Vision-Language-Action (VLA) models, which combine vision, language, and action capabilities, have become foundational for robotic manipulation. However, their multi-billion parameter architectures demand massive computational resources for fine-tuning and real-time inference. A new study from researchers at multiple institutions reveals that these models contain significant layer-wise redundancy, enabling a training-free compression that reduces model depth by up to 50% while maintaining or improving performance.
The paper, titled "Finetuning Vision-Language-Action Models Requires Fewer Layers Than You Think" and authored by Gia-Binh Ho, Trong-Bao Ha, Thien-Loc Vo, Khoa Møller, Philip Lund, Quang T Dinh, Long Dam, Tuan Duong, Vu Luu, Tung M Le, Trung Tran Nguyen, Minh An Thai, Ngan Sonntag, Daniel Zou, James Peters, Jan Duy M H, and Vien Ngo Anh, introduces a structural compression pipeline that is entirely training-free. According to the paper, existing methods require loading full-scale models to learn optimized token reductions or dynamic layer selectors, but the new approach bypasses this need entirely.
A Single Forward Pass to Identify Redundancy
The core innovation is the use of Centered Kernel Alignment (CKA) to identify redundant layer features with just a single forward pass. The researchers found that models like pi_0 and GR00T-N1.5 exhibit severe layer-wise representational redundancy despite being trained on diverse physical trajectories. By removing twin layers, the pipeline permanently compresses model depth by up to 50% across both the VLM backbone and the continuous control policy head.
Dual Acceleration Benefits
Downstream fine-tuning of the streamlined architecture yields a dual acceleration benefit: a 40-50% reduction in training time and up to 30% faster real-time inference, according to the study. Importantly, the compressed model matches or exceeds the performance of the full-scale base model, challenging the assumption that more layers are always better for VLA models.
Validation Across Diverse Benchmarks
The method was comprehensively validated across three simulation benchmarks (LIBERO, RoboCasa, SimplerEnv) and 10 diverse real-world manipulation tasks across 4 unique robotic embodiments. The results consistently showed that advanced VLAs require significantly fewer layers than previously assumed, offering a highly compute-efficient paradigm for scalable robot learning.
Implications for Deployment
The training-free nature of the compression is particularly valuable for enterprise settings where computational budgets are constrained. By eliminating the need to load full-scale models for optimization, the pipeline reduces infrastructure costs and simplifies deployment of VLA models in real-time systems. For logistics and supply chain applications involving robotic manipulation, this could accelerate the adoption of AI-driven automation without additional hardware investment.
The paper is available on arXiv under the identifier 2606.20246. The authors have not announced plans to release the code or pre-compressed models, but the method is described in sufficient detail for other teams to replicate the results.