From 7c3b21f21b521c4c8f83600590199fe4e41f5efd Mon Sep 17 00:00:00 2001
From: shulaoda <165626830+shulaoda@users.noreply.github.com>
Date: Fri, 19 Jun 2026 19:39:32 +0800
Subject: [PATCH] fix(css): inject inlined CSS after the shebang line

---
 .../src/node/__tests__/plugins/css.spec.ts    | 25 +++++++++++++++++++
 packages/vite/src/node/plugins/css.ts         | 11 +++++---
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/packages/vite/src/node/__tests__/plugins/css.spec.ts b/packages/vite/src/node/__tests__/plugins/css.spec.ts
index d925ee96a45dc8..231a934eca425f 100644
--- a/packages/vite/src/node/__tests__/plugins/css.spec.ts
+++ b/packages/vite/src/node/__tests__/plugins/css.spec.ts
@@ -829,4 +829,29 @@ exports.foo = foo;
       })();"
     `)
   })
+
+  test('should inject CSS after the shebang line for es', async () => {
+    const result = getInlinedCSSInjectedCode(
+      `#!/usr/bin/env node
+console.log("foo");`,
+      'es',
+    )
+    expect(result).toMatchInlineSnapshot(`
+      "#!/usr/bin/env node
+      injectCSS();console.log("foo");"
+    `)
+  })
+
+  test('should inject CSS at the start for es without shebang', async () => {
+    const result = getInlinedCSSInjectedCode(`console.log("foo");`, 'es')
+    expect(result).toMatchInlineSnapshot(`"injectCSS();console.log("foo");"`)
+  })
+
+  test('should inject CSS for es shebang without trailing newline', async () => {
+    const result = getInlinedCSSInjectedCode(`#!/usr/bin/env node`, 'es')
+    expect(result).toMatchInlineSnapshot(`
+      "#!/usr/bin/env node
+      injectCSS();"
+    `)
+  })
 })
diff --git a/packages/vite/src/node/plugins/css.ts b/packages/vite/src/node/plugins/css.ts
index 3669462c422d53..72ca6fa40a8990 100644
--- a/packages/vite/src/node/plugins/css.ts
+++ b/packages/vite/src/node/plugins/css.ts
@@ -1159,11 +1159,14 @@ export function injectInlinedCSS(
   } else if (format === 'es') {
     // legacy build
     if (code.startsWith('#!')) {
-      let secondLinePos = code.indexOf('\n')
-      if (secondLinePos === -1) {
-        secondLinePos = 0
+      // inject after the shebang line instead of into it
+      const newlinePos = code.indexOf('\n')
+      if (newlinePos === -1) {
+        // the shebang has no trailing newline, add one so it stays intact
+        s.append(`\n${injectCode}`)
+        return
       }
-      injectionPoint = secondLinePos
+      injectionPoint = newlinePos + 1
     } else {
       injectionPoint = 0
     }