> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sglang.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Spectrum Acceleration

> Approximate request-scoped denoising-step acceleration.

Spectrum forecasts DiT features and skips selected denoising steps. It is an
approximation: validate visual or video quality and latency on the exact model,
shape, hardware, and sampling settings you plan to deploy.

## Quick start

```bash theme={null}
sglang generate \
  --model-path Wan-AI/Wan2.1-T2V-1.3B-Diffusers \
  --prompt "A paper boat floating through a misty mountain lake" \
  --enable-spectrum \
  --save-output
```

## Scope and constraints

* Available only on native FLUX.1, Wan, HunyuanVideo, and SD3 implementation
  paths. It is not a `--backend diffusers` feature and does not currently
  cover FLUX.2.
* The request control is available through `sglang generate` and Python
  sampling parameters. It is not a `sglang serve` or OpenAI-server request
  option yet.
* Spectrum and `--enable-teacache` are mutually exclusive.
* Start with the defaults. `--debug` adds shadow-prediction validation work, so
  its latency is not representative of normal Spectrum execution.

## Advanced controls

Use `--enable-spectrum` explicitly. Providing any Spectrum override also
enables it, but that implicit behavior is intended for scripts rather than new
commands.

| Flag                       | Default | Purpose                                  |
| -------------------------- | ------- | ---------------------------------------- |
| `--spectrum-window-size`   | `2.0`   | Initial step-skipping window             |
| `--spectrum-flex-window`   | `0.75`  | Window growth after a real forward       |
| `--spectrum-warmup-steps`  | `5`     | Initial exact DiT forwards               |
| `--spectrum-m`             | `4`     | Chebyshev basis count                    |
| `--spectrum-lam`           | `0.1`   | Ridge regularization                     |
| `--spectrum-tau-num-steps` | `50`    | Chebyshev time horizon                   |
| `--history-size`           | `100`   | Recent feature-history capacity          |
| `--taylor-order`           | `1`     | Local predictor order (`1`, `2`, or `3`) |
| `--w`                      | `1.0`   | Chebyshev/Taylor blend weight            |

<Warning>
  These controls trade speed against output fidelity. Change one control at a
  time and retain a lossless baseline for comparison.
</Warning>