LongCat-Image - SGLang Documentation

1. Model Introduction

LongCat-Image is a text-to-image model from Meituan. SGLang runs its Qwen2.5-VL prompt rewriter in process with the native SGLang runtime before text encoding and denoising. The native pipeline keeps prompt rewriting and diffusion behind one OpenAI-compatible image endpoint. Rewriting is enabled by default for stronger prompt expansion, but each request can disable it when lower latency matters more than the rewritten prompt.

2. Installation

Install SGLang with the diffusion dependencies:

Command

pip install -e "python[diffusion]"

For other installation options, see the SGLang Diffusion installation guide.

3. Serve the model

Command

sglang serve \
  --model-path meituan-longcat/LongCat-Image \
  --performance-mode auto \
  --port 30010

Prompt rewriting is enabled by default for LongCat-Image. It adds an autoregressive Qwen2.5-VL pass before diffusion; set enable_prompt_rewrite=false on a request when lower latency is more important than rewritten prompt quality.

4. Generate an image

Python

import base64
from openai import OpenAI

client = OpenAI(api_key="EMPTY", base_url="http://127.0.0.1:30010/v1")

response = client.images.generate(
    model="meituan-longcat/LongCat-Image",
    prompt="A quiet bookshop on a rainy evening, warm light in the windows",
    n=1,
    response_format="b64_json",
)

image_bytes = base64.b64decode(response.data[0].b64_json)
with open("longcat_image.png", "wb") as f:
    f.write(image_bytes)

To skip prompt rewriting with the OpenAI client, pass the model-specific request field through extra_body:

Python

response = client.images.generate(
    model="meituan-longcat/LongCat-Image",
    prompt="A quiet bookshop on a rainy evening",
    extra_body={"enable_prompt_rewrite": False},
)

5. Memory placement

Use the unified component-residency selector when the complete pipeline does not fit on the accelerator. For example, keep the repeatedly used DiT resident while moving auxiliary components to CPU between stages:

Command

sglang serve \
  --model-path meituan-longcat/LongCat-Image \
  --component-residency dit=resident text_encoder=component-offload vae=component-offload \
  --pin-cpu-memory \
  --port 30010

See Component Residency for mode semantics and compatibility with the existing CPU-offload flags.

​1. Model Introduction

​2. Installation

​3. Serve the model

​4. Generate an image

​5. Memory placement

1. Model Introduction

2. Installation

3. Serve the model

4. Generate an image

5. Memory placement