---
id: pr-vllm-28763
repo: vllm-project/vllm
pr: 28763
title: '[Attention] FA2 support more head sizes, ViT support, make default backend'
author: MatthewBonanni
date: '2025-11-19'
url: https://github.com/vllm-project/vllm/pull/28763
source_category: upstream-code
architectures:
- sm100
tags: []
techniques: []
hardware_features: []
kernel_types: []
languages: []
captured_at: '2026-05-16'
status: merged
merge_sha: 4c23690f43e51eccf6ce5866ac47adcf39215e4d
inclusion_reason: defer
changed_paths:
- cmake/external_projects/vllm_flash_attn.cmake
- tests/kernels/attention/test_flash_attn.py
- tests/kernels/attention/test_mha_attn.py
- vllm/platforms/cuda.py
- vllm/v1/attention/backends/flash_attn.py
artifact_dir: evidence/pull-bundles/vllm/gh-28763
head_ref_oid: edc6675ba39ac349695c3989489da27528753db8
---
# [Attention] FA2 support more head sizes, ViT support, make default backend

- Repository: `vllm-project/vllm`
- PR: [28763](https://github.com/vllm-project/vllm/pull/28763)
- Decision: `defer`
- Reason: defer

## Changed Paths

- `cmake/external_projects/vllm_flash_attn.cmake`
- `tests/kernels/attention/test_flash_attn.py`
- `tests/kernels/attention/test_mha_attn.py`
- `vllm/platforms/cuda.py`
- `vllm/v1/attention/backends/flash_attn.py`

## Evidence Bundle

`evidence/pull-bundles/vllm/gh-28763`
