diff --git a/test/core/completions/installers/bash-installer.test.ts b/test/core/completions/installers/bash-installer.test.ts
index 7b72f5c30..948a36221 100644
--- a/test/core/completions/installers/bash-installer.test.ts
+++ b/test/core/completions/installers/bash-installer.test.ts
@@ -140,7 +140,11 @@ describe('BashInstaller', () => {
 
     it('should handle installation errors gracefully', async () => {
       // Create installer with non-existent/invalid home directory
-      const invalidInstaller = new BashInstaller('/root/invalid/nonexistent/path');
+      // Use a path that will fail on both Unix and Windows
+      const invalidPath = process.platform === 'win32'
+        ? 'Z:\\nonexistent\\invalid\\path'  // Non-existent drive letter on Windows
+        : '/root/invalid/nonexistent/path';  // Permission-denied path on Unix
+      const invalidInstaller = new BashInstaller(invalidPath);
 
       const result = await invalidInstaller.install(testScript);
 
@@ -374,7 +378,11 @@ describe('BashInstaller', () => {
 
     it('should handle write permission errors gracefully', async () => {
       // Create installer with path that can't be written
-      const invalidInstaller = new BashInstaller('/root/invalid/path');
+      // Use a path that will fail on both Unix and Windows
+      const invalidPath = process.platform === 'win32'
+        ? 'Z:\\nonexistent\\invalid\\path'  // Non-existent drive letter on Windows
+        : '/root/invalid/path';  // Permission-denied path on Unix
+      const invalidInstaller = new BashInstaller(invalidPath);
 
       const result = await invalidInstaller.configureBashrc(completionsDir);
 
diff --git a/test/core/completions/installers/fish-installer.test.ts b/test/core/completions/installers/fish-installer.test.ts
index d5608ca24..db54f8b0b 100644
--- a/test/core/completions/installers/fish-installer.test.ts
+++ b/test/core/completions/installers/fish-installer.test.ts
@@ -192,7 +192,9 @@ complete -c openspec -a 'validate' -d 'Validate specs'
       await fs.rm(spacedHomeDir, { recursive: true, force: true });
     });
 
-    it('should return failure on permission error', async () => {
+    // Skip on Windows: fs.chmod() on directories doesn't restrict write access on Windows
+    // Windows uses ACLs which Node.js chmod doesn't control
+    it.skipIf(process.platform === 'win32')('should return failure on permission error', async () => {
       // Create a read-only directory to simulate permission error
       const restrictedDir = path.join(testHomeDir, '.config', 'fish', 'completions');
       await fs.mkdir(restrictedDir, { recursive: true });
diff --git a/test/core/completions/installers/powershell-installer.test.ts b/test/core/completions/installers/powershell-installer.test.ts
index 315f2a458..780f63103 100644
--- a/test/core/completions/installers/powershell-installer.test.ts
+++ b/test/core/completions/installers/powershell-installer.test.ts
@@ -237,7 +237,9 @@ describe('PowerShellInstaller', () => {
       expect(content).toContain('# OPENSPEC:END');
     });
 
-    it('should return false on write permission error', async () => {
+    // Skip on Windows: fs.chmod() doesn't reliably restrict write access on Windows
+    // (admin users can bypass read-only attribute, and CI runners often have elevated privileges)
+    it.skipIf(process.platform === 'win32')('should return false on write permission error', async () => {
       delete process.env.OPENSPEC_NO_AUTO_CONFIG;
       const profilePath = installer.getProfilePath();
       await fs.mkdir(path.dirname(profilePath), { recursive: true });
@@ -451,7 +453,9 @@ Register-ArgumentCompleter -CommandName openspec -ScriptBlock $openspecCompleter
     // Note: OPENSPEC_NO_AUTO_CONFIG support was removed from PowerShell installer
     // Profile is now always auto-configured if possible
 
-    it('should provide instructions when profile cannot be configured', async () => {
+    // Skip on Windows: fs.chmod() doesn't reliably restrict write access on Windows
+    // (admin users can bypass read-only attribute, and CI runners often have elevated privileges)
+    it.skipIf(process.platform === 'win32')('should provide instructions when profile cannot be configured', async () => {
       delete process.env.OPENSPEC_NO_AUTO_CONFIG;
       // Make profile directory read-only to prevent configuration
       const profilePath = installer.getProfilePath();
@@ -496,7 +500,9 @@ Register-ArgumentCompleter -CommandName openspec -ScriptBlock $openspecCompleter
       await fs.rm(spacedHomeDir, { recursive: true, force: true });
     });
 
-    it('should return failure on permission error', async () => {
+    // Skip on Windows: fs.chmod() on directories doesn't restrict write access on Windows
+    // Windows uses ACLs which Node.js chmod doesn't control
+    it.skipIf(process.platform === 'win32')('should return failure on permission error', async () => {
       const targetPath = installer.getInstallationPath();
       const targetDir = path.dirname(targetPath);
       await fs.mkdir(targetDir, { recursive: true });
@@ -614,7 +620,9 @@ Register-ArgumentCompleter -CommandName openspec -ScriptBlock $openspecCompleter
       expect(profileContentAfter).not.toContain('# OPENSPEC:START');
     });
 
-    it('should return failure on permission error', async () => {
+    // Skip on Windows: fs.chmod() on directories doesn't restrict write access on Windows
+    // Windows uses ACLs which Node.js chmod doesn't control
+    it.skipIf(process.platform === 'win32')('should return failure on permission error', async () => {
       delete process.env.OPENSPEC_NO_AUTO_CONFIG;
       await installer.install(mockCompletionScript);
       const targetPath = installer.getInstallationPath();
diff --git a/test/utils/file-system.test.ts b/test/utils/file-system.test.ts
index 2f427a531..ffa888cae 100644
--- a/test/utils/file-system.test.ts
+++ b/test/utils/file-system.test.ts
@@ -196,7 +196,9 @@ describe('FileSystemUtils', () => {
       expect(canWrite).toBe(true);
     });
 
-    it('should return false for non-existent file in read-only directory', async () => {
+    // Skip on Windows: fs.chmod() on directories doesn't restrict write access on Windows
+    // Windows uses ACLs which Node.js chmod doesn't control
+    it.skipIf(process.platform === 'win32')('should return false for non-existent file in read-only directory', async () => {
       const readOnlyDir = path.join(testDir, 'readonly-dir');
       await fs.mkdir(readOnlyDir);
       await fs.chmod(readOnlyDir, 0o555); // Read-only + execute