Skip to content

[Bugfix] Fix crash when tool_choice=required exceeds max_tokens #36841

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
vllm-bot merged 5 commits into from
Mar 12, 2026
+36 −9
Merged

[Bugfix] Fix crash when tool_choice=required exceeds max_tokens #36841

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
a477e4f
[Bugfix] Fix crash when tool_choice=required exceeds max_tokens
chaunceyjiang Mar 12, 2026
1be8bdf
[Bugfix] Fix crash when tool_choice=required exceeds max_tokens
chaunceyjiang Mar 12, 2026
377798e
[Bugfix] Fix crash when tool_choice=required exceeds max_tokens
chaunceyjiang Mar 12, 2026
6307876
[Bugfix] Fix crash when tool_choice=required exceeds max_tokens
chaunceyjiang Mar 12, 2026
d253375
[Bugfix] Fix crash when tool_choice=required exceeds max_tokens
chaunceyjiang Mar 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 24 additions & 0 deletions tests/entrypoints/openai/test_completion_with_function_calling.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -514,3 +514,27 @@ async def test_inconsistent_tool_choice_and_tools(
],
tool_choice={},
)


@pytest.mark.asyncio
async def test_max_tokens_with_tool_choice_required(client: openai.AsyncOpenAI):
""" """
models = await client.models.list()
model_name: str = models.data[0].id

# This combination previously crashed the engine
chat_completion = await client.chat.completions.create(
messages=messages,
temperature=0,
max_completion_tokens=1,
model=model_name,
tools=tools,
tool_choice="required",
)
# When `tool_choice="required"` and the tokens of `tools` exceed `max_tokens`,
# both `tool_calls` and `content` should be empty.
# This behavior should be consistent with OpenAI.
Copy link
Copy Markdown
Member

@DarkLight1337 DarkLight1337 Mar 12, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Have you confirmed that OpenAI does this as well?

Copy link
Copy Markdown
Collaborator Author

@chaunceyjiang chaunceyjiang Mar 12, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more. 

chat_completion = client.chat.completions.create(
    messages=messages,
    model="gpt-5",
    tools=tools,
    tool_choice="required",
    max_completion_tokens=10,
)
print(chat_completion)



ChatCompletion(id='chatcmpl-DIU1M3ic0iPTxtnxit59rWDxUpaEH', choices=[Choice(finish_reason='length', index=0, logprobs=None, message=ChatCompletionMessage(content='', refusal=None, role='assistant', annotations=None, audio=None, function_call=None, tool_calls=None))], created=1773297678, model='gpt-5', object='chat.completion', service_tier=None, system_fingerprint=None, usage=CompletionUsage(completion_tokens=10, prompt_tokens=340, total_tokens=350, completion_tokens_details=CompletionTokensDetails(accepted_prediction_tokens=0, audio_tokens=0, reasoning_tokens=10, rejected_prediction_tokens=0), prompt_tokens_details=PromptTokensDetails(audio_tokens=0, cached_tokens=0), input_tokens=0, output_tokens=0, input_tokens_details=None))

Copy link
Copy Markdown
Collaborator Author

@chaunceyjiang chaunceyjiang Mar 12, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Have you confirmed that OpenAI does this as well?

This is the result from my test with GPT-5.

choice = chat_completion.choices[0]
assert choice.finish_reason == "length"
assert len(choice.message.tool_calls) == 0
assert choice.message.content == ""
2 changes: 1 addition & 1 deletion vllm/entrypoints/openai/chat_completion/serving.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1507,7 +1507,7 @@ async def chat_completion_full_generator(

elif request.tool_choice and request.tool_choice == "required":
tool_call_class_items = []
assert tool_calls is not None and len(tool_calls) > 0
tool_calls = tool_calls or []
for idx, tool_call in enumerate(tool_calls):
# Use native ID if available,
# otherwise generate ID with correct id_type
Expand Down
19 changes: 11 additions & 8 deletions vllm/entrypoints/openai/engine/serving.py
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import asyncio
import contextlib
import json
import time
from collections.abc import AsyncGenerator, Callable, Mapping, Sequence
Expand All @@ -13,7 +14,7 @@
from openai.types.responses import (
ToolChoiceFunction,
)
from pydantic import ConfigDict, TypeAdapter
from pydantic import ConfigDict, TypeAdapter, ValidationError
from starlette.datastructures import Headers

import vllm.envs as envs
Expand Down Expand Up @@ -1125,17 +1126,19 @@ def _parse_tool_calls_from_content(
)
content = None # Clear content since tool is called.
elif request.tool_choice == "required":
assert content is not None
tool_calls = TypeAdapter(list[FunctionDefinition]).validate_json(content)
function_calls.extend(
[
tool_calls = []
with contextlib.suppress(ValidationError):
content = content or ""
tool_calls = TypeAdapter(list[FunctionDefinition]).validate_json(
content
)
for tool_call in tool_calls:
function_calls.append(
FunctionCall(
name=tool_call.name,
arguments=json.dumps(tool_call.parameters, ensure_ascii=False),
)
for tool_call in tool_calls
]
)
)
content = None # Clear content since tool is called.
elif (
tool_parser_cls
Expand Down
Loading