---
id: pr-flash-attention-2513
repo: Dao-AILab/flash-attention
pr: 2513
title: SM90 FA4 QuACK 0.4 Compatibility
author: EduardDurech
date: '2026-04-28'
url: https://github.com/Dao-AILab/flash-attention/pull/2513
source_category: upstream-code
architectures:
- sm100
- sm90
tags:
- sm100
- sm90
techniques: []
hardware_features:
- blackwell
- hopper
kernel_types:
- attention
languages: []
captured_at: '2026-05-16'
status: merged
merge_sha: ebeff90781648b33d487231c9d006776bd4390d1
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- CLAUDE.md
- flash_attn/cute/flash_bwd_sm90.py
- flash_attn/cute/pyproject.toml
artifact_dir: evidence/pull-bundles/flash-attention/gh-2513
head_ref_oid: 666b5341f728eb704bff016f406845aded8cf78a
---
# SM90 FA4 QuACK 0.4 Compatibility

- Repository: `Dao-AILab/flash-attention`
- PR: [2513](https://github.com/Dao-AILab/flash-attention/pull/2513)
- Decision: `Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.`
- Reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.

## Changed Paths

- `CLAUDE.md`
- `flash_attn/cute/flash_bwd_sm90.py`
- `flash_attn/cute/pyproject.toml`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2513`
