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Verifier-free Test-Time Sampling for Vision-Language-Action Models

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arxiv 2510.05681 v2 pith:V6CLMZYC submitted 2025-10-07 cs.RO cs.AIcs.LG

Verifier-free Test-Time Sampling for Vision-Language-Action Models

classification cs.RO cs.AIcs.LG
keywords distributionactionreferenceconditionsmodelstest-timetrainingadditional
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Vision-Language-Action models (VLAs) have demonstrated remarkable performance in robot control. However, they remain fundamentally limited in tasks that require high precision due to their single-inference paradigm. While test-time scaling approaches using external verifiers have shown promise, they require additional training and fail to generalize to unseen conditions. We propose Masking Distribution Guided Selection (MG-Select), a novel test-time scaling framework for VLAs that leverages the model's internal properties without requiring additional training or external modules. Our approach utilizes KL divergence from a reference action token distribution as a confidence metric for selecting the optimal action from multiple candidates. We introduce a reference distribution generated by the same VLA but with randomly masked states and language conditions as inputs, providing action uncertainty while remaining aligned with the target task distribution. Additionally, we propose a joint training strategy that enables the model to learn both conditional and unconditional distributions by applying dropout to state and language conditions, thereby further improving the quality of the reference distribution. Our experiments demonstrate that MG-Select provides a reliable reference for action selection through task-relevant condition masking and consistently improves base models across diverse simulation and real-world benchmarks.

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Forward citations

Cited by 10 Pith papers

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

  1. BOKBO (Best of K Bad Options): Calibrated Abstention for VLA Policies

    cs.LG 2026-05 unverdicted novelty 7.0

    BOKBO is the first conformal abstention method for K-sample VLA policies that supplies finite-sample distribution-free guarantees on executed violation rates, with global and Mondrian per-task variants.

  2. E-TTS: A New Embodied Test-Time Scaling Framework for Robotic Manipulation

    cs.RO 2026-06 unverdicted novelty 6.0

    E-TTS introduces a plug-and-play test-time scaling method for embodied tasks that unifies reasoning-action sampling with history buffers and closed-loop refinement to improve performance on manipulation benchmarks.

  3. Robot Critics that Sweat the Small Stuff

    cs.RO 2026-06 unverdicted novelty 6.0

    Fine-tuning VLMs with pairwise progress supervision from policy rollouts improves fine-grained failure detection and boosts robot manipulation success by 11% real-world and 5.9% in simulation.

  4. VeriSpace: Spatially Grounded Action Verification for Vision-Language-Action Models

    cs.RO 2026-06 unverdicted novelty 6.0

    VeriSpace is a 3D-aware action verifier that improves test-time action selection in VLA models by encoding scenes with visual and geometric information and reasoning over spatial relations and goal progress.

  5. Retrieve-then-Steer: Online Success Memory for Test-Time Adaptation of Generative VLAs

    cs.RO 2026-05 unverdicted novelty 6.0

    Retrieve-then-steer stores successful observation-action segments in memory, retrieves relevant chunks, filters them, and uses an elite prior with confidence-adaptive guidance to steer a flow-matching action sampler f...

  6. Retrieve-then-Steer: Online Success Memory for Test-Time Adaptation of Generative VLAs

    cs.RO 2026-05 unverdicted novelty 6.0

    A retrieve-then-steer method stores successful robot actions in memory and uses them to steer a frozen VLA's flow-matching sampler for better test-time reliability without parameter updates.

  7. Test-Time Perturbation Learning with Delayed Feedback for Vision-Language-Action Models

    cs.CV 2026-04 unverdicted novelty 6.0

    PDF improves VLA success rates on LIBERO and Atari by applying test-time perturbation learning with delayed feedback to correct trajectory overfitting and overconfidence.

  8. Real-Time Execution with Autoregressive Policies

    cs.RO 2026-06 unverdicted novelty 5.0

    Autoregressive VLA policies achieve real-time execution via tokenization horizon adjustment and constrained decoding, outperforming flow-matching policies in speed and performance across simulated and real environments.

  9. Test-Time Scaling in Multimodal Foundation Models: A Comprehensive Survey of Generation and Reasoning

    cs.CV 2026-06 unverdicted novelty 5.0

    A survey of test-time scaling for multimodal foundation models that introduces a three-way taxonomy of sampling, feedback, and search approaches along with applications and benchmarks.

  10. Is the Future Compatible? Diagnosing Dynamic Consistency in World Action Models

    cs.RO 2026-05 unverdicted novelty 5.0

    Action-state consistency in World Action Models distinguishes successful from failed imagined futures and supports value-free selection of better rollouts via consensus among predictions.