Detect, Remask, Repair: Diffusion Editing for Faithful Summarization of Evolving Contexts

Hao Zou, Zachary Horvitz, Chandhru Karthick, Zhou Yu, Kathleen McKeown


Abstract
Summaries of real-world events can become outdated as contexts evolve and new information arrives. A common response is to generate a new summary from the updated context, but full regeneration discards the previous draft, can obscure what changed, and may be unnecessary when only a few claims are unsupported. We study localized faithfulness repair: updating outdated spans in an existing summary while preserving supported content. We propose Detect-Remask-Repair, a diffusion-based framework that identifies, remasks, and repairs outdated regions with masked diffusion language models. To evaluate evolving-context summarization, we introduce StreamSum, a benchmark of synthetic event timelines. Experiments on DialogSum and StreamSum show that localized diffusion repair provides a controllable alternative to full rewriting: faithfulness-steered repair improves early drafts, one-step repair reduces repair cost to under half a second, with the framework enabling faithfulness–speed–preservation tradeoffs across datasets. We also find that the framework can provide a post-hoc correction step that improves faithfulness for autoregressive systems.
Anthology ID:
2026.emnlp-main.1876
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:
42763–42784
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1876/
DOI:
Bibkey:
Cite (ACL):
Hao Zou, Zachary Horvitz, Chandhru Karthick, Zhou Yu, and Kathleen McKeown. 2026. Detect, Remask, Repair: Diffusion Editing for Faithful Summarization of Evolving Contexts. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 42763–42784, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Detect, Remask, Repair: Diffusion Editing for Faithful Summarization of Evolving Contexts (Zou et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1876.pdf