Scaling Near-Optimal SFT-RL Annotation Budget Allocation from Small to Large LLMs

Jingtan Wang, Arun Verma, Xiaoqiang Lin, Zhengyuan Liu, Nancy F. Chen, Daniela Rus, Bryan Kian Hsiang Low


Abstract
How to divide a fixed annotation budget between supervised fine-tuning (SFT) and reinforcement learning (RL) during LLM post-training remains an open problem. Existing work characterizes only broad trends (e.g., SFT dominates in low-data regimes), lacks a principled allocation framework, and does not examine whether the optimal ratio transfers across model sizes. We frame this problem in terms of near-optimality: rather than seeking a single optimal SFT–RL ratio, we characterize the near-optimal region, the set of allocations within a specified tolerance of peak performance. Empirically, this region is wide even for small tolerances (2–10%), widens with model scale, and transfers reliably from small proxy models to large target models. This yields a practical strategy: small proxy-model experiments suffice to identify a transferable near-optimal region, eliminating the need for exhaustive large-scale search. Our results hold consistently across tasks, model families, and both preference-based off-policy and reward-supervision on-policy RL methods. We further analyze how the asymmetry in annotation costs between SFT and RL data shifts the near-optimal region.
Anthology ID:
2026.emnlp-main.2450
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:
55601–55630
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2450/
DOI:
Bibkey:
Cite (ACL):
Jingtan Wang, Arun Verma, Xiaoqiang Lin, Zhengyuan Liu, Nancy F. Chen, Daniela Rus, and Bryan Kian Hsiang Low. 2026. Scaling Near-Optimal SFT-RL Annotation Budget Allocation from Small to Large LLMs. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 55601–55630, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Scaling Near-Optimal SFT-RL Annotation Budget Allocation from Small to Large LLMs (Wang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2450.pdf