fix: Restore previous responses to input list, not messages

This adjusts the restoration of previous responses to prepend them to
the list of Responses API inputs instead of our converted list of Chat
Completion messages. This matches the expected behavior of the
Responses API, and I misinterpreted the nuances here in the initial implementation.

Signed-off-by: Ben Browning <bbrownin@redhat.com>

tests/unit/providers/agents/meta_reference/test_openai_responses.py

@@ -4,13 +4,19 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-from unittest.mock import AsyncMock
+from unittest.mock import AsyncMock, patch
 
 import pytest
 
 from llama_stack.apis.agents.openai_responses import (
+    OpenAIResponseInputItemList,
+    OpenAIResponseInputMessageContentText,
     OpenAIResponseInputToolWebSearch,
-    OpenAIResponseOutputMessage,
+    OpenAIResponseMessage,
+    OpenAIResponseObject,
+    OpenAIResponseOutputMessageContentOutputText,
+    OpenAIResponseOutputMessageWebSearchToolCall,
+    OpenAIResponsePreviousResponseWithInputItems,
 )
 from llama_stack.apis.inference.inference import (
     OpenAIAssistantMessageParam,
@@ -100,7 +106,7 @@ async def test_create_openai_response_with_string_input(openai_responses_impl, m
     openai_responses_impl.persistence_store.set.assert_called_once()
     assert result.model == model
     assert len(result.output) == 1
-    assert isinstance(result.output[0], OpenAIResponseOutputMessage)
+    assert isinstance(result.output[0], OpenAIResponseMessage)
     assert result.output[0].content[0].text == "Hello! How can I help you?"
 
 
@@ -198,5 +204,108 @@ async def test_create_openai_response_with_string_input_with_tools(openai_respon
 
     # Check that we got the content from our mocked tool execution result
     assert len(result.output) >= 1
-    assert isinstance(result.output[1], OpenAIResponseOutputMessage)
+    assert isinstance(result.output[1], OpenAIResponseMessage)
     assert result.output[1].content[0].text == "The score of todays game was 10-12"
+
+
+@pytest.mark.asyncio
+async def test_prepend_previous_response_none(openai_responses_impl):
+    """Test prepending no previous response to a new response."""
+
+    input = await openai_responses_impl._prepend_previous_response("fake_input", None)
+    assert input == "fake_input"
+
+
+@pytest.mark.asyncio
+@patch.object(OpenAIResponsesImpl, "_get_previous_response_with_input")
+async def test_prepend_previous_response_basic(get_previous_response_with_input, openai_responses_impl):
+    """Test prepending a basic previous response to a new response."""
+
+    input_item_message = OpenAIResponseMessage(
+        id="123",
+        content=[OpenAIResponseInputMessageContentText(text="fake_previous_input")],
+        role="user",
+    )
+    input_items = OpenAIResponseInputItemList(data=[input_item_message])
+    response_output_message = OpenAIResponseMessage(
+        id="123",
+        content=[OpenAIResponseOutputMessageContentOutputText(text="fake_response")],
+        status="completed",
+        role="assistant",
+    )
+    response = OpenAIResponseObject(
+        created_at=1,
+        id="resp_123",
+        model="fake_model",
+        output=[response_output_message],
+        status="completed",
+    )
+    previous_response = OpenAIResponsePreviousResponseWithInputItems(
+        input_items=input_items,
+        response=response,
+    )
+    get_previous_response_with_input.return_value = previous_response
+
+    input = await openai_responses_impl._prepend_previous_response("fake_input", "resp_123")
+
+    assert len(input) == 3
+    # Check for previous input
+    assert isinstance(input[0], OpenAIResponseMessage)
+    assert input[0].content[0].text == "fake_previous_input"
+    # Check for previous output
+    assert isinstance(input[1], OpenAIResponseMessage)
+    assert input[1].content[0].text == "fake_response"
+    # Check for new input
+    assert isinstance(input[2], OpenAIResponseMessage)
+    assert input[2].content == "fake_input"
+
+
+@pytest.mark.asyncio
+@patch.object(OpenAIResponsesImpl, "_get_previous_response_with_input")
+async def test_prepend_previous_response_web_search(get_previous_response_with_input, openai_responses_impl):
+    """Test prepending a web search previous response to a new response."""
+
+    input_item_message = OpenAIResponseMessage(
+        id="123",
+        content=[OpenAIResponseInputMessageContentText(text="fake_previous_input")],
+        role="user",
+    )
+    input_items = OpenAIResponseInputItemList(data=[input_item_message])
+    output_web_search = OpenAIResponseOutputMessageWebSearchToolCall(
+        id="ws_123",
+        status="completed",
+    )
+    output_message = OpenAIResponseMessage(
+        id="123",
+        content=[OpenAIResponseOutputMessageContentOutputText(text="fake_web_search_response")],
+        status="completed",
+        role="assistant",
+    )
+    response = OpenAIResponseObject(
+        created_at=1,
+        id="resp_123",
+        model="fake_model",
+        output=[output_web_search, output_message],
+        status="completed",
+    )
+    previous_response = OpenAIResponsePreviousResponseWithInputItems(
+        input_items=input_items,
+        response=response,
+    )
+    get_previous_response_with_input.return_value = previous_response
+
+    input_messages = [OpenAIResponseMessage(content="fake_input", role="user")]
+    input = await openai_responses_impl._prepend_previous_response(input_messages, "resp_123")
+
+    assert len(input) == 4
+    # Check for previous input
+    assert isinstance(input[0], OpenAIResponseMessage)
+    assert input[0].content[0].text == "fake_previous_input"
+    # Check for previous output web search tool call
+    assert isinstance(input[1], OpenAIResponseOutputMessageWebSearchToolCall)
+    # Check for previous output web search response
+    assert isinstance(input[2], OpenAIResponseMessage)
+    assert input[2].content[0].text == "fake_web_search_response"
+    # Check for new input
+    assert isinstance(input[3], OpenAIResponseMessage)
+    assert input[3].content == "fake_input"