Source examples/online_serving/openai_chat_completion_with_reasoning.py.

OpenAI Chat Completion With Reasoning

# SPDX-License-Identifier: Apache-2.0
"""
An example shows how to generate chat completions from reasoning models
like DeepSeekR1.

To run this example, you need to start the vLLM server
with the reasoning parser:

```bash
vllm serve deepseek-ai/DeepSeek-R1-Distill-Qwen-1.5B \
    --reasoning-parser deepseek_r1
```

This example demonstrates how to generate chat completions from reasoning models
using the OpenAI Python client library.
"""

from openai import OpenAI

# Modify OpenAI's API key and API base to use vLLM's API server.
openai_api_key = "EMPTY"
openai_api_base = "http://localhost:8000/v1"


def main():
    client = OpenAI(
        api_key=openai_api_key,
        base_url=openai_api_base,
    )

    models = client.models.list()
    model = models.data[0].id

    # Round 1
    messages = [{"role": "user", "content": "9.11 and 9.8, which is greater?"}]
    # ruff: noqa: E501
    # For granite, add: `extra_body={"chat_template_kwargs": {"thinking": True}}`
    response = client.chat.completions.create(model=model, messages=messages)

    reasoning_content = response.choices[0].message.reasoning_content
    content = response.choices[0].message.content

    print("reasoning_content for Round 1:", reasoning_content)
    print("content for Round 1:", content)

    # Round 2
    messages.append({"role": "assistant", "content": content})
    messages.append({
        "role":
        "user",
        "content":
        "How many Rs are there in the word 'strawberry'?",
    })
    response = client.chat.completions.create(model=model, messages=messages)

    reasoning_content = response.choices[0].message.reasoning_content
    content = response.choices[0].message.content

    print("reasoning_content for Round 2:", reasoning_content)
    print("content for Round 2:", content)


if __name__ == "__main__":
    main()