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lerobot/docs/source/lingbot_va.mdx
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pepijn223 e3deff00ad feat(lingbot_va): RoboTwin eef-pose eval, single-file model, Hub checkpoints
Make the LingBot-VA port runnable on both LIBERO and RoboTwin and clean up the
package to LeRobot conventions.

- Consolidate all vendored Wan2.2 model code (transformer, attention, VAE helpers,
  flow-matching scheduler, grid utils, flex-attention) into a single
  modeling_lingbot_va.py; remove the separate wan_*/schedulers modules.
- Move the fixed action (un)normalization quantiles out of the config and into the
  post-processor (LIBERO 7-DoF + RoboTwin 16-d eef); remove the conversion script in
  favour of ready-to-use LeRobot-format checkpoints on the Hub.
- Fixes found via on-sim validation: undo LIBERO's 180-degree image flip
  (image_hflip), encode obs as a multi-frame streaming-VAE clip, reset the streaming
  VAE cache between episodes, run the transformer in config.dtype, lazy-load frozen
  VAE/UMT5 by subfolder with the text encoder on CPU.
- RoboTwin: add an end-effector-pose action mode to RoboTwinEnv (16-d per-arm
  xyz+quat+gripper deltas composed onto the initial eef pose, executed via CuRobo IK)
  and the robotwin_tshape latent layout (full-res head + half-res wrists via a second
  streaming VAE) with the upstream RoboTwin action quantiles + camera mapping.
- Predicted-video saving works for both benchmarks; docs + tests updated.

Co-authored-by: Cursor <cursoragent@cursor.com>
2026-06-06 15:20:51 +02:00

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# LingBot-VA
LingBot-VA is an **autoregressive video-action world-model policy** built on the **Wan2.2**
video-diffusion stack. It interleaves, in one autoregressive sequence, the prediction of
future **video latents** and **robot actions** ("VA" = Video-Action). The LeRobot
integration wires LingBot-VA into the standard training, evaluation and processor
interfaces.
## Model Overview
LingBot-VA is a **dual-stream "mixture-of-transformers"**: a video/latent stream
(`patch_embedding_mlp → blocks → proj_out`) and an action stream
(`action_embedder → blocks → action_proj_out`) share the same 30 transformer blocks and
text conditioning. Actions are produced by the dedicated `action_proj_out` head — they are
**not** decoded from predicted pixels, though video and action are co-trained.
| Component | Class | Role |
|---|---|---|
| DiT backbone (trainable) | `WanTransformer3DModel` | ~5B-param dual-stream transformer (the only weights stored in the LeRobot checkpoint). |
| VAE (frozen) | `AutoencoderKLWan` | Wan2.2 VAE, `z_dim=48`. Lazy-pulled from the source repo. |
| Text encoder (frozen) | `UMT5EncoderModel` | UMT5-XXL, `d_model=4096`. Lazy-pulled from the source repo. |
At inference the policy runs an autoregressive loop per chunk: it denoises the video-latent
stream (CFG, ~20 steps) and the action stream (~50 steps) with two independent
flow-matching schedulers, maintaining a KV cache across chunks. Real observed keyframes are
fed back into the KV cache as the chunk is executed (closed-loop world modeling).
### What the LeRobot Integration Covers
- Standard `policy.type=lingbot_va` configuration through LeRobot.
- Ready-to-use LeRobot-format checkpoints on the Hub (converted from the released upstream ones).
- Autoregressive dual-stream inference behind the standard `select_action` interface
(single-environment eval, `--eval.batch_size=1`).
- Opt-in saving of the policy's **predicted (imagined) videos** during eval / training.
- Evaluation with `lerobot-eval` on the LIBERO benchmark.
Training (the flow-matching dual-stream loss + latent dataset) is part of a follow-up
training port and is not yet wired into `lerobot-train`.
## Installation
1. Install LeRobot by following the [Installation Guide](./installation).
2. Install the LingBot-VA extra (brings in `diffusers>=0.36` for the Wan2.2 stack):
```bash
pip install -e ".[lingbot_va]"
# For LIBERO evaluation (Linux only):
pip install -e ".[lingbot_va,libero]"
```
## Checkpoints
The released upstream checkpoints have been converted to LeRobot format and pushed to the Hub:
| Variant | LeRobot checkpoint |
|---|---|
| LIBERO-Long post-train | `pepijn223/lingbot_va_libero_long` |
| RoboTwin post-train | `pepijn223/lingbot_va_robotwin` |
| Pretrained base | `pepijn223/lingbot_va_base` |
**Packaging:** only the trainable ~5B transformer is stored in the LeRobot
`model.safetensors`. The frozen VAE + UMT5 + tokenizer (~20 GB) are **lazily pulled** from
`config.wan_pretrained_path` at load time (defaults to the source `robbyant/*` repo). The
UMT5-XXL text encoder runs on CPU by default (`config.text_encoder_device`) so the 5B
transformer + VAE fit on a single 2432 GB GPU.
## Evaluation (LIBERO)
```bash
lerobot-eval \
--policy.path=pepijn223/lingbot_va_libero_long \
--policy.device=cuda \
--env.type=libero --env.task=libero_10 \
--env.observation_height=128 --env.observation_width=128 \
--eval.n_episodes=50 --eval.batch_size=1 \
--output_dir=outputs/eval/lingbot_va_libero
```
Native LeRobot eval reproduces **96% success on `libero_10` (LIBERO-Long)** (48/50 episodes).
LingBot-VA's streaming inference (KV cache + observed-keyframe feedback) is implemented for
single-environment eval; use `--eval.batch_size=1`.
## Evaluation (RoboTwin)
RoboTwin 2.0 needs the SAPIEN + CuRobo simulator stack — use the benchmark Docker image
(`docker/Dockerfile.benchmark.robotwin`, which also needs `warp-lang==1.3.1` and CuRobo built
with the GPU's compute capability in `TORCH_CUDA_ARCH_LIST`). RoboTwin uses **end-effector-pose
control**, so run with `--env.action_mode=ee`: the policy predicts per-arm `xyz+quaternion+gripper`
deltas (`robotwin_tshape` latent layout) that are composed onto the episode's initial eef pose and
executed via CuRobo IK.
```bash
lerobot-eval \
--policy.path=pepijn223/lingbot_va_robotwin \
--policy.device=cuda \
--env.type=robotwin --env.task=beat_block_hammer --env.action_mode=ee \
--eval.n_episodes=10 --eval.batch_size=1 \
--output_dir=outputs/eval/lingbot_va_robotwin
```
### Saving predicted (imagined) videos
Set `--policy.save_predicted_video=true` to additionally VAE-decode the predicted video
latents and write `pred_episode_*.mp4` next to the env-rendered `eval_episode_*.mp4` videos.
The same flag works for the periodic eval during `lerobot-train`.
## Inference Hyperparameters (LIBERO)
| Key | Value |
|---|---|
| height × width | 128 × 128 |
| cameras | `observation.images.image` (agentview), `observation.images.image2` (eye-in-hand) |
| action channels used | 06 (7-DoF arm + gripper) |
| action_per_frame / frame_chunk_size | 4 / 4 |
| attn_window | 30 |
| video / action denoising steps | 20 / 50 |
| guidance_scale / action_guidance_scale | 5 / 1 |
| snr_shift / action_snr_shift | 5.0 / 0.05 |
These are the defaults of `LingBotVAConfig`; override any of them via `--policy.<name>=...`.
## Notes & Limitations
- **Correctness gate:** matching the upstream LIBERO success rate requires validating the
converted checkpoint on a GPU and tensor-diffing intermediate activations against the
upstream implementation. The most sensitive parts are the action quantile normalization,
the camera ordering, the `action_per_frame`/`frame_chunk_size` alignment, and `attn_mode`.
- **Attention backend:** inference uses the `torch` SDPA backend (always available). The
`flashattn` and `flex` backends are optional; `flex` is only needed for training.
- **Model size:** the DiT is ~5B params and the frozen VAE+UMT5 add ~20 GB; inference needs
roughly 1824 GB of VRAM.
## License
LingBot-VA is released under Apache-2.0. See the
[upstream repository](https://github.com/Robbyant/lingbot-va).