---
id: pr-flash-attention-2174
repo: Dao-AILab/flash-attention
pr: 2174
title: '[Cute] update row_max before safe overwrite for online_softmax'
author: jayhshah
date: '2026-01-13'
url: https://github.com/Dao-AILab/flash-attention/pull/2174
source_category: upstream-code
architectures:
- sm90
tags:
- online-softmax
- sm90
techniques:
- async-copy
hardware_features:
- hopper
- tma
kernel_types:
- attention
- softmax
languages:
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: 13696f2e5e235696a6851eada1780f7753226a68
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- flash_attn/cute/softmax.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-2174
head_ref_oid: e1d81d84244a5aaa7c8ba721b65a592a46cfee13
---
# [Cute] update row_max before safe overwrite for online_softmax

- Repository: `Dao-AILab/flash-attention`
- PR: [2174](https://github.com/Dao-AILab/flash-attention/pull/2174)
- 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/softmax.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2174`
