---
id: pr-flash-attention-2136
repo: Dao-AILab/flash-attention
pr: 2136
title: block-sparse backward SM90
author: drisspg
date: '2026-01-10'
url: https://github.com/Dao-AILab/flash-attention/pull/2136
source_category: upstream-code
architectures:
- sm90
tags:
- sm90
techniques: []
hardware_features:
- hopper
kernel_types:
- attention
languages: []
captured_at: '2026-05-16'
status: merged
merge_sha: 27a3b54c456701fd7a46375b723b37b2db14e728
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- flash_attn/cute/block_sparse_utils.py
- flash_attn/cute/flash_bwd_sm90.py
- flash_attn/cute/interface.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-2136
head_ref_oid: edd5b157e84e0d55800143497e4be771e16b1b50
---
# block-sparse backward SM90

- Repository: `Dao-AILab/flash-attention`
- PR: [2136](https://github.com/Dao-AILab/flash-attention/pull/2136)
- 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

- `flash_attn/cute/block_sparse_utils.py`
- `flash_attn/cute/flash_bwd_sm90.py`
- `flash_attn/cute/interface.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2136`
