PACT-VLA: Speculative Action-Chunk Verification with Pre-Commit Observations

Key points

• By the time the new chunk is committed, the robot and scene have changed, so the chunk is conditioned on a stale observation and task success drops sharply as this inference delay grows.1
• We propose PACT-VLA, a training-free framework that generates candidates from the inference-start observation and selects one using this pre-commit observation.1
• At a four-step delay, PACT-VLA improves average success by 15.0 percentage points over RTC on Kinetix and by 5.2 points over single-candidate asynchronous execution with GR00T N1.7 on LIBERO, and it further improves existing delay-robust methods.1
• On three real-robot tasks, it raises average success from 60% to 82% over naive asynchronous execution with the same frozen $π{0.5}$ checkpoint.1

Sources (1)

• [1]PACT-VLA: Speculative Action-Chunk Verification with Pre-Commit Observations
  arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 20, 11:08 AM

  Vision-language-action (VLA) policies are commonly deployed with asynchronous inference in real-world settings, where the next action chunk is generated while the robot is still executing the previous one.

  By the time the new chunk is committed, the robot and scene have changed, so the chunk is conditioned on a stale observation and task success drops sharply as this inference delay grows.

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