---
license: apache-2.0
base_model: Nanbeige/Nanbeige4.2-3B
base_model_relation: quantized
pipeline_tag: text-generation
language: [en, zh]
tags: [fp8, nvfp4, quantized, compressed-tensors, vllm, looped-transformer, nanbeige]
model-index:
- name: Nanbeige4.2-3B-NVFP4-FP8-LoopShield
  results:
  - task:
      type: text-generation
    dataset:
      name: GSM8K
      type: gsm8k
    metrics:
    - name: GSM8K (strict, thinking, n=100)
      type: exact_match
      value: 89.0
      verified: false
  - task:
      type: text-generation
    dataset:
      name: GSM8K
      type: gsm8k
    metrics:
    - name: GSM8K (flexible)
      type: exact_match
      value: 96.0
      verified: false
  - task:
      type: text-generation
    dataset:
      name: IFEval
      type: ifeval
    metrics:
    - name: IFEval prompt-strict (non-thinking, n=250)
      type: exact_match
      value: 76.0
      verified: false
  - task:
      type: text-generation
    dataset:
      name: MMLU-Pro
      type: mmlu_pro
    metrics:
    - name: MMLU-Pro (non-thinking, 25/category)
      type: exact_match
      value: 64.9
      verified: false
  - task:
      type: text-generation
    dataset:
      name: BBH
      type: bbh
    metrics:
    - name: BBH CoT few-shot (non-thinking)
      type: exact_match
      value: 59.5
      verified: false
  - task:
      type: text-generation
    dataset:
      name: MultiHop-RAG
      type: multihop_rag
    metrics:
    - name: MultiHop-RAG generator-only, gold evidence (n=248)
      type: exact_match
      value: 74.6
      verified: false
---

# Nanbeige4.2-3B-NVFP4-FP8-LoopShield

Mixed-precision quantization of
[Nanbeige/Nanbeige4.2-3B](https://huggingface.co/Nanbeige/Nanbeige4.2-3B) (looped
transformer, 22 layers × 2 passes/token): **FP8-dynamic on attention, `down_proj`, and
the first/last 3 layers' MLP; NVFP4 (weight-only, group-16) on middle-layer
`gate/up_proj`**. 4.5 GB. `format: mixed-precision` (compressed-tensors).

## The nitty gritty

Naive uniform NVFP4 on this looped architecture loses **8 points of GSM8K strict**
(quantization error compounds across the two loop passes — consistent with LoopQ,
arXiv:2605.16343, the only prior looped-LLM PTQ study, which tested INT only; these
are, as far as I can tell, the first FP4-family numbers for a looped LLM). The
protection recipe that llama.cpp's quant mixes, Unsloth's ablations, and
llmcompressor's own non-uniform example all converge on recovered it completely:

| step | GSM8K strict (n=100) |
|---|---|
| uniform NVFP4A16 | 81 |
| + FP8 attention & down_proj (all layers) | 84 |
| **+ FP8 gate/up in layers 0-2 & 19-21 (this repo)** | **89 — bf16/FP8 parity** |

The edge-band ratio follows APEX's ablation (~12.5% of depth per side); the tensor
priority (down_proj > attention > gate/up) matches llama.cpp's quant mixes, Unsloth's
sensitivity ablations, and llmcompressor's own non-uniform example.

**Super-weight verification (2026-07-23)**: this model's super weight (the
single most load-bearing scalar, [Apple 2411.07191](https://arxiv.org/abs/2411.07191))
sits at `layers.1.mlp.down_proj.weight[1252, 6883]` (largest weight in its tensor,
11.4x p99.99; drives a 26,752-magnitude activation spike, 1,300x the median). This
recipe protects both the weight (all-layer FP8 down_proj) and its production path
(L1 gate/up in the FP8 edge band) — verified by direct scan, not assumed. One
looped-arch novelty from the scan: the spike is pass-asymmetric (26,752 on loop
pass 1 of 2; 1,352 on pass 2).

## Quality evals (RTX 5090, vLLM v0.25.1, 64k ctx, fp8 KV; champion = my FP8-Dynamic quant)

| bench | mode | bf16 original | FP8-Dynamic | **this repo** |
|---|---|---|---|---|
| GSM8K strict (n=100) | thinking | not measured | 89 | **89** |
| GSM8K flexible | thinking | not measured | 93 | **96** |
| IFEval prompt-strict (n=250) | non-thinking | not measured | 76.4 | 76.0 |
| IFEval inst-strict | non-thinking | not measured | 83.5 | 83.3 |
| MMLU-Pro (25/category) | non-thinking | not measured | 62.6 | **64.9** |
| BBH CoT few-shot | non-thinking | not measured | 64.9 | 59.5 |
| MultiHop-RAG (gold evidence, n=248) | non-thinking | not measured | 74.2 | **74.6** |
| Blind-judge summarization (closed, same-judge pair, n=46) | non-thinking | n/c (judged in a separate pass; scores only comparable within a pass) | 4.57 | 4.41 (coverage −0.24, ~1.5σ) |
| Judged faithfulness (closed) | non-thinking | n/c | 4.90 | 4.87 |
| Judged fabrication / leaks (closed) | non-thinking | 0% / 0% | 2% / 0% | 2% / 0% |
| Dictation-rewrite taxonomy (closed) | non-thinking | 18/20 | 18/20 | 17/20 |
| JSON parse rate (closed, /48) | non-thinking | 44 | 42 | **46** |

The trade: **reasoning at full parity, best-in-family structured-output
reliability, small summarization-coverage cost.** If you want maximum quality use my
FP8-Dynamic; if you want the smallest artifact that keeps reasoning intact on this
architecture, use this one.

## Speed (RTX 5090, batch-1, vLLM v0.25.1, 64k ctx, fp8 KV)

Decode tok/s, single stream, per-workload best speculative config:

| workload | spec decode | bf16 | FP8-Dynamic | **this repo** |
|---|---|---|---|---|
| freeform / chat / agent | off | 96 | 154 | **159** |
| summarize / RAG (2k+ ctx prompts) | ngram, 8 tok | 136 | 206 | 202 |

Two workload anchors, not an ISL sweep; decode speed shifts with context
length, batch size, and attention backend. The mid-MLP NVFP4 weights serve
via the Marlin W4A16 kernel; the FP8 tensors via the FP8 path; the small
freeform edge over FP8-Dynamic comes from the lighter weight reads, the small
summarize deficit from mixed-kernel overhead under the ngram verify batch.

## Serving (vLLM)

Arch not yet upstream ([vLLM PR #49433](https://github.com/vllm-project/vllm/pull/49433));
install the bundled plugin first:

```bash
pip install --no-deps ./vllm_plugin
vllm serve <this-repo> --trust-remote-code \
  --max-model-len 65536 --kv-cache-dtype fp8 \
  --reasoning-parser qwen3 --enable-auto-tool-choice --tool-call-parser qwen3_xml
```

Thinking/sampling notes as in the base model: thinking ON by default
(`chat_template_kwargs.enable_thinking=false` to disable), T=0.6/top_p=.95/top_k=20
defaults ship in `generation_config.json`, T=1.0 for agentic use.

Download just this artifact:

```bash
hf download NullSense/Nanbeige4.2-3B-NVFP4-FP8-LoopShield --local-dir Nanbeige4.2-3B-NVFP4-FP8-LoopShield
```

## Creation (llmcompressor, data-free)

```python
g_fp8 = dict(FP8_DYNAMIC)
g_fp8["targets"] = ["re:.*self_attn\\.q_proj.*", "re:.*self_attn\\.k_proj.*",
                    "re:.*self_attn\\.v_proj.*", "re:.*self_attn\\.o_proj.*",
                    "re:.*down_proj.*"] + \
                   [f"re:model\\.layers\\.{i}\\.mlp\\.(gate|up)_proj.*" for i in (0,1,2,19,20,21)]
g_fp4 = dict(NVFP4A16)
g_fp4["targets"] = [f"re:model\\.layers\\.{i}\\.mlp\\.(gate|up)_proj.*" for i in range(3,19)]
QuantizationModifier(config_groups={"group_0": g_fp8, "group_1": g_fp4}, ignore=["lm_head"])
```
GPTQ/AWQ were NOT usable on this architecture in llmcompressor 0.12: GPTQ's Hessian
inversion fails on all 154 modules (root cause unknown — the double-fire
hook was checked and is not the cause); AWQ lacks arch mappings. Reported upstream:
[#2952](https://github.com/vllm-project/llm-compressor/issues/2952), [#2953](https://github.com/vllm-project/llm-compressor/issues/2953).

## Limitations

- vLLM-only until PR #49433 merges. Bundled `modeling_nanbeige.py` carries two
  one-line transformers-5 compat patches (rope key, tied-weights type).
- W4A4 config-variant possible (same bytes) but NOT recommended: batch-1 decode is
  faster via the Marlin W4A16 path on consumer Blackwell, and activation quantization
  is the looped arch's worst failure mode.
- English-only evals; n=100/46 — directional, not leaderboard-grade.


## Which artifact should I choose?

![Quality across benchmarks](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic/resolve/main/assets/chart_quality_benches.png)

![Quality vs size](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic/resolve/main/assets/chart_quality_vs_size.png)

![Decode speed per workload](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic/resolve/main/assets/chart_speed_workloads.png)

| artifact | size | tok/s (freeform / summ) | pick when |
|---|---|---|---|
| [FP8-Dynamic](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic) | 4.9 GB | 154 / 206 | default: no measured quality loss on any gate. Recommended. |
| [NVFP4-FP8-LoopShield](https://huggingface.co/NullSense/Nanbeige4.2-3B-NVFP4-FP8-LoopShield) (this repo) | 4.5 GB | 159 / 202 | smallest artifact that keeps reasoning at FP8 parity; best JSON reliability. Recommended for tight VRAM. |
| [NVFP4A16](https://huggingface.co/NullSense/Nanbeige4.2-3B-NVFP4A16) | 3.6 GB | 175 / 220 | fastest; summarization/extraction only (reasoning drops 8 GSM8K points). Not for math/agentic. |
| [EAGLE3 draft](https://huggingface.co/NullSense/Nanbeige4.2-3B-EAGLE3) | +1.5 GB | +12-41% decode | add-on speculator for any of the above; thinking-aware retrain (2026-07-24), thinking-mode acceptance 0.41, lossless. Serve with TRITON_ATTN. |

All three serve identically (same plugin, same flags); only the checkpoint differs.

Comparison chain: the columns here use my FP8-Dynamic quant as reference; the FP8 card carries the [bf16-original matrix](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic) linking the chain back to the unquantized model.

## Links & provenance

- Base model: [Nanbeige/Nanbeige4.2-3B](https://huggingface.co/Nanbeige/Nanbeige4.2-3B)
- Family: [FP8-Dynamic](https://huggingface.co/NullSense/Nanbeige4.2-3B-FP8-Dynamic) · [NVFP4-FP8-LoopShield](https://huggingface.co/NullSense/Nanbeige4.2-3B-NVFP4-FP8-LoopShield) · [NVFP4A16](https://huggingface.co/NullSense/Nanbeige4.2-3B-NVFP4A16) · [EAGLE3 draft](https://huggingface.co/NullSense/Nanbeige4.2-3B-EAGLE3)
- Arch serving support: [vLLM PR #49433](https://github.com/vllm-project/vllm/pull/49433) (until merged, the bundled `vllm_plugin/` registers it out-of-tree)
- Upstream tooling reports I filed from this work: [llm-compressor#2952](https://github.com/vllm-project/llm-compressor/issues/2952) (GPTQ Hessian inversion fails on all modules of this looped arch — root cause unknown; silent RTN fallback) · [llm-compressor#2953](https://github.com/vllm-project/llm-compressor/issues/2953) (AWQ lacks arch mappings)
- Quantized with [llm-compressor](https://github.com/vllm-project/llm-compressor) 0.12.0 (compressed-tensors format)

## Benchmark provenance (ordered: public-harness first, then my closed harnesses)

**Public, reproducible** (lm-eval-harness `local-chat-completions`, exact configs in each row's annotation):
1. [GSM8K](https://github.com/EleutherAI/lm-evaluation-harness/tree/main/lm_eval/tasks/gsm8k) — grade-school math, the reasoning gate (thinking mode, n=100, max_tokens 8192)
2. [IFEval](https://github.com/EleutherAI/lm-evaluation-harness/tree/main/lm_eval/tasks/ifeval) — verifiable instruction following (non-thinking, n=250)
3. [MMLU-Pro](https://github.com/EleutherAI/lm-evaluation-harness/tree/main/lm_eval/tasks/mmlu_pro) — 10-choice knowledge/reasoning (non-thinking, 25/category)
4. [BBH](https://github.com/EleutherAI/lm-evaluation-harness/tree/main/lm_eval/tasks/bbh) — hard reasoning suite, CoT few-shot (non-thinking, 15/subtask)
5. [MultiHop-RAG](https://huggingface.co/datasets/yixuantt/MultiHopRAG) — multi-doc news QA; I run generator-only with gold evidence (custom harness, dataset public)

**Closed/personal harnesses** (not publicly reproducible — my own serving-workload gates; treat as relative signals between artifacts in THIS family, not cross-model scores):
- **Blind-judge summarization** — 48 stratified real articles, per-article anonymized+shuffled candidates, single LLM judge scoring faithfulness/coverage/fabrication. Tests: does the quant change long-form grounded generation quality?
- **Rewrite taxonomy** — 20 dictation-cleanup cases from a production ASR pipeline. Tests: instruction-constrained short-form editing.
- **JSON parse rate** — structured-output emission over the summarization set. Tests: format discipline under quantization.

## Citation

```bibtex
@misc{peciukonis2026nanbeige42loopshield,
  author       = {Pe{\v{c}}iukonis, Matas (NullSense)},
  title        = {NVFP4-FP8-LoopShield: loop-aware mixed-precision NVFP4 quantization of Nanbeige4.2-3B},
  year         = {2026},
  howpublished = {Hugging Face},
  url          = {https://huggingface.co/NullSense/Nanbeige4.2-3B-NVFP4-FP8-LoopShield},
  note         = {Placement recipe recovering GSM8K 81->89 on a looped/weight-shared LLM; first FP4-family results for the architecture class.}
}
```