We present a scalable pipeline for automatically generating high-quality training data for web agents. In particular, a major challenge in identifying high-quality training instances is trajectory evaluation - quantifying how much progress was made towards task completion. We introduce a novel constraint-based evaluation framework that provides fine-grained assessment of progress towards task completion. This enables us to leverage partially successful trajectories, which significantly expands the amount of usable training data. We evaluate our method on a new benchmark we propose called BookingArena, which consists of complex booking tasks across 20 popular websites, and demonstrate that our distilled student model outperforms open-source approaches and matches or exceeds commercial systems, while being a significantly smaller model. Our work addresses the challenge of efficiently creating diverse, realistic web interaction datasets and provides a systematic evaluation methodology for complex structured web tasks.
@article{arxiv.2602.12544,
title = {Scaling Web Agent Training through Automatic Data Generation and Fine-grained Evaluation},
author = {Lajanugen Logeswaran and Jaekyeom Kim and Sungryull Sohn and Creighton Glasscock and Honglak Lee},
journal= {arXiv preprint arXiv:2602.12544},
year = {2026}
}