Semantic-level watermarking (SWM) improves robustness against text modifications by treating sentences as the basic unit. However, robustness to paragraph-level paraphrasing remains difficult because such attacks globally disrupt watermark signals by changing sentence order. In this work, we propose SAMark, a self-anchored watermarking framework that removes the dependency on sentence order by establishing a step-independent green region in semantic space. To improve detectability, we introduce a multi-channel hyperbolic scoring mechanism that amplifies watermark signals while suppressing noise from weakly aligned candidates. We further propose a diversity-aware filtering strategy that combines hard filtering with soft regularization, extending beyond simple n-gram repetition filters to address semantic redundancy. Experimental results show that SAMark achieves up to 90.2% TP@FP1% under typical paragraph-level paraphrasing attacks, outperforming the strongest prior baseline by more than 30% on average, while maintaining generation quality competitive with unwatermarked text and breaking the robustness-quality trade-off that limits prior methods.
@article{arxiv.2605.25796,
title = {SAMark: A Self-Anchored Text Watermarking with Paragraph-Level Paraphrase Robustness},
author = {Jiahao Huo and Wenjie Qu and Yibo Yan and Kening Zheng and Jiaheng Zhang and Xuming Hu and Philip S. Yu and Mingxun Zhou},
journal= {arXiv preprint arXiv:2605.25796},
year = {2026}
}