Learnability-Informed Fine-Tuning of Diffusion Language Models
To improve reasoning in diffusion language models (DLMs), researchers propose LIFT, a fine-tuning algorithm that adapts to token learnability across diffusion steps, outperforming baselines on six benchmarks with up to 3x relative gains on AIME'24 and AIME'25.
Article intelligence
Key points
- Standard SFT overlooks learnability, potentially harming DLM performance.
- LIFT learns easy tokens when masked and hard tokens when context is available.
- Achieves up to 3x relative improvement on AIME'24 and AIME'25.
Why it matters
This matters because standard SFT overlooks learnability, potentially harming DLM performance.
Technical impact
May affect model selection, inference cost, product capability, and evaluation benchmarks.
[2605.22939] Learnability-Informed Fine-Tuning of Diffusion Language Models
[Submitted on 21 May 2026]
Title:Learnability-Informed Fine-Tuning of Diffusion Language Models
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Abstract:We aim to improve the reasoning capabilities of diffusion language models (DLMs). While SFT is a popular post-training recipe for autoregressive models, its use in DLMs faces challenges and can even hurt performance, though the underlying causes remain understudied. Our analysis reveals that vanilla SFT overlooks learnability, namely what and when tokens are learned. Specifically, rare tokens are difficult to learn when most of the input is masked, whereas it is straightforward and thus of little value to learn common tokens when most of the input is unmasked. Motivated by our analysis, we propose LIFT, an efficient SFT-based post-training algorithm for DLMs. LIFT learns easy tokens when most of the input is masked and hard tokens when more context is available, thus aligning the training with the information available at different diffusion time steps. Our results show that LIFT outperforms existing SFT baselines across six reasoning benchmarks, achieving up to a 3x relative gain on AIME'24 and AIME'25. Our code is publicly available at this https URL.
Subjects:
Computation and Language (cs.CL); Machine Learning (cs.LG)
Cite as: arXiv:2605.22939 [cs.CL]
(or arXiv:2605.22939v1 [cs.CL] for this version)
https://doi.org/10.48550/arXiv.2605.22939
arXiv-issued DOI via DataCite (pending registration)
Submission history
From: Shubham Parashar [view email] [v1] Thu, 21 May 2026 18:16:17 UTC (3,786 KB)
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