Stipe Frković, Metod Jazbec, Dan Zhang, Christian A. Naesseth, Ilija Bogunovic, Eric Nalisnick
Masked diffusion language models (dLLMs) have recently emerged as a competitive alternative to autoregressive language models, with the promise of faster inference via parallel token generation. A notable limitation of the masked formulation, however, is that once a token has been unmasked it can no longer be revised, leaving dLLMs vulnerable to early sampling mistakes. Confidence-based remasking methods aim to address this in a training-free manner by revising low-confidence tokens, with encouraging early results. In this work, we compare the accuracy-compute Pareto frontiers of three such methods (WINO, Saber, and COVER) to those of confidence-based unmasking alone (Fast-dLLM). We find that under greedy decoding, all three perform on par with Fast-dLLM at commonly used shorter block lengths; gains of remasking appear only at longer block lengths, where confidence-based unmasking is known to degrade. Under stochastic decoding, WINO reduces generation diversity beyond that of unmasking alone, while it helps recover from errors introduced by learned Bernoulli unmasking policies. Our results show that the benefits of confidence-based remasking are highly setting-dependent, underscoring the need for more comprehensive evaluation. Finally, our analyses point to the dLLM, not the remasking rule, as the bottleneck, suggesting that effective remasking may require changes to training, not only to inference.
Continuous diffusion language models involve two coupled design choices: how to corrupt continuous token representations and how to invert that corruption at generation time. Recent work has explored language generation on the unit sphere through geodesic and von Mises--Fisher (vMF) paths, raising the question of which forward process to use on this geometry and how much that choice matters relative to inference. We introduce Spherical Brownian Diffusion, using Brownian motion as the canonical isotropic diffusion on the sphere. Its heat semigroup provides a principled forward process, an additive dimension-free noise clock, and an exact ancestral bridge, while a clean-token posterior learned with cross-entropy supports multiple samplers. To separate corruption from inference, we derive high-dimensional approximation rates between Brownian and moment-matched vMF corruption and use this relationship for controlled substitutions. On Sudoku, Brownian and moment-matched vMF give nearly identical results across four samplers and five budgets under otherwise identical settings. In contrast, with the corruption process fixed, sampler choice produces a 25.0-point spread at a sampler budget of 180 calls. Using the ancestral bridge, we split this gain into a memory effect from re-noising the state, present on Sudoku and GSM8K, and a token-selection effect on GSM8K and largest at small budgets. Across reasoning tasks, categorical refinement improves performance, whereas unconditional text generation benefits from stochastic updates that preserve diversity.