A Pre-Generation Epistemic Routing Axis in Language Models

Steve Bakos, Heidar Davoudi, Aijun An


Abstract
When answering factual questions, language models may respond correctly, hallucinate, or abstain. We investigate whether this epistemic disposition is encoded in hidden states before any answer token is generated. Using a balanced Wikipedia QA corpus with pre/post article-date splits and rollout-consensus labels, we analyze prompt-only MLP activations from four instruction-tuned 7–9B models. PCA reveals a dominant pre-generation epistemic routing axis that orders outcomes as ABSTAIN, HALLUCINATION, and CORRECT. We then apply activation steering as a bounded causal stress test. Dense residual-write edits can shift many hallucinations toward abstention or correctness, while sparse MLP-intermediate edits localize the steering signal. These results frame the axis as a steering audit: it identifies where fixed edits improve factual behavior and where correct loss or broken outputs call for conditional controllers.
Anthology ID:
2026.findings-emnlp.1324
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
28066–28091
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1324/
DOI:
10.18653/2026.findings-emnlp.1324
Bibkey:
Cite (ACL):
Steve Bakos, Heidar Davoudi, and Aijun An. 2026. A Pre-Generation Epistemic Routing Axis in Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 28066–28091, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
A Pre-Generation Epistemic Routing Axis in Language Models (Bakos et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1324.pdf