System 1 models: a practitioner's guide to the fast decision layer that routes, gates and scores inside agent stacks
AspireAI community · arXiv (cs.AI / cs.CL)
Autoregressive token-by-token inference is the wrong tool for routine decisions like routing, gating, scoring and classification, and a growing class of System 1 models maps an input directly to a typed decision in a single forward pass. This guide lays out a five-family taxonomy of those architectures, develops the theory of proper scoring rules for calibration, and covers phenomena including independence-of-axioms violations, ordinal-scale bias and few-shot recalibration under distribution shift. It also maps the open-source ecosystem of more than 70 model reproductions, provides runnable code and an open-source model zoo, and explains how System 1 models act as decision infrastructure inside agentic workflows and System 1 plus System 2 cascades. The limitation: it is a synthesis of the field rather than new experimental evidence, so the calibration findings it reports are drawn from other authors' results.
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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.