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arxiv 2506.01953 v1 pith:N474HSTI submitted 2025-06-02 cs.RO

Fast-in-Slow: A Dual-System Foundation Model Unifying Fast Manipulation within Slow Reasoning

classification cs.RO
keywords systemexecutionmodelreasoningactiondual-systemfast-in-slowfoundation
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Generalized policy and execution efficiency constitute the two critical challenges in robotic manipulation. While recent foundation policies benefit from the common-sense reasoning capabilities of internet-scale pretrained vision-language models (VLMs), they often suffer from low execution frequency. To mitigate this dilemma, dual-system approaches, inspired by Kahneman's theory, have been proposed to leverage a VLM-based System 2 model handling high-level reasoning and a separate System 1 action model ensuring real-time control. However, existing designs maintain both systems as separate models, limiting System 1 from fully leveraging the rich pretrained knowledge from the VLM-based System 2. In this work, we propose Fast-in-Slow (FiS), a unified dual-system vision-language-action (VLA) model that embeds the System 1 execution module within the VLM-based System 2 by partially sharing parameters. This innovative paradigm not only enables high-frequency execution in System 1 but also facilitates coordination between the reasoning and execution components within a single foundation model of System 2. Given their fundamentally distinct roles within FiS-VLA, we design the two systems to incorporate heterogeneous modality inputs alongside asynchronous operating frequencies, enabling both fast and precise manipulation. To enable coordination between the two systems, a dual-aware co-training strategy is proposed that equips System 1 with action generation capabilities while preserving System 2's contextual reasoning representation. For evaluation, FiS-VLA outperforms previous state-of-the-art methods by 8% in simulation and 11% in real-world tasks in terms of average success rate, while achieving a 117.7 Hz control frequency with action chunk set to eight. Project web page: fast-in-slow.github.io.

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Cited by 22 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Embodied.cpp: A Portable Inference Runtime of Embodied AI Models on Heterogeneous Robots

    cs.RO 2026-07 unverdicted novelty 7.0

    Embodied.cpp introduces a portable C++ inference runtime with modular layers for deploying VLA and WAM models on heterogeneous robots, reporting 100% and 91% task success on two models plus memory reduction on a WAM b...

  2. AT-VLA: Adaptive Tactile Injection for Enhanced Feedback Reaction in Vision-Language-Action Models

    cs.RO 2026-05 unverdicted novelty 7.0

    AT-VLA proposes adaptive tactile injection and a dual-stream tactile reaction mechanism to enhance VLA models for contact-rich robotic manipulation with real-time responses.

  3. From Fixed to Free Cameras: Calibration-Free View-Robust Vision-Language-Action Model

    cs.CV 2026-07 conditional novelty 6.0

    CamVLA decouples robot actions into camera-frame movements and a learned hand-eye pose, enabling calibration-free manipulation under unseen camera viewpoints from a single RGB image.

  4. VLA-Corrector: Lightweight Detect-and-Correct Inference for Adaptive Action Horizon

    cs.RO 2026-07 unverdicted novelty 6.0

    VLA-Corrector adds a detect-and-correct inference layer using a latent vision monitor and online gradient guidance to enable adaptive action horizons in chunked VLA policies.

  5. UniTacVLA: Unified Tactile Understanding and Prediction in Vision Language Action Models

    cs.RO 2026-06 unverdicted novelty 6.0

    UniTacVLA builds a state-aware and dynamics-aware tactile prior via unified latent space, tactile chain-of-thought, and mixed real/predicted feedback controller to boost dexterous manipulation performance.

  6. UniFS: Unified Fast-to-Slow Hierarchical Architecture for Vision-Language-Action Models

    cs.RO 2026-06 unverdicted novelty 6.0

    UniFS achieves 98.3% success on LIBERO with 2.1x lower latency than prior fast-slow VLA models by stratifying VLM layer update frequencies, inverting latent interactions, and applying multi-level supervision.

  7. Vesta: A Generalist Embodied Reasoning Model

    cs.RO 2026-06 unverdicted novelty 6.0

    Vesta is a unified embodied generalist model that outperforms specialist baselines by over 20% on average and improves real-world robotic task success by over 35%.

  8. T-Rex: Tactile-Reactive Dexterous Manipulation

    cs.RO 2026-06 unverdicted novelty 6.0

    T-Rex introduces a large tactile dataset and MoT architecture that achieves over 30% higher success rates than baselines on 12 tasks requiring force control and deformable object handling.

  9. HarmoWAM: Harmonizing Generalizable and Precise Manipulation via Adaptive World Action Models

    cs.RO 2026-05 unverdicted novelty 6.0

    HarmoWAM unifies predictive and reactive control in world action models via an adaptive gating mechanism to deliver improved zero-shot generalization and precision in robotic manipulation.

  10. AT-VLA: Adaptive Tactile Injection for Enhanced Feedback Reaction in Vision-Language-Action Models

    cs.RO 2026-05 unverdicted novelty 6.0

    AT-VLA introduces adaptive tactile injection and a dual-stream tactile reaction mechanism to integrate real-time tactile feedback into pretrained VLA models for contact-rich robotic manipulation.

  11. LaST-R1: Reinforcing Robotic Manipulation via Adaptive Physical Latent Reasoning

    cs.RO 2026-04 unverdicted novelty 6.0

    LaST-R1 introduces a RL post-training method called LAPO that optimizes latent Chain-of-Thought reasoning in vision-language-action models, yielding 99.9% success on LIBERO and up to 22.5% real-world gains.

  12. LaST-R1: Reinforcing Robotic Manipulation via Adaptive Physical Latent Reasoning

    cs.RO 2026-04 unverdicted novelty 6.0

    LaST-R1 reaches 99.8% average success on the LIBERO benchmark using one-shot warm-up plus LAPO reinforcement learning on latent physical reasoning, with up to 44% real-world gains on complex single- and dual-arm tasks.

  13. Adaptive Action Chunking at Inference-time for Vision-Language-Action Models

    cs.RO 2026-04 unverdicted novelty 6.0

    Adaptive Action Chunking uses action entropy to dynamically adjust chunk sizes in VLA models, improving performance on simulated and real robotic manipulation tasks.

  14. TwinRL: Digital Twin-Driven Reinforcement Learning for Real-World Robotic Manipulation

    cs.RO 2026-02 unverdicted novelty 6.0

    TwinRL expands RL exploration via digital twin reconstruction and twin RL warm-up to guide real-world learning, reaching near-100% success with 20 minutes of on-robot time across four tasks.

  15. IGen: Scalable Data Generation for Robot Learning from Open-World Images

    cs.RO 2025-12 unverdicted novelty 6.0

    IGen generates realistic visuomotor training data including actions and temporally coherent visuals from unstructured open-world images via 3D reconstruction and VLM reasoning.

  16. Lift3D-VLA: Lifting VLA Models to 3D Geometry and Dynamics-Aware Manipulation

    cs.RO 2026-07 conditional novelty 5.0

    Lift3D-VLA integrates 3D point cloud encoding and temporal action modeling into Vision-Language-Action models, achieving higher success rates on simulated and real-world robotic manipulation tasks.

  17. Position: Vision-Language-Action Models Cannot Be Verified to Perform Physical Reasoning

    cs.RO 2026-06 conditional novelty 5.0

    VLA benchmark success rates cannot distinguish semantic generalization from physical reasoning due to an identifiability gap in current evaluation protocols.

  18. LaST-HD: Learning Latent Physical Reasoning from Scalable Human Data for Robot Manipulation

    cs.RO 2026-06 unverdicted novelty 5.0

    LaST-HD creates a shared latent dynamics space via a world model to transfer physical reasoning from scalable human-hand demonstrations to robots, achieving over 90% accuracy with 20 minutes of new data after mixed training.

  19. Slow Brain, Fast Planner: Latency-Resilient VLM-Augmented Urban Navigation

    cs.RO 2026-06 unverdicted novelty 5.0

    A training-free fusion layer enables stale VLM selections to improve a real-time planner's trajectory scoring for urban sidewalk navigation, yielding 30% ADE reduction in challenging scenarios.

  20. From Abstraction to Instantiation: Learning Behavioral Representation for Vision-Language-Action Model

    cs.CV 2026-05 unverdicted novelty 5.0

    BehaviorVLA introduces a symmetric encoder-decoder architecture with causal Mamba and phase conditioning to learn unified long-horizon behavioral representations for improved generalization in VLA models.

  21. Large VLM-based Vision-Language-Action Models for Robotic Manipulation: A Survey

    cs.RO 2025-08 unverdicted novelty 5.0

    This survey organizes large VLM-based VLA models for robotic manipulation into monolithic and hierarchical paradigms, reviews their integrations and datasets, and outlines future directions.

  22. From Abstraction to Instantiation: Learning Behavioral Representation for Vision-Language-Action Model

    cs.CV 2026-05 unverdicted novelty 4.0

    BehaviorVLA learns long-horizon behavioral representations via causal Mamba encoder and phase-conditioned decoder, reporting SOTA results of 58% on RoboTwin 2.0, 98% on LIBERO, 4.36 on CALVIN, and matching OpenVLA-OFT...