diff --git a/tests/entrypoints/openai/responses/test_simple.py b/tests/entrypoints/openai/responses/test_simple.py
index b67f0d34115a..bbf3cc80ad43 100644
--- a/tests/entrypoints/openai/responses/test_simple.py
+++ b/tests/entrypoints/openai/responses/test_simple.py
@@ -6,6 +6,7 @@
 from openai import OpenAI
 
 from ....utils import RemoteOpenAIServer
+from .conftest import validate_streaming_event_stack
 
 MODEL_NAME = "Qwen/Qwen3-8B"
 
@@ -219,3 +220,23 @@ async def test_extra_sampling_params(client: OpenAI, model_name: str):
     assert response.status in ["completed", "incomplete"]
     assert len(response.output) > 0
     assert response.output[0].content[0].text  # Has text output
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+async def test_streaming_types(
+    pairs_of_event_types: dict[str, str], client: OpenAI, model_name: str
+):
+    stream = await client.responses.create(
+        model=model_name,
+        input="tell me a story about a cat in 20 words",
+        reasoning={"effort": "low"},
+        tools=[],
+        stream=True,
+        background=False,
+    )
+    events = []
+    async for event in stream:
+        events.append(event)
+
+    validate_streaming_event_stack(events, pairs_of_event_types)
diff --git a/vllm/entrypoints/openai/responses/serving.py b/vllm/entrypoints/openai/responses/serving.py
index b9d526e25def..3cfb6fffc3ea 100644
--- a/vllm/entrypoints/openai/responses/serving.py
+++ b/vllm/entrypoints/openai/responses/serving.py
@@ -85,6 +85,8 @@
     ResponseCreatedEvent,
     ResponseInProgressEvent,
     ResponseInputOutputMessage,
+    ResponseReasoningPartAddedEvent,
+    ResponseReasoningPartDoneEvent,
     ResponsesRequest,
     ResponsesResponse,
     ResponseUsage,
@@ -1339,6 +1341,19 @@ async def _process_simple_streaming_events(
                                 ),
                             )
                         )
+                        yield _increment_sequence_number_and_return(
+                            ResponseReasoningPartAddedEvent(
+                                type="response.reasoning_part.added",
+                                sequence_number=-1,
+                                output_index=current_output_index,
+                                item_id=current_item_id,
+                                content_index=current_content_index,
+                                part=ResponseReasoningTextContent(
+                                    text="",
+                                    type="reasoning_text",
+                                ),
+                            )
+                        )
                     else:
                         yield _increment_sequence_number_and_return(
                             ResponseOutputItemAddedEvent(
@@ -1354,22 +1369,21 @@ async def _process_simple_streaming_events(
                                 ),
                             )
                         )
-                    yield _increment_sequence_number_and_return(
-                        ResponseContentPartAddedEvent(
-                            type="response.content_part.added",
-                            sequence_number=-1,
-                            output_index=current_output_index,
-                            item_id=current_item_id,
-                            content_index=current_content_index,
-                            part=ResponseOutputText(
-                                type="output_text",
-                                text="",
-                                annotations=[],
-                                logprobs=[],
-                            ),
+                        yield _increment_sequence_number_and_return(
+                            ResponseContentPartAddedEvent(
+                                type="response.content_part.added",
+                                sequence_number=-1,
+                                output_index=current_output_index,
+                                item_id=current_item_id,
+                                content_index=current_content_index,
+                                part=ResponseOutputText(
+                                    type="output_text",
+                                    text="",
+                                    annotations=[],
+                                    logprobs=[],
+                                ),
+                            )
                         )
-                    )
-                    current_content_index += 1
                     first_delta_sent = True
                 # todo(kebe7jun) tool call support
 
@@ -1397,6 +1411,19 @@ async def _process_simple_streaming_events(
                             text=reason_content,
                         )
                     )
+                    yield _increment_sequence_number_and_return(
+                        ResponseReasoningPartDoneEvent(
+                            type="response.reasoning_part.done",
+                            sequence_number=-1,
+                            item_id=current_item_id,
+                            output_index=current_output_index,
+                            content_index=current_content_index,
+                            part=ResponseReasoningTextContent(
+                                text=reason_content,
+                                type="reasoning_text",
+                            ),
+                        )
+                    )
                     current_content_index = 0
                     reasoning_item = ResponseReasoningItem(
                         type="reasoning",
@@ -1418,6 +1445,8 @@ async def _process_simple_streaming_events(
                             item=reasoning_item,
                         )
                     )
+                    current_output_index += 1
+                    current_item_id = str(uuid.uuid4())
                     yield _increment_sequence_number_and_return(
                         ResponseOutputItemAddedEvent(
                             type="response.output_item.added",
@@ -1432,8 +1461,6 @@ async def _process_simple_streaming_events(
                             ),
                         )
                     )
-                    current_output_index += 1
-                    current_item_id = str(uuid.uuid4())
                     yield _increment_sequence_number_and_return(
                         ResponseContentPartAddedEvent(
                             type="response.content_part.added",
@@ -1449,7 +1476,6 @@ async def _process_simple_streaming_events(
                             ),
                         )
                     )
-                    current_content_index += 1
                     # reset previous delta messages
                     previous_delta_messages = []
 
@@ -1485,7 +1511,6 @@ async def _process_simple_streaming_events(
                             ),
                         )
                     )
-                current_content_index += 1
 
                 previous_delta_messages.append(delta_message)
         if previous_delta_messages:
@@ -1505,7 +1530,19 @@ async def _process_simple_streaming_events(
                         text=reason_content,
                     )
                 )
-                current_content_index += 1
+                yield _increment_sequence_number_and_return(
+                    ResponseReasoningPartDoneEvent(
+                        type="response.reasoning_part.done",
+                        sequence_number=-1,
+                        item_id=current_item_id,
+                        output_index=current_output_index,
+                        content_index=current_content_index,
+                        part=ResponseReasoningTextContent(
+                            text=reason_content,
+                            type="reasoning_text",
+                        ),
+                    )
+                )
                 reasoning_item = ResponseReasoningItem(
                     type="reasoning",
                     content=[
@@ -1543,7 +1580,6 @@ async def _process_simple_streaming_events(
                         item_id=current_item_id,
                     )
                 )
-                current_content_index += 1
                 part = ResponseOutputText(
                     text=final_content,
                     type="output_text",
@@ -1559,7 +1595,6 @@ async def _process_simple_streaming_events(
                         part=part,
                     )
                 )
-                current_content_index += 1
                 item = ResponseOutputMessage(
                     type="message",
                     role="assistant",