Gemma 4 26B-A4B IT FP8 Dynamic Norouter

Production-ready offline FP8 checkpoint for vLLM — 47% less VRAM, 80% more concurrency vs BF16.

We searched for a usable offline FP8 checkpoint of Gemma 4 26B-A4B-it but couldn't find one that worked cleanly with vLLM. So we vibe-coded our own and are sharing it with the community.

This repository hosts an offline FP8 checkpoint derived from google/gemma-4-26B-A4B-it for vLLM serving. No on-the-fly quantization needed at startup.

Published by Largitdata Inc.

Note: This is a derived operational checkpoint, not an official Google release. The original model's license terms, safety guidance, and documentation remain authoritative.

📖 中文說明 / Chinese Version

Model Details

• Base model: google/gemma-4-26B-A4B-it
• Derived format: offline FP8 checkpoint for vLLM
• Quantization tool: llmcompressor
• Quantization method: FP8_DYNAMIC
• Calibration data: None required (dynamic quantization)
• Excluded weights:
  • norm-class 1D tensors — excluded to avoid expected 2D linear weight validation errors during quantization
  • re:.*router\.proj$ — MoE router weights excluded to maintain compatibility with the Gemma4 vLLM loading path
• Output directory name: gemma-4-26B-A4B-it-FP8-DYNAMIC-NOROUTER
• Primary serving target: vllm/vllm-openai:gemma4
• Organization: Largitdata Inc.

Test Environment

• GPU: NVIDIA H200 NVL (143 GB VRAM)
• Runtime: vllm/vllm-openai:gemma4
• KV cache dtype: fp8
• max_model_len: 32768
• gpu_memory_utilization: 0.55

Observed vLLM startup characteristics:

• model weight loading: 15.76 s
• model loading total: 16.88 s
• torch.compile: 56.98 s
• engine init: 102.17 s
• total time to /v1/models ready: about 153 s

Observed runtime capacity:

• max_num_batched_tokens = 8192
• available KV cache memory: 46.37 GiB
• GPU KV cache size: 405,184 tokens
• maximum concurrency at 32,768 tokens/request: 38.87x

Serving Capacity Comparison

Basic Benchmark

Single-request warm benchmark against the OpenAI-compatible vLLM endpoint:

• prompt tokens: 38
• completion tokens: 256
• temperature: 0

These numbers are single-request warm-path measurements, not multi-client throughput tests. In production multi-client scenarios, the FP8 variant's larger KV cache is expected to provide superior aggregate throughput.

BF16 is ~6% faster on single-request latency, but the FP8 variant uses 47% less VRAM and provides 80% more KV cache capacity. For production environments serving multiple concurrent users, the FP8 variant offers a better trade-off.

Accuracy Evaluation — MMLU-Pro

We ran MMLU-Pro (full set, 14 categories) comparing this FP8 checkpoint against its BF16 baseline on the same harness and prompt template.

FP8 quantization cost is essentially zero — the 0.26 pp gap sits inside benchmark noise. Our 26B BF16 number (81.59%) is ~1.0 pp below Google's reported 82.6%, consistent with harness/prompt differences rather than a quantization defect; both BF16 and FP8 shift together.

For context, we also evaluated the sibling 31B variant under identical conditions:

See also: LargitData/gemma-4-31b-it-fp8.

Usage

Example vLLM launch:

docker run -d \
  --name vllm-gemma4-26b-fp8-norouter \
  --restart unless-stopped \
  --ipc=host \
  --shm-size 16G \
  --gpus all \
  -v /models \
  -p 8001:8000 \
  -e NVIDIA_VISIBLE_DEVICES=0 \
  vllm/vllm-openai:gemma4 \
  --model /models/gemma-4-26B-A4B-it-FP8-DYNAMIC-NOROUTER \
  --trust-remote-code \
  --kv-cache-dtype fp8 \
  --gpu-memory-utilization 0.55 \
  --max-model-len 32768 \
  --enable-auto-tool-choice \
  --tool-call-parser gemma4 \
  --host 0.0.0.0 \
  --port 8000

Known Limitations

• Single-request latency is ~6% higher than BF16 due to FP8 dequantization overhead.
• MMLU-Pro measured (see above); MT-Bench and other benchmarks not yet run. Community contributions are welcome.
• Only tested on NVIDIA H200 NVL. Other GPUs (A100, H100) may require adjusting gpu-memory-utilization.
• MoE router weights (router.proj) and norm-class 1D tensors are excluded from quantization for vLLM compatibility. No routing degradation has been observed, but systematic evaluation has not been performed.

Intended Use

This artifact is intended for:

• Operational vLLM deployment on H200-class hardware
• Reproducible offline FP8 serving experiments
• Environments where startup-time on-the-fly quantization is undesirable
• Production inference with higher concurrency requirements

This artifact is not intended to replace the original base model documentation, safety guidance, or license terms.

License

This repository contains a derived checkpoint based on google/gemma-4-26B-A4B-it. Usage is subject to the Gemma Terms of Use.

Citation

If you use this artifact, please cite both the derived checkpoint and the upstream base model.

@misc{largitdata_gemma4_26b_a4b_it_fp8_dynamic_norouter_2026,
  title        = {Gemma 4 26B-A4B IT FP8 Dynamic Norouter},
  author       = {David Chiu},
  year         = {2026},
  howpublished = {\url{https://huggingface.co/largitdata-inc/gemma-4-26b-a4b-it-fp8-dynamic-norouter}},
  note         = {Derived offline FP8 checkpoint from google/gemma-4-26B-A4B-it for vLLM serving, published by Largitdata Inc. \url{https://www.largitdata.com/}}
}

@misc{google_gemma4_26b_a4b_it,
  title        = {Gemma 4 26B-A4B IT},
  author       = {Google},
  year         = {2026},
  howpublished = {\url{https://huggingface.co/google/gemma-4-26B-A4B-it}}
}

Disclaimer

Users are responsible for verifying license compatibility, downstream serving behavior, numerical quality, and safety characteristics for their own environment.

中文說明

給 vLLM 用的離線 FP8 checkpoint — 比 BF16 省 47% VRAM，平行處理能力多 80%。

我們在網路上找了一輪，沒有找到堪用的 Gemma 4 26B 離線 FP8 版本，索性自己 vibe coding 做了一版，貢獻給社群。

這個 Repo 提供從 google/gemma-4-26B-A4B-it 衍生出的離線 FP8 checkpoint，讓 vLLM 可以直接載入服務，不需要在啟動時執行 on-the-fly 量化。

由 Largitdata Inc. 發佈。

注意： 這是衍生的操作用 checkpoint，並非 Google 官方發佈。原始模型的授權條款、安全指引與文件仍以官方為準。

模型細節

• 基底模型： google/gemma-4-26B-A4B-it
• 格式： 離線 FP8 checkpoint，供 vLLM 使用
• 量化工具： llmcompressor
• 量化方式： FP8_DYNAMIC
• 校準資料： 不需要（動態量化）
• 排除的權重：
  • norm 類一維 tensor — 避免量化驗證時產生 expected 2D linear weight 類錯誤
  • re:.*router\.proj$ — MoE router 權重，維持與 Gemma4 vLLM 載入路徑的相容性
• 主要部署目標： vllm/vllm-openai:gemma4

測試環境

• GPU： NVIDIA H200 NVL（143 GB VRAM）
• Runtime： vllm/vllm-openai:gemma4
• KV cache dtype： fp8
• max_model_len： 32768
• gpu_memory_utilization： 0.55

啟動實測數據：

• 模型權重載入：15.76 s
• 模型載入總計：16.88 s
• torch.compile：56.98 s
• 引擎初始化：102.17 s
• /v1/models 就緒總時間：約 153 s

執行期容量：

• max_num_batched_tokens = 8192
• 可用 KV cache 記憶體：46.37 GiB
• GPU KV cache 大小：405,184 tokens
• 最大平行處理量（32,768 tokens/request）：38.87x

服務容量比較

基礎效能測試

單請求暖機測試（OpenAI 相容 vLLM endpoint）：

• prompt tokens：38
• completion tokens：256
• temperature：0

以上為單請求暖機路徑測量值，非多用戶吞吐量測試。在生產環境多用戶場景下，FP8 版本更大的 KV cache 預期能提供更好的整體吞吐量。

結論：BF16 單請求略快（約 6%），但 FP8 版本 VRAM 用量減少 47%，可用 KV cache 增加 80%。需要同時服務多用戶的生產環境，FP8 版本更具優勢。

精度評估 — MMLU-Pro

使用相同 harness 與 prompt template，對 FP8 checkpoint 與 BF16 原版同時執行 MMLU-Pro（全集，14 類別）：

FP8 量化的代價基本為零 — 0.26 pp 的差距落在 benchmark 噪音範圍內。我們的 26B BF16 成績（81.59%）比 Google 官方的 82.6% 低約 1.0 pp，這是 harness / prompt 差異造成，非量化問題；BF16 與 FP8 兩者一起偏移。

作為對照，同條件下 31B 版本結果：

另見：LargitData/gemma-4-31b-it-fp8。

使用方式

vLLM 啟動範例：

docker run -d \
  --name vllm-gemma4-26b-fp8-norouter \
  --restart unless-stopped \
  --ipc=host \
  --shm-size 16G \
  --gpus all \
  -v /models \
  -p 8001:8000 \
  -e NVIDIA_VISIBLE_DEVICES=0 \
  vllm/vllm-openai:gemma4 \
  --model /models/gemma-4-26B-A4B-it-FP8-DYNAMIC-NOROUTER \
  --trust-remote-code \
  --kv-cache-dtype fp8 \
  --gpu-memory-utilization 0.55 \
  --max-model-len 32768 \
  --enable-auto-tool-choice \
  --tool-call-parser gemma4 \
  --host 0.0.0.0 \
  --port 8000

已知限制

• 單請求延遲比 BF16 高約 6%，主因為 FP8 dequantization 的額外開銷
• MMLU-Pro 已完成（見上），MT-Bench 等其他 benchmark 尚未執行，歡迎社群補充
• 僅在 H200 NVL 上實測，其他 GPU（如 A100、H100）可能需要調整 gpu-memory-utilization
• MoE router 權重（router.proj）與 norm 類一維 tensor 被排除在量化範圍外以維持 vLLM 相容性，目前未觀察到分流品質下降，但尚無系統性評估

使用場景

此 checkpoint 適用於：

• 在 H200 等級硬體上以 vLLM 進行生產部署
• 可重現的離線 FP8 服務實驗
• 不希望在啟動時執行 on-the-fly 量化的環境
• 需要更高平行處理能力的生產推論場景

此 checkpoint 不取代原始基底模型的文件、安全指引或授權條款。

授權

此 Repo 包含基於 google/gemma-4-26B-A4B-it 的衍生 checkpoint，使用須遵守 Gemma 使用條款。

免責聲明

使用者需自行驗證授權相容性、下游服務行為、數值品質與安全特性。