openai[patch]: add attribute to always use previous_response_id (#31734)

libs/partners/openai/langchain_openai/chat_models/base.py

@@ -607,6 +607,40 @@ class BaseChatOpenAI(BaseChatModel):
     .. versionadded:: 0.3.24
     """
 
+    use_previous_response_id: bool = False
+    """If True, always pass ``previous_response_id`` using the ID of the most recent
+    response. Responses API only.
+
+    Input messages up to the most recent response will be dropped from request
+    payloads.
+
+    For example, the following two are equivalent:
+
+    .. code-block:: python
+
+        llm = ChatOpenAI(
+            model="o4-mini",
+            use_previous_response_id=True,
+        )
+        llm.invoke(
+            [
+                HumanMessage("Hello"),
+                AIMessage("Hi there!", response_metadata={"id": "resp_123"}),
+                HumanMessage("How are you?"),
+            ]
+        )
+
+    .. code-block:: python
+
+        llm = ChatOpenAI(
+            model="o4-mini",
+            use_responses_api=True,
+        )
+        llm.invoke([HumanMessage("How are you?")], previous_response_id="resp_123")
+
+    .. versionadded:: 0.3.26
+    """
+
     use_responses_api: Optional[bool] = None
     """Whether to use the Responses API instead of the Chat API.
 
@@ -1081,6 +1115,8 @@ class BaseChatOpenAI(BaseChatModel):
             return True
         elif self.truncation is not None:
             return True
+        elif self.use_previous_response_id:
+            return True
         else:
             return _use_responses_api(payload)
 
@@ -1097,7 +1133,14 @@ class BaseChatOpenAI(BaseChatModel):
 
         payload = {**self._default_params, **kwargs}
         if self._use_responses_api(payload):
-            payload = _construct_responses_api_payload(messages, payload)
+            if self.use_previous_response_id:
+                last_messages, previous_response_id = _get_last_messages(messages)
+                payload_to_use = last_messages if previous_response_id else messages
+                if previous_response_id:
+                    payload["previous_response_id"] = previous_response_id
+                payload = _construct_responses_api_payload(payload_to_use, payload)
+            else:
+                payload = _construct_responses_api_payload(messages, payload)
         else:
             payload["messages"] = [_convert_message_to_dict(m) for m in messages]
         return payload
@@ -3202,6 +3245,30 @@ def _use_responses_api(payload: dict) -> bool:
     return bool(uses_builtin_tools or responses_only_args.intersection(payload))
 
 
+def _get_last_messages(
+    messages: Sequence[BaseMessage],
+) -> tuple[Sequence[BaseMessage], Optional[str]]:
+    """
+    Return
+        1. Every message after the most-recent AIMessage that has a non-empty
+           ``response_metadata["id"]`` (may be an empty list),
+        2. That id.
+
+    If the most-recent AIMessage does not have an id (or there is no
+    AIMessage at all) the entire conversation is returned together with ``None``.
+    """
+    for i in range(len(messages) - 1, -1, -1):
+        msg = messages[i]
+        if isinstance(msg, AIMessage):
+            response_id = msg.response_metadata.get("id")
+            if response_id:
+                return messages[i + 1 :], response_id
+            else:
+                return messages, None
+
+    return messages, None
+
+
 def _construct_responses_api_payload(
     messages: Sequence[BaseMessage], payload: dict
 ) -> dict: