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bjf-frzandbjfwhite 1fa734419e [Refactor]Rename diffusion benchmark backend to endpoint (#3137 )

Signed-off-by: bjf-frz <frz123db@gmail.com>
Signed-off-by: bjfwhite <baijingfan1@huawei.com>
Co-authored-by: bjfwhite <baijingfan1@huawei.com>

2026-05-19 11:30:33 +08:00

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Chat Completions API

vLLM-Omni supports generating and editing images via the /v1/chat/completions endpoint using diffusion models. This page explains how to pass generation parameters (such as num_inference_steps, height, width) to diffusion models through this endpoint.

!!! tip For dedicated endpoints that accept generation parameters as top-level fields, see Image Generation API and Image Edit API.

Passing Generation Parameters

The /v1/chat/completions endpoint follows the OpenAI Chat API schema, which does not natively include diffusion-specific fields like num_inference_steps or height. How you pass these extra fields depends on your client.

curl / Python `requests`

Wrap generation parameters inside an "extra_body" key in the JSON body:

curl -s http://localhost:8091/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [
      {"role": "user", "content": "A beautiful landscape painting"}
    ],
    "extra_body": {
      "num_inference_steps": 50,
      "seed": 42
    }
  }'

OpenAI Python SDK

Use the extra_body keyword argument. The SDK automatically merges these fields into the top-level request body:

response = client.chat.completions.create(
    model="Qwen/Qwen-Image",
    messages=[{"role": "user", "content": "A beautiful landscape painting"}],
    extra_body={
        "num_inference_steps": 50,
        "seed": 42,
    },
)

!!! note "SDK extra_body vs. JSON extra_body" These two extra_body usages look similar but work differently under the hood. The SDK flattens the dict into the top-level request JSON, while the curl/requests approach sends it as a nested "extra_body" key. Both are handled correctly by the server.

!!! note "About the ignored fields warning" You may see a log message like:

```
WARNING: The following fields were present in the request but ignored: {'height', 'width', ...}
```

This is **harmless**. It is emitted by vLLM's request validation layer
because these fields are not part of the standard OpenAI
`ChatCompletionRequest` schema. The fields are still stored internally
and correctly forwarded to the diffusion pipeline.

Model-Specific Examples

For complete examples with full request/response details, see the model-specific guides:

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