Contrastive Attribution in the Wild: An Interpretability Analysis of LLM Failures on Realistic Benchmarks

Rongyuan Tan, Jue Zhang, Zhuozhao Li, Qingwei Lin, Saravan Rajmohan, Dongmei Zhang


Abstract
Interpretability methods are increasingly invoked to diagnose Large Language Model (LLM) failures, but most evidence comes from short prompts or toy templates, leaving their utility on practical benchmarks unclear. We cast failure diagnosis as contrastive attribution over target–contrast token pairs, attributing the logit gap between incorrect and correct output tokens to input tokens and internal states, and introduce a batch-packed multi-target backpropagation scheme that scales cross-layer attribution graphs to long-context inputs. Instantiated with LRP-style attribution, the framework is evaluated on IFEval, GAIA2, MATH, and EvalPlus across multiple model sizes and post-training checkpoints. Along the four axes of coverage, visibility, reliability, and dynamics, contrastive attribution surfaces recurring failure modes such as underweighting task-relevant tokens and overweighting distractors, demonstrating its practical value as a scalable diagnostic tool for realistic LLM failures.
Anthology ID:
2026.emnlp-main.2003
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
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Pages:
45618–45649
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URL:
https://aclanthology.org/2026.emnlp-main.2003/
DOI:
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Cite (ACL):
Rongyuan Tan, Jue Zhang, Zhuozhao Li, Qingwei Lin, Saravan Rajmohan, and Dongmei Zhang. 2026. Contrastive Attribution in the Wild: An Interpretability Analysis of LLM Failures on Realistic Benchmarks. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 45618–45649, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Contrastive Attribution in the Wild: An Interpretability Analysis of LLM Failures on Realistic Benchmarks (Tan et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.2003.pdf