Self-distillation stalls when the teacher cannot teach, so train the teacher first
AspireAI community · arXiv
On-policy self-distillation aligns a student with a self-teacher that has been shown privileged context, and it has become a common way to get around reward sparsity in sequence-level post-training. It often fails to keep improving. This paper attributes that to the model's own limited self-teaching capability - the teacher produces unreliable guidance on some samples. TESD splits the fix in two: teacher-oriented optimisation that uses task correctness and context independence as rewards to improve the self-teacher's ability to teach, and student-oriented optimisation that estimates the reliability of each piece of teacher guidance and down-weights the unreliable samples. Across multiple datasets and model scales, the authors report consistent gains over representative token-level and sequence-level methods, with the conclusion that supervision quality is the constraint. The distinction that matters: this treats the teacher as something to be trained rather than something to be trusted.
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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.