[Attention] Bump FA for removed method

[MatthewBonanni]

Purpose

vLLM-side PR for vllm-project/flash-attention#107. Removes unused flash_attn_with_kvcache and sets flags for build speedup + size reduction.

It looks like we see a 20% reduction in wheel size (481MB --> 380MB)

Recent commit on main:

[2025-11-14T16:34:18Z] #30 0.877 Wheel dist/vllm-0.11.1rc7.dev169+gc934caee8.cu129-cp38-abi3-linux_x86_64.whl is within the allowed size (481.69 MB).

This PR:

[2025-11-14T15:05:58Z] #30 0.953 Wheel dist/vllm-0.11.1rc7.dev174+g843768001.cu129-cp38-abi3-linux_x86_64.whl is within the allowed size (380.61 MB).

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @MatthewBonanni.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[gemini-code-assist]

Code Review

This pull request updates the flash-attention dependency. However, this change introduces two critical issues. First, the new dependency version removes the flash_attn_with_kvcache function, but this function is still used in the test file tests/kernels/attention/test_flash_attn.py, which will likely cause the tests to fail. The test code needs to be updated to reflect this change in the dependency. Second, the dependency now points to a temporary branch on a personal fork. This is a major risk for build stability and security, and it should be pointed to an official repository and a stable commit/tag before merging into a main branch.

[mgoin]

Wow, it looks like we see a 20% reduction in wheel size (481MB --> 380MB)

Recent commit on main:

[2025-11-14T16:34:18Z] #30 0.877 Wheel dist/vllm-0.11.1rc7.dev169+gc934caee8.cu129-cp38-abi3-linux_x86_64.whl is within the allowed size (481.69 MB).

This PR:

[2025-11-14T15:05:58Z] #30 0.953 Wheel dist/vllm-0.11.1rc7.dev174+g843768001.cu129-cp38-abi3-linux_x86_64.whl is within the allowed size (380.61 MB).