diff --git a/packages/cli/__tests__/commands/mcp.test.ts b/packages/cli/__tests__/commands/mcp.test.ts
index 919c29d7..faeb7784 100644
--- a/packages/cli/__tests__/commands/mcp.test.ts
+++ b/packages/cli/__tests__/commands/mcp.test.ts
@@ -229,7 +229,7 @@ describe('--dir', () => {
 
     await run(['mcp', 'status', '--ide', 'claude', '--dir', '/tmp/my-project', '--json']);
 
-    expect(mockIntegration.detectMcpStatuses).toHaveBeenCalledWith('/tmp/my-project');
+    expect(mockIntegration.detectMcpStatuses).toHaveBeenCalledWith(resolve('/tmp/my-project'));
   });
 
   it('passes --dir through to auth refresh', async () => {
@@ -239,7 +239,7 @@ describe('--dir', () => {
     await run(['mcp', 'auth', '--ide', 'claude', '--dir', '/tmp/my-project']);
 
     expect(mockIntegration.connectMcpServer).toHaveBeenCalledWith(
-      expect.objectContaining({ projectDir: '/tmp/my-project' }),
+      expect.objectContaining({ projectDir: resolve('/tmp/my-project') }),
     );
   });
 });
diff --git a/packages/cli/__tests__/commands/plugin.test.ts b/packages/cli/__tests__/commands/plugin.test.ts
index 845069c5..11e2ce8a 100644
--- a/packages/cli/__tests__/commands/plugin.test.ts
+++ b/packages/cli/__tests__/commands/plugin.test.ts
@@ -124,7 +124,7 @@ describe('plugin update', () => {
 
     await run(['plugin', 'update', '--ide', 'claude', '--dir', '/tmp/my-project']);
 
-    expect(mockUpdatePlugin).toHaveBeenCalledWith('claude', '/tmp/my-project', 'project');
+    expect(mockUpdatePlugin).toHaveBeenCalledWith('claude', resolve('/tmp/my-project'), 'project');
   });
 
   it('passes --scope to the updater', async () => {
@@ -163,7 +163,11 @@ describe('plugin uninstall', () => {
 
     await run(['plugin', 'uninstall', '--ide', 'claude', '--dir', '/tmp/my-project']);
 
-    expect(mockUninstallPlugin).toHaveBeenCalledWith('claude', '/tmp/my-project', 'project');
+    expect(mockUninstallPlugin).toHaveBeenCalledWith(
+      'claude',
+      resolve('/tmp/my-project'),
+      'project',
+    );
   });
 
   it('passes --scope to the uninstaller', async () => {
diff --git a/packages/core/__tests__/auth/credentials/store.test.ts b/packages/core/__tests__/auth/credentials/store.test.ts
index 2090ce08..129a1f31 100644
--- a/packages/core/__tests__/auth/credentials/store.test.ts
+++ b/packages/core/__tests__/auth/credentials/store.test.ts
@@ -1,5 +1,6 @@
 import { existsSync, statSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
+import { isWindows } from '@spotify-confidence/shared-kernel';
 import { prepareAuthTokens } from '@spotify-confidence/testing/auth';
 import { getConfigDir } from '@config/index.js';
 import {
@@ -20,7 +21,7 @@ describe('writeCredentials / readCredentials', () => {
     expect(sut).toEqual(creds);
   });
 
-  it('creates the config directory with 0700 permissions', () => {
+  it.skipIf(isWindows)('creates the config directory with 0700 permissions', () => {
     using _auth = prepareAuthTokens('none');
 
     writeCredentials({ accessToken: 'tok' });
@@ -30,7 +31,7 @@ describe('writeCredentials / readCredentials', () => {
     expect(mode).toBe(0o700);
   });
 
-  it('writes the credentials file with 0600 permissions', () => {
+  it.skipIf(isWindows)('writes the credentials file with 0600 permissions', () => {
     using _auth = prepareAuthTokens('none');
 
     writeCredentials({ accessToken: 'tok' });
diff --git a/packages/testing/__tests__/home-scaffold.test.ts b/packages/testing/__tests__/home-scaffold.test.ts
new file mode 100644
index 00000000..56122b93
--- /dev/null
+++ b/packages/testing/__tests__/home-scaffold.test.ts
@@ -0,0 +1,26 @@
+import { homedir } from 'node:os';
+import { describe, it, expect } from 'vitest';
+import { isolateHome } from '../src/scaffold/home-scaffold.js';
+
+describe('isolateHome', () => {
+  it('stubs both HOME and USERPROFILE to isolate os.homedir() across platforms', () => {
+    const fakeDir = process.platform === 'win32' ? 'C:\\fake\\home' : '/fake/home';
+    {
+      using _home = isolateHome(fakeDir);
+      expect(process.env.HOME).toBe(fakeDir);
+      expect(process.env.USERPROFILE).toBe(fakeDir);
+      expect(homedir()).toBe(fakeDir);
+    }
+  });
+
+  it('restores previous environment when disposed', () => {
+    const origHome = process.env.HOME;
+    const origUserProfile = process.env.USERPROFILE;
+    {
+      using _home = isolateHome('/temporary/test/dir');
+      expect(process.env.HOME).toBe('/temporary/test/dir');
+    }
+    expect(process.env.HOME).toBe(origHome);
+    expect(process.env.USERPROFILE).toBe(origUserProfile);
+  });
+});
diff --git a/packages/testing/__tests__/overlay-env.test.ts b/packages/testing/__tests__/overlay-env.test.ts
index 1816d674..c97203b3 100644
--- a/packages/testing/__tests__/overlay-env.test.ts
+++ b/packages/testing/__tests__/overlay-env.test.ts
@@ -1,3 +1,4 @@
+import { describe, it, expect } from 'vitest';
 import { overlayEnv } from '../src/env/overlay-env.js';
 
 describe('overlayEnv', () => {
diff --git a/packages/testing/package.json b/packages/testing/package.json
index 576f46bb..b77ef9a5 100644
--- a/packages/testing/package.json
+++ b/packages/testing/package.json
@@ -19,6 +19,7 @@
     "node-pty": "1.2.0-beta.14"
   },
   "scripts": {
+    "test": "vitest run",
     "typecheck": "tsc --noEmit"
   },
   "devDependencies": {
diff --git a/packages/testing/src/scaffold/home-scaffold.ts b/packages/testing/src/scaffold/home-scaffold.ts
index 688923e5..70bea2b3 100644
--- a/packages/testing/src/scaffold/home-scaffold.ts
+++ b/packages/testing/src/scaffold/home-scaffold.ts
@@ -1,8 +1,8 @@
 import { vi } from 'vitest';
 
 /**
- * Stubs the `HOME` environment variable to `dir`, isolating the test
- * from real user config files (`~/.cursor/`, `~/.claude.json`, etc.).
+ * Stubs `HOME` and `USERPROFILE` environment variables to `dir`, isolating the test
+ * from real user config files (`~/.cursor/`, `~/.claude.json`, etc.) across platforms.
  * Supports `Symbol.dispose` for automatic cleanup via `vi.unstubAllEnvs`.
  *
  * @example
@@ -13,6 +13,7 @@ import { vi } from 'vitest';
  */
 export function isolateHome(dir: string) {
   vi.stubEnv('HOME', dir);
+  vi.stubEnv('USERPROFILE', dir);
 
   return {
     [Symbol.dispose]() {