fix(test): preserve string-literal tabs in convertTabsToSpaces

packages/cli/snap-tests/test-inline-snapshot-indent/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "test-inline-snapshot-indent",
+  "private": true
+}

packages/cli/snap-tests/test-inline-snapshot-indent/snap.txt

@@ -0,0 +1,23 @@
+> vp test run -u src/inline-snapshot.test.ts # write inline snapshot via --update (regression test for #1553)
+ RUN  <cwd>
+
+ ✓ src/inline-snapshot.test.ts (1 test) <variable>ms
+
+  Snapshots  1 written
+ Test Files  1 passed (1)
+      Tests  1 passed (1)
+   Start at  <date>
+   Duration  <variable>ms (transform <variable>ms, setup <variable>ms, import <variable>ms, tests <variable>ms, environment <variable>ms)
+
+
+> cat src/inline-snapshot.test.ts # snapshot must use 2-space indentation, not tabs
+import { describe, expect, it } from 'vite-plus/test';
+
+describe('inline snapshot indentation', () => {
+  it('writes multiline snapshots using the surrounding file indentation style', () => {
+    expect('alpha\nbeta').toMatchInlineSnapshot(`
+      "alpha
+      beta"
+    `);
+  });
+});

packages/cli/snap-tests/test-inline-snapshot-indent/src/inline-snapshot.test.ts

@@ -0,0 +1,7 @@
+import { describe, expect, it } from 'vite-plus/test';
+
+describe('inline snapshot indentation', () => {
+  it('writes multiline snapshots using the surrounding file indentation style', () => {
+    expect('alpha\nbeta').toMatchInlineSnapshot();
+  });
+});

packages/cli/snap-tests/test-inline-snapshot-indent/steps.json

@@ -0,0 +1,7 @@
+{
+  "ignoredPlatforms": ["win32"],
+  "commands": [
+    "vp test run -u src/inline-snapshot.test.ts # write inline snapshot via --update (regression test for #1553)",
+    "cat src/inline-snapshot.test.ts # snapshot must use 2-space indentation, not tabs"
+  ]
+}

packages/test/__tests__/build-artifacts.spec.ts

@@ -65,6 +65,27 @@ describe('build artifacts', () => {
     });
   });
 
+  /**
+   * `convertTabsToSpaces()` in build.ts must not touch tabs inside string
+   * literals. Upstream `@vitest/snapshot` decides multi-line snapshot
+   * indentation via `indent.includes("\t")` — where `"\t"` is a literal
+   * tab byte in the bundled source. A blanket tab→spaces rewrite turned
+   * this into `indent.includes("  ")`, so every 2-space indent matched
+   * and the tab-appending branch always ran, producing tab-indented
+   * snapshots in 2-space files.
+   *
+   * See: https://github.com/voidzero-dev/vite-plus/issues/1553
+   */
+  describe('snapshot indent check (regression test for #1553)', () => {
+    const snapshotIndexPath = path.join(distDir, '@vitest/snapshot/index.js');
+
+    it('preserves the literal tab byte inside the indent.includes string', () => {
+      const content = fs.readFileSync(snapshotIndexPath, 'utf-8');
+      expect(content).toContain('indent.includes("\t")');
+      expect(content).not.toMatch(/indent\.includes\("  "\)/);
+    });
+  });
+
   /**
    * Third-party packages that call `expect.extend()` internally
    * (e.g., @testing-library/jest-dom) break under npm override because

packages/test/build.ts

@@ -1365,18 +1365,26 @@ async function patchVitestCoreResolver() {
 }
 
 /**
- * Convert tabs to spaces in all JS files in dist/ for consistent formatting.
- * This allows our patching code to use space-based patterns instead of tabs.
+ * Convert leading tabs to spaces in all JS files in dist/ for consistent
+ * formatting. This allows our patching code to use space-based patterns
+ * instead of tabs.
+ *
+ * Only leading whitespace is rewritten — tabs inside string or template
+ * literals are semantically meaningful (e.g. `indent.includes("\t")` in
+ * @vitest/snapshot picks the snapshot indent style by checking for a
+ * literal tab byte) and must be preserved.
+ *
+ * See: https://github.com/voidzero-dev/vite-plus/issues/1553
  */
 async function convertTabsToSpaces() {
-  console.log('\nConverting tabs to spaces in dist/...');
+  console.log('\nConverting leading tabs to spaces in dist/...');
 
   let convertedCount = 0;
 
   for await (const file of fsGlob(resolve(distDir, '**/*.js'))) {
     const content = await readFile(file, 'utf-8');
-    if (content.includes('\t')) {
-      const converted = content.replace(/\t/g, '  ');
+    const converted = content.replace(/^\t+/gm, (match) => '  '.repeat(match.length));
+    if (converted !== content) {
       await writeFile(file, converted);
       convertedCount++;
     }