diff --git a/src/utils/browser/chrome-reuse.ts b/src/utils/browser/chrome-reuse.ts
index 8fd77903..eacefe8b 100644
--- a/src/utils/browser/chrome-reuse.ts
+++ b/src/utils/browser/chrome-reuse.ts
@@ -19,24 +19,23 @@ export interface BrowserRuntimeEnv {
 const DEVTOOLS_HOST = '127.0.0.1';
 const DEVTOOLS_ACTIVE_PORT_FILE = 'DevToolsActivePort';
 
-export function resolveDefaultChromeUserDataDir(platform = process.platform): string {
+export function resolveDefaultChromeUserDataDir(
+  platform = process.platform,
+  env: NodeJS.ProcessEnv = process.env
+): string {
   switch (platform) {
     case 'darwin':
       return path.join(
-        process.env.HOME || process.env.USERPROFILE || '',
+        env.HOME || env.USERPROFILE || '',
         'Library',
         'Application Support',
         'Google',
         'Chrome'
       );
     case 'linux':
-      return path.join(
-        process.env.HOME || process.env.USERPROFILE || '',
-        '.config',
-        'google-chrome'
-      );
+      return path.join(env.HOME || env.USERPROFILE || '', '.config', 'google-chrome');
     case 'win32': {
-      const localAppData = process.env.LOCALAPPDATA;
+      const localAppData = env.LOCALAPPDATA;
       if (!localAppData) {
         throw new Error(
           'LOCALAPPDATA is required to resolve the default Chrome user-data-dir on Windows'
@@ -45,11 +44,7 @@ export function resolveDefaultChromeUserDataDir(platform = process.platform): st
       return path.join(localAppData, 'Google', 'Chrome', 'User Data');
     }
     default:
-      return path.join(
-        process.env.HOME || process.env.USERPROFILE || '',
-        '.config',
-        'google-chrome'
-      );
+      return path.join(env.HOME || env.USERPROFILE || '', '.config', 'google-chrome');
   }
 }
 
diff --git a/tests/unit/utils/browser/chrome-reuse.test.ts b/tests/unit/utils/browser/chrome-reuse.test.ts
index 79a78e81..e0b8ac8a 100644
--- a/tests/unit/utils/browser/chrome-reuse.test.ts
+++ b/tests/unit/utils/browser/chrome-reuse.test.ts
@@ -135,7 +135,9 @@ describe('chrome reuse resolver', () => {
     });
 
     expect(runtimeEnv.CCS_BROWSER_DEVTOOLS_PORT).toBe(String(server.port));
-    expect(runtimeEnv.CCS_BROWSER_DEVTOOLS_WS_URL).toBe('ws://127.0.0.1/devtools/browser/explicit-port');
+    expect(runtimeEnv.CCS_BROWSER_DEVTOOLS_WS_URL).toBe(
+      'ws://127.0.0.1/devtools/browser/explicit-port'
+    );
   });
 
   it('throws a clear error when DevToolsActivePort metadata is missing', async () => {
@@ -196,15 +198,20 @@ describe('chrome reuse resolver', () => {
   });
 
   it('resolves platform default Chrome user-data-dir paths', () => {
-    process.env.LOCALAPPDATA = 'C:/Users/test/AppData/Local';
+    const isolatedHome = createTempDir('ccs-chrome-home-');
+    const env = {
+      HOME: isolatedHome,
+      USERPROFILE: isolatedHome,
+      LOCALAPPDATA: 'C:/Users/test/AppData/Local',
+    };
 
-    expect(resolveDefaultChromeUserDataDir('darwin')).toBe(
-      path.join(os.homedir(), 'Library', 'Application Support', 'Google', 'Chrome')
+    expect(resolveDefaultChromeUserDataDir('darwin', env)).toBe(
+      path.join(isolatedHome, 'Library', 'Application Support', 'Google', 'Chrome')
     );
-    expect(resolveDefaultChromeUserDataDir('linux')).toBe(
-      path.join(os.homedir(), '.config', 'google-chrome')
+    expect(resolveDefaultChromeUserDataDir('linux', env)).toBe(
+      path.join(isolatedHome, '.config', 'google-chrome')
     );
-    expect(resolveDefaultChromeUserDataDir('win32')).toBe(
+    expect(resolveDefaultChromeUserDataDir('win32', env)).toBe(
       path.normalize('C:/Users/test/AppData/Local/Google/Chrome/User Data')
     );
   });
@@ -218,7 +225,10 @@ describe('chrome reuse resolver', () => {
   });
 
   it('throws a clear error when the resolved profile directory does not exist', async () => {
-    const missingProfileDir = path.join(createTempDir('ccs-chrome-missing-dir-'), 'missing-profile');
+    const missingProfileDir = path.join(
+      createTempDir('ccs-chrome-missing-dir-'),
+      'missing-profile'
+    );
 
     await expect(resolveBrowserRuntimeEnv({ profileDir: missingProfileDir })).rejects.toThrow(
       `Chrome profile directory is invalid: ${missingProfileDir}`