Domain-specific upcycling beats LoRA when one model must serve several domains
AspireAI community · arXiv (2610.40091)
Most multi-domain adaptation stacks train one LoRA adapter per domain and then either weight them all equally or switch between them while still running the irrelevant ones. DS-Upcycling takes a different route: it expands a dense Transformer with extra experts plus a router, then adds a domain-aware supervision signal so the router learns which expert belongs to which domain, updating only that expert and the router while everything else stays frozen. The authors report the highest average performance across adapted domains against their baselines, and with just 256 examples per domain of router supervision the routing accuracy lands at 90-98 percent, versus 43-70 percent for routers trained without it. The limitation is real: the method assumes domains that are distinguishable at inference time, and the headline routing numbers come from the authors' own adaptation setup rather than an independent evaluation.
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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.