From Final Artifacts to Trajectories: Retrospective Process Supervision for Evidence-Grounded Long-Form Generation

Junjie Huang, Jiarui Qin, di Yin, Weiwen Liu, Yong Yu, Xing Sun, Weinan Zhang


Abstract
Trajectory data is getting more vital for training large language models for boosting the agentic abilities. Unlike the verifiable domains such as coding or mathematics, scaling trajectory data for open-ended tasks are much more difficult because these tasks lack singular ground truth and are costly to annotate or verify. In this paper, we propose RetroGen, a self-improving framework of retrospective process supervision. Our key observation is that although expert trajectories are scarce, high-quality final artifacts such as literature reviews, analyst reports and legal judgments, are abundant in pre-training data and can be viewed as compressed traces of the evidence-seeking processes that produced them. RetroGen reconstructs candidate latent trajectories from expert artifacts, verifies them against both the artifact and supporting evidence, and trains models on their own successful reconstruction data, without requiring trajectory data from stronger models. Experiments show that RetroGen improves grounding, faithful synthesis, and long-form evidence-seeking agent tasks.
Anthology ID:
2026.findings-emnlp.1249
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:
26422–26434
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1249/
DOI:
10.18653/2026.findings-emnlp.1249
Bibkey:
Cite (ACL):
Junjie Huang, Jiarui Qin, di Yin, Weiwen Liu, Yong Yu, Xing Sun, and Weinan Zhang. 2026. From Final Artifacts to Trajectories: Retrospective Process Supervision for Evidence-Grounded Long-Form Generation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 26422–26434, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Final Artifacts to Trajectories: Retrospective Process Supervision for Evidence-Grounded Long-Form Generation (Huang et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1249.pdf