Beyond Final Success: Semantic Progress Diagnostics for Agent Trajectory Evaluation

Nan Xue, Tinghao Wang, Li Tang


Abstract
Large language model agents are increasingly expected to handle complex, long-horizon tasks that require sustained tool use and stateful interaction. Final outcome labels in existing agent benchmarks provide only a coarse view of long-horizon agent execution. They obscure differences in the execution process among successful trajectories and collapse failed trajectories that may have achieved different amounts of task-relevant progress. We introduce the Auditable Semantic Reference Graph (ASRG), a post-hoc framework that represents task-relevant progress with task-specific Semantic Reference Units (SRUs) and matches trajectories against these references. Each SRU is a checkable task milestone with an explicit verifier. Deterministic matching quantifies process coverage and coverage-weighted first-hit timing, while an action-level diagnostic records actions unexplained by the labeling rules. We apply ASRG to 4,740 Toolathlon evaluation trajectories from 22 models across 108 tasks. ASRG reveals process-coverage differences between models with identical final-success rates and first-support timing differences between same-task trajectories with matched coverage. By relating measured progress to resource use, ASRG also supports process-efficiency analysis. ASRG complements final outcome evaluation with auditable, reference-conditioned process diagnostics.
Anthology ID:
2026.emnlp-main.2140
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:
48652–48672
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2140/
DOI:
Bibkey:
Cite (ACL):
Nan Xue, Tinghao Wang, and Li Tang. 2026. Beyond Final Success: Semantic Progress Diagnostics for Agent Trajectory Evaluation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 48652–48672, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond Final Success: Semantic Progress Diagnostics for Agent Trajectory Evaluation (Xue et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2140.pdf