---
id: pr-sglang-20047
repo: sgl-project/sglang
pr: 20047
title: 'fix: default FP4 GEMM backend to flashinfer_cudnn on SM120 (Blackwell)'
author: voipmonitor
date: '2026-03-09'
url: https://github.com/sgl-project/sglang/pull/20047
source_category: upstream-code
architectures:
- sm100
tags:
- PDL
- arch_pipeline
- attention_kv
- cutlass
- gemm_quant
techniques:
- fine-grained-quantization
- pipeline-stages
hardware_features:
- blackwell
- fp4
- pdl
kernel_types:
- attention
- gemm
- runtime
languages:
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: d39ed074cf11ae9247dbcb04170e6921ca727559
inclusion_reason: Inspect scale layout, accumulator type, tile/schedule choice, epilogue fusion, and partial-tile guards before deriving a candidate.
changed_paths:
- python/sglang/srt/layers/quantization/fp4_utils.py
- python/sglang/srt/server_args.py
artifact_dir: evidence/pull-bundles/sglang/gh-20047
head_ref_oid: c83957578541ab5c9970e76e4047b4235a1e23e1
---
# fix: default FP4 GEMM backend to flashinfer_cudnn on SM120 (Blackwell)

- Repository: `sgl-project/sglang`
- PR: [20047](https://github.com/sgl-project/sglang/pull/20047)
- Decision: `Inspect scale layout, accumulator type, tile/schedule choice, epilogue fusion, and partial-tile guards before deriving a candidate.`
- Reason: Inspect scale layout, accumulator type, tile/schedule choice, epilogue fusion, and partial-tile guards before deriving a candidate.

## Changed Paths

- `python/sglang/srt/layers/quantization/fp4_utils.py`
- `python/sglang/srt/server_args.py`

## Evidence Bundle

`evidence/pull-bundles/sglang/gh-20047`
