Atomic-WAM

Atomic-WAM

Execution-Grounded Atomic-Motion
Reasoning for World Action Models

Shijun Shi1*†Zhe Liu2*Zhi Hou3Yinan Chen1†Tao Zhang1
Kai Hu4‡Yong Liu1Jiangning Zhang1‡

1 Zhejiang University   2 University of Hong Kong   3 ACE Robotics   4 Jiangnan University

* Equal contribution   ·   † Work completed during an internship at ACE Robotics   ·   ‡ Equal advising
arXiv ↗Code ↗Weights ↗
Inside the dataset

Atomic-motion annotation

  1. 01 Segment the motionUse robot movement and gripper changes to define physical motion segments.
  2. 02 Ground across viewsRead the scene through synchronized left, right, and wrist observations.
  3. 03 Describe & assessAssign atomic motions, task relevance, execution success, and task completion.
  4. 04 Check the annotationsReview the resulting labels with a checker before accepting the annotation.

Loading annotated demonstrations…

Execution-grounded GRPO

Execution-grounded rewards

With the WAM fixed, EG-GRPO trains the reasoner using rewards for motion appropriateness and execution success.

Propose motions→Execute with WAM→Evaluate rollouts→Update reasoner ↻

Reward definition

rtask · Is this the right next step?1 if the proposed motion is a suitable next step toward the task from the current state; 0 otherwise.

rexec · Did the robot execute it?1 if the rollout successfully completes the specified motion; 0 otherwise.

r = rtask × (0.5 + 0.5 × rexec)

Paper ablation · RoboLab-120, default instructions, three runs: supervised reasoner 36.7% → GRPO without execution reward 34.2% → EG-GRPO 39.2%.

Out-of-distribution benchmark

Atomic-WAM on RoboLab-120

✓ Officially reproduced with our released weights

The RoboLab organizers have reproduced Atomic-WAM using our released weights.

View official leaderboard ↗

Vague instructions

PolicySRScore
Atomic-WAM31.6%48.6
BiMind v0.130.2%44.9
VoLo29.5%45.4
Cosmos3-Nano-Policy20.6%33.2
Cosmos3-Edge-Policy15.4%—
π0.515.2%28.1
DreamZero14.9%27.0
π0-FAST9.2%16.8
GR00T N1.65.4%14.0
paligemma-binning3.1%8.6
π02.8%8.5

Default instructions

PolicySRScore
Lakeside51.0%65.3
FLUX 3 Action42.9%—
HiDream-O1-Embodied39.9%50.5
Atomic-WAM39.6%55.5
OASIS WAM39.0%53.7
Cosmos3-Nano-Policy36.8%51.9
Phoenix34.4%45.9
BiMind v0.133.3%47.2
VoLo28.2%44.1
π0.528.0%43.4
DreamZero25.7%39.8

RoboLab-120 · October 13, 2026 snapshot

Due to version differences, the official leaderboard computes scores slightly differently from our paper.

Real-world evaluation

Real-world demonstrations

We train on DROID and deploy on our Franka setup without further fine-tuning.

Our setup uses a RealSense D435 wrist camera instead of DROID’s ZED Mini, with different camera placements and viewpoints.

01 · Thin-object manipulation

Put the blue pens into the bowl.

02 · Sequential task execution

Wipe the spill, then put the red block into the cup.

03 · Color understanding

Put the yellow objects into the cup.

04 · Spatial understanding

Place the toy fox to the right of the bin.

05 · Long-horizon

Put all blocks in the right bin and all batteries in the left bowl.

Our current real-world setup uses synchronous inference. In the videos, pauses are sped up 8× and robot motion is sped up 2×.

Citation

@article{shi2026atomicwam,
  title={Atomic-WAM: Execution-Grounded Atomic-Motion Reasoning for World Action Models},
  author={Shi, Shijun and Liu, Zhe and Hou, Zhi and Chen, Yinan and Zhang, Tao and Hu, Kai and Liu, Yong and Zhang, Jiangning},
  journal={arXiv preprint arXiv:2610.20157},
  year={2026}
}