YAMBox2 groceries — MolmoAct2 Think

This is the depth-reasoning MolmoAct2-Think checkpoint fine-tuned on Jiafei1224/as for a bimanual YAM robot putting groceries into a container. This repository contains the 10,000-step checkpoint from the 50,000-step training run.

Adaptive depth is enabled by default. config.json contains "enable_depth_reasoning": true, and calling predict_action without an enable_depth_reasoning argument reads that checkpoint default. Pass the returned depth_cache into the next frame to reuse unchanged depth regions and regenerate changed regions adaptively. No dataset depth_updated_mask is required at inference time.

Policy contract

• Base checkpoint: allenai/MolmoAct2-Think
• Cameras, in order: observation.images.top, observation.images.left, observation.images.right
• State: observation.state, 14 dimensions
• Output: 14-dimensional absolute joint targets
• Action horizon / returned steps: 30 / 30
• Normalization tag: yam_dual_molmoact2
• Grippers are not separately normalized
• Training sequence length: 896
• Depth representation: 10 x 10 discrete bins (100 codes)
• Default output style: robot_depth_action

The converted action expert has a padded internal width of 32, but norm_stats.json defines the real robot action width as 14 and predict_action returns only those 14 dimensions.

Install

pip install "torch" "transformers==5.14.1" accelerate pillow numpy safetensors

The model uses custom Transformers code included in this repository, so loading requires trust_remote_code=True.

Run with adaptive depth

import numpy as np
import torch
from PIL import Image
from transformers import AutoModelForImageTextToText, AutoProcessor

model_id = "hqfang/think"

processor = AutoProcessor.from_pretrained(model_id, trust_remote_code=True)
model = AutoModelForImageTextToText.from_pretrained(
    model_id,
    trust_remote_code=True,
    torch_dtype=torch.bfloat16,
).to("cuda").eval()

assert model.config.enable_depth_reasoning is True
depth_cache = None

def predict(top_path, left_path, right_path, state):
    global depth_cache
    # Keep this exact camera order. Adaptive change detection uses the first image.
    images = [
        Image.open(top_path).convert("RGB"),
        Image.open(left_path).convert("RGB"),
        Image.open(right_path).convert("RGB"),
    ]
    with torch.inference_mode():
        result = model.predict_action(
            processor=processor,
            images=images,
            task="put the groceries into the container",
            state=np.asarray(state, dtype=np.float32),
            norm_tag="yam_dual_molmoact2",
            expected_action_representation="absolute",
            inference_action_mode="continuous",
            num_steps=10,
            n_action_steps=30,
            depth_cache=depth_cache,
            # No enable_depth_reasoning argument: the checkpoint default is True.
        )
    depth_cache = result.depth_cache
    actions = result.actions[0].float().cpu().numpy()
    assert actions.shape == (30, 14)
    assert result.depth_bins.shape[-1] == 100
    return actions

actions = predict("top.png", "left.png", "right.png", [0.0] * 14)

The first frame generates the complete depth representation. On later frames, passing depth_cache enables adaptive selective regeneration. To explicitly disable depth for an ablation, pass enable_depth_reasoning=False and omit the cache.

actions[t] is an absolute 14-dimensional joint target, not a delta. Validate joint ordering, limits, timing, and emergency-stop behavior before commanding physical hardware.

Open-loop check

The fixed-random open-loop evaluation used episode 2 from Jiafei1224/as (1,488 frames, continuous inference, adaptive depth, 10 flow steps). Raw action MSE was 0.0012067767 at step 10,000. This is an offline reconstruction metric, not a robot task-success measurement.

Citation

@misc{fang2026molmoact2actionreasoningmodels,
  title={MolmoAct2: Action Reasoning Models for Real-world Deployment},
  author={Haoquan Fang and Jiafei Duan and Donovan Clay and Sam Wang and Shuo Liu and Weikai Huang and Xiang Fan and Wei-Chuan Tsai and Shirui Chen and Yi Ru Wang and Shanli Xing and Jaemin Cho and Jae Sung Park and Ainaz Eftekhar and Peter Sushko and Karen Farley and Angad Wadhwa and Cole Harrison and Winson Han and Ying-Chun Lee and Eli VanderBilt and Rose Hendrix and Suveen Ellawela and Lucas Ngoo and Joyce Chai and Zhongzheng Ren and Ali Farhadi and Dieter Fox and Ranjay Krishna},
  year={2026},
  eprint={2605.02881},
  archivePrefix={arXiv},
  primaryClass={cs.RO}
}