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vLLM Semantic Router released d3-ultra, a 27B open multimodal decision model that answers 255 questions from one read

AspireAI community · Hugging Face / vLLM Semantic Router
d3-ultra is a 27B multimodal decision model from vLLM Semantic Router, Apache-2.0 licensed, built on a 26.09B backbone including a 0.46B vision encoder. You hand it text or JSON plus optional images and video, ask typed questions (choose one of these options, yes or no, rate on a scale, or point to a box in an image or a moment in a video), and it returns a probability for every answer without generating text. The headline capability is reading the input once and answering every question on it: on one AMD Instinct MI325X with AutoModel, one question about a photo takes a median of 304 ms and 255 questions take 2.16 s, roughly 7.3 ms per additional question. Context runs to 131,072 tokens per question on a single MI325X. On the authors own private SR-Text test d3-ultra scores 87.2 against 81.4 for d3 and 73.1 for Jev 1.14, and on SR-Box it scores 58.2 percent against 60.0 percent for d3-turbo, which remains the stronger Box model on natural images. The evaluation sets are the authors own and unpublished, so the ranking is not an independent leaderboard result, and the 255-question speed figure comes from a single accelerator.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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.
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