LTX2 & LTX2.3 - SGLang Documentation

1. Model Introduction

LTX-2 and LTX-2.3 are Lightricks video models for text-to-video and image-conditioned generation. Their defining deployment choice is the pipeline: one-stage minimizes latency, standard two-stage refines quality, and LTX-2.3 adds a 1920×1088 HQ path. Choose LTX when one model family must span fast generation, higher-quality refinement, and LoRA adaptation. Two-stage quality costs substantially more memory and startup work because both DiTs and the spatial upsampler participate; use the one-stage path when latency or capacity matters more than final detail. Use Lightricks/LTX-2 or Lightricks/LTX-2.3 as --model-path. SGLang loads the two-stage upsampler and distilled components from the selected snapshot.

License notice: LTX-2 and LTX-2.3 are released under the LTX-2 Community License Agreement, not Apache 2.0. The license includes commercial-use restrictions for some entities. Review the official Lightricks license before production or commercial use; SGLang support does not grant additional model usage rights.

2. SGLang-diffusion Installation

Install SGLang with diffusion dependencies:

uv pip install "sglang[diffusion]" --prerelease=allow

For platform-specific setup, see the SGLang Diffusion installation guide.

3. Model Deployment

This section provides deployment configurations optimized for different LTX pipelines and hardware targets.

3.1 Basic Configuration

The LTX series supports one-stage and two-stage pipelines. LTX-2.3 also supports the HQ two-stage pipeline. The recommended launch configuration depends on whether the target GPU can keep both two-stage DiTs resident. Interactive Command Generator: Use the configuration selector below to generate a deployment command. The default selection targets a single NVIDIA H200 with resident two-stage mode. For multi-GPU serving, start from the 2-GPU or 4-GPU presets and only change parallelism if you need more memory headroom.

3.2 Configuration Tips

Choose the pipeline class based on the quality and latency target:

Use case	Pipeline class	Notes
One-stage generation	`LTX2Pipeline`	Fastest LTX native path. Supports T2V and TI2V.
Two-stage generation	`LTX2TwoStagePipeline`	Uses a base stage and a refinement stage. Supported by LTX-2 and LTX-2.3.
Two-stage High Quality (HQ) generation	`LTX2TwoStageHQPipeline`	LTX-2.3 HQ path; defaults to 1920x1088 unless you override `--width` and `--height`.

Feature compatibility:

Pipeline class	T2V	TI2V (`--image-path`)	LoRA (`--lora-path`)	Notes
`LTX2Pipeline`	Yes	Yes	Yes	One-stage path. Cannot be combined with HQ because HQ is a separate two-stage pipeline class.
`LTX2TwoStagePipeline`	Yes	Yes	Yes	Standard two-stage path for LTX-2 and LTX-2.3.
`LTX2TwoStageHQPipeline`	Yes	Yes	Yes	High Quality two-stage path for LTX-2.3. Use this instead of `LTX2Pipeline`; it is not a one-stage mode flag.

For two-stage pipelines, --ltx2-two-stage-device-mode controls transformer residency:

Mode	When to use it
`resident`	Best latency on high-VRAM GPUs because both DiTs can stay resident.
`original`	Closest to the original two-stage switching semantics.

Other deployment flags:

--lora-path: Preload a community LoRA adapter.
--lora-weight-name: Select the exact safetensors file when the LoRA repository contains multiple weight files.

For native LTX-2.3 two-stage serving without a user LoRA, resident is the fastest high-VRAM path. LTX-2 still applies the distilled LoRA during the stage switch, so --ltx2-two-stage-device-mode is mainly an LTX-2.3 optimization. When you pass --lora-path, SGLang still applies the user LoRA during the two-stage switch, so use resident on H200-class GPUs for enough VRAM, but do not expect the same premerged-stage2 benefit as the no-user-LoRA path.

3.3 Fast multi-GPU presets

For latency-oriented LTX serving, prefer CFG parallel over sequence parallelism. CFG parallel splits guidance branches across GPUs, while SP/Ulysses is mainly a memory/long-sequence tool for LTX.

Target	Recommended server flags	Notes
LTX-2.3, 1 high-VRAM GPU	`--ltx2-two-stage-device-mode resident`	Fastest two-stage setup when both DiTs fit.
LTX-2.3, 1 standard GPU	`--ltx2-two-stage-device-mode original`	Lower VRAM than `resident`; use this when H100-class memory is tight.
LTX-2, 2 GPUs	`--num-gpus 2 --enable-cfg-parallel`	Fastest verified 2-GPU setup; keep `--dit-layerwise-offload` disabled unless memory is tight.
LTX-2.3, 2 GPUs	`--num-gpus 2 --enable-cfg-parallel --ltx2-two-stage-device-mode resident`	Fastest common 2-GPU setup.
LTX-2.3, 4 GPUs	`--num-gpus 4 --tp-size 2 --enable-cfg-parallel --ltx2-two-stage-device-mode resident`	Fastest common 4-GPU layout: TP2 inside each CFG branch.
Official comparison	`--ltx2-two-stage-device-mode original`	Use this only when matching the original LTX-2.3 stage-switch semantics matters.

Use --enable-cfg-parallel for degree-2 CFG parallel. Use --cfg-parallel-size only when you explicitly need a different CFG branch count. If resident exceeds available VRAM, keep the same parallelism preset and switch only the device mode to original. On high-VRAM GPUs, add --text-encoder-cpu-offload false if text encoding latency matters and you have enough memory.

3.3.1 Two GPUs

sglang serve \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --num-gpus 2 \
  --enable-cfg-parallel \
  --ltx2-two-stage-device-mode resident

3.3.2 Four GPUs

sglang serve \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --num-gpus 4 \
  --tp-size 2 \
  --enable-cfg-parallel \
  --ltx2-two-stage-device-mode resident

4. Model Invocation

4.1 Basic Usage

The examples below spell out the current SGLang sampling defaults for reproducibility:

Model path	Default output	Default frames	Default steps
`Lightricks/LTX-2`	768x512	121	40
`Lightricks/LTX-2.3`	768x512	121	30
`Lightricks/LTX-2.3` with `LTX2TwoStageHQPipeline`	1920x1088	121	15

4.1.1 LTX-2 one-stage text-to-video

sglang generate \
  --model-path Lightricks/LTX-2 \
  --pipeline-class-name LTX2Pipeline \
  --prompt "A quiet coastal town at sunrise, fishing boats moving slowly through golden mist, cinematic camera movement" \
  --save-output

4.1.2 LTX-2.3 one-stage text-to-video

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2Pipeline \
  --prompt "A quiet coastal town at sunrise, fishing boats moving slowly through golden mist, cinematic camera movement" \
  --save-output

4.1.3 LTX-2 two-stage text-to-video

sglang generate \
  --model-path Lightricks/LTX-2 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --prompt "A handheld shot follows a red tram crossing a rainy city square at night, reflections on the pavement, cinematic lighting" \
  --save-output

4.1.4 LTX-2.3 two-stage text-to-video

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --prompt "A handheld shot follows a red tram crossing a rainy city square at night, reflections on the pavement, cinematic lighting" \
  --save-output

4.1.5 LTX-2.3 HQ text-to-video

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStageHQPipeline \
  --prompt "A wide cinematic shot of alpine clouds rolling over a mountain ridge, soft morning light, slow aerial camera movement" \
  --save-output

4.1.6 Image-to-video with one reference image

Pass one image to --image-path for image-conditioned generation:

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --image-path ./inputs/start.png \
  --prompt "The camera slowly pushes forward as the subject turns toward warm window light, subtle natural motion, cinematic" \
  --save-output

4.1.7 First-to-last-frame transition with two reference images

Pass two images to --image-path for transition-style TI2V. The first image is used as the starting condition and the second image is used as the ending condition.

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --image-path ./inputs/start.png ./inputs/end.png \
  --prompt "A smooth cinematic transition from the first scene into the final scene, dynamic camera motion, motion blur, zhuanchang" \
  --save-output

4.2 Advanced Usage

4.2.1 Use community LoRAs

Use --lora-path to load a LoRA adapter. If the Hugging Face repo contains multiple safetensors files, use --lora-weight-name to select the exact file. --lora-scale maps to the standard LoRA merge scale and defaults to 1.0. The following example uses valiantcat/LTX-2.3-Transition-LORA:

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --lora-path valiantcat/LTX-2.3-Transition-LORA \
  --lora-weight-name ltx2.3-transition.safetensors \
  --prompt "A low-angle tracking shot moves through a foggy forest road. The camera rises above the treetops and transitions into a clear view of a snowy mountain peak under bright sunlight, zhuanchang" \
  --save-output

You can combine the Transition LoRA with two reference images:

sglang generate \
  --model-path Lightricks/LTX-2.3 \
  --pipeline-class-name LTX2TwoStagePipeline \
  --image-path ./inputs/start.png ./inputs/end.png \
  --lora-path valiantcat/LTX-2.3-Transition-LORA \
  --lora-weight-name ltx2.3-transition.safetensors \
  --prompt "A fast cinematic transition from the first image to the second image, whip-pan motion, atmospheric lighting, zhuanchang" \
  --save-output

Some community LoRAs only include weights for transformer blocks. In that case, SGLang logs a concise coverage summary and leaves unmatched LoRA-capable layers on the base model weights. This is expected when the adapter format intentionally omits those layers.

5. Practical Tips

Use --pipeline-class-name LTX2TwoStagePipeline as the default LTX two-stage quality path.
Use --pipeline-class-name LTX2TwoStageHQPipeline when you want the HQ path and have enough VRAM for larger outputs.
Use --ltx2-two-stage-device-mode resident on high-VRAM GPUs if latency matters more than memory usage.
Use --ltx2-two-stage-device-mode original when comparing against official two-stage behavior.
Keep --width and --height aligned with the target model resolution; for LTX models, these are output video dimensions.

​1. Model Introduction

​2. SGLang-diffusion Installation

​3. Model Deployment

​3.1 Basic Configuration

​3.2 Configuration Tips

​3.3 Fast multi-GPU presets

​3.3.1 Two GPUs

​3.3.2 Four GPUs

​4. Model Invocation

​4.1 Basic Usage

​4.1.1 LTX-2 one-stage text-to-video

​4.1.2 LTX-2.3 one-stage text-to-video

​4.1.3 LTX-2 two-stage text-to-video

​4.1.4 LTX-2.3 two-stage text-to-video

​4.1.5 LTX-2.3 HQ text-to-video

​4.1.6 Image-to-video with one reference image

​4.1.7 First-to-last-frame transition with two reference images

​4.2 Advanced Usage

​4.2.1 Use community LoRAs

​5. Practical Tips

1. Model Introduction

2. SGLang-diffusion Installation

3. Model Deployment

3.1 Basic Configuration

3.2 Configuration Tips

3.3 Fast multi-GPU presets

3.3.1 Two GPUs

3.3.2 Four GPUs

4. Model Invocation

4.1 Basic Usage

4.1.1 LTX-2 one-stage text-to-video

4.1.2 LTX-2.3 one-stage text-to-video

4.1.3 LTX-2 two-stage text-to-video

4.1.4 LTX-2.3 two-stage text-to-video

4.1.5 LTX-2.3 HQ text-to-video

4.1.6 Image-to-video with one reference image

4.1.7 First-to-last-frame transition with two reference images

4.2 Advanced Usage

4.2.1 Use community LoRAs

5. Practical Tips