arXiv Machine Learning By Guy Tennenholtz, Ofer Meshi, Amir Globerson, Uri Shalit, Jihwan Jeong, Craig Boutilier

Controllable User Simulation

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The paper formalizes controllable user simulation as a causal inference problem, showing that standard supervised fine‑tuning on post‑hoc trajectory labels introduces a look‑ahead bias that breaks causal consistency. This bias leads to a phenomenon called controllability collapse, where evaluation metric variance explodes under policy shift. The authors propose theoretical conditions for accurate simulation and practical training mitigations—such as a priori controls, step‑wise dynamic controls, and direct policy‑conditioned learning—to eliminate look‑ahead bias, preserve natural variance, and achieve robust zero‑shot generalization to unseen agent behaviors.

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