thinking_text = "Lorem ipsum is pseudo-Latin..."
+        sap_final_result = {
+            "id": "msg_stream_01",
+            "object": "chat.completion",
+            "model": "gpt-4o",
+            "choices": [
+                {
+                    "index": 0,
+                    "message": {
+                        "role": "assistant",
+                        "content": "The text is Lorem Ipsum.",
+                        "reasoning_content": [{"content": thinking_text, "signature": signature}],
+                    },
+                    "finish_reason": "stop",
+                }
+            ],
+        }
+        normalized = normalize_reasoning_content(sap_final_result)
+        assembled_message = {"role": "assistant", **normalized["choices"][0]["message"]}
+
+        messages = [
+            {"role": "user", "content": "Translate it."},
+            assembled_message,
+            {"role": "user", "content": "Summarize it."},
+        ]
+
+        result = _messages_to_sap_template(messages)
+        assistant = next(m for m in result if m.get("role") == "assistant")
+
+        reasoning = assistant.get("reasoning_content")
+        assert isinstance(reasoning, list)
+        assert any(block.get("signature") == signature for block in reasoning)
\ No newline at end of file