InfiniteWeb: Scalable Web Environment Synthesis for GUI Agent Training
Paper · 2026 · Ziyun Zhang, Zezhou Wang, Xiaoyi Zhang et al.
Summary
Reinforcement-learning training of GUI agents needs many interactive environments. Existing benchmarks such as WebArena or OSWorld are built by hand and cover only a limited number of applications. InfiniteWeb addresses this by automatically synthesizing complete multi-page websites together with tasks and programmatic evaluators.
The pipeline starts from a short website seed and a reference design image, both mined from Common Crawl. It first produces tasks and derives from them a shared specification of data models and interfaces, so that all pages remain mutually compatible. The backend is then built with task-centric test-driven development (TCTDD), iterating until task-relevant tests succeed. In parallel, the frontend is generated to follow visual traits extracted from the design image. The evaluators monitor task-related variables, which yields dense rewards.
The system outperforms commercial coding agents on WebGen-Bench. Agents trained in its environments improve on OSWorld, Online-Mind2Web and MobileWorld. This makes cheap, scalable environment generation a practical alternative to manual benchmark construction.
Key points
- Downstream gains from training on generated sites:
- +6.9% on OSWorld, +5.7% on Online-Mind2Web and +3.9% on MobileWorld.
- Multi-application OSWorld tasks rose from 3.8% to 9.7%.
- WebGen-Bench results:
- The full system with a GPT-5 backbone scores 85.6.
- With GPT-4.1 it scores 77.4, still above Claude-Code using GPT-5 (75.8).
- Removing TCTDD costs 5.0 points (80.6, roughly Codex level).
- Dense vs. binary reward: UI-TARS-1.5-7B was run on 4,000 tasks with 4 trajectories each. Dense reward gave 767 tasks usable for GRPO, versus 174 with binary reward (4.4×).
- Difficulty and discriminability of the environments:
- Agents score much lower than on OSWorld: UI-TARS-1.5-7B 7.4% vs 24.5%, Agent S2 14.1% vs 27.3%.
- The gap between the two agents is wider (6.7 vs 2.8 points).
- Generation cost and availability:
- About $1.93 per website (≈0.36M input / 0.34M output tokens), with a median of about 20 minutes per site.
- 600 sites were produced in about 125 minutes in parallel.
- Code and websites are released at github.com/microsoft/FIVE-UI-Evol.
Fields, topics and concepts
📚 Shelves 3The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksInformation Systems · 1,437 works
Cite
Cite as Ziyun Zhang, Zezhou Wang, Xiaoyi Zhang, Zongyu Guo, Jiahao Li, Bin Li and Yan Lu. 2026. InfiniteWeb: Scalable Web Environment Synthesis for GUI Agent Training. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers).
@inproceedings{zhang2026infiniteweb,
title = {{InfiniteWeb: Scalable Web Environment Synthesis for GUI Agent Training}},
author = {Ziyun Zhang, Zezhou Wang, Xiaoyi Zhang, Zongyu Guo, Jiahao Li, Bin Li and Yan Lu},
booktitle = {Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)},
year = {2026},
doi = {10.18653/v1/2026.acl-long.1313},
url = {https://doi.org/10.18653/v1/2026.acl-long.1313}
}References
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