Merge abe66cb278 into 2c9b0e00ac

litellm/llms/sap/chat/models.py

@@ -2,31 +2,44 @@ import warnings
 from enum import Enum
 from typing import Final, Literal
 
-from pydantic import BaseModel, Field, field_validator, model_validator
+from pydantic import (
+    BaseModel,
+    Field,
+    SerializationInfo,
+    SerializerFunctionWrapHandler,
+    field_validator,
+    model_serializer,
+    model_validator,
+)
 
 
-def validate_different_content(v: str | dict | list) -> str:
-    if v in ((), {}, []):
-        return ""
-    elif isinstance(v, dict) and "text" in v:
-        return v["text"]
-    elif isinstance(v, list):
-        new_v: Final = []
-        for item in v:
-            if isinstance(item, dict) and "text" in item:
-                if item["text"]:
-                    new_v.append(item["text"])
-            elif isinstance(item, str):
-                new_v.append(item)
-        return "\n".join(new_v)
-    elif isinstance(v, str):
-        return v
-    raise ValueError("Content must be a string")
+class CacheControl(BaseModel):
+    type: Literal["ephemeral"]
+    ttl: Literal["5m", "1h"] | None = None
+
+    @model_serializer(mode="wrap")
+    def _serialize(
+        self, handler: SerializerFunctionWrapHandler, info: SerializationInfo
+    ) -> dict:  # mutable-ok: pydantic serializer contract requires bare dict return
+        result = handler(self)
+        if result.get("ttl") is None:
+            result.pop("ttl", None)
+        return result
 
 
 class TextContent(BaseModel):
     type_: Literal["text"] = Field(default="text", alias="type")
     text: str
+    cache_control: CacheControl | None = None
+
+    @model_serializer(mode="wrap")
+    def _serialize(
+        self, handler: SerializerFunctionWrapHandler, info: SerializationInfo
+    ) -> dict:  # mutable-ok: pydantic serializer contract requires bare dict return
+        result = handler(self)
+        if result.get("cache_control") is None:
+            result.pop("cache_control", None)
+        return result
 
 
 class ImageURLContent(BaseModel):
@@ -37,6 +50,16 @@ class ImageURLContent(BaseModel):
 class ImageContent(BaseModel):
     type_: Literal["image_url"] = Field(default="image_url", alias="type")
     image_url: ImageURLContent
+    cache_control: CacheControl | None = None
+
+    @model_serializer(mode="wrap")
+    def _serialize(
+        self, handler: SerializerFunctionWrapHandler, info: SerializationInfo
+    ) -> dict:  # mutable-ok: pydantic serializer contract requires bare dict return
+        result = handler(self)
+        if result.get("cache_control") is None:
+            result.pop("cache_control", None)
+        return result
 
 
 class FunctionObj(BaseModel):
@@ -50,9 +73,9 @@ class FunctionTool(BaseModel):
     parameters: dict = {"type": "object", "properties": {}}
     strict: bool = False
 
-    def model_dump(self, **kwargs) -> dict:
+    def model_dump(self, **kwargs: object) -> dict:
         kwargs["exclude_unset"] = False
-        return super().model_dump(**kwargs)
+        return super().model_dump(**kwargs)  # pyright: ignore[reportArgumentType]  # kwargs forwarded verbatim to pydantic model_dump
 
     @field_validator("parameters", mode="before")
     @classmethod
@@ -70,10 +93,14 @@ class FunctionTool(BaseModel):
 class ChatCompletionTool(BaseModel):
     type_: Literal["function"] = Field(default="function", alias="type")
     function: FunctionTool
+    cache_control: CacheControl | None = None
 
-    def model_dump(self, **kwargs) -> dict:
+    def model_dump(self, **kwargs: object) -> dict:
         kwargs["exclude_unset"] = False
-        return super().model_dump(**kwargs)
+        result = super().model_dump(**kwargs)  # pyright: ignore[reportArgumentType]  # kwargs forwarded verbatim to pydantic model_dump
+        if result.get("cache_control") is None:
+            result.pop("cache_control", None)
+        return result
 
 
 class MessageToolCall(BaseModel):
@@ -88,9 +115,7 @@ class SAPMessage(BaseModel):
     """
 
     role: Literal["system", "developer"] = "system"
-    content: str
-
-    _content_validator = field_validator("content", mode="before")(validate_different_content)
+    content: str | TextContent | list[TextContent]
 
 
 class SAPUserMessage(BaseModel):
@@ -100,19 +125,15 @@ class SAPUserMessage(BaseModel):
 
 class SAPAssistantMessage(BaseModel):
     role: Literal["assistant"] = "assistant"
-    content: str = ""
+    content: str | TextContent | list[TextContent] = ""
     refusal: str = ""
     tool_calls: list[MessageToolCall] = []
 
-    _content_validator = field_validator("content", mode="before")(validate_different_content)
-
 
 class SAPToolChatMessage(BaseModel):
     role: Literal["tool"] = "tool"
     tool_call_id: str
-    content: str
-
-    _content_validator = field_validator("content", mode="before")(validate_different_content)
+    content: str | TextContent | list[TextContent]
 
 
 ChatMessage = SAPMessage | SAPUserMessage | SAPAssistantMessage | SAPToolChatMessage

litellm/llms/sap/chat/transformation.py

@@ -30,6 +30,7 @@ from .handler import (
 )
 from .models import (
     ChatCompletionTool,
+    ChatMessage,
     OrchestrationRequest,
     ResponseFormat,
     ResponseFormatJSONSchema,
@@ -52,50 +53,61 @@ _SAP_MODEL_PARAMS_EXCLUDED_KEYS: Final[frozenset[str]] = frozenset(
 )
 
 
-def validate_dict(data: dict, model) -> dict:
+def validate_dict(
+    data: dict, model: type
+) -> dict:  # mutable-ok: pydantic validation boundary; both input and output are untyped wire dicts
     return model(**data).model_dump(by_alias=True, exclude_unset=True)
 
 
+def _fold_message_cache_control(
+    message: dict[str, object],
+) -> dict[str, object]:
+    """Move a message-level cache_control marker onto the content block.
+
+    litellm's cache_control_injection_points hook attaches cache_control to the
+    message dict itself when content is a plain string.  The SAP message models
+    have no such top-level field, so it would be silently dropped.  When content
+    is a string, promote it to a one-element list so the marker survives.
+    When content is already a non-empty list whose last element is a
+        dict, propagate the marker onto that element — it marks the cache
+    breakpoint for the whole block.  In all other cases (empty list, None,
+    unrecognized type) the marker is silently dropped.
+    """
+    cache_control = message.get("cache_control")
+    if cache_control is None:
+        return message
+    base = {k: v for k, v in message.items() if k != "cache_control"}
+    content = message.get("content")
+    if isinstance(content, str):
+        base["content"] = [{"type": "text", "text": content, "cache_control": cache_control}]
+        return base
+    if isinstance(content, list) and content and isinstance(content[-1], dict):
+        base["content"] = [
+            *content[:-1],
+            {**content[-1], "cache_control": cache_control},
+        ]
+        return base
+    return base
+
+
+def _message_role_mapping(role: str) -> type[ChatMessage]:  # returns the SAP message model class, not an instance
+    return {  # mutable-ok: ephemeral dispatch dict; not stored
+        "user": SAPUserMessage,
+        "assistant": SAPAssistantMessage,
+        "tool": SAPToolChatMessage,
+    }.get(role, SAPMessage)
+
+
 def _messages_to_sap_template(messages: list[AllMessageValues]) -> list:
     template: Final = []
     for message in messages:
-        if message["role"] == "user":
-            template.append(validate_dict(message, SAPUserMessage))
-        elif message["role"] == "assistant":
-            template.append(validate_dict(message, SAPAssistantMessage))
-        elif message["role"] == "tool":
-            template.append(validate_dict(message, SAPToolChatMessage))
-        else:
-            template.append(validate_dict(message, SAPMessage))
+        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)
+        template.append(validated_message)
     return template
 
 
-def _tools_response_format_and_stream(optional_params: dict, model_params: dict) -> tuple[dict, dict, dict]:
-    tools_ = optional_params.pop("tools", [])
-    tools_ = [validate_dict(tool, ChatCompletionTool) for tool in tools_]
-    tools: Final[dict] = {"tools": tools_} if tools_ else {}
-
-    response_format = model_params.pop("response_format", {})
-    resp_type: Final = response_format.get("type", None)
-    if resp_type:
-        if resp_type == "json_schema":
-            response_format = validate_dict(response_format, ResponseFormatJSONSchema)
-        else:
-            response_format = validate_dict(response_format, ResponseFormat)
-        response_format = {"response_format": response_format}
-
-    model_params.pop("stream", False)
-    stream_config: Final[dict] = {}
-    if "stream_options" in optional_params:
-        stream_options: Final = optional_params.pop("stream_options", {})
-        if "chunk_size" in stream_options:
-            stream_config["chunk_size"] = stream_options.get("chunk_size")
-        if "delimiters" in stream_options:
-            stream_config["delimiters"] = stream_options.get("delimiters")
-
-    return tools, response_format, stream_config
-
-
 class GenAIHubOrchestrationConfig(OpenAIGPTConfig):
     frequency_penalty: int | None = None
     function_call: str | dict | None = None
@@ -431,6 +443,6 @@ class GenAIHubOrchestrationConfig(OpenAIGPTConfig):
         json_mode: bool | None = False,
     ):
         if sync_stream:
-            return SAPStreamIterator(response=streaming_response)
+            return SAPStreamIterator(response=streaming_response)  # pyright: ignore[reportArgumentType]  # streaming_response type matches at runtime
         else:
-            return AsyncSAPStreamIterator(response=streaming_response)
+            return AsyncSAPStreamIterator(response=streaming_response)  # pyright: ignore[reportArgumentType]  # streaming_response type matches at runtime

tests/unit/llms/sap/chat/test_sap_models.py

@@ -0,0 +1,221 @@
+import pytest
+from pydantic import ValidationError
+
+from litellm.llms.sap.chat.models import (
+    SAPAssistantMessage,
+    SAPMessage,
+    SAPToolChatMessage,
+    SAPUserMessage,
+    TextContent,
+)
+
+
+class TestSAPMessage:
+    def test_role_system(self):
+        msg = SAPMessage.model_validate({"role": "system", "content": "Hi"})
+        assert msg.role == "system"
+
+    def test_role_developer(self):
+        msg = SAPMessage.model_validate({"role": "developer", "content": "Hi"})
+        assert msg.role == "developer"
+
+    def test_role_defaults_to_system(self):
+        msg = SAPMessage.model_validate({"content": "Hi"})
+        assert msg.role == "system"
+
+    def test_invalid_role_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPMessage.model_validate({"role": "user", "content": "Hi"})
+
+    def test_missing_content_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPMessage.model_validate({"role": "system"})
+
+    def test_string_content_accepted(self):
+        msg = SAPMessage.model_validate({"role": "system", "content": "Hello"})
+        assert msg.content == "Hello"
+
+    def test_text_content_block_accepted(self):
+        msg = SAPMessage.model_validate({"role": "system", "content": {"type": "text", "text": "Hello"}})
+        assert isinstance(msg.content, TextContent)
+        assert msg.content.text == "Hello"
+
+    def test_list_of_text_content_blocks_accepted(self):
+        msg = SAPMessage.model_validate({
+            "role": "system",
+            "content": [{"type": "text", "text": "A"}, {"type": "text", "text": "B"}],
+        })
+        assert isinstance(msg.content, list)
+        assert len(msg.content) == 2
+        assert isinstance(msg.content[0], TextContent)
+
+    def test_invalid_content_type_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPMessage.model_validate({"role": "system", "content": 123})
+
+    def test_cache_control_on_content_block(self):
+        msg = SAPMessage.model_validate({
+            "role": "system",
+            "content": {"type": "text", "text": "Hi", "cache_control": {"type": "ephemeral"}},
+        })
+        assert isinstance(msg.content, TextContent)
+        assert msg.content.cache_control is not None
+        assert msg.content.cache_control.type == "ephemeral"
+
+
+class TestSAPUserMessage:
+    def test_role_is_always_user(self):
+        msg = SAPUserMessage.model_validate({"content": "Hi"})
+        assert msg.role == "user"
+
+    def test_invalid_role_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPUserMessage.model_validate({"role": "system", "content": "Hi"})
+
+    def test_missing_content_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPUserMessage.model_validate({})
+
+    def test_string_content_accepted(self):
+        msg = SAPUserMessage.model_validate({"content": "Hello"})
+        assert msg.content == "Hello"
+
+    def test_text_content_block_accepted(self):
+        msg = SAPUserMessage.model_validate({"content": {"type": "text", "text": "Hello"}})
+        assert isinstance(msg.content, TextContent)
+
+    def test_image_content_accepted(self):
+        from litellm.llms.sap.chat.models import ImageContent
+
+        msg = SAPUserMessage.model_validate({
+            "content": {"type": "image_url", "image_url": {"url": "https://example.com/img.png"}}
+        })
+        assert isinstance(msg.content, ImageContent)
+
+    def test_mixed_list_of_text_and_image_accepted(self):
+        msg = SAPUserMessage.model_validate({
+            "content": [
+                {"type": "text", "text": "Look at this:"},
+                {"type": "image_url", "image_url": {"url": "https://example.com/img.png"}},
+            ]
+        })
+        assert isinstance(msg.content, list)
+        assert len(msg.content) == 2
+
+    def test_invalid_content_type_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPUserMessage.model_validate({"content": 123})
+
+    def test_cache_control_on_content_block(self):
+        msg = SAPUserMessage.model_validate({
+            "content": {"type": "text", "text": "Hi", "cache_control": {"type": "ephemeral"}},
+        })
+        assert isinstance(msg.content, TextContent)
+        assert msg.content.cache_control is not None
+        assert msg.content.cache_control.type == "ephemeral"
+
+
+class TestSAPAssistantMessage:
+    def test_role_is_always_assistant(self):
+        msg = SAPAssistantMessage.model_validate({"content": "Hi"})
+        assert msg.role == "assistant"
+
+    def test_invalid_role_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPAssistantMessage.model_validate({"role": "user", "content": "Hi"})
+
+    def test_refusal_defaults_to_empty_string(self):
+        msg = SAPAssistantMessage.model_validate({})
+        assert msg.refusal == ""
+
+    def test_refusal_accepted(self):
+        msg = SAPAssistantMessage.model_validate({"refusal": "I cannot help with that."})
+        assert msg.refusal == "I cannot help with that."
+
+    def test_tool_calls_default_to_empty_list(self):
+        msg = SAPAssistantMessage.model_validate({})
+        assert msg.tool_calls == []
+
+    def test_string_content_accepted(self):
+        msg = SAPAssistantMessage.model_validate({"content": "Hello"})
+        assert msg.content == "Hello"
+
+    def test_default_empty_string(self):
+        msg = SAPAssistantMessage.model_validate({})
+        assert msg.content == ""
+
+    def test_text_content_block_accepted(self):
+        msg = SAPAssistantMessage.model_validate({"content": {"type": "text", "text": "Hello"}})
+        assert isinstance(msg.content, TextContent)
+
+    def test_list_of_text_blocks_accepted(self):
+        msg = SAPAssistantMessage.model_validate({
+            "content": [{"type": "text", "text": "A"}, {"type": "text", "text": "B"}]
+        })
+        assert isinstance(msg.content, list)
+        assert len(msg.content) == 2
+
+    def test_invalid_content_type_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPAssistantMessage.model_validate({"content": {"type": "image_url", "image_url": {"url": "x"}}})
+
+    def test_cache_control_on_content_block(self):
+        msg = SAPAssistantMessage.model_validate({
+            "content": {"type": "text", "text": "Hi", "cache_control": {"type": "ephemeral"}},
+        })
+        assert isinstance(msg.content, TextContent)
+        assert msg.content.cache_control is not None
+        assert msg.content.cache_control.type == "ephemeral"
+
+
+class TestSAPToolChatMessage:
+    def test_role_is_always_tool(self):
+        msg = SAPToolChatMessage.model_validate({"tool_call_id": "call_1", "content": "ok"})
+        assert msg.role == "tool"
+
+    def test_invalid_role_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPToolChatMessage.model_validate({"role": "user", "tool_call_id": "call_1", "content": "ok"})
+
+    def test_tool_call_id_accepted(self):
+        msg = SAPToolChatMessage.model_validate({"tool_call_id": "call_abc123", "content": "result"})
+        assert msg.tool_call_id == "call_abc123"
+
+    def test_missing_tool_call_id_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPToolChatMessage.model_validate({"content": "result"})
+
+    def test_string_content_accepted(self):
+        msg = SAPToolChatMessage.model_validate({"tool_call_id": "call_1", "content": "result"})
+        assert msg.content == "result"
+
+    def test_text_content_block_accepted(self):
+        msg = SAPToolChatMessage.model_validate({
+            "tool_call_id": "call_1", "content": {"type": "text", "text": "result"}
+        })
+        assert isinstance(msg.content, TextContent)
+
+    def test_list_of_text_blocks_accepted(self):
+        msg = SAPToolChatMessage.model_validate({
+            "tool_call_id": "call_1",
+            "content": [{"type": "text", "text": "A"}, {"type": "text", "text": "B"}],
+        })
+        assert isinstance(msg.content, list)
+        assert len(msg.content) == 2
+
+    def test_missing_content_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPToolChatMessage.model_validate({"tool_call_id": "call_1"})
+
+    def test_invalid_content_type_rejected(self):
+        with pytest.raises(ValidationError):
+            SAPToolChatMessage.model_validate({"tool_call_id": "call_1", "content": 99})
+
+    def test_cache_control_on_content_block(self):
+        msg = SAPToolChatMessage.model_validate({
+            "tool_call_id": "call_1",
+            "content": {"type": "text", "text": "result", "cache_control": {"type": "ephemeral"}},
+        })
+        assert isinstance(msg.content, TextContent)
+        assert msg.content.cache_control is not None
+        assert msg.content.cache_control.type == "ephemeral"

tests/unit/llms/sap/chat/test_sap_transformation.py

@@ -611,6 +611,7 @@ class TestSAPTransformationIntegration:
             assert translation["input"]["config"]["source_language"] == "en-US"
             assert translation["input"]["config"]["target_language"] == "de-DE"
             assert translation["output"]["config"]["target_language"] == "fr-FR"
+
             assert (
                 config["config"]["modules"][1]["prompt_templating"]["model"]["name"]
                 == "gpt-5"
@@ -639,3 +640,286 @@ class TestSAPTransformationIntegration:
                 config["config"]["modules"][1]["translation"]["input"]["type"]
                 == "sap_document_translation"
             )
+
+
+class TestCacheControl:
+    """Unit tests for cache_control preservation on message content parts."""
+
+    def _transform(self, model: str, messages: list) -> dict:
+        from litellm.llms.sap.chat.transformation import GenAIHubOrchestrationConfig
+
+        cfg = GenAIHubOrchestrationConfig()
+        return cfg.transform_request(
+            model=model,
+            messages=messages,
+            optional_params={},
+            litellm_params={},
+            headers={},
+        )
+
+    def _template(self, body: dict) -> list:
+        return body["config"]["modules"]["prompt_templating"]["prompt"]["template"]
+
+    def test_cache_control_preserved_on_text_content(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {
+                        "type": "text",
+                        "text": "Hello",
+                        "cache_control": {"type": "ephemeral"},
+                    }
+                ],
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        content = template[0]["content"]
+        assert isinstance(content, list)
+        assert content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_plain_text_content_unaffected(self):
+        messages = [{"role": "user", "content": "Hello"}]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        assert template[0]["content"] == "Hello"
+
+    def test_cache_control_preserved_on_multiple_parts(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Part A", "cache_control": {"type": "ephemeral"}},
+                    {"type": "text", "text": "Part B"},
+                ],
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        content = self._template(body)[0]["content"]
+        assert content[0].get("cache_control") == {"type": "ephemeral"}
+        assert "cache_control" not in content[1]
+
+    def test_cache_control_preserved_on_system_message(self):
+        messages = [
+            {
+                "role": "system",
+                "content": [
+                    {
+                        "type": "text",
+                        "text": "You are a helpful assistant.",
+                        "cache_control": {"type": "ephemeral"},
+                    }
+                ],
+            },
+            {"role": "user", "content": "Hello"},
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        system_content = template[0]["content"]
+        assert isinstance(system_content, list)
+        assert system_content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_system_message_without_cache_control_stays_string(self):
+        messages = [
+            {"role": "system", "content": "You are a helpful assistant."},
+            {"role": "user", "content": "Hello"},
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        assert isinstance(template[0]["content"], str)
+
+    def test_cache_control_preserved_on_tool_definition(self):
+        tool = {
+            "type": "function",
+            "function": {
+                "name": "get_weather",
+                "description": "Get weather",
+                "parameters": {"type": "object", "properties": {}},
+            },
+            "cache_control": {"type": "ephemeral"},
+        }
+        messages = [{"role": "user", "content": "Hi"}]
+        from litellm.llms.sap.chat.transformation import GenAIHubOrchestrationConfig
+
+        cfg = GenAIHubOrchestrationConfig()
+        body = cfg.transform_request(
+            model="anthropic--claude-3-5-sonnet",
+            messages=messages,
+            optional_params={"tools": [tool]},
+            litellm_params={},
+            headers={},
+        )
+        tools = body["config"]["modules"]["prompt_templating"]["prompt"]["tools"]
+        assert tools[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_tool_without_cache_control_omits_field(self):
+        tool = {
+            "type": "function",
+            "function": {
+                "name": "get_weather",
+                "description": "Get weather",
+                "parameters": {"type": "object", "properties": {}},
+            },
+        }
+        messages = [{"role": "user", "content": "Hi"}]
+        from litellm.llms.sap.chat.transformation import GenAIHubOrchestrationConfig
+
+        cfg = GenAIHubOrchestrationConfig()
+        body = cfg.transform_request(
+            model="anthropic--claude-3-5-sonnet",
+            messages=messages,
+            optional_params={"tools": [tool]},
+            litellm_params={},
+            headers={},
+        )
+        tools = body["config"]["modules"]["prompt_templating"]["prompt"]["tools"]
+        assert "cache_control" not in tools[0]
+
+    def test_message_level_cache_control_folded_onto_string_content(self):
+        messages = [
+            {
+                "role": "system",
+                "content": "You are a helpful assistant.",
+                "cache_control": {"type": "ephemeral"},
+            },
+            {"role": "user", "content": "Hello"},
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        system_content = template[0]["content"]
+        assert isinstance(system_content, list), "string content should have been promoted to a list"
+        assert system_content[0]["text"] == "You are a helpful assistant."
+        assert system_content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_null_cache_control_on_content_block_is_omitted(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Hello", "cache_control": None},
+                ],
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        content = self._template(body)[0]["content"]
+        assert isinstance(content, list)
+        assert "cache_control" not in content[0]
+
+    def test_message_level_cache_control_folded_on_user_message(self):
+        messages = [
+            {
+                "role": "user",
+                "content": "What is the weather today?",
+                "cache_control": {"type": "ephemeral"},
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        content = self._template(body)[0]["content"]
+        assert isinstance(content, list), "string content should have been promoted to a list"
+        assert content[0]["text"] == "What is the weather today?"
+        assert content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_cache_control_ttl_omitted_when_absent(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Hello", "cache_control": {"type": "ephemeral"}},
+                ],
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        cc = self._template(body)[0]["content"][0]["cache_control"]
+        assert cc == {"type": "ephemeral"}
+        assert "ttl" not in cc
+
+    def test_cache_control_ttl_preserved_when_set(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Hello", "cache_control": {"type": "ephemeral", "ttl": "5m"}},
+                ],
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        cc = self._template(body)[0]["content"][0]["cache_control"]
+        assert cc == {"type": "ephemeral", "ttl": "5m"}
+
+    def test_message_level_cache_control_folded_on_assistant_message(self):
+        messages = [
+            {"role": "user", "content": "Hi"},
+            {
+                "role": "assistant",
+                "content": "Hello! How can I help?",
+                "cache_control": {"type": "ephemeral"},
+            },
+            {"role": "user", "content": "Continue"},
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        assistant_content = template[1]["content"]
+        assert isinstance(assistant_content, list), "string content should have been promoted to a list"
+        assert assistant_content[0]["text"] == "Hello! How can I help?"
+        assert assistant_content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_message_level_cache_control_folded_on_tool_message(self):
+        messages = [
+            {"role": "user", "content": "What is the weather?"},
+            {
+                "role": "assistant",
+                "content": "",
+                "tool_calls": [
+                    {
+                        "id": "call_1",
+                        "type": "function",
+                        "function": {"name": "get_weather", "arguments": "{}"},
+                    }
+                ],
+            },
+            {
+                "role": "tool",
+                "tool_call_id": "call_1",
+                "content": "Sunny, 22C",
+                "cache_control": {"type": "ephemeral"},
+            },
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        template = self._template(body)
+        tool_content = template[2]["content"]
+        assert isinstance(tool_content, list), "string content should have been promoted to a list"
+        assert tool_content[0]["text"] == "Sunny, 22C"
+        assert tool_content[0].get("cache_control") == {"type": "ephemeral"}
+
+    def test_message_level_cache_control_folded_onto_last_list_element(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Part A"},
+                    {"type": "text", "text": "Part B"},
+                ],
+                "cache_control": {"type": "ephemeral"},
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        content = self._template(body)[0]["content"]
+        assert "cache_control" not in content[0]
+        assert content[1].get("cache_control") == {"type": "ephemeral"}
+
+    def test_message_level_cache_control_folded_onto_trailing_image_block(self):
+        messages = [
+            {
+                "role": "user",
+                "content": [
+                    {"type": "text", "text": "Describe this image."},
+                    {"type": "image_url", "image_url": {"url": "data:image/png;base64,abc="}},
+                ],
+                "cache_control": {"type": "ephemeral"},
+            }
+        ]
+        body = self._transform("anthropic--claude-3-5-sonnet", messages)
+        content = self._template(body)[0]["content"]
+        assert "cache_control" not in content[0]
+        assert content[1].get("cache_control") == {"type": "ephemeral"}