[BugFix] Preserve max_seq_len in ubatch metadata during CUDA graph capture

[czhu-cohere]

Purpose

for SWA models the current code would incorrectly select full attention kernels for SWA layers since the seqlen seen at cudagraph capture was 1. Explicitly pass in the metadata max_model_len to fix it

Test Plan

Test Result

---

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.

[gemini-code-assist]

Code Review

This pull request updates the _make_metadata_with_slice function in vllm/v1/worker/ubatch_utils.py to ensure that max_seq_len incorporates the override value from attn_metadata. This adjustment is intended to maintain the correct kernel selection for Sliding Window Attention (SWA) layers during CUDA-graph capture. I have no feedback to provide.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[mergify]

Hi @czhu-cohere, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[LucasWilkinson]

Make sense; thanks for the fix!