A white-box trace that shows how a reasoning failure develops, not just that it happened
AspireAI community · arXiv
Endpoint labels do not reveal how a failure develops, so this paper builds a diagnostic framework - CauTrace - that locates the root cause inside the model. It works from three inspections: seven defined functional states representing support and constraint processing; propagation of representation change, measuring how changes among those states persist across subsequent transformer blocks; and temporal-state coordination and trajectory topology, capturing when commitment and verification occur relative to support and how the dominant state sequence evolves. Across Qwen and LLaMA-family models, failed traces show weaker attention-MLP agreement on support-state updates and less verification activity relative to commitment, though the exact representation-level signatures and timing shifts vary by architecture. Held-out repair and steering tests produce operational signals aligned with the claims for certain models and settings, with aligned steering moving process measures in the predicted direction. The caveat is in the paper's own wording: the signals are consistent for some models in specific settings, not universally.
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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.