This repo contains Codex-24B-Small-3.2 quantized with NVFP4, a 4-bit compression suitable for max performance on all hardware with 8-bit-like accuracy.

ℹ️ Unlike NVFP4 format (4-bit weights + 4-bit activation), NVFP4A16 is not limited to Blackwell GPUs and will be supported efficiently in vLLM with RTX 3000s and RTX 4000s GPUs.

Original Model:
- Gryphe/Codex-24B-Small-3.2
Hopper and Blackwell (RTX 5000s series) optimized model:
- mratsim/Codex-24B-Small-3.2-NVFP4

NVFP4 writeups:

📥 Usage & Running Instructions

The model was tested with vLLM + 1x RTX Pro 6000.

Recommendations

It is however recommended to use at most 65K context to avoid significant degradation (https://fiction.live/stories/Fiction-liveBench-Sept-29-2025/oQdzQvKHw8JyXbN87) especially with a model as small as 24B.

This model is recommended with "min-p" sampling, this sampling is available through both the oldest Text completions API and the Chat completions API (and there is a new Response API), however most LLM frontends only support modifying min-p when using Text completions. You can however use --override-generation-config "${SAMPLER_JSONCONFIG}" to override the sampler (which is a merge of generation_config.json and vLLM defaults)

Running script

bash

# Model configuration (Mandatory)
MODEL="mratsim/Codex-24B-Small-3.2-NVFP4A16"
MODELNAME="Codex-24B-Small-3.2"
CONTEXT_SIZE=32768
GPU_UTIL=0.95

# Sampling configuration (Optional, if departing from `generation_config.json`)
SAMPLER_OVERRIDE='{"temperature": 0.5, "min_p": 0.05, "top_p": 1, "repetition_penalty": 1.05}'

# Prevent vLLM from using 100% CPU when idle (Very Recommended)
export VLLM_SLEEP_WHEN_IDLE=1

# Use FlashInfer backend (fastest, recommended, "instant" context reprocessing)
export VLLM_ATTENTION_BACKEND=FLASHINFER

vllm serve "${MODEL}" \
  --served-model-name "${MODELNAME}" \
  --gpu-memory-utilization ${GPU_UTIL} \
  --max-model-len "${CONTEXT_SIZE}" \
  --override-generation-config "${SAMPLER_OVERRIDE}"

ℹ️ The FlashInfer backend may fail with an error similar to Failed to allocate memory for batch_prefill_tmp_v with size XYZ and alignment 16 in AlignedAllocator.

A workaround is running a sed replacement command within vllm install to increase buffer space

sed -i 's/FLASHINFER_WORKSPACE_BUFFER_SIZE = 256 \* 1024 \* 1024/FLASHINFER_WORKSPACE_BUFFER_SIZE = 512 \* 1024 \* 1024/g' vllm/v1/attention/backends/flashinfer.py

This will be fixed by PR https://github.com/vllm-project/vllm/pull/25344

🔬 Quantization method

The llmcompressor library was used with the following recipe:

yaml

default_stage:
  default_modifiers:
    QuantizationModifier:
      targets: [Linear]
      ignore: [lm_head]
      scheme: NVFP4A16

NVFP4A16 doesn't require any calibration dataset.