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arXiv · 2603.22213

SPA: A Simple but Tough-to-Beat Baseline for Knowledge Injection

Kexian Tang·Jiani Wang·Shaowen Wang·Kaifeng Lyu
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Abstract

While large language models (LLMs) are pretrained on massive amounts of data, their knowledge coverage remains incomplete in specialized, data-scarce domains, motivating extensive efforts to study synthetic data generation for knowledge injection. We propose SPA (Scaling Prompt-engineered Augmentation), a simple but tough-to-beat baseline that uses a small set of carefully designed prompts to generate large-scale synthetic data for knowledge injection. Through systematic comparisons, we find that SPA outperforms several strong baselines. Furthermore, we identify two key limitations of prior approaches: (1) while RL-based methods may improve the token efficiency of LLM-based data augmentation at small scale, they suffer from diversity collapse as data scales, leading to diminishing returns; and (2) while multi-stage prompting may outperform simple augmentation methods, their advantages can disappear after careful prompt tuning. Our results suggest that, for knowledge injection, careful prompt design combined with straightforward large-scale augmentation can be surprisingly effective, and we hope SPA can serve as a strong baseline for future studies in this area. Our code is available at https://github.com/Tangkexian/SPA.

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Kexian Tang, Jiani Wang, Shaowen Wang, Kaifeng Lyu. 2026-03-23. SPA: A Simple but Tough-to-Beat Baseline for Knowledge Injection. https://arxiv.org/abs/2603.22213

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