One Forward Beats Two: InnerZoom for Accurate and Efficient GUI Grounding

Chen Liu, Ling Chen, Hanzhang Zhou, Liangyu Chen, Chenglin Cai, Xin Yu, Steven Hoi, Yue Wang


Abstract
MLLM-based GUI grounding methods commonly formulate target localization as autoregressive coordinate generation, enabling models to leverage strong instruction following and semantic understanding. However, by casting localization as coordinate-token prediction, these methods rely on implicit decoding to convert region-level target evidence into precise click coordinates, making point-level spatial alignment unreliable. Through diagnostic analysis, we find that intermediate decoder layers already exhibit target-region awareness, yet such region-level evidence fails to guide final point-level decisions. To address this, we propose InnerZoom, a single-forward cross-layer evidence bridging framework that refines target evidence inside the model during decoding, avoiding extra inferences required by Zoom-In. InnerZoom reframes coordinate decoding as an evidence-preserving process by identifying target-related cues within the original forward pass, refining them across decoder layers, and reinjecting the refined evidence into coordinate prediction. Extensive experiments show that InnerZoom-4B achieves state-of-the-art performance on all six mainstream GUI grounding benchmarks, outperforming the second-best result by 4.1 points on OSWorld-G.Under the 4B setting, InnerZoom improves the same SFT+RL baseline by 5.3 points on average and outperforms two-pass Zoom-In by 1.3 points on average, while reducing measured GPU inference latency by 44% and estimated TFLOPs by 29%. Code and models will be at https://github.com/YenanLiu/InnerZoom.
Anthology ID:
2026.emnlp-main.843
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
19560–19581
Language:
URL:
https://aclanthology.org/2026.emnlp-main.843/
DOI:
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Cite (ACL):
Chen Liu, Ling Chen, Hanzhang Zhou, Liangyu Chen, Chenglin Cai, Xin Yu, Steven Hoi, and Yue Wang. 2026. One Forward Beats Two: InnerZoom for Accurate and Efficient GUI Grounding. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 19560–19581, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
One Forward Beats Two: InnerZoom for Accurate and Efficient GUI Grounding (Liu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.843.pdf