FullFront: Benchmarking MLLMs Across the Full Front-End Engineering Workflow

Haoyu Sun, Huichen Will Wang, Jiawei Gu, Linjie Li, Yu Cheng


Abstract
We present FullFront, a workflow-grounded benchmark for Multimodal Large Language Models (MLLMs) across the front-end engineering pipeline—conceptualization, comprehension, and implementation—rather than evaluating any single stage in isolation. FullFront contributes along three axes: (i) a unified task formulation covering Webpage Design, Webpage Perception QA, and Webpage Code Generation (8 subtasks, 2,700 items); (ii) a controlled two-stage data construction pipeline that converts real-world webpages into standardized HTML with a 15-category copyright-safe image substitution scheme; and (iii) a reliability-oriented evaluation framework whose Code Score and Gemini Visual Score are validated against human judgment, cross-judge agreement, pipeline bias, and sensitivity stress tests. Across 12 MLLMs we observe a stable closed-source top tier, a Perception–Implementation Gap with distinct failure modes (Coding Bottleneck” for open-source, Grounding Failure” for proprietary), and heterogeneous open/closed capability profiles—patterns that isolated benchmarks cannot expose.
Anthology ID:
2026.emnlp-main.1358
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:
30948–30994
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1358/
DOI:
Bibkey:
Cite (ACL):
Haoyu Sun, Huichen Will Wang, Jiawei Gu, Linjie Li, and Yu Cheng. 2026. FullFront: Benchmarking MLLMs Across the Full Front-End Engineering Workflow. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 30948–30994, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
FullFront: Benchmarking MLLMs Across the Full Front-End Engineering Workflow (Sun et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1358.pdf