LCORE-2914: address PR review feedback for A2A executor refactor

- Fix conversation_id not passed to _convert_stream_to_events (regression)
- Use Optional[Type] per contributing guide conventions
- Merge doubled pydantic_ai.messages import, alias A2A TextPart instead
- Use tool_call_id + tool_name in tool call status events
- Rename mismatched test, add AgentRunError and compacted turn tests
- Fix stream mock to yield AgentRunResultEvent instead of setting .result
- Add test asserting artifact carries conversation_id

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: are-ces

src/app/endpoints/a2a.py

@@ -27,7 +27,9 @@
     TaskState,
     TaskStatus,
     TaskStatusUpdateEvent,
-    TextPart,
+)
+from a2a.types import (
+    TextPart as A2ATextPart,
 )
 from a2a.utils import new_agent_text_message, new_task
 from fastapi import APIRouter, Depends, HTTPException, Request, status
@@ -41,11 +43,9 @@
     PartDeltaEvent,
     PartEndEvent,
     PartStartEvent,
+    TextPart,
     TextPartDelta,
 )
-from pydantic_ai.messages import (
-    TextPart as PydanticTextPart,
-)
 from pydantic_ai.run import AgentRunResult
 from starlette.responses import Response, StreamingResponse
 
@@ -80,8 +80,8 @@
 # Task store and context store are created lazily based on configuration.
 # For multi-worker deployments, configure 'a2a_state' with 'sqlite' or 'postgres'
 # to share state across workers.
-_TASK_STORE: TaskStore | None = None
-_CONTEXT_STORE: A2AContextStore | None = None
+_TASK_STORE: Optional[TaskStore] = None
+_CONTEXT_STORE: Optional[A2AContextStore] = None
 
 
 async def _get_task_store() -> TaskStore:
@@ -111,7 +111,7 @@ async def _get_context_store() -> A2AContextStore:
 
 
 def _build_a2a_parts_from_agent_result(
-    run_result: AgentRunResult[str] | None,
+    run_result: Optional[AgentRunResult[str]],
     accumulated_text: list[str],
 ) -> list[Part]:
     """Convert a pydantic-ai agent run result to A2A Parts.
@@ -133,7 +133,7 @@ def _build_a2a_parts_from_agent_result(
         final_text = "".join(accumulated_text)
     if not final_text:
         return []
-    return [Part(root=TextPart(text=final_text))]
+    return [Part(root=A2ATextPart(text=final_text))]
 
 
 class TaskResultAggregator:
@@ -467,7 +467,7 @@ async def _convert_stream_to_events(
         prompt: str,
         task_id: str,
         context_id: str,
-        conversation_id: str | None = None,
+        conversation_id: Optional[str] = None,
     ) -> AsyncIterator[Any]:
         """Run an agent and convert stream events to A2A events.
 
@@ -486,7 +486,7 @@ async def _convert_stream_to_events(
 
         artifact_id = str(uuid.uuid4())
         text_parts: list[str] = []
-        run_result: AgentRunResult[str] | None = None
+        run_result: Optional[AgentRunResult[str]] = None
 
         async with agent.run_stream_events(prompt) as stream:
             async for event in stream:
@@ -520,7 +520,7 @@ def _dispatch_agent_event(  # pylint: disable=too-many-arguments,too-many-positi
         context_id: str,
         text_parts: list[str],
         artifact_id: str,
-    ) -> TaskStatusUpdateEvent | None:
+    ) -> Optional[TaskStatusUpdateEvent]:
         """Map a single pydantic-ai stream event to an A2A status update.
 
         Parameters:
@@ -536,7 +536,7 @@ def _dispatch_agent_event(  # pylint: disable=too-many-arguments,too-many-positi
         _ = artifact_id
 
         if isinstance(event, PartStartEvent):
-            if isinstance(event.part, PydanticTextPart):
+            if isinstance(event.part, TextPart):
                 text_parts.append(event.part.content)
                 return self._text_status_event(event.part.content, task_id, context_id)
 
@@ -553,7 +553,7 @@ def _dispatch_agent_event(  # pylint: disable=too-many-arguments,too-many-positi
                 status=TaskStatus(
                     state=TaskState.working,
                     message=new_agent_text_message(
-                        f"Tool call: {event.part.tool_name}",
+                        f"Tool call: {event.part.tool_call_id} ({event.part.tool_name})",
                         context_id=context_id,
                         task_id=task_id,
                     ),
@@ -570,7 +570,7 @@ def _dispatch_agent_event(  # pylint: disable=too-many-arguments,too-many-positi
                     status=TaskStatus(
                         state=TaskState.working,
                         message=new_agent_text_message(
-                            f"MCP call: {event.part.tool_name}",
+                            f"Tool call: {event.part.tool_call_id} ({event.part.tool_name})",
                             context_id=context_id,
                             task_id=task_id,
                         ),

tests/unit/app/endpoints/test_a2a.py

@@ -965,7 +965,7 @@ async def test_process_task_streaming_applies_compaction(  # pylint: disable=too
         result_event = mocker.MagicMock(spec=AgentRunResultEvent)
         result_event.result = mock_run_result
 
-        async def _event_stream():
+        async def _event_stream() -> Any:
             yield result_event
 
         mock_stream_ctx = mocker.AsyncMock()
@@ -996,7 +996,7 @@ async def test_convert_stream_artifact_carries_conversation_id(
         result_event = mocker.MagicMock(spec=AgentRunResultEvent)
         result_event.result = mock_run_result
 
-        async def _event_stream():
+        async def _event_stream() -> Any:
             yield result_event
 
         mock_stream_ctx = mocker.AsyncMock()
@@ -1015,9 +1015,9 @@ async def _event_stream():
 
         artifact_events = [e for e in events if isinstance(e, TaskArtifactUpdateEvent)]
         assert len(artifact_events) == 1
-        assert (
-            artifact_events[0].artifact.metadata["conversation_id"] == conversation_id
-        )
+        metadata = artifact_events[0].artifact.metadata
+        assert metadata is not None
+        assert metadata["conversation_id"] == conversation_id
 
     @pytest.mark.asyncio
     async def test_cancel_raises_not_implemented(self, mocker: MockerFixture) -> None:
@@ -1127,6 +1127,7 @@ def test_function_tool_call_emits_status_update(
         text_parts: list[str] = []
         tool_call_part = mocker.MagicMock(spec=ToolCallPart)
         tool_call_part.tool_name = "search_docs"
+        tool_call_part.tool_call_id = "call_xyz789"
         event = FunctionToolCallEvent(
             part=tool_call_part,
             event_kind="function_tool_call",
@@ -1136,7 +1137,7 @@ def test_function_tool_call_emits_status_update(
         )
         assert result is not None
         assert isinstance(result, TaskStatusUpdateEvent)
-        assert "Tool call: search_docs" in str(result.status.message)
+        assert "Tool call: call_xyz789 (search_docs)" in str(result.status.message)
 
     def test_native_tool_call_end_emits_status_update(
         self, mocker: MockerFixture
@@ -1145,7 +1146,8 @@ def test_native_tool_call_end_emits_status_update(
         executor = self._make_executor()
         text_parts: list[str] = []
         native_part = mocker.MagicMock(spec=NativeToolCallPart)
-        native_part.tool_name = "mcp_server_tool"
+        native_part.tool_name = "file_search"
+        native_part.tool_call_id = "call_abc123"
         event = PartEndEvent(
             index=0,
             part=native_part,
@@ -1156,7 +1158,7 @@ def test_native_tool_call_end_emits_status_update(
         )
         assert result is not None
         assert isinstance(result, TaskStatusUpdateEvent)
-        assert "MCP call: mcp_server_tool" in str(result.status.message)
+        assert "Tool call: call_abc123 (file_search)" in str(result.status.message)
 
     def test_agent_run_result_returns_none(self, mocker: MockerFixture) -> None:
         """Test that AgentRunResultEvent is not mapped to a status update."""