---
id: pr-flash-attention-2550
repo: Dao-AILab/flash-attention
pr: 2550
title: fix varlen w/ paging split kv bug
author: liangel-02
date: '2026-05-12'
url: https://github.com/Dao-AILab/flash-attention/pull/2550
source_category: upstream-code
architectures:
- sm100
tags:
- attention
- attention kernel
techniques: []
hardware_features: []
kernel_types:
- attention
languages:
- cuda-cpp
captured_at: '2026-05-16'
status: merged
merge_sha: 9bad4bec7326ad28edb5516b8878fd283f8991c0
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- csrc/flash_attn/flash_api.cpp
- tests/test_flash_attn.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-2550
head_ref_oid: 88c8bef02d3ea28b16bf93149a76c0c6525ddd50
---
# fix varlen w/ paging split kv bug

- Repository: `Dao-AILab/flash-attention`
- PR: [2550](https://github.com/Dao-AILab/flash-attention/pull/2550)
- 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

- `csrc/flash_attn/flash_api.cpp`
- `tests/test_flash_attn.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2550`
