ReasoningFlow: Discourse Structures for Understanding LLM Reasoning Traces

Jinu Lee, Shivam Agarwal, Amruta Parulekar, Siddarth Madala, Dilek Hakkani-Tür, Julia Hockenmaier


Abstract
Large reasoning models (LRMs) produce reasoning traces with non-linear structures, such as backtracking and self-correction, that complicate the evaluation and monitoring of the reasoning process. We introduce ReasoningFlow, a framework that captures the discourse structures of LRM reasoning traces into fine-grained directed acyclic graphs (DAGs). We develop and validate our annotation schema through careful manual annotation of 31 traces (2.1k steps), achieving high inter-annotator agreement, then scale to automatic annotation of 1,260 traces (247.7k steps) spanning three tasks (math, science, argumentation) and five models (Qwen2.5-32B-Inst, QwQ-32B, DeepSeek-V3, DeepSeek-R1, GPT-oss-120B). By analyzing ReasoningFlow graphs, we find: (1) LRMs exhibit structurally similar traces, despite being trained from different base models and potentially non-overlapping post-training data. (2) ReasoningFlow reveals diverse fine-grained reasoning behaviors (e.g., local verification, self-reflection, and assumptions) that can be used for better reasoning trace monitorability. (3) In LRMs, most of the erroneous steps are not used to derive final answers. (4) Mechanistic causal dependencies between steps do not reflect the language-level discourse structure.
Anthology ID:
2026.emnlp-main.670
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:
15430–15463
Language:
URL:
https://aclanthology.org/2026.emnlp-main.670/
DOI:
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Cite (ACL):
Jinu Lee, Shivam Agarwal, Amruta Parulekar, Siddarth Madala, Dilek Hakkani-Tür, and Julia Hockenmaier. 2026. ReasoningFlow: Discourse Structures for Understanding LLM Reasoning Traces. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 15430–15463, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ReasoningFlow: Discourse Structures for Understanding LLM Reasoning Traces (Lee et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.670.pdf