VISTA: A Versatile Interactive User Simulation Toolkit for Agent Evaluation

Yunan Lu; Ryan Shea; Yusen Zhang; Zhou Yu

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arXiv · 2606.11079

VISTA: A Versatile Interactive User Simulation Toolkit for Agent Evaluation

Yunan Lu·Ryan Shea·Yusen Zhang·Zhou Yu

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Abstract

Evaluation remains a critical bottleneck for interactive agent development. Existing evaluation methods often rely on static benchmarks, which fail to capture the dynamic, multi-step nature of agentic behavior and struggle to expose meaningful failure modes. While user-simulation-based evaluation offers a promising alternative, existing simulation frameworks suffer from two major limitations. First, they provide limited mechanisms for evaluating the quality and comprehensiveness of simulated interactions, making it difficult to assess whether a simulator sufficiently explores an agent's capabilities and failure modes. Second, most frameworks are restricted to either UI-only actions or API-only actions, limiting their ability to model the full range of realistic user behaviors. To address these limitations, we propose VISTA, a Versatile Interactive user Simulation Toolkit for Agent evaluation. Our toolkit includes a suite of six metrics for measuring the realism, capability coverage, and interaction effectiveness of simulated interactions. In addition, we develop a hybrid user simulator that integrates both UI-based interactions and API-based interactions, enabling more realistic and comprehensive evaluation across diverse interactive environments. We evaluate VISTA in e-commerce shopping and education customer service settings and demonstrate that it produces more realistic and comprehensive evaluations than existing methods.

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Yunan Lu, Ryan Shea, Yusen Zhang, Zhou Yu. 2026-06-09. VISTA: A Versatile Interactive User Simulation Toolkit for Agent Evaluation. https://arxiv.org/abs/2606.11079

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