Conditioning Activation Interventions on Evolving Reasoning States in Large Language Models

Tae-Won Kim, Hee-Dong Kim, Jumin Han, Seong-Whan Lee


Abstract
Activation steering controls language model behavior at inference time by injecting behavior-relevant directions into internal representations. In the standard steering interface, a steering direction is estimated once before generation and then applied throughout decoding. However, during multi-step reasoning, the model’s internal state shifts continuously as reasoning progresses, while standard steering continues to apply the same fixed direction across these changing states. This creates a mismatch between the model’s evolving reasoning state and the static intervention applied to it. To address this mismatch, we introduce State-Conditioned Steering (SCS), which recomputes the additive update itself from the hidden states encountered during generation while keeping the same additive intervention interface. Rather than adapting when or how strongly to intervene, SCS re-estimates the update from intermediate reasoning states as generation proceeds. In a paired comparison setting, we compare fixed and state-conditioned updates and find that predefined directions often exhibit unstable effects, while SCS yields more consistent intervention behavior across decoding steps. Across reasoning benchmarks with explicit step structure and three instruction-tuned backbones, SCS achieves larger average gains than prompting-only decoding and baseline activation steering methods.
Anthology ID:
2026.findings-emnlp.2187
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:
46826–46846
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2187/
DOI:
Bibkey:
Cite (ACL):
Tae-Won Kim, Hee-Dong Kim, Jumin Han, and Seong-Whan Lee. 2026. Conditioning Activation Interventions on Evolving Reasoning States in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 46826–46846, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Conditioning Activation Interventions on Evolving Reasoning States in Large Language Models (Kim et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2187.pdf