diff --git a/packages/vite/src/node/__tests__/html.spec.ts b/packages/vite/src/node/__tests__/html.spec.ts
new file mode 100644
index 00000000000000..30df8e18bba545
--- /dev/null
+++ b/packages/vite/src/node/__tests__/html.spec.ts
@@ -0,0 +1,174 @@
+import { describe, expect, test } from 'vitest'
+import type { OutputBundle, OutputChunk } from 'rolldown'
+import { getCssFilesForChunk } from '../plugins/html'
+
+function createChunk(
+  fileName: string,
+  imports: string[],
+  importedCss: string[],
+): OutputChunk {
+  return {
+    type: 'chunk',
+    fileName,
+    imports,
+    viteMetadata: { importedCss: new Set(importedCss) },
+  } as unknown as OutputChunk
+}
+
+function createBundle(...chunks: OutputChunk[]): OutputBundle {
+  const bundle: Record<string, OutputChunk> = {}
+  for (const chunk of chunks) {
+    bundle[chunk.fileName] = chunk
+  }
+  return bundle as unknown as OutputBundle
+}
+
+describe('getCssFilesForChunk', () => {
+  test('single chunk with own CSS', () => {
+    const chunk = createChunk('entry.js', [], ['style.css'])
+    const bundle = createBundle(chunk)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(chunk, bundle, cache)).toStrictEqual([
+      'style.css',
+    ])
+  })
+
+  test('chunk with no CSS returns empty array', () => {
+    const chunk = createChunk('entry.js', [], [])
+    const bundle = createBundle(chunk)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(chunk, bundle, cache)).toStrictEqual([])
+  })
+
+  test('imported chunk CSS comes before own CSS', () => {
+    const dep = createChunk('dep.js', [], ['dep.css'])
+    const entry = createChunk('entry.js', ['dep.js'], ['entry.css'])
+    const bundle = createBundle(entry, dep)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(entry, bundle, cache)).toStrictEqual([
+      'dep.css',
+      'entry.css',
+    ])
+  })
+
+  test('deep import chain preserves order', () => {
+    const c = createChunk('c.js', [], ['c.css'])
+    const b = createChunk('b.js', ['c.js'], ['b.css'])
+    const a = createChunk('a.js', ['b.js'], ['a.css'])
+    const bundle = createBundle(a, b, c)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(a, bundle, cache)).toStrictEqual([
+      'c.css',
+      'b.css',
+      'a.css',
+    ])
+  })
+
+  test('cache is populated and used on second call', () => {
+    const dep = createChunk('dep.js', [], ['dep.css'])
+    const entry = createChunk('entry.js', ['dep.js'], ['entry.css'])
+    const bundle = createBundle(entry, dep)
+    const cache = new Map<OutputChunk, string[]>()
+
+    const result = getCssFilesForChunk(entry, bundle, cache)
+    expect(result).toStrictEqual(['dep.css', 'entry.css'])
+    expect(cache.has(dep)).toBe(true)
+    expect(cache.has(entry)).toBe(true)
+
+    expect(getCssFilesForChunk(entry, bundle, cache)).toStrictEqual(result)
+  })
+
+  test('shared dependency CSS is output for each entry point', () => {
+    const shared = createChunk('shared.js', [], ['shared.css'])
+    const entryA = createChunk('a.js', ['shared.js'], ['a.css'])
+    const entryB = createChunk('b.js', ['shared.js'], ['b.css'])
+    const bundle = createBundle(entryA, entryB, shared)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(entryA, bundle, cache)).toStrictEqual([
+      'shared.css',
+      'a.css',
+    ])
+    expect(getCssFilesForChunk(entryB, bundle, cache)).toStrictEqual([
+      'shared.css',
+      'b.css',
+    ])
+  })
+
+  test('diamond dependency deduplicates CSS and preserves order', () => {
+    //   A
+    //  / \
+    // B   C
+    //  \ /
+    //   D
+    const d = createChunk('d.js', [], ['d.css'])
+    const b = createChunk('b.js', ['d.js'], ['b.css'])
+    const c = createChunk('c.js', ['d.js'], ['c.css'])
+    const a = createChunk('a.js', ['b.js', 'c.js'], ['a.css'])
+    const bundle = createBundle(a, b, c, d)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(a, bundle, cache)).toStrictEqual([
+      'd.css',
+      'b.css',
+      'c.css',
+      'a.css',
+    ])
+  })
+
+  test('multiple shared dependencies with different CSS', () => {
+    const shared1 = createChunk('shared1.js', [], ['shared1.css'])
+    const shared2 = createChunk('shared2.js', [], ['shared2.css'])
+    const entryA = createChunk('a.js', ['shared1.js', 'shared2.js'], ['a.css'])
+    const entryB = createChunk('b.js', ['shared2.js', 'shared1.js'], ['b.css'])
+    const bundle = createBundle(entryA, entryB, shared1, shared2)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(entryA, bundle, cache)).toStrictEqual([
+      'shared1.css',
+      'shared2.css',
+      'a.css',
+    ])
+    expect(getCssFilesForChunk(entryB, bundle, cache)).toStrictEqual([
+      'shared2.css',
+      'shared1.css',
+      'b.css',
+    ])
+  })
+
+  test('cache from one entry does not corrupt results for another with overlapping subgraph', () => {
+    //        entryA        entryB
+    //       /      \          |
+    //    mid1     mid2      mid2
+    //      |       |          |
+    //    leaf    shared     shared
+    const shared = createChunk('shared.js', [], ['shared.css'])
+    const leaf = createChunk('leaf.js', [], ['leaf.css'])
+    const mid1 = createChunk('mid1.js', ['leaf.js'], ['mid1.css'])
+    const mid2 = createChunk('mid2.js', ['shared.js'], ['mid2.css'])
+    const entryA = createChunk('a.js', ['mid1.js', 'mid2.js'], ['a.css'])
+    const entryB = createChunk('b.js', ['mid2.js'], ['b.css'])
+    const bundle = createBundle(entryA, entryB, mid1, mid2, leaf, shared)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(entryA, bundle, cache)).toStrictEqual([
+      'leaf.css',
+      'mid1.css',
+      'shared.css',
+      'mid2.css',
+      'a.css',
+    ])
+    expect(getCssFilesForChunk(entryB, bundle, cache)).toStrictEqual([
+      'shared.css',
+      'mid2.css',
+      'b.css',
+    ])
+  })
+
+  test('circular imports do not cause infinite loop', () => {
+    const a = createChunk('a.js', ['b.js'], ['a.css'])
+    const b = createChunk('b.js', ['a.js'], ['b.css'])
+    const bundle = createBundle(a, b)
+    const cache = new Map<OutputChunk, string[]>()
+    expect(getCssFilesForChunk(a, bundle, cache)).toStrictEqual([
+      'b.css',
+      'a.css',
+    ])
+  })
+})
diff --git a/packages/vite/src/node/plugins/html.ts b/packages/vite/src/node/plugins/html.ts
index 02305b45387c38..8adab33e6f9874 100644
--- a/packages/vite/src/node/plugins/html.ts
+++ b/packages/vite/src/node/plugins/html.ts
@@ -346,6 +346,57 @@ function handleParseError(
     parseError.frame
 }
 
+/**
+ * Collects CSS files for a chunk by traversing its imports depth-first,
+ * using a cache to avoid re-analyzing chunks while still returning the
+ * correct files when the same chunk is reached via different entry points.
+ */
+export function getCssFilesForChunk(
+  chunk: OutputChunk,
+  bundle: OutputBundle,
+  analyzedImportedCssFiles: Map<OutputChunk, string[]>,
+  seenChunks: Set<string> = new Set(),
+  seenCss: Set<string> = new Set(),
+): string[] {
+  if (seenChunks.has(chunk.fileName)) {
+    return []
+  }
+  seenChunks.add(chunk.fileName)
+
+  if (analyzedImportedCssFiles.has(chunk)) {
+    const files = analyzedImportedCssFiles.get(chunk)!
+    const additionals = files.filter((file) => !seenCss.has(file))
+    additionals.forEach((file) => seenCss.add(file))
+    return additionals
+  }
+
+  const files: string[] = []
+  chunk.imports.forEach((file) => {
+    const importee = bundle[file]
+    if (importee?.type === 'chunk') {
+      files.push(
+        ...getCssFilesForChunk(
+          importee,
+          bundle,
+          analyzedImportedCssFiles,
+          seenChunks,
+          seenCss,
+        ),
+      )
+    }
+  })
+  analyzedImportedCssFiles.set(chunk, files)
+
+  chunk.viteMetadata!.importedCss.forEach((file) => {
+    if (!seenCss.has(file)) {
+      seenCss.add(file)
+      files.push(file)
+    }
+  })
+
+  return files
+}
+
 /**
  * Compiles index.html into an entry js module
  */
@@ -820,48 +871,12 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
         },
       })
 
-      const getCssFilesForChunk = (
-        chunk: OutputChunk,
-        seenChunks: Set<string> = new Set(),
-        seenCss: Set<string> = new Set(),
-      ): string[] => {
-        if (seenChunks.has(chunk.fileName)) {
-          return []
-        }
-        seenChunks.add(chunk.fileName)
-
-        if (analyzedImportedCssFiles.has(chunk)) {
-          const files = analyzedImportedCssFiles.get(chunk)!
-          const additionals = files.filter((file) => !seenCss.has(file))
-          additionals.forEach((file) => seenCss.add(file))
-          return additionals
-        }
-
-        const files: string[] = []
-        chunk.imports.forEach((file) => {
-          const importee = bundle[file]
-          if (importee?.type === 'chunk') {
-            files.push(...getCssFilesForChunk(importee, seenChunks, seenCss))
-          }
-        })
-        analyzedImportedCssFiles.set(chunk, files)
-
-        chunk.viteMetadata!.importedCss.forEach((file) => {
-          if (!seenCss.has(file)) {
-            seenCss.add(file)
-            files.push(file)
-          }
-        })
-
-        return files
-      }
-
       const getCssTagsForChunk = (
         chunk: OutputChunk,
         toOutputPath: (filename: string) => string,
       ) =>
-        getCssFilesForChunk(chunk).map((file) =>
-          toStyleSheetLinkTag(file, toOutputPath),
+        getCssFilesForChunk(chunk, bundle, analyzedImportedCssFiles).map(
+          (file) => toStyleSheetLinkTag(file, toOutputPath),
         )
 
       for (const [normalizedId, html] of processedHtml(this)) {