Paper Detail

AgentHER: Hindsight Experience Replay for LLM Agent Trajectory Relabeling

Liang Ding

arxiv Score 12.0

Published 2026-03-22 · First seen 2026-03-27

Research Track B · General AI

Abstract

LLM agents fail on the majority of real-world tasks -- GPT-4o succeeds on fewer than 15% of WebArena navigation tasks and below 55% pass@1 on ToolBench (Zhou et al., 2024; Qin et al., 2024) -- yet every failed trajectory is routinely discarded, wasting the dominant source of collected experience. We introduce AgentHER, a framework that recovers this lost training signal by adapting the Hindsight Experience Replay (HER; Andrychowicz et al., 2017) principle to natural-language agent trajectories for offline data augmentation. The key insight is simple: a trajectory that fails goal A is often a correct demonstration for some achievable alternative goal B. AgentHER realises this idea through a four-stage pipeline -- failure classification, outcome extraction, LLM-guided prompt relabeling with confidence gating, and data packaging -- that converts discarded failures into high-quality SFT, DPO, and ShareGPT training data, with both zero-cost rule-based and LLM-judge implementations. On WebArena (Zhou et al., 2024) and ToolBench (Qin et al., 2024), AgentHER improves over success-only SFT by +7.1-11.7 pp across four model families (GPT-4o, Qwen2.5-72B/7B, LLaMA-3.1-8B), while achieving 2x data efficiency -- matching baseline performance with only 50% of successful demonstrations. Gains are consistent from 1.5B to 72B parameters (+5.8-9.2 pp) and compound under iterative redeployment (+2.1 pp over additional rounds). Human evaluation confirms 97.7% relabeling precision under multi-judge verification.

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BibTeX

@article{ding2026agenther,
  title = {AgentHER: Hindsight Experience Replay for LLM Agent Trajectory Relabeling},
  author = {Liang Ding},
  year = {2026},
  abstract = {LLM agents fail on the majority of real-world tasks -- GPT-4o succeeds on fewer than 15\% of WebArena navigation tasks and below 55\% pass@1 on ToolBench (Zhou et al., 2024; Qin et al., 2024) -- yet every failed trajectory is routinely discarded, wasting the dominant source of collected experience. We introduce AgentHER, a framework that recovers this lost training signal by adapting the Hindsight Experience Replay (HER; Andrychowicz et al., 2017) principle to natural-language agent trajectories f},
  url = {https://arxiv.org/abs/2603.21357},
  keywords = {cs.AI, cs.CL},
  eprint = {2603.21357},
  archiveprefix = {arXiv},
}

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