diff --git a/libs/partners/anthropic/langchain_anthropic/chat_models.py b/libs/partners/anthropic/langchain_anthropic/chat_models.py
index b9d410d8288..42a9117ab7d 100644
--- a/libs/partners/anthropic/langchain_anthropic/chat_models.py
+++ b/libs/partners/anthropic/langchain_anthropic/chat_models.py
@@ -172,50 +172,45 @@ def _format_messages(messages: List[BaseMessage]) -> Tuple[Optional[str], List[D
             content = []
             for item in message.content:
                 if isinstance(item, str):
-                    content.append(
-                        {
-                            "type": "text",
-                            "text": item,
-                        }
-                    )
+                    content.append({"type": "text", "text": item})
                 elif isinstance(item, dict):
                     if "type" not in item:
                         raise ValueError("Dict content item must have a type key")
                     elif item["type"] == "image_url":
                         # convert format
                         source = _format_image(item["image_url"]["url"])
-                        content.append(
-                            {
-                                "type": "image",
-                                "source": source,
-                            }
-                        )
+                        content.append({"type": "image", "source": source})
                     elif item["type"] == "tool_use":
-                        item.pop("text", None)
-                        content.append(item)
+                        # If a tool_call with the same id as a tool_use content block
+                        # exists, the tool_call is preferred.
+                        if isinstance(message, AIMessage) and item["id"] in [
+                            tc["id"] for tc in message.tool_calls
+                        ]:
+                            overlapping = [
+                                tc
+                                for tc in message.tool_calls
+                                if tc["id"] == item["id"]
+                            ]
+                            content.extend(
+                                _lc_tool_calls_to_anthropic_tool_use_blocks(overlapping)
+                            )
+                        else:
+                            item.pop("text", None)
+                            content.append(item)
                     elif item["type"] == "text":
                         text = item.get("text", "")
                         # Only add non-empty strings for now as empty ones are not
                         # accepted.
                         # https://github.com/anthropics/anthropic-sdk-python/issues/461
                         if text.strip():
-                            content.append(
-                                {
-                                    "type": "text",
-                                    "text": text,
-                                }
-                            )
+                            content.append({"type": "text", "text": text})
                     else:
                         content.append(item)
                 else:
                     raise ValueError(
                         f"Content items must be str or dict, instead was: {type(item)}"
                     )
-        elif (
-            isinstance(message, AIMessage)
-            and not isinstance(message.content, list)
-            and message.tool_calls
-        ):
+        elif isinstance(message, AIMessage) and message.tool_calls:
             content = (
                 []
                 if not message.content
@@ -228,12 +223,7 @@ def _format_messages(messages: List[BaseMessage]) -> Tuple[Optional[str], List[D
         else:
             content = message.content
 
-        formatted_messages.append(
-            {
-                "role": role,
-                "content": content,
-            }
-        )
+        formatted_messages.append({"role": role, "content": content})
     return system, formatted_messages
 
 
diff --git a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
index d9e382b6cf2..3c5c5b2691c 100644
--- a/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/anthropic/tests/unit_tests/test_chat_models.py
@@ -352,10 +352,7 @@ def test__format_messages_with_str_content_and_tool_calls() -> None:
         "thought",
         tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "buzz"}}],
     )
-    tool = ToolMessage(
-        "blurb",
-        tool_call_id="1",
-    )
+    tool = ToolMessage("blurb", tool_call_id="1")
     messages = [system, human, ai, tool]
     expected = (
         "fuzz",
@@ -364,10 +361,7 @@ def test__format_messages_with_str_content_and_tool_calls() -> None:
             {
                 "role": "assistant",
                 "content": [
-                    {
-                        "type": "text",
-                        "text": "thought",
-                    },
+                    {"type": "text", "text": "thought"},
                     {
                         "type": "tool_use",
                         "name": "bar",
@@ -394,12 +388,7 @@ def test__format_messages_with_list_content_and_tool_calls() -> None:
     # If content and tool_calls are specified and content is a list, then content is
     # preferred.
     ai = AIMessage(
-        [
-            {
-                "type": "text",
-                "text": "thought",
-            }
-        ],
+        [{"type": "text", "text": "thought"}],
         tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "buzz"}}],
     )
     tool = ToolMessage(
@@ -413,11 +402,53 @@ def test__format_messages_with_list_content_and_tool_calls() -> None:
             {"role": "user", "content": "foo"},
             {
                 "role": "assistant",
+                "content": [{"type": "text", "text": "thought"}],
+            },
+            {
+                "role": "user",
                 "content": [
+                    {"type": "tool_result", "content": "blurb", "tool_use_id": "1"}
+                ],
+            },
+        ],
+    )
+    actual = _format_messages(messages)
+    assert expected == actual
+
+
+def test__format_messages_with_tool_use_blocks_and_tool_calls() -> None:
+    """Show that tool_calls are preferred to tool_use blocks when both have same id."""
+    system = SystemMessage("fuzz")
+    human = HumanMessage("foo")
+    # NOTE: tool_use block in contents and tool_calls have different arguments.
+    ai = AIMessage(
+        [
+            {"type": "text", "text": "thought"},
+            {
+                "type": "tool_use",
+                "name": "bar",
+                "id": "1",
+                "input": {"baz": "NOT_BUZZ"},
+            },
+        ],
+        tool_calls=[{"name": "bar", "id": "1", "args": {"baz": "BUZZ"}}],
+    )
+    tool = ToolMessage("blurb", tool_call_id="1")
+    messages = [system, human, ai, tool]
+    expected = (
+        "fuzz",
+        [
+            {"role": "user", "content": "foo"},
+            {
+                "role": "assistant",
+                "content": [
+                    {"type": "text", "text": "thought"},
                     {
-                        "type": "text",
-                        "text": "thought",
-                    }
+                        "type": "tool_use",
+                        "name": "bar",
+                        "id": "1",
+                        "input": {"baz": "BUZZ"},  # tool_calls value preferred.
+                    },
                 ],
             },
             {