[gpt-oss] Support streaming in response API #22431

heheda12345 · 2025-08-07T06:10:33Z

Essential Elements of an Effective PR Description Checklist

The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
The test plan, such as providing test command.
The test results, such as pasting the results comparison before and after, or e2e results
(Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Purpose。

Support streaming in response API. Note that only part of the APIs are supported.

Test Plan

All tests in tests/v1/entrypoints/openai/responses to test whether it breaks existing model. Harmony integration is not tested yet.

Test Result

Passed

(Optional) Documentation Update

Originally authored by @simon-mo
Should be merged after #22427

github-actions · 2025-08-07T06:10:42Z

👋 Hi! Thank you for contributing to the vLLM project.

💬 Join our developer Slack at https://slack.vllm.ai to discuss your PR in #pr-reviews, coordinate on features in #feat- channels, or join special interest groups in #sig- channels.

Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can either: Add ready label to the PR or enable auto-merge.

🚀

mergify · 2025-08-07T06:11:11Z

⚠️ The sha of the head commit of this PR conflicts with #22427. Mergify cannot evaluate rules on this PR. ⚠️

gemini-code-assist

Code Review

This pull request introduces support for streaming in the response API, primarily for the Harmony protocol (gpt-oss models). This involves significant refactoring in serving_responses.py to handle different conversation contexts and response generation logic for Harmony and non-Harmony models. It also adds MCPToolServer for integration with external tool servers.

My review found a few critical and high-severity issues. In harmony_utils.py, there's an unsafe dictionary key access that could lead to a KeyError, and an incorrect instantiation of ResponseReasoningItem that will cause a TypeError. In tool_server.py, the new MCPToolServer has two issues: it doesn't correctly implement the new_session abstract method from its base class, which is a critical bug, and its URL construction for tool servers is not robust.

gemini-code-assist · 2025-08-07T06:11:56Z

vllm/entrypoints/tool_server.py

The method get_tool_session should be named new_session to correctly implement the abstract method from the ToolServer base class. The current implementation will result in a TypeError at runtime because MCPToolServer does not implement the abstract method new_session.

Suggested change

@asynccontextmanager

async def get_tool_session(self, tool_name: str):

from mcp import ClientSession

from mcp.client.sse import sse_client

url = self.urls.get(tool_name)

if url:

async with sse_client(url=url) as streams, ClientSession(

*streams) as session:

await session.initialize()

yield session

else:

logger.warning("Tool %s not found", tool_name)

@asynccontextmanager

async def new_session(self, tool_name: str):

from mcp import ClientSession

from mcp.client.sse import sse_client

url = self.urls.get(tool_name)

if url:

async with sse_client(url=url) as streams, ClientSession(

*streams) as session:

await session.initialize()

yield session

else:

logger.warning("Tool %s not found", tool_name)

gemini-code-assist · 2025-08-07T06:11:56Z

vllm/entrypoints/harmony_utils.py

The direct access browser_call["pattern"] is unsafe and can lead to a KeyError if the 'pattern' key is missing in the browser_call dictionary. This is inconsistent with the usage of .get() for other keys in this function, such as 'query' and 'url'. To prevent potential crashes, consider using .get() and handling the case where the key might be missing, or wrapping this access in a try-except block for better error handling.

gemini-code-assist · 2025-08-07T06:11:57Z

vllm/entrypoints/harmony_utils.py

The ResponseReasoningItem is being instantiated with a text parameter, but the openai.types.responses.ResponseReasoningItem class does not accept text as a direct argument. It expects a content argument which should be a list of Content objects (like ResponseReasoningTextContent). This will cause a TypeError at runtime.

Suggested change

reasoning_item = ResponseReasoningItem(

id=f"rs_{random_uuid()}",

summary=[],

type="reasoning",

text=content.text,

status=None,

)

reasoning_item = ResponseReasoningItem(

id=f"rs_{random_uuid()}",

summary=[],

type="reasoning",

content=[

ResponseReasoningTextContent(text=content.text,

type="reasoning_text")

],

status=None,

)

gemini-code-assist · 2025-08-07T06:11:57Z

vllm/entrypoints/tool_server.py

The URL construction url = f"http://{url}/sse" is not robust. It unconditionally prepends http://, which will lead to incorrect URLs if the user provides a full URL with a scheme (e.g., http://... or https://...) in the --tool-server argument. You should check if the URL already has a scheme before prepending http://.

mergify · 2025-08-07T16:57:26Z

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @heheda12345.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

Signed-off-by: Chen Zhang <[email protected]>

WoosukKwon · 2025-08-11T19:40:10Z

vllm/entrypoints/openai/serving_responses.py

+            if False:
+                yield


Is if False needed?

Yes. This tricks Python to think this is a generator but in fact it immediately returns.

WoosukKwon · 2025-08-11T19:41:41Z

vllm/entrypoints/openai/serving_responses.py

+                                # TODO: migrate this to
+                                # ResponseReasoningTextContent for now


Is this TODO already done?

I think so. CC @simon-mo

Correct. You can remove the TODO.

WoosukKwon · 2025-08-11T19:42:00Z

vllm/entrypoints/openai/serving_responses.py

+                                    logprobs=[],
+                                ),
+                            ))
+                    # TODO: migrate to OpenAI types once updated.


This is done. Removed the comments.

WoosukKwon

LGTM overall. Can we explicitly specify which APIs are supported or unsupported yet?

Signed-off-by: Chen Zhang <[email protected]>

heheda12345 · 2025-08-11T20:18:20Z

The supported APIs are listed here #22554 . All other APIs are unverified.

Signed-off-by: Chen Zhang <[email protected]>

heheda12345 · 2025-08-11T22:21:13Z

@WoosukKwon addressed your comments.

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Paul Pak <[email protected]>

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Diego-Castan <[email protected]>

Signed-off-by: Chen Zhang <[email protected]>

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Xiao Yu <[email protected]>

Signed-off-by: Chen Zhang <[email protected]>

heheda12345 requested a review from aarnphm as a code owner August 7, 2025 06:10

gemini-code-assist bot reviewed Aug 7, 2025

View reviewed changes

mergify bot added frontend v1 labels Aug 7, 2025

mergify bot added the needs-rebase label Aug 7, 2025

houseroad requested a review from morgendave August 7, 2025 22:23

heheda12345 mentioned this pull request Aug 8, 2025

[gpt-oss] Small bug fixes for frontend #22512

Merged

4 tasks

streaming

f79e1e6

Signed-off-by: Chen Zhang <[email protected]>

heheda12345 force-pushed the streaming branch from f019f83 to f79e1e6 Compare August 9, 2025 00:29

mergify bot removed the needs-rebase label Aug 9, 2025

fix precommit

ece698b

Signed-off-by: Chen Zhang <[email protected]>

mergify bot added the gpt-oss Related to GPT-OSS models label Aug 11, 2025

WoosukKwon reviewed Aug 11, 2025

View reviewed changes

WoosukKwon approved these changes Aug 11, 2025

View reviewed changes

remove todo

1aa1133

Signed-off-by: Chen Zhang <[email protected]>

heheda12345 added 2 commits August 11, 2025 15:15

remove todo

1a51b71

Signed-off-by: Chen Zhang <[email protected]>

add comments

8f00b4b

Signed-off-by: Chen Zhang <[email protected]>

simon-mo enabled auto-merge (squash) August 12, 2025 00:40

github-actions bot added the ready ONLY add when PR is ready to merge/full CI is needed label Aug 12, 2025

simon-mo disabled auto-merge August 12, 2025 00:46

simon-mo merged commit 95a935f into vllm-project:main Aug 12, 2025
15 of 51 checks passed

paulpak58 pushed a commit to paulpak58/vllm that referenced this pull request Aug 13, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

f1f1bc7

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Paul Pak <[email protected]>

diegocastanibm pushed a commit to diegocastanibm/vllm that referenced this pull request Aug 15, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

f40aa00

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Diego-Castan <[email protected]>

yiliu30 pushed a commit to yiliu30/vllm-fork that referenced this pull request Aug 19, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

922b436

Signed-off-by: Chen Zhang <[email protected]>

epwalsh pushed a commit to epwalsh/vllm that referenced this pull request Aug 28, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

84917fd

Signed-off-by: Chen Zhang <[email protected]>

xiao-llm pushed a commit to xiao-llm/vllm that referenced this pull request Aug 28, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

cb0368c

Signed-off-by: Chen Zhang <[email protected]> Signed-off-by: Xiao Yu <[email protected]>

zhewenl pushed a commit to zhewenl/vllm that referenced this pull request Aug 28, 2025

[gpt-oss] Support streaming in response API (vllm-project#22431)

ce82c5a

Signed-off-by: Chen Zhang <[email protected]>

-    @asynccontextmanager
-    async def get_tool_session(self, tool_name: str):
-        from mcp import ClientSession
-        from mcp.client.sse import sse_client
-        url = self.urls.get(tool_name)
-        if url:
-            async with sse_client(url=url) as streams, ClientSession(
-                    *streams) as session:
-                await session.initialize()
-                yield session
-        else:
-            logger.warning("Tool %s not found", tool_name)
+    @asynccontextmanager
+    async def new_session(self, tool_name: str):
+        from mcp import ClientSession
+        from mcp.client.sse import sse_client
+        url = self.urls.get(tool_name)
+        if url:
+            async with sse_client(url=url) as streams, ClientSession(
+                    *streams) as session:
+                await session.initialize()
+                yield session
+        else:
+            logger.warning("Tool %s not found", tool_name)

-                reasoning_item = ResponseReasoningItem(
-                    id=f"rs_{random_uuid()}",
-                    summary=[],
-                    type="reasoning",
-                    text=content.text,
-                    status=None,
-                )
+                reasoning_item = ResponseReasoningItem(
+                    id=f"rs_{random_uuid()}",
+                    summary=[],
+                    type="reasoning",
+                    content=[
+                        ResponseReasoningTextContent(text=content.text,
+                                                     type="reasoning_text")
+                    ],
+                    status=None,
+                )

		# TODO: migrate this to
		# ResponseReasoningTextContent for now

Uh oh!

[gpt-oss] Support streaming in response API #22431

[gpt-oss] Support streaming in response API #22431

Uh oh!

Conversation

heheda12345 commented Aug 7, 2025 • edited by github-actions bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Essential Elements of an Effective PR Description Checklist

Purpose。

Test Plan

Test Result

(Optional) Documentation Update

Uh oh!

github-actions bot commented Aug 7, 2025

Uh oh!

mergify bot commented Aug 7, 2025

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

gemini-code-assist bot Aug 7, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Aug 7, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Aug 7, 2025

Choose a reason for hiding this comment

Uh oh!

gemini-code-assist bot Aug 7, 2025

Choose a reason for hiding this comment

Uh oh!

mergify bot commented Aug 7, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

WoosukKwon left a comment

Choose a reason for hiding this comment

Uh oh!

heheda12345 commented Aug 11, 2025

Uh oh!

heheda12345 commented Aug 11, 2025

Uh oh!

Uh oh!

Uh oh!

heheda12345 commented Aug 7, 2025 •

edited by github-actions bot

Loading