rfc(anthropic): support cache_control as a kwarg

libs/partners/anthropic/langchain_anthropic/chat_models.py

@@ -1291,6 +1291,26 @@ def _get_request_payload(
     ) -> dict:
         messages = self._convert_input(input_).to_messages()
         system, formatted_messages = _format_messages(messages)
+
+        # If cache_control is provided in kwargs, add it to last message
+        # and content block.
+        if "cache_control" in kwargs and formatted_messages:
+            if isinstance(formatted_messages[-1]["content"], list):
+                formatted_messages[-1]["content"][-1]["cache_control"] = kwargs.pop(
+                    "cache_control"
+                )
+            elif isinstance(formatted_messages[-1]["content"], str):
+                formatted_messages[-1]["content"] = [
+                    {
+                        "type": "text",
+                        "text": formatted_messages[-1]["content"],
+                        "cache_control": kwargs.pop("cache_control"),
+                    }
+                ]
+            else:
+                pass
+        _ = kwargs.pop("cache_control", None)
+
         payload = {
             "model": self.model,
             "max_tokens": self.max_tokens,

libs/partners/anthropic/tests/unit_tests/test_chat_models.py

@@ -1056,3 +1056,50 @@ def mock_create(*args: Any, **kwargs: Any) -> Message:
     # Test headers are correctly propagated to request
     payload = llm._get_request_payload([input_message])
     assert payload["mcp_servers"][0]["authorization_token"] == "PLACEHOLDER"
+
+
+def test_cache_control_kwarg() -> None:
+    llm = ChatAnthropic(model="claude-3-5-haiku-latest")
+
+    messages = [HumanMessage("foo"), AIMessage("bar"), HumanMessage("baz")]
+    payload = llm._get_request_payload(messages)
+    assert payload["messages"] == [
+        {"role": "user", "content": "foo"},
+        {"role": "assistant", "content": "bar"},
+        {"role": "user", "content": "baz"},
+    ]
+
+    payload = llm._get_request_payload(messages, cache_control={"type": "ephemeral"})
+    assert payload["messages"] == [
+        {"role": "user", "content": "foo"},
+        {"role": "assistant", "content": "bar"},
+        {
+            "role": "user",
+            "content": [
+                {"type": "text", "text": "baz", "cache_control": {"type": "ephemeral"}}
+            ],
+        },
+    ]
+
+    messages = [
+        HumanMessage("foo"),
+        AIMessage("bar"),
+        HumanMessage(
+            content=[
+                {"type": "text", "text": "baz"},
+                {"type": "text", "text": "qux"},
+            ]
+        ),
+    ]
+    payload = llm._get_request_payload(messages, cache_control={"type": "ephemeral"})
+    assert payload["messages"] == [
+        {"role": "user", "content": "foo"},
+        {"role": "assistant", "content": "bar"},
+        {
+            "role": "user",
+            "content": [
+                {"type": "text", "text": "baz"},
+                {"type": "text", "text": "qux", "cache_control": {"type": "ephemeral"}},
+            ],
+        },
+    ]