NVIDIA releases Nemotron 3.5 Bolt E4B 4GB open weights: 8B total / 4B active, 64K context, Q4_K_M GGUF
AspireAI · NVIDIA Research
A 4GB AI model that actually calls tools — NVIDIA's Nemotron 3.5 Bolt E4B just shipped with open weights.
It packs an 8B-parameter model (4B effective) built on Gemma 4 E4B and tuned by NVIDIA for voice assistants, game characters and robot interfaces. Multi-turn tool calling, 64K context, 35 languages.
Think of it as a spare tire: not the fastest car, but the one that fits in the trunk and starts every time.
NVIDIA claims roughly 40% higher average quality than its own previous small model and up to 80% fewer output tokens. Those benchmark tables are NVIDIA's own runs, and two of the listed suites are not public yet, so treat the numbers as vendor-reported.
Weights, the GGUF file and a parallel drafter are on Hugging Face today. The 4GB in the name is the memory footprint NVIDIA targets; the published Q4_K_M file itself is about 6.2GB.
https://research.nvidia.com/labs/nemotron/NVIDIA-Nemotron-3.5-Bolt-E4B-4GB/
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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.