This model is a lightweight transformer encoder-decoder which takes inputs from a frozen Pi-05 VLA backbone. The encoder compresses the VLA final-layer prefix embeddings into a single RL token via a learned query. The decoder autoregressively reconstructs the original embeddings from only this token, forcing it to act as an information bottleneck. See Xu et al. (2026), Precise Manipulation with Efficient Online RL for the method.
