cs.AIOct 23, 2026

Watermarking Diffusion Language Models with Learned Foresight and Balanced Bands

Authors: Hyojun Kim, Hyeseon An, Yo-Sub Han

Organizations: Yonsei University, Seoul, Republic of Korea

Abstract

Green-red watermarks favor tokens from a green list that a secret key derives from the preceding tokens. Diffusion language models, however, often choose a token before its preceding tokens, and the token later shapes its neighbors' green lists. Prior work therefore tilts each choice to raise the expected number of green tokens at its own and its neighbors' positions. Building on this objective, we first learn two components that prior work keeps fixed: vocabulary bands that serve as green lists, separate competing candidates and keep the null distribution exact, and a foresight predictor that estimates how each candidate shifts its neighbors' predictions. Second, we count green tokens as the detector does, once per distinct context-token pair, so repetition earns nothing. On WaterBench with LLaDA-8B-Instruct, each learned component raises the z-score at equal distortion, and their gains are nearly additive. With a strong watermark, ours detects at least 96% of responses at a 1% false-positive rate while matching the LLM-judge score of unwatermarked text. Ours also detects more responses on Dream and as many or more on code and question answering without a significant loss in task accuracy.

Figures & tables

Appendix figures & tables27 assets

Supplementary material from the paper’s appendix.

Appendix

Explore similar work

CardsList
  1. Watermarking Diffusion Language Models

    Sep 29, 2025Thibaud Gloaguen, Robin Staab, Nikola Jovanović +1Diffusion Model WatermarkingLLM Watermarking

  2. Chainwash: Multi-Step Rewriting Attacks on Diffusion Language Model Watermarks

    May 6, 2026Mohd Ruhul Ameen, Akif Islam, Nadim Mahmud +1Diffusion Model WatermarkingWatermark Removal