Changes following review

libs/community/langchain_community/chat_message_histories/in_memory.py

@@ -13,7 +13,7 @@ class ChatMessageHistory(BaseChatMessageHistory, BaseModel):
 
     messages: List[BaseMessage] = Field(default_factory=list)
 
-    async def amessages(self) -> List[BaseMessage]:
+    async def aget_messages(self) -> List[BaseMessage]:
         return self.messages
 
     def add_message(self, message: BaseMessage) -> None:

libs/core/langchain_core/chat_history.py

@@ -15,11 +15,26 @@
 class BaseChatMessageHistory(ABC):
     """Abstract base class for storing chat message history.
 
-    Implementations should over-ride the add_messages method to handle bulk addition
-    of messages.
+    Implementations guidelines:
 
-    The default implementation of add_message will correctly call add_messages, so
-    it is not necessary to implement both methods.
+    Implementations are expected to over-ride all or some of the following methods:
+
+    * add_messages: sync variant for bulk addition of messages
+    * aadd_messages: async variant for bulk addition of messages
+    * messages: sync variant for getting messages
+    * aget_messages: async variant for getting messages
+    * clear: sync variant for clearing messages
+    * aclear: async variant for clearing messages
+
+    add_messages contains a default implementation that calls add_message
+    for each message in the sequence. This is provided for backwards compatibility
+    with existing implementations which only had add_message.
+
+    Async variants all have default implementations that call the sync variants.
+    Implementers can choose to over-ride the async implementations to provide
+    truly async implementations.
+
+    Usage guidelines:
 
     When used for updating history, users should favor usage of `add_messages`
     over `add_message` or other variants like `add_user_message` and `add_ai_message`
@@ -55,10 +70,21 @@ def clear(self):
     """
 
     messages: List[BaseMessage]
-    """A list of Messages stored in-memory."""
+    """A property or attribute that returns a list of messages.
+
+    In general, getting the messages may involve IO to the underlying
+    persistence layer, so this operation is expected to incur some
+    latency.
+    """
+
+    async def aget_messages(self) -> List[BaseMessage]:
+        """Async version of getting messages.
+
+        Can over-ride this method to provide an efficient async implementation.
 
-    async def amessages(self) -> List[BaseMessage]:
-        """Return messages stored in memory."""
+        In general, fetching messages may involve IO to the underlying
+        persistence layer.
+        """
         return await run_in_executor(None, lambda: self.messages)
 
     def add_user_message(self, message: Union[HumanMessage, str]) -> None:

libs/core/tests/unit_tests/chat_history/test_chat_history.py

@@ -66,3 +66,36 @@ def clear(self) -> None:
     assert len(store) == 4
     assert store[2] == HumanMessage(content="Hello")
     assert store[3] == HumanMessage(content="World")
+
+
+async def test_async_interface() -> None:
+    """Test async interface for BaseChatMessageHistory."""
+
+    class BulkAddHistory(BaseChatMessageHistory):
+        def __init__(self) -> None:
+            self.messages = []
+
+        def add_messages(self, message: Sequence[BaseMessage]) -> None:
+            """Add a message to the store."""
+            self.messages.extend(message)
+
+        def clear(self) -> None:
+            """Clear the store."""
+            self.messages.clear()
+
+    chat_history = BulkAddHistory()
+    await chat_history.aadd_messages(
+        [HumanMessage(content="Hello"), HumanMessage(content="World")]
+    )
+    assert await chat_history.aget_messages() == [
+        HumanMessage(content="Hello"),
+        HumanMessage(content="World"),
+    ]
+    await chat_history.aadd_messages([HumanMessage(content="!")])
+    assert await chat_history.aget_messages() == [
+        HumanMessage(content="Hello"),
+        HumanMessage(content="World"),
+        HumanMessage(content="!"),
+    ]
+    await chat_history.aclear()
+    assert await chat_history.aget_messages() == []

libs/langchain/langchain/memory/buffer.py

@@ -41,7 +41,7 @@ def buffer_as_str(self) -> str:
 
     async def abuffer_as_str(self) -> str:
         """Exposes the buffer as a string in case return_messages is True."""
-        messages = await self.chat_memory.amessages()
+        messages = await self.chat_memory.aget_messages()
         return self._buffer_as_str(messages)
 
     @property
@@ -51,7 +51,7 @@ def buffer_as_messages(self) -> List[BaseMessage]:
 
     async def abuffer_as_messages(self) -> List[BaseMessage]:
         """Exposes the buffer as a list of messages in case return_messages is False."""
-        return await self.chat_memory.amessages()
+        return await self.chat_memory.aget_messages()
 
     @property
     def memory_variables(self) -> List[str]: