Prompt2Box: Improving LLM Weakness Discovery and Specificity Estimation by Uncovering Entailment Structure among Prompts

Neeladri Bhuiya, Shib Sankar Dasgupta, Andrew McCallum, Haw-Shiuan Chang


Abstract
To discover the weaknesses of LLMs, researchers often embed prompts into a vector space and cluster them to extract insightful patterns. However, vector embeddings primarily capture topical similarity. As a result, prompts that share a topic but differ in specificity, and consequently in difficulty, are often represented similarly, making fine-grained weakness analysis difficult. To address this limitation, we propose Prompt2Box:, which embeds prompts into a box embedding space using a trained encoder. The encoder, trained on existing and synthesized datasets, outputs box embeddings that capture not only semantic similarity but also specificity relations between prompts (e.g., "writing an adventure story" is more specific than "writing a story". We further develop a novel dimension reduction technique for box embeddings to facilitate dataset visualization and comparison. Our experiments demonstrate that box embeddings consistently capture prompt specificity better than vector baselines and achieve up to 45% error reduction compared to the prompt length baseline. On the downstream task of creating hierarchical clustering trees for 17 LLMs from the UltraFeedback dataset, Prompt2Box: can identify 13.5% more LLM weaknesses than vector baselines and achieves an approximately 33% stronger correlation between hierarchical depth and instruction specificity.
Anthology ID:
2026.emnlp-main.2495
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:
56643–56670
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2495/
DOI:
Bibkey:
Cite (ACL):
Neeladri Bhuiya, Shib Sankar Dasgupta, Andrew McCallum, and Haw-Shiuan Chang. 2026. Prompt2Box: Improving LLM Weakness Discovery and Specificity Estimation by Uncovering Entailment Structure among Prompts. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 56643–56670, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Prompt2Box: Improving LLM Weakness Discovery and Specificity Estimation by Uncovering Entailment Structure among Prompts (Bhuiya et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2495.pdf