CROP: Token-Efficient Reasoning in Large Language Models via Regularized Prompt Optimization

Deep Shah, Sanket Badhe, Nehal Kathrotia, Priyanka Tiwari


Abstract
Large Language Models utilizing reasoning techniques improve task performance but incur significant latency and token costs due to verbose generation. Existing automatic prompt optimization(APO) frameworks target task accuracy exclusively at the expense of generating long reasoning traces. We propose Cost-Regularized Optimization of Prompts (CROP), an APO method that introduces regularization on response length by generating textual feedback in addition to standard accuracy feedback. This forces the optimization process to produce prompts that elicit concise responses containing only critical information and reasoning. We evaluate our approach on complex reasoning datasets, specifically GSM8K, LogiQA and BIG-Bench Hard. We achieved an average 68% reduction in token consumption across diverse reasoning benchmarks (and up to 80.6% on algorithmic tasks) while maintaining competitive accuracy, seeing only a nominal decline in performance. This presents a pragmatic solution for deploying token-efficient and cost-effective agentic AI systems in production pipelines.
Anthology ID:
2026.aacl-long.45
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
934–951
Language:
URL:
https://aclanthology.org/2026.aacl-long.45/
DOI:
Bibkey:
Cite (ACL):
Deep Shah, Sanket Badhe, Nehal Kathrotia, and Priyanka Tiwari. 2026. CROP: Token-Efficient Reasoning in Large Language Models via Regularized Prompt Optimization. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 934–951, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
CROP: Token-Efficient Reasoning in Large Language Models via Regularized Prompt Optimization (Shah et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.45.pdf