LEASH: training-free uncertainty framework cuts computer-use agent cost via weak-to-strong escalation

Qingni Wang · hf · 2026-10-17

LEASH, a training-free framework from Similar and UW–Madison, tackles the cost problem of computer-use agents where running a frontier model at every step is expensive but a small open-weight model alone often fails.

It uses weak-to-strong escalation: a weak agent acts by default and hands control to a strong one only when needed, with continued oversight afterward. Since the strong agent is a black-box API, LEASH uses latent uncertainty as fuel for three layers: (1) task-level uncertainty for early routing, (2) step-level uncertainty for runtime escalation, and (3) a shadow observer monitoring the strong black-box agent after handoff. Uncertainty is estimated by comparing the weak model's hidden states against those from its past successful and failed trajectories.

Result: reduced cost while maintaining high success rates.

Related event: LEASH: Training-Free Framework Cuts Computer-Use Agent Costs by 19.2%(3 posts)→

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