Faster serving
In our vLLM 0.28 test on one H100, group-64 dispatches to the Machete kernel while Google's group-32 goes to Marlin: 4,225 vs 3,111 output tokens/s at the same batch (BF16: 4,823). Single-request latency is at parity.
Downstream benchmarks
Higher point estimates on all 8 downstream benchmarks than Google's QAT model.
Table with columns: Benchmark, QUASAR, Google QAT| Benchmark | QUASAR | Google QAT |
|---|
| TriviaQA | 23.8 | 20.1 |
| NQ-open | 4.7 | 2.4 |
| TruthfulQA | 58.2 | 55.4 |
| ARC-Easy | 79.8 | 78.3 |
| ARC-Challenge | 56.2 | 56.0 |
| GSM8K | 82.0 | 81.5 |
| IFEval | 82.6 | 81.9 |
| MATH-hard | 60.7 | 59.4 |
| Average | 56.0 | 54.4 |
Same harness and backend for both checkpoints; full configs, BF16 results and paired-bootstrap CIs are in EVAL.md.
Native QAT checkpoint
Native QAT checkpoint: the INT4 codes come directly from training, rather than a post-training re-quantization. export_receipt.json verifies the export per tensor. The GGUF twin carries the same codes and scales and ships a --verify script that checks the two files against each other.
Run it
- vLLM:
vllm serve QUASAR-QAT/gemma-4-E4B-it-QUASAR-W4A16-G64 --dtype float16 (tested on vLLM 0.28.0 and 0.29.0; --dtype float16 keeps the stored fp16 scales exact), then any OpenAI-compatible client. Text, image and audio inputs; 131,072-token context.
- transformers:
AutoModelForCausalLM.from_pretrained("QUASAR-QAT/gemma-4-E4B-it-QUASAR-W4A16-G64", dtype=torch.bfloat16) with compressed-tensors installed.
- Format: 258 decoder linears (
q/k/v/o/gate/up/down) int4 symmetric, group_size 64, fp16 scales, compressed-tensors pack-quantized; embeddings, norms, per-layer-input tables and the vision/audio towers untouched (bf16). 10.2 GB. Loads wherever Google's W4A16 release loads.
QUASAR
QUASAR is loss-aware quantization-aware training. It improves the low-bit reconstruction during training, then exports to standard deployment formats with zero inference overhead.
This checkpoint was healed against the BF16 teacher for 626M tokens: one epoch over ~398k prompts self-distilled from BF16 Gemma 4 E4B-it with thinking on, fp32 master weights, INT4 group-64.
License
Based on Gemma 4 by Google DeepMind. Upstream LICENSE/NOTICE apply.
Citation
arxiv.org/abs/2608.13966
@article{counathe2026quasar,
title={QUASAR: Lowering the Loss Floor of Quantization-Aware Training with Loss-Aware Reconstruction},
author={Counathe, Vincent and Athiwaratkun, Ben and De Sa, Christopher and Zhang, Tianyi},
journal={arXiv preprint arXiv:2608.13966},
year={2026}
}