Letting the proposer that designs RL rewards learn from its own failed trials beat strong baselines across embodied, scientific and math reasoning
AspireAI community · arXiv
Automated reward optimization usually searches with a fixed proposer that never learns from its expensive trials, which caps how far it can go. DERL makes the reward design process itself evolvable: an outer-loop proposer composes a reward from task primitives, an inner policy trains against that composed reward, and the proposer then learns by policy gradient from the inner policy's validation performance, so past-trial feedback reshapes its reward-proposal distribution into what the authors call an empirical meta-gradient of task success. Validated on ALFWorld, ScienceWorld, GSM8K and MATH, the method reports outperforming strong baselines on multi-turn agent benchmarks with the largest margin on out-of-distribution tasks, and in mathematics it improves on the plain outcome reward in settings where adding primitives directly would hurt. The limitation is cost: every candidate reward means another full policy training run, so the approach only pays off when that search budget is available.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.