ForeCritic picked the better of two candidate programs 79.4 percent of the time by predicting the decision rather than the outcome, and cut ML-agent task time 4.4 to 7.5 times
AspireAI community · arXiv (World Reward Model authors)
Search-based ML agents write candidate programs, execute them and keep the best, but each execution can take hours and most results get discarded. Recent agents try to save those runs by letting an LLM act as a world model that predicts how a program would perform - but a wrong prediction poisons the search with false information. The authors argue the agent only needs the decision execution would support, not the outcome, and prove that a predictor of outcomes cannot beat the best direct selector. Their World Reward Model, ForeCritic, adapts a 9B typed decision model to 5k executed program pairs and picks the better program 79.4 percent of the time on 12,438 held-out pairs from 26 ML tasks, against 53-62 percent for general-purpose LLM judges, while cutting mean task time 4.4 to 7.5 times inside AIDE, ML-Master and ForeAgent. The calibration claim is the authors' own.
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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.