> ## 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.

# LingBot World 2.0

export const DiffusionModelTags = ({tags = []}) => {
  const normalizedTags = Array.isArray(tags) ? tags : [tags];
  return <div className="not-prose sgd-model-tags">
      {normalizedTags.map(tag => <span key={tag} className="sgd-chip">
          {tag}
        </span>)}
    </div>;
};

<DiffusionModelTags tags={["realtime", "world model", "14B causal DiT", "camera control", "interactive KV window"]} />

## 1. Model Introduction

[LingBot World 2.0](https://huggingface.co/robbyant/lingbot-world-v2-14b-causal-fast-diffusers) is the 14B realtime camera-controlled world model in the LingBot family. It generates continuously from a live causal session, accepts control updates between chunks, and reuses DiT and VAE state for incremental frame delivery.

Choose 2.0 when the larger model and interactive KV-window path justify an 8-GPU deployment. Like the earlier LingBot release, it prioritizes responsive control and bounded causal state over the full-clip global context of offline video diffusion.

## 2. Deployment

```bash Command theme={null}
export SGLANG_LINGBOT_LAZY_VAE_ENCODE_BLACK_FRAMES=60
export SGLANG_LINGBOT_ENABLE_INTERACTIVE_KV_WINDOW=true
sglang serve \
  --model-path robbyant/lingbot-world-v2-14b-causal-fast-diffusers \
  --pipeline-class-name LingBotWorldCausalDMDPipeline \
  --num-gpus 8 \
  --ulysses-degree 8 \
  --dit-cpu-offload false \
  --text-encoder-cpu-offload false \
  --vae-config.use-parallel-decode true \
  --vae-config.parallel-decode-mode spatial \
  --enable-torch-compile false
```

### Optional KV-Cache Compression

Long-running sessions can enable lossy int4 PRQ compression for completed
causal KV-cache chunks by installing `quant-videogen` as described in the
quantization guide and adding `--kv-cache-quant int4` to the server command.
The current and most recent completed chunks remain in BF16. See
[Causal KV-Cache Quantization](/docs/sglang-diffusion/quantization#causal-kv-cache-quantization)
for the algorithm, tuning options, measured memory-latency tradeoff, and
support limits.

## 3. Realtime WebUI

The lightweight local WebUI is useful for validating latency, frame transport, and camera control behavior.

```bash Command theme={null}
python -m http.server 18080 -d python/sglang/multimodal_gen/apps/realtime_webui
```

Open `http://127.0.0.1:18080` and use:

```text Example theme={null}
ws://127.0.0.1:30000/v1/realtime_video/generate
```

## 4. HTTP and WebSocket API

LingBot World 2.0 uses the realtime video WebSocket endpoint. The server keeps one live session, generates one chunk at a time, and accepts runtime control events while generation is running.

### Endpoints

| API                           | Method      | Purpose                                                                | Notes                                                                               |
| ----------------------------- | ----------- | ---------------------------------------------------------------------- | ----------------------------------------------------------------------------------- |
| `/v1/models`                  | `GET`       | Query the served model id before opening a session.                    | The WebUI uses this to fill the model field when the server exposes model metadata. |
| `/v1/realtime_video/generate` | `WebSocket` | Create one realtime LingBot session and stream generated video chunks. | The first client message must be an `init` message encoded with MessagePack.        |

### `init` message

Send this MessagePack map immediately after the WebSocket opens.

| Parameter                             | Type                        | Required | Meaning                                                                                                                         |
| ------------------------------------- | --------------------------- | -------- | ------------------------------------------------------------------------------------------------------------------------------- |
| `type`                                | string                      | Yes      | Must be `"init"`.                                                                                                               |
| `model`                               | string                      | No       | Model id. Leave empty to use the served model.                                                                                  |
| `prompt`                              | string                      | Yes      | Text prompt for the initial scene and motion style.                                                                             |
| `first_frame`                         | bytes or string             | Yes      | Initial reference image. Send bytes from the WebUI/client, or a server-readable image path/string.                              |
| `size`                                | string                      | Yes      | Generation size as `WIDTHxHEIGHT`, for example `832x480`.                                                                       |
| `fps`                                 | number                      | Yes      | Target playback FPS for the generated stream.                                                                                   |
| `num_frames`                          | integer                     | Yes      | Frames per generated chunk. LingBot uses chunked causal generation, so this controls per-chunk latency and queue size.          |
| `seed`                                | integer                     | No       | Random seed for deterministic sampling.                                                                                         |
| `num_inference_steps`                 | integer                     | No       | Denoising steps per chunk. LingBot defaults to `4` when omitted.                                                                |
| `guidance_scale`                      | number                      | No       | Classifier-free guidance scale. Realtime LingBot commonly uses `1`.                                                             |
| `negative_prompt`                     | string                      | No       | Negative prompt passed to the diffusion pipeline.                                                                               |
| `quality`                             | `"lossless"`, `"high"`      | No       | `lossless` keeps FP32 VAE decode. `high` uses the validated BF16 decode path for lower per-chunk latency.                       |
| `max_chunks`                          | integer                     | No       | Stop after this many chunks. Omit for a continuous session.                                                                     |
| `realtime_causal_sink_size`           | integer                     | No       | Number of sink frames/tokens retained in the causal attention window.                                                           |
| `realtime_causal_kv_cache_num_frames` | integer                     | No       | Number of recent frames retained in the causal KV cache window.                                                                 |
| `realtime_output_format`              | `"webp"`, `"jpeg"`, `"raw"` | No       | Preview/output transport. `webp` and `jpeg` send encoded preview frames; `raw` sends raw RGB; omit for lossless delta-gzip RGB. |
| `output_compression`                  | integer                     | No       | Preview quality for `webp` or `jpeg`, from `1` to `100`.                                                                        |
| `enable_upscaling`                    | boolean                     | No       | Enable server-side super resolution after frame decode.                                                                         |
| `upscaling_scale`                     | integer                     | No       | Super-resolution scale. Current default is `4` when upscaling is enabled.                                                       |
| `upscaling_model_path`                | string                      | No       | Optional Real-ESRGAN model path.                                                                                                |
| `enable_frame_interpolation`          | boolean                     | No       | Enable frame interpolation. Keep this disabled when measuring true generated FPS.                                               |
| `frame_interpolation_exp`             | integer                     | No       | Interpolation multiplier exponent. `1` means 2x frames.                                                                         |
| `frame_interpolation_scale`           | number                      | No       | RIFE internal scale for interpolation.                                                                                          |
| `frame_interpolation_model_path`      | string                      | No       | Optional RIFE model path.                                                                                                       |
| `condition_inputs.camera_actions`     | `list[list[string]]`        | No       | Initial scripted camera actions, one action list per frame.                                                                     |

### Runtime `event` messages

After `init`, send MessagePack event maps to update the live session.

| Parameter  | Type                                                   | Required | Meaning                                                                                                                                                                                          |
| ---------- | ------------------------------------------------------ | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `type`     | string                                                 | Yes      | Must be `"event"`.                                                                                                                                                                               |
| `kind`     | `"prompt"`, `"camera_actions"`, or `"composite_input"` | Yes      | Runtime event kind.                                                                                                                                                                              |
| `payload`  | string, object, or list                                | Yes      | For `prompt`, a non-empty string. For `camera_actions`, either scripted `list[list[string]]` or state-mode payload. For `composite_input`, a map containing `input_types` plus each named input. |
| `event_id` | integer                                                | No       | Client sequence id. The server echoes it in chunk/frame metadata after the event is sampled.                                                                                                     |

`camera_actions` supports two payload modes:

| Mode   | Payload shape                                                                   | Meaning                                                            |
| ------ | ------------------------------------------------------------------------------- | ------------------------------------------------------------------ |
| Script | `list[list[string]]`                                                            | A fixed sequence of per-frame actions consumed by upcoming chunks. |
| State  | `{ "mode": "state", "transitions": [{"actions": [...], "client_ts_ms": ...}] }` | Live control state transitions from keyboard or UI controls.       |

Supported LingBot action tokens include `w`, `a`, `s`, `d` for camera movement and `i`, `j`, `k`, `l` for look controls.

Use `composite_input` when multiple runtime inputs should be sampled together, such as updating the prompt and camera controls in one event.

### Server messages

| Message       | Payload                              | Meaning                                                                                                                                                   |
| ------------- | ------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `frame_batch` | MessagePack map with `payload` bytes | One batch of frames. The map includes `chunk_index`, `num_frames`, `content_type`, `encoding`, `width`, `height`, and frame-batch metadata.               |
| `chunk_stats` | MessagePack map                      | Per-chunk timing and transport metrics, including `scheduler_forward_ms`, `raw_payload_build_ms`, `chunk_total_ms`, `num_frames`, and `ws_payload_bytes`. |
| `error`       | MessagePack map                      | Server-side validation or generation error.                                                                                                               |

### Minimal client sketch

```python Python theme={null}
import msgspec.msgpack
import websocket

ws = websocket.create_connection("ws://127.0.0.1:30000/v1/realtime_video/generate")
ws.send_binary(msgspec.msgpack.encode({
    "type": "init",
    "prompt": "A quiet rainy London alley, stable camera motion.",
    "first_frame": open("reference.jpg", "rb").read(),
    "size": "832x480",
    "fps": 25,
    "num_frames": 9,
    "num_inference_steps": 4,
    "guidance_scale": 1,
    "realtime_output_format": "webp",
    "output_compression": 95,
}))

ws.send_binary(msgspec.msgpack.encode({
    "type": "event",
    "kind": "camera_actions",
    "event_id": 1,
    "payload": {"mode": "state", "transitions": [{"actions": ["w"], "client_ts_ms": 0}]},
}))

ws.send_binary(msgspec.msgpack.encode({
    "type": "event",
    "kind": "prompt",
    "event_id": 2,
    "payload": "A quiet snowy Tokyo alley, stable camera motion.",
}))

ws.send_binary(msgspec.msgpack.encode({
    "type": "event",
    "kind": "composite_input",
    "event_id": 3,
    "payload": {
        "input_types": ["prompt", "camera_actions"],
        "prompt": "A quiet neon Shanghai alley, stable forward camera motion.",
        "camera_actions": [["w"], ["w"], []],
    },
}))
```

## 5. Consistency

LingBot World 2.0 uses raw-frame websocket GT plus per-chunk latency guards for consistency checks.

## 6. Notes

* Use the realtime endpoint for interactive sessions: `/v1/realtime_video/generate`.
* Prefer WebP preview transport for interactive testing; use raw-frame transport for consistency checks.
* Long-running sessions should be validated with raw-frame consistency before changing causal cache, condition sampling, or VAE decode behavior.