fix(paths): Add cross-platform path normalization (#18939)

packages/core/src/utils/paths.test.ts

@@ -13,6 +13,7 @@ import {
   unescapePath,
   isSubpath,
   shortenPath,
+  normalizePath,
   resolveToRealPath,
 } from './paths.js';
 
@@ -521,3 +522,46 @@ describe('resolveToRealPath', () => {
     expect(resolveToRealPath(input)).toBe(expected);
   });
 });
+
+describe('normalizePath', () => {
+  it('should resolve a relative path to an absolute path', () => {
+    const result = normalizePath('some/relative/path');
+    expect(result).toMatch(/^\/|^[a-z]:\//);
+  });
+
+  it('should convert all backslashes to forward slashes', () => {
+    const result = normalizePath(path.resolve('some', 'path'));
+    expect(result).not.toContain('\\');
+  });
+
+  describe.skipIf(process.platform !== 'win32')('on Windows', () => {
+    it('should lowercase the entire path', () => {
+      const result = normalizePath('C:\\Users\\TEST');
+      expect(result).toBe(result.toLowerCase());
+    });
+
+    it('should normalize drive letters to lowercase', () => {
+      const result = normalizePath('C:\\');
+      expect(result).toMatch(/^c:\//);
+    });
+
+    it('should handle mixed separators', () => {
+      const result = normalizePath('C:/Users\\Test/file.txt');
+      expect(result).not.toContain('\\');
+      expect(result).toMatch(/^c:\/users\/test\/file\.txt$/);
+    });
+  });
+
+  describe.skipIf(process.platform === 'win32')('on POSIX', () => {
+    it('should preserve case', () => {
+      const result = normalizePath('/usr/Local/Bin');
+      expect(result).toContain('Local');
+      expect(result).toContain('Bin');
+    });
+
+    it('should use forward slashes', () => {
+      const result = normalizePath('/usr/local/bin');
+      expect(result).toBe('/usr/local/bin');
+    });
+  });
+});

packages/core/src/utils/paths.ts

@@ -319,13 +319,15 @@ export function getProjectHash(projectRoot: string): string {
 }
 
 /**
- * Normalizes a path for reliable comparison.
+ * Normalizes a path for reliable comparison across platforms.
  * - Resolves to an absolute path.
+ * - Converts all path separators to forward slashes.
  * - On Windows, converts to lowercase for case-insensitivity.
  */
 export function normalizePath(p: string): string {
   const resolved = path.resolve(p);
-  return process.platform === 'win32' ? resolved.toLowerCase() : resolved;
+  const normalized = resolved.replace(/\\/g, '/');
+  return process.platform === 'win32' ? normalized.toLowerCase() : normalized;
 }
 
 /**