---
id: pr-flash-attention-1934
repo: Dao-AILab/flash-attention
pr: 1934
title: 'feat: Adding varlen support to cute-dsl sm80 bwd'
author: imbr92
date: '2025-10-13'
url: https://github.com/Dao-AILab/flash-attention/pull/1934
source_category: upstream-code
architectures:
- sm90
tags:
- attention_kv
- benchmark_test
- compiler_runtime
- cute dsl
- scheduler_autotune
- sm90
techniques:
- autotuning
- tile-scheduling
hardware_features:
- hopper
kernel_types:
- attention
- compiler
- scheduler
languages:
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: 25f5d092b21d2d6b005ccd34092479a620ae4ceb
inclusion_reason: Treat scheduler/autotune configs as shape-specific evidence; replay benchmark shapes before generalizing.
changed_paths:
- flash_attn/cute/flash_bwd.py
- flash_attn/cute/flash_bwd_postprocess.py
- flash_attn/cute/flash_bwd_preprocess.py
- flash_attn/cute/interface.py
- flash_attn/cute/mask.py
- tests/cute/test_flash_attn_varlen.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-1934
head_ref_oid: 2f7f70639169c01ab21e373c3f07ffa54d9a23d5
---
# feat: Adding varlen support to cute-dsl sm80 bwd

- Repository: `Dao-AILab/flash-attention`
- PR: [1934](https://github.com/Dao-AILab/flash-attention/pull/1934)
- Decision: `Treat scheduler/autotune configs as shape-specific evidence; replay benchmark shapes before generalizing.`
- Reason: Treat scheduler/autotune configs as shape-specific evidence; replay benchmark shapes before generalizing.

## Changed Paths

- `flash_attn/cute/flash_bwd.py`
- `flash_attn/cute/flash_bwd_postprocess.py`
- `flash_attn/cute/flash_bwd_preprocess.py`
- `flash_attn/cute/interface.py`
- `flash_attn/cute/mask.py`
- `tests/cute/test_flash_attn_varlen.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-1934`
