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Paper breakdownLarge Language ModelsPRO2026

Nemotron 3 Super

Open, Efficient Mixture-of-Experts Hybrid Mamba-Transformer for Agentic Reasoning

NVIDIA

7

Concepts

Paper Overview

Nemotron 3 Super is NVIDIA's open-weight large language model that combines three architectural innovations — Hybrid Mamba-Attention, LatentMoE, and Multi-Token Prediction — into a single 120B total parameter model with only 12B active parameters per forward pass (12.7B including embeddings). The model uses a vocabulary of 131,072 tokens, a hidden dimension of d=4096d = 4096, and spans 88 layers with a mix of Mamba-2 SSM blocks and grouped-query attention layers.

The model achieves comparable or better accuracy than GPT-OSS-120B (DeepSeek-V3-0324) and Qwen3.5-122B across reasoning, coding, agentic, and long-context benchmarks, while delivering dramatically better serving efficiency: 2.2x higher throughput than GPT-OSS-120B and 7.5x higher throughput than Qwen3.5-122B on realistic workloads (8K input / 64K output tokens) on NVIDIA B300 GPUs. This efficiency advantage comes from three sources: (1) Mamba-2 blocks eliminate KV cache growth for the majority of layers, (2) LatentMoE reduces memory bandwidth per expert by 4x through latent projection, and (3) Multi-Token Prediction enables native speculative decoding with an average acceptance length of 3.45 tokens — no external draft model required.

Key architectural and training advances:

  • LatentMoE: Projects tokens from d=4096d = 4096 to a latent space of ℓ=1024\ell = 1024 before expert routing, enabling 512 total experts with top-22 activation at the same inference cost as standard MoE with ~64 experts. Expert weight matrices shrink from d×md \times m to ℓ×m\ell \times m (4x smaller), reducing memory bandwidth by 4x per expert read — critical for low-latency serving where expert weight loading dominates
  • Hybrid Mamba-2 + Attention: 88 layers with a periodic pattern of Mamba-2 blocks (O(n)O(n) linear time, constant-size recurrent state of dimension 128) and sparse attention "anchors" using GQA (32 Q-heads / 2 KV-heads). Mamba blocks handle local sequential patterns cheaply; attention anchors enable global information routing. Only the attention layers produce KV cache entries, keeping total cache small
  • Multi-Token Prediction (MTP): 2 shared-weight auxiliary prediction heads trained across multiple future offsets. The shared-weight design is critical — it makes the heads robust to the distribution shift of conditioning on self-generated states during speculative decoding. Average acceptance length: 3.45 tokens on SPEED-Bench (best among all tested models, beating DeepSeek-R1's 2.70)
  • NVFP4 pretraining: First model to demonstrate stable large-scale training in NVFP4 (E2M1) precision across 25 trillion tokens on NVIDIA Blackwell GPUs, with a two-phase data curriculum (20T diverse + 5T high-quality). Mixed precision strategy: NVFP4 for most linear layers, BF16 for attention, latent projections, MTP heads, and the final 15% of layers
  • Agentic post-training: 4-stage pipeline — SFT (7M samples) → multi-environment RLVR (37 datasets, 21 environments, up to 1K GPUs) → SWE-RL (end-to-end RL on real GitHub issues) → RLHF (GenRM on Qwen3-235B-Thinking) + MTP healing. PivotRL technique for efficient agentic RL training on "pivot" turns in expert trajectories

Nemotron 3 Super is fully open-sourced on HuggingFace — base, post-trained, FP8, and NVFP4 checkpoints — along with all training datasets (Nemotron-Pretraining-Specialized-v1.1 and Nemotron-Super-Post-Training-Data).

Chapter Roadmap

Click any topic to jump in

1
Pipeline Summary

LatentMoE → hybrid SSM → NVFP4 pretrain → multi-env RL → deployment quantization compound into 3× efficiency.

combines compute + memory wins via
2
LatentMoE

Latent projection before expert compute makes wall-clock cost invariant to expert count, enabling 256 experts.

3
Hybrid Mamba-2 + Attn

Interleaved SSM and attention layers give linear-context reasoning with 5× smaller KV cache at 128K.

scaled efficiently by
4
Multi-Token Prediction

Auxiliary heads predicting k future tokens densify supervision and enable free speculative decoding.

5
NVFP4 Pretraining

4-bit microscaled format halves memory and doubles tensor-core throughput with <0.3% loss gap.

aligned and shipped via
6
Multi-Env RL

Simultaneous RL across math/code/tool/chat with per-env rewards prevents single-domain reward hacking.

7
Deployment Quantization

Per-layer FP4/FP8/INT8 search yields 4× throughput with <1% quality loss via error-budget optimization.

Concept by concept

7 sections, in reading order.

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  1. 01Pipeline Summary
  2. 02LatentMoE: Hardware-Aware Expert Design
  3. 03Hybrid Mamba-2 + Attention Architecture
  4. 04Multi-Token Prediction (MTP)
  5. 05NVFP4 Pretraining at Scale
  6. 06Multi-Environment Reinforcement Learning
  7. 07Quantization for Deployment