Full-duplex speech models degrade because acoustic and semantic training fight over the same weights
AspireAI community · arXiv
Native full-duplex spoken language models are a long-standing goal, and existing attempts are constrained by severe modality interference that degrades knowledge and semantic integrity, making the models feel unnatural. Analyzing optimization dynamics in fine detail, this paper traces the interference to inherent gradient conflicts between acoustic and semantic modeling when both are forced to share a deep parameter space. The resulting Lychee-FD framework is native and end-to-end, and its key move is a hierarchical parameter separation strategy that decouples the conflicting modalities in deep layers while preserving cross-modality coherence through a dedicated semantic alignment channel. The authors report significant advances on multiple full-duplex benchmarks. The original preprint is from July with a v5 on October 29, so this is an iterated result rather than a brand new line.
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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.