b12x is an SM120/SM121 CuTe DSL kernel library for (primarily) NVFP4 LLM inference.

It is intentionally narrow. This is not a generic CUDA kernel collection or a full model-serving stack. It does not intend to target any other GPU architectures, including SM100. It is a focused package for a small number of high-performance kernels plus the runtime glue needed to launch them cleanly from sglang/vllm.

Currently supported kernels:

• NVFP4 fused MoE GEMM
• NVFP4 dense GEMM
• BF16/FP8 paged attention
• Sparse MLA attention (for DSA/NSA only).

pip install b12x

Ask your friendly neighborhood AI agent for further information on how to use this library.