TAP: Policy Interfaces for Diffusion Language Models

Preeti, Ankita Kushwaha, Kiran Ravish, Pawan Kumar


Abstract
Diffusion language models denoise a masked canvas, making them a natural setting for selective generation decisions such as answering, waiting, clarifying, or refusing. We introduce TAP-DiLM, which adds a typed policy variable to masked diffusion LMs, and study how this policy should be attached to the denoising process. Across BERT-base, MDLM-OWT, LLaDA-8B, and Dream-7B, we compare shared-vocabulary slots, dedicated slot heads, and CLS-based external heads. The results reveal a clear interface-backbone interaction: dedicated heads provide robust policy learning across scales, while shared-vocabulary heads can be effective when the LM-head geometry is favorable. A simple LM-head sharpness probe predicts when shared-head policy internalization is reliable, giving a practical diagnostic for interface selection. Causal clamp and slot-injection tests show that dedicated policy slots can influence body denoising through feedback, especially at 8B scale. Safety-refusal experiments further show that TAP-DiLM supports competitive typed refusal behavior when trained with diverse unsafe prompts.
Anthology ID:
2026.emnlp-main.2623
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:
59616–59657
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2623/
DOI:
Bibkey:
Cite (ACL):
Preeti, Ankita Kushwaha, Kiran Ravish, and Pawan Kumar. 2026. TAP: Policy Interfaces for Diffusion Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 59616–59657, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
TAP: Policy Interfaces for Diffusion Language Models (Preeti et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2623.pdf