diff --git a/src/main/services/editor/ProjectFileService.ts b/src/main/services/editor/ProjectFileService.ts
index 7ac0a2ee..bfc2c33a 100644
--- a/src/main/services/editor/ProjectFileService.ts
+++ b/src/main/services/editor/ProjectFileService.ts
@@ -505,7 +505,7 @@ export class ProjectFileService {
     const newPath = path.join(normalizedDest, path.basename(normalizedSrc));
 
     // 8. Prevent parent → child move (moving dir into itself)
-    if (normalizedDest.startsWith(normalizedSrc + '/') || normalizedDest === normalizedSrc) {
+    if (normalizedDest.startsWith(normalizedSrc + path.sep) || normalizedDest === normalizedSrc) {
       throw new Error('Cannot move a directory into itself');
     }
 
diff --git a/test/main/services/editor/FileSearchService.test.ts b/test/main/services/editor/FileSearchService.test.ts
index bbe40f34..f9fa4d45 100644
--- a/test/main/services/editor/FileSearchService.test.ts
+++ b/test/main/services/editor/FileSearchService.test.ts
@@ -29,7 +29,7 @@ import { isBinaryFile } from 'isbinaryfile';
 
 import { FileSearchService } from '@main/services/editor/FileSearchService';
 
-const PROJECT_ROOT = '/test/project';
+const PROJECT_ROOT = path.resolve('/test/project');
 
 describe('FileSearchService', () => {
   let service: FileSearchService;
@@ -40,6 +40,12 @@ describe('FileSearchService', () => {
   });
 
   function mockFileSystem(files: Record<string, string>) {
+    // Normalize keys so lookups work on Windows (backslash vs forward slash)
+    const normalizedFiles: Record<string, string> = {};
+    for (const [key, value] of Object.entries(files)) {
+      normalizedFiles[path.normalize(key)] = value;
+    }
+
     const entries = Object.keys(files).map((filePath) => {
       const name = path.basename(filePath);
       return { name, isFile: () => true, isDirectory: () => false };
@@ -49,15 +55,15 @@ describe('FileSearchService', () => {
     vi.mocked(isBinaryFile).mockResolvedValue(false);
 
     vi.mocked(fs.stat).mockImplementation(async (filePath: unknown) => {
-      const p = String(filePath);
-      const content = files[p];
+      const p = path.normalize(String(filePath));
+      const content = normalizedFiles[p];
       if (content === undefined) throw new Error('ENOENT');
       return { size: content.length } as never;
     });
 
     vi.mocked(fs.readFile).mockImplementation(async (filePath: unknown) => {
-      const p = String(filePath);
-      const content = files[p];
+      const p = path.normalize(String(filePath));
+      const content = normalizedFiles[p];
       if (content === undefined) throw new Error('ENOENT');
       return content as never;
     });
diff --git a/test/main/services/editor/ProjectFileService.test.ts b/test/main/services/editor/ProjectFileService.test.ts
index 73da1892..42843527 100644
--- a/test/main/services/editor/ProjectFileService.test.ts
+++ b/test/main/services/editor/ProjectFileService.test.ts
@@ -55,7 +55,7 @@ import { ProjectFileService } from '../../../../src/main/services/editor/Project
 // Setup
 // =============================================================================
 
-const PROJECT_ROOT = '/Users/test/my-project';
+const PROJECT_ROOT = path.resolve('/Users/test/my-project');
 let service: ProjectFileService;
 
 const mockLstat = vi.mocked(fs.lstat);
@@ -219,7 +219,7 @@ describe('ProjectFileService.readDir', () => {
 
     mockRealpath.mockImplementation(async (p) => {
       const name = path.basename(String(p));
-      if (name === 'safe-link') return PROJECT_ROOT + '/actual-dir';
+      if (name === 'safe-link') return path.join(PROJECT_ROOT, 'actual-dir');
       return '/etc/shadow'; // escapes project
     });
 
@@ -559,8 +559,8 @@ describe('ProjectFileService.deleteFile', () => {
 // =============================================================================
 
 describe('ProjectFileService.moveFile', () => {
-  const SRC_DIR = PROJECT_ROOT + '/src';
-  const DEST_DIR = PROJECT_ROOT + '/lib';
+  const SRC_DIR = path.join(PROJECT_ROOT, 'src');
+  const DEST_DIR = path.join(PROJECT_ROOT, 'lib');
 
   beforeEach(() => {
     mockRename.mockResolvedValue(undefined);