[robobun]

Summary

• Fixes When the --production flag is used, CSS is not included correctly when there are multiple html entrypoints #23668: When multiple HTML entrypoints shared the same CSS file with --production, only the first HTML file included the <link> tag for CSS. The second (and subsequent) entrypoints were missing it entirely.
• Root cause was two bugs in CSS chunk handling:
  1. getCSSChunkForHTML matched by entry_point_id, but deduplicated CSS chunks only stored the first entry point's ID. Fixed by resolving CSS chunks through the JS chunk's css_chunks indices.
  2. CSS chunk index remapping in computeChunks used js_chunks.count() as the base offset, not accounting for interleaved HTML chunks. Fixed by using sorted_chunks.len.

Test plan

• New test html/SharedCSSProductionMultipleEntries in test/bundler/bundler_html.test.ts — verifies both HTML entrypoints get CSS <link> tags pointing to the same deduplicated CSS chunk
• Test fails with USE_SYSTEM_BUN=1 (reproduces the bug) and passes with debug build (confirms the fix)
• All 19 existing HTML bundler tests continue to pass

🤖 Generated with Claude Code

[robobun]

^{Updated 2:17 AM PT - Feb 15th, 2026}

❌ Your commit f0cae21a has 2 failures in Build #37342 (All Failures):

• test/js/node/http/node-http-backpressure-max.test.ts - 1 failing on 🍎 14 x64
• test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🍎 13 aarch64

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🧪   To try this PR locally:

bunx bun-pr 27040

That installs a local version of the PR into your bun-27040 executable, so you can run:

bun-27040 --bun

[coderabbitai]

Walkthrough

Resolve CSS deduplication and HTML linking: CSS chunk lookup for HTML now prefers the related JS chunk's css_chunks (with fallback to entry_point_id), and CSS chunk remapping iterates over sorted chunks to handle interleaved HTML/JS. Adds a regression test for shared CSS across multiple production HTML entries.

Changes

Cohort / File(s)	Summary
CSS chunk resolution src/bundler/Chunk.zig	getCSSChunkForHTML now attempts to find the related JS chunk and returns its first referenced CSS chunk via css_chunks; falls back to prior entry_point_id matching when absent.
CSS deduplication & remapping src/bundler/linker_context/computeChunks.zig	Always compute CSS dedup key from content/order (remove conditional on css_chunking). Adjust remapping loop to use sorted_chunks.len as start index to account for interleaved HTML/JS chunks.
Tests test/bundler/bundler_html.test.ts, test/bundler/esbuild/css.test.ts	Add SharedCSSProductionMultipleEntries regression test verifying deduplicated CSS is linked by multiple production HTML entries; re-enable the previously skipped MetafileCSSBundleTwoToOne test.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Merge Conflict Detection	⚠️ Warning	❌ Merge conflicts detected (11 files): ⚔️ src/bundler/Chunk.zig (content) ⚔️ src/bundler/linker_context/computeChunks.zig (content) ⚔️ src/runtime.js (content) ⚔️ test/bundler/__snapshots__/bun-build-api.test.ts.snap (content) ⚔️ test/bundler/bundler_edgecase.test.ts (content) ⚔️ test/bundler/bundler_html.test.ts (content) ⚔️ test/bundler/bundler_npm.test.ts (content) ⚔️ test/bundler/bundler_promiseall_deadcode.test.ts (content) ⚔️ test/bundler/esbuild/css.test.ts (content) ⚔️ test/bundler/html-import-manifest.test.ts (content) ⚔️ test/regression/issue/cyclic-imports-async-bundler.test.js (content) These conflicts must be resolved before merging into main.	Resolve conflicts locally and push changes to this branch.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly describes the main fix: ensuring CSS is included in all HTML entrypoints when sharing deduplicated CSS chunks, which matches the core objective from issue #23668.
Description check	✅ Passed	The PR description comprehensively covers both the root causes of the bugs and the test plan, exceeding the basic template requirements with detailed technical explanations.
Linked Issues check	✅ Passed	The code changes directly address issue #23668 by fixing CSS chunk association for multiple HTML entrypoints through two targeted bug fixes: resolving CSS chunks via JS chunk indices and correcting index remapping.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the CSS deduplication issue: modifications to getCSSChunkForHTML, computeChunks logic, test additions, and unskipping a related test are all in scope.

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[claude]

Code Review

Newest first

✅ 630f8 — Looks good!

Reviewed 3 files across src/bundler/ and test/bundler/: This PR fixes CSS chunk index calculation when multiple HTML entry points share CSS files, ensuring the correct CSS chunks are referenced from their corresponding JavaScript chunks.

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[claude]

Code Review

Newest first

✅ d1a0e — Looks good!

Reviewed 10 files across src/bundler/, src/bun.js/, src/js/builtins/, and test/: Fixes CSS chunk handling in the bundler to ensure all HTML entrypoints include link tags for shared CSS files in production builds.

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[claude]

Code Review

Newest first

✅ f0cae — Looks good!

Reviewed 2 files across src/bundler/ and test/bundler/: fixes CSS bundling bug where multiple HTML entrypoints sharing deduplicated CSS chunks would only emit the CSS link tag in the first HTML file, by resolving CSS chunks through the JS chunk's indirection table and correcting the CSS chunk index remapping offset.

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