fix(streaming): push processed_response.new_items (including HandoffCallItem) to event_queue

src/agents/run.py

@@ -45,6 +45,7 @@
 )
 from .handoffs import Handoff, HandoffInputFilter, handoff
 from .items import (
+    HandoffCallItem,
     ItemHelpers,
     ModelResponse,
     RunItem,
@@ -60,7 +61,12 @@
 from .models.multi_provider import MultiProvider
 from .result import RunResult, RunResultStreaming
 from .run_context import RunContextWrapper, TContext
-from .stream_events import AgentUpdatedStreamEvent, RawResponsesStreamEvent, RunItemStreamEvent
+from .stream_events import (
+    AgentUpdatedStreamEvent,
+    RawResponsesStreamEvent,
+    RunItemStreamEvent,
+    StreamEvent,
+)
 from .tool import Tool
 from .tracing import Span, SpanError, agent_span, get_current_trace, trace
 from .tracing.span_data import AgentSpanData
@@ -1095,14 +1101,19 @@ async def _run_single_turn_streamed(
             context_wrapper=context_wrapper,
             run_config=run_config,
             tool_use_tracker=tool_use_tracker,
+            event_queue=streamed_result._event_queue,
         )
 
-        if emitted_tool_call_ids:
-            import dataclasses as _dc
+        import dataclasses as _dc
+
+        # Filter out items that have already been sent to avoid duplicates
+        items_to_filter = single_step_result.new_step_items
 
-            filtered_items = [
+        if emitted_tool_call_ids:
+            # Filter out tool call items that were already emitted during streaming
+            items_to_filter = [
                 item
-                for item in single_step_result.new_step_items
+                for item in items_to_filter
                 if not (
                     isinstance(item, ToolCallItem)
                     and (
@@ -1114,15 +1125,17 @@ async def _run_single_turn_streamed(
                 )
             ]
 
-            single_step_result_filtered = _dc.replace(
-                single_step_result, new_step_items=filtered_items
-            )
+        # Filter out HandoffCallItem to avoid duplicates (already sent earlier)
+        items_to_filter = [
+            item for item in items_to_filter
+            if not isinstance(item, HandoffCallItem)
+        ]
 
-            RunImpl.stream_step_result_to_queue(
-                single_step_result_filtered, streamed_result._event_queue
-            )
-        else:
-            RunImpl.stream_step_result_to_queue(single_step_result, streamed_result._event_queue)
+        # Create filtered result and send to queue
+        filtered_result = _dc.replace(
+            single_step_result, new_step_items=items_to_filter
+        )
+        RunImpl.stream_step_result_to_queue(filtered_result, streamed_result._event_queue)
         return single_step_result
 
     @classmethod
@@ -1207,6 +1220,7 @@ async def _get_single_step_result_from_response(
         context_wrapper: RunContextWrapper[TContext],
         run_config: RunConfig,
         tool_use_tracker: AgentToolUseTracker,
+        event_queue: asyncio.Queue[StreamEvent | QueueCompleteSentinel] | None = None,
     ) -> SingleStepResult:
         processed_response = RunImpl.process_model_response(
             agent=agent,
@@ -1218,6 +1232,15 @@ async def _get_single_step_result_from_response(
 
         tool_use_tracker.add_tool_use(agent, processed_response.tools_used)
 
+        # Send handoff items immediately for streaming, but avoid duplicates
+        if event_queue is not None and processed_response.new_items:
+            handoff_items = [
+                item for item in processed_response.new_items
+                if isinstance(item, HandoffCallItem)
+            ]
+            if handoff_items:
+                RunImpl.stream_step_items_to_queue(cast(list[RunItem], handoff_items), event_queue)
+
         return await RunImpl.execute_tools_and_side_effects(
             agent=agent,
             original_input=original_input,

tests/test_stream_events.py

@@ -3,10 +3,12 @@
 
 import pytest
 
-from agents import Agent, Runner, function_tool
+from agents import Agent, HandoffCallItem, Runner, function_tool
+from agents.extensions.handoff_filters import remove_all_tools
+from agents.handoffs import handoff
 
 from .fake_model import FakeModel
-from .test_responses import get_function_tool_call, get_text_message
+from .test_responses import get_function_tool_call, get_handoff_tool_call, get_text_message
 
 
 @function_tool
@@ -52,3 +54,57 @@ async def test_stream_events_main():
     assert tool_call_start_time > 0, "tool_call_item was not observed"
     assert tool_call_end_time > 0, "tool_call_output_item was not observed"
     assert tool_call_start_time < tool_call_end_time, "Tool call ended before or equals it started?"
+
+
+@pytest.mark.asyncio
+async def test_stream_events_main_with_handoff():
+    @function_tool
+    async def foo(args: str) -> str:
+        return f"foo_result_{args}"
+
+    english_agent = Agent(
+        name="EnglishAgent",
+        instructions="You only speak English.",
+        model=FakeModel(),
+    )
+
+    model = FakeModel()
+    model.add_multiple_turn_outputs(
+        [
+            [
+                get_text_message("Hello"),
+                get_function_tool_call("foo", '{"args": "arg1"}'),
+                get_handoff_tool_call(english_agent),
+            ],
+            [get_text_message("Done")],
+        ]
+    )
+
+    triage_agent = Agent(
+        name="TriageAgent",
+        instructions="Handoff to the appropriate agent based on the language of the request.",
+        handoffs=[
+            handoff(english_agent, input_filter=remove_all_tools),
+        ],
+        tools=[foo],
+        model=model,
+    )
+
+    result = Runner.run_streamed(
+        triage_agent,
+        input="Start",
+    )
+
+    handoff_requested_seen = False
+    agent_switched_to_english = False
+
+    async for event in result.stream_events():
+        if event.type == "run_item_stream_event":
+            if isinstance(event.item, HandoffCallItem):
+                handoff_requested_seen = True
+        elif event.type == "agent_updated_stream_event":
+            if hasattr(event, "new_agent") and event.new_agent.name == "EnglishAgent":
+                agent_switched_to_english = True
+
+    assert handoff_requested_seen, "handoff_requested event not observed"
+    assert agent_switched_to_english, "Agent did not switch to EnglishAgent"