start on duplicate content

libs/core/langchain_core/messages/ai.py

@@ -202,11 +202,16 @@ class AIMessage(BaseMessage):
         **kwargs: Any,
     ) -> None:
         """Specify content as a positional arg or content_blocks for typing support."""
-        if content_blocks is not None:
+        if content is not None and content_blocks is None:
+            super().__init__(content=content, **kwargs)
+        elif content is None and content_blocks is not None:
             super().__init__(
                 content=cast("Union[str, list[Union[str, dict]]]", content_blocks),
+                content_blocks=content_blocks,
                 **kwargs,
             )
+        elif content is not None and content_blocks is not None:
+            super().__init__(content=content, content_blocks=content_blocks, **kwargs)
         else:
             super().__init__(content=content, **kwargs)
 
@@ -218,32 +223,45 @@ class AIMessage(BaseMessage):
             "invalid_tool_calls": self.invalid_tool_calls,
         }
 
-    @property
-    def content_blocks(self) -> list[types.ContentBlock]:
-        """Return content blocks of the message."""
-        blocks = super().content_blocks
+    @model_validator(mode="after")
+    def _init_content_blocks(self) -> Self:
+        """Assign the content as a list of standard ContentBlocks.
 
-        # Add from tool_calls if missing from content
-        content_tool_call_ids = {
-            block.get("id")
-            for block in self.content
-            if isinstance(block, dict) and block.get("type") == "tool_call"
-        }
-        for tool_call in self.tool_calls:
-            if (id_ := tool_call.get("id")) and id_ not in content_tool_call_ids:
-                tool_call_block: types.ToolCall = {
-                    "type": "tool_call",
-                    "id": id_,
-                    "name": tool_call["name"],
-                    "args": tool_call["args"],
-                }
-                if "index" in tool_call:
-                    tool_call_block["index"] = tool_call["index"]
-                if "extras" in tool_call:
-                    tool_call_block["extras"] = tool_call["extras"]
-                blocks.append(tool_call_block)
+        To use this property, the corresponding chat model must support
+        ``message_version="v1"`` or higher:
 
-        return blocks
+        .. code-block:: python
+
+            from langchain.chat_models import init_chat_model
+            llm = init_chat_model("...", message_version="v1")
+
+        otherwise, does best-effort parsing to standard types.
+        """
+        if not self.content_blocks:
+            self.content_blocks = self._init_text_content(self.content)
+
+        if self.tool_calls or self.invalid_tool_calls:
+            # Add from tool_calls if missing from content
+            content_tool_call_ids = {
+                block.get("id")
+                for block in self.content_blocks
+                if isinstance(block, dict) and block.get("type") == "tool_call"
+            }
+            for tool_call in self.tool_calls:
+                if (id_ := tool_call.get("id")) and id_ not in content_tool_call_ids:
+                    tool_call_block: types.ToolCall = {
+                        "type": "tool_call",
+                        "id": id_,
+                        "name": tool_call["name"],
+                        "args": tool_call["args"],
+                    }
+                    if "index" in tool_call:
+                        tool_call_block["index"] = tool_call["index"]
+                    if "extras" in tool_call:
+                        tool_call_block["extras"] = tool_call["extras"]
+                    self.content_blocks.append(tool_call_block)
+
+        return self
 
     # TODO: remove this logic if possible, reducing breaking nature of changes
     @model_validator(mode="before")

libs/core/langchain_core/messages/base.py

@@ -4,7 +4,8 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING, Any, Optional, Union, cast, overload
 
-from pydantic import ConfigDict, Field
+from pydantic import ConfigDict, Field, model_validator
+from typing_extensions import Self
 
 from langchain_core.load.serializable import Serializable
 from langchain_core.messages import content_blocks as types
@@ -27,6 +28,9 @@ class BaseMessage(Serializable):
     content: Union[str, list[Union[str, dict]]]
     """The string contents of the message."""
 
+    content_blocks: list[types.ContentBlock] = Field(default_factory=list)
+    """The content of the message as a list of standard ContentBlocks."""
+
     additional_kwargs: dict = Field(default_factory=dict)
     """Reserved for additional payload data associated with the message.
 
@@ -84,8 +88,14 @@ class BaseMessage(Serializable):
         **kwargs: Any,
     ) -> None:
         """Specify content as a positional arg or content_blocks for typing support."""
-        if content_blocks is not None:
-            super().__init__(content=content_blocks, **kwargs)
+        if content is not None and content_blocks is None:
+            super().__init__(content=content, **kwargs)
+        elif content is None and content_blocks is not None:
+            super().__init__(
+                content=content_blocks, content_blocks=content_blocks, **kwargs
+            )
+        elif content is not None and content_blocks is not None:
+            super().__init__(content=content, content_blocks=content_blocks, **kwargs)
         else:
             super().__init__(content=content, **kwargs)
 
@@ -106,9 +116,30 @@ class BaseMessage(Serializable):
         """
         return ["langchain", "schema", "messages"]
 
-    @property
-    def content_blocks(self) -> list[types.ContentBlock]:
-        """Return the content as a list of standard ContentBlocks.
+    @staticmethod
+    def _init_text_content(
+        content: Union[str, list[Union[str, dict]]],
+    ) -> list[types.ContentBlock]:
+        """Parse string content into a list of ContentBlocks."""
+        blocks: list[types.ContentBlock] = []
+        content = [content] if isinstance(content, str) and content else content
+        for item in content:
+            if isinstance(item, str):
+                blocks.append({"type": "text", "text": item})
+            elif isinstance(item, dict):
+                item_type = item.get("type")
+                if item_type not in types.KNOWN_BLOCK_TYPES:
+                    blocks.append({"type": "non_standard", "value": item})
+                else:
+                    blocks.append(cast("types.ContentBlock", item))
+            else:
+                pass
+
+        return blocks
+
+    @model_validator(mode="after")
+    def _init_content_blocks(self) -> Self:
+        """Assign the content as a list of standard ContentBlocks.
 
         To use this property, the corresponding chat model must support
         ``message_version="v1"`` or higher:
@@ -120,29 +151,11 @@ class BaseMessage(Serializable):
 
         otherwise, does best-effort parsing to standard types.
         """
-        blocks: list[types.ContentBlock] = []
-        content = (
-            [self.content]
-            if isinstance(self.content, str) and self.content
-            else self.content
-        )
-        for item in content:
-            if isinstance(item, str):
-                blocks.append({"type": "text", "text": item})
-            elif isinstance(item, dict):
-                item_type = item.get("type")
-                if item_type not in types.KNOWN_BLOCK_TYPES:
-                    msg = (
-                        f"Non-standard content block type '{item_type}'. Ensure "
-                        "the model supports `output_version='v1'` or higher and "
-                        "that this attribute is set on initialization."
-                    )
-                    raise ValueError(msg)
-                blocks.append(cast("types.ContentBlock", item))
-            else:
-                pass
+        if not self.content_blocks:
+            blocks = self._init_text_content(self.content)
+            self.content_blocks = blocks
 
-        return blocks
+        return self
 
     def text(self) -> str:
         """Get the text content of the message.

libs/core/langchain_core/messages/human.py

@@ -64,11 +64,16 @@ class HumanMessage(BaseMessage):
         **kwargs: Any,
     ) -> None:
         """Specify content as a positional arg or content_blocks for typing support."""
-        if content_blocks is not None:
+        if content is not None and content_blocks is None:
+            super().__init__(content=content, **kwargs)
+        elif content is None and content_blocks is not None:
             super().__init__(
                 content=cast("Union[str, list[Union[str, dict]]]", content_blocks),
+                content_blocks=content_blocks,
                 **kwargs,
             )
+        elif content is not None and content_blocks is not None:
+            super().__init__(content=content, content_blocks=content_blocks, **kwargs)
         else:
             super().__init__(content=content, **kwargs)
 

libs/core/langchain_core/messages/system.py

@@ -57,11 +57,16 @@ class SystemMessage(BaseMessage):
         **kwargs: Any,
     ) -> None:
         """Specify content as a positional arg or content_blocks for typing support."""
-        if content_blocks is not None:
+        if content is not None and content_blocks is None:
+            super().__init__(content=content, **kwargs)
+        elif content is None and content_blocks is not None:
             super().__init__(
                 content=cast("Union[str, list[Union[str, dict]]]", content_blocks),
+                content_blocks=content_blocks,
                 **kwargs,
             )
+        elif content is not None and content_blocks is not None:
+            super().__init__(content=content, content_blocks=content_blocks, **kwargs)
         else:
             super().__init__(content=content, **kwargs)
 

libs/core/langchain_core/messages/tool.py

@@ -158,11 +158,16 @@ class ToolMessage(BaseMessage, ToolOutputMixin):
         **kwargs: Any,
     ) -> None:
         """Specify content as a positional arg or content_blocks for typing support."""
-        if content_blocks is not None:
+        if content is not None and content_blocks is None:
+            super().__init__(content=content, **kwargs)
+        elif content is None and content_blocks is not None:
             super().__init__(
                 content=cast("Union[str, list[Union[str, dict]]]", content_blocks),
+                content_blocks=content_blocks,
                 **kwargs,
             )
+        elif content is not None and content_blocks is not None:
+            super().__init__(content=content, content_blocks=content_blocks, **kwargs)
         else:
             super().__init__(content=content, **kwargs)
 

libs/core/tests/unit_tests/language_models/chat_models/test_base.py

@@ -443,19 +443,11 @@ def test_trace_images_in_openai_format() -> None:
     ]
     tracer = FakeChatModelStartTracer()
     response = llm.invoke(messages, config={"callbacks": [tracer]})
-    assert tracer.messages == [
-        [
-            [
-                HumanMessage(
-                    content=[
-                        {
-                            "type": "image_url",
-                            "image_url": {"url": "https://example.com/image.png"},
-                        }
-                    ]
-                )
-            ]
-        ]
+    assert tracer.messages[0][0][0].content == [
+        {
+            "type": "image_url",
+            "image_url": {"url": "https://example.com/image.png"},
+        }
     ]
     # Test no mutation
     assert response.content == [
@@ -486,23 +478,15 @@ def test_trace_content_blocks_with_no_type_key() -> None:
     ]
     tracer = FakeChatModelStartTracer()
     response = llm.invoke(messages, config={"callbacks": [tracer]})
-    assert tracer.messages == [
-        [
-            [
-                HumanMessage(
-                    [
-                        {
-                            "type": "text",
-                            "text": "Hello",
-                        },
-                        {
-                            "type": "cachePoint",
-                            "cachePoint": {"type": "default"},
-                        },
-                    ]
-                )
-            ]
-        ]
+    assert tracer.messages[0][0][0].content == [
+        {
+            "type": "text",
+            "text": "Hello",
+        },
+        {
+            "type": "cachePoint",
+            "cachePoint": {"type": "default"},
+        },
     ]
     # Test no mutation
     assert response.content == [

libs/core/tests/unit_tests/test_messages.py

@@ -3,6 +3,7 @@ import uuid
 from typing import Optional, Union
 
 import pytest
+from pydantic import ValidationError
 from typing_extensions import get_args
 
 from langchain_core.documents import Document
@@ -1267,10 +1268,14 @@ def test_typed_init() -> None:
 
     # Test we get type errors for malformed blocks (type checker will complain if
     # below type-ignores are unused).
-    _ = AIMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
-    _ = HumanMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
-    _ = SystemMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
-    _ = ToolMessage(
-        content_blocks=[{"type": "text", "bad": "Hello"}],  # type: ignore[list-item]
-        tool_call_id="abc123",
-    )
+    with pytest.raises(ValidationError):
+        _ = AIMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
+    with pytest.raises(ValidationError):
+        _ = HumanMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
+    with pytest.raises(ValidationError):
+        _ = SystemMessage(content_blocks=[{"type": "text", "bad": "Hello"}])  # type: ignore[list-item]
+    with pytest.raises(ValidationError):
+        _ = ToolMessage(
+            content_blocks=[{"type": "text", "bad": "Hello"}],  # type: ignore[list-item]
+            tool_call_id="abc123",
+        )