store prev messages

# What does this PR do?


## Test Plan

llama_stack/providers/utils/responses/responses_store.py

@@ -17,6 +17,7 @@ from llama_stack.apis.agents.openai_responses import (
     OpenAIResponseObject,
     OpenAIResponseObjectWithInput,
 )
+from llama_stack.apis.inference import OpenAIMessageParam
 from llama_stack.core.datatypes import AccessRule, ResponsesStoreConfig
 from llama_stack.core.utils.config_dirs import RUNTIME_BASE_DIR
 from llama_stack.log import get_logger
@@ -28,6 +29,19 @@ from ..sqlstore.sqlstore import SqliteSqlStoreConfig, SqlStoreConfig, SqlStoreTy
 logger = get_logger(name=__name__, category="responses_store")
 
 
+class _OpenAIResponseObjectWithInputAndMessages(OpenAIResponseObjectWithInput):
+    """Internal class for storing responses with chat completion messages.
+
+    This extends the public OpenAIResponseObjectWithInput with messages field
+    for internal storage. The messages field is not exposed in the public API.
+
+    The messages field is optional for backward compatibility with responses
+    stored before this feature was added.
+    """
+
+    messages: list[OpenAIMessageParam] | None = None
+
+
 class ResponsesStore:
     def __init__(
         self,
@@ -54,7 +68,9 @@ class ResponsesStore:
         self.enable_write_queue = self.sql_store_config.type != SqlStoreType.sqlite
 
         # Async write queue and worker control
-        self._queue: asyncio.Queue[tuple[OpenAIResponseObject, list[OpenAIResponseInput]]] | None = None
+        self._queue: (
+            asyncio.Queue[tuple[OpenAIResponseObject, list[OpenAIResponseInput], list[OpenAIMessageParam]]] | None
+        ) = None
         self._worker_tasks: list[asyncio.Task[Any]] = []
         self._max_write_queue_size: int = config.max_write_queue_size
         self._num_writers: int = max(1, config.num_writers)
@@ -100,18 +116,21 @@ class ResponsesStore:
             await self._queue.join()
 
     async def store_response_object(
-        self, response_object: OpenAIResponseObject, input: list[OpenAIResponseInput]
+        self,
+        response_object: OpenAIResponseObject,
+        input: list[OpenAIResponseInput],
+        messages: list[OpenAIMessageParam],
     ) -> None:
         if self.enable_write_queue:
             if self._queue is None:
                 raise ValueError("Responses store is not initialized")
             try:
-                self._queue.put_nowait((response_object, input))
+                self._queue.put_nowait((response_object, input, messages))
             except asyncio.QueueFull:
                 logger.warning(f"Write queue full; adding response id={getattr(response_object, 'id', '<unknown>')}")
-                await self._queue.put((response_object, input))
+                await self._queue.put((response_object, input, messages))
         else:
-            await self._write_response_object(response_object, input)
+            await self._write_response_object(response_object, input, messages)
 
     async def _worker_loop(self) -> None:
         assert self._queue is not None
@@ -120,22 +139,26 @@ class ResponsesStore:
                 item = await self._queue.get()
             except asyncio.CancelledError:
                 break
-            response_object, input = item
+            response_object, input, messages = item
             try:
-                await self._write_response_object(response_object, input)
+                await self._write_response_object(response_object, input, messages)
             except Exception as e:  # noqa: BLE001
                 logger.error(f"Error writing response object: {e}")
             finally:
                 self._queue.task_done()
 
     async def _write_response_object(
-        self, response_object: OpenAIResponseObject, input: list[OpenAIResponseInput]
+        self,
+        response_object: OpenAIResponseObject,
+        input: list[OpenAIResponseInput],
+        messages: list[OpenAIMessageParam],
     ) -> None:
         if self.sql_store is None:
             raise ValueError("Responses store is not initialized")
 
         data = response_object.model_dump()
         data["input"] = [input_item.model_dump() for input_item in input]
+        data["messages"] = [msg.model_dump() for msg in messages]
 
         await self.sql_store.insert(
             "openai_responses",
@@ -188,7 +211,7 @@ class ResponsesStore:
             last_id=data[-1].id if data else "",
         )
 
-    async def get_response_object(self, response_id: str) -> OpenAIResponseObjectWithInput:
+    async def get_response_object(self, response_id: str) -> _OpenAIResponseObjectWithInputAndMessages:
         """
         Get a response object with automatic access control checking.
         """
@@ -205,7 +228,7 @@ class ResponsesStore:
             # This provides security by not revealing whether the record exists
             raise ValueError(f"Response with id {response_id} not found") from None
 
-        return OpenAIResponseObjectWithInput(**row["response_object"])
+        return _OpenAIResponseObjectWithInputAndMessages(**row["response_object"])
 
     async def delete_response_object(self, response_id: str) -> OpenAIDeleteResponseObject:
         if not self.sql_store:
@@ -241,8 +264,8 @@ class ResponsesStore:
         if before and after:
             raise ValueError("Cannot specify both 'before' and 'after' parameters")
 
-        response_with_input = await self.get_response_object(response_id)
-        items = response_with_input.input
+        response_with_input_and_messages = await self.get_response_object(response_id)
+        items = response_with_input_and_messages.input
 
         if order == Order.desc:
             items = list(reversed(items))