Dependency-Aware Trajectory Refinement for Efficient Multi-Turn Agent Fine-Tuning

Zhuo Chen, Zhen Zhang, Xinyu Wang, Kewei Tu


Abstract
Multi-turn agent trajectories often contain redundant rounds (failed tool calls, parallel sub-queries, verification-only steps) that inflate both training and inference cost. We propose viewing each trajectory as a round-level dependency DAG that exposes which rounds are globally load-bearing for the final answer, and fine-tune agents on trajectories refined through this DAG. Operating on the DAG lets us apply deterministic and interpretable edits, pruning rounds whose outputs are never consumed and merging interchangeable sibling rounds, with optional LLM-based rephrasing. Models trained on these refined trajectories consistently outperform those trained on the original trajectories at lower inference cost. Specifically, across four multi-modal QA benchmarks, our refinements improve downstream accuracy by up to ,pp over vanilla SFT (and ,pp over an LLM-deletion baseline) while reducing per-sample inference messages by up to and inference tokens by up to , translating to substantial savings in compute and serving cost. Code is released.
Anthology ID:
2026.findings-aacl.65
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1287–1302
Language:
URL:
https://aclanthology.org/2026.findings-aacl.65/
DOI:
Bibkey:
Cite (ACL):
Zhuo Chen, Zhen Zhang, Xinyu Wang, and Kewei Tu. 2026. Dependency-Aware Trajectory Refinement for Efficient Multi-Turn Agent Fine-Tuning. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 1287–1302, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Dependency-Aware Trajectory Refinement for Efficient Multi-Turn Agent Fine-Tuning (Chen et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.65.pdf