Vision-language-action robots can be monitored with probes of their own activations, and beat the external-supervisor baseline
AspireAI community · Carnegie Mellon University and Cornell University (arXiv)
Vision-language-action models fail suddenly - a deadlocked gripper, a misheard instruction - and the usual runtime monitor is another foundation model watching the policy, which adds both complexity and inference cost exactly when a robot is unsupervised. Progress Probes asks whether the policy's own internals already contain the signal, training linear probes on demonstration activations to estimate how far the task has progressed and flagging executions that fall off that track. On the open-source pi-0.5 policy across simulated and real manipulation tasks, the probes matched or beat VLM-based monitors at detecting task failure, and they also beat approaches that require failure data for training, which is the expensive part of building a monitor. The limitation is scope: the results are on one open policy and manipulation tasks, so the paper shows the signal exists rather than that every robot policy exposes it.
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