[Nic-Polumeyv]

A Bun.file route opens and fstats the file before it evaluates If-None-Match, so its 304 costs more than one returned from a JS handler (found in sveltejs/kit#17123). When the request matches an ETag the route was given, this answers from one stat instead: 47.5 -> 26.8 µs CPU per 304 on a debug build, 200s unchanged, and a missing file still falls through.

[claude]

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[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between b52d513 and d82dbb5.

📒 Files selected for processing (2)

• src/runtime/server/FileRoute.rs
• test/js/bun/http/bun-serve-file.test.ts

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Walkthrough

Changes

File cache validation

Layer / File(s)	Summary
Metadata-only 304 path src/runtime/server/FileRoute.rs	Eligible GET and HEAD requests now validate file metadata before opening the file and return a bodyless 304 response when the conditions match.
Conditional request coverage test/js/bun/http/bun-serve-file.test.ts	Tests cover matching ETags, unreadable and deleted files, conflicting conditions, and GET and HEAD behavior.

Suggested reviewers: robobun

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to d82db

The metadata-based conditional-file response preserves the stated fallback cases, and no remaining issue requires changes before merge.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description explains the performance change, the affected behavior, and the reported verification results. It does not use the template headings or state the exact test commands, but it provides t…
Title check	✅ Passed	The title clearly and concisely describes the main change: returning a matching If-None-Match response for a Bun.file route without opening the file.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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