diff --git a/src-tauri/src/api_client.rs b/src-tauri/src/api_client.rs
index 70eb5d7..72ab57d 100644
--- a/src-tauri/src/api_client.rs
+++ b/src-tauri/src/api_client.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use reqwest::Client;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
@@ -464,13 +463,7 @@ impl ApiClient {
   }
 
   fn get_cache_dir() -> Result<PathBuf, Box<dyn std::error::Error + Send + Sync>> {
-    let base_dirs = BaseDirs::new().ok_or("Failed to get base directories")?;
-    let app_name = if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    };
-    let cache_dir = base_dirs.cache_dir().join(app_name).join("version_cache");
+    let cache_dir = crate::app_dirs::cache_dir().join("version_cache");
     fs::create_dir_all(&cache_dir)?;
     Ok(cache_dir)
   }
diff --git a/src-tauri/src/app_dirs.rs b/src-tauri/src/app_dirs.rs
new file mode 100644
index 0000000..9728bb8
--- /dev/null
+++ b/src-tauri/src/app_dirs.rs
@@ -0,0 +1,185 @@
+use directories::BaseDirs;
+use std::path::PathBuf;
+use std::sync::OnceLock;
+
+static BASE_DIRS: OnceLock<BaseDirs> = OnceLock::new();
+
+fn base_dirs() -> &'static BaseDirs {
+  BASE_DIRS.get_or_init(|| BaseDirs::new().expect("Failed to get base directories"))
+}
+
+pub fn app_name() -> &'static str {
+  if cfg!(debug_assertions) {
+    "DonutBrowserDev"
+  } else {
+    "DonutBrowser"
+  }
+}
+
+pub fn data_dir() -> PathBuf {
+  #[cfg(test)]
+  {
+    if let Some(dir) = TEST_DATA_DIR.with(|cell| cell.borrow().clone()) {
+      return dir;
+    }
+  }
+
+  if let Ok(dir) = std::env::var("DONUTBROWSER_DATA_DIR") {
+    return PathBuf::from(dir);
+  }
+
+  base_dirs().data_local_dir().join(app_name())
+}
+
+pub fn cache_dir() -> PathBuf {
+  #[cfg(test)]
+  {
+    if let Some(dir) = TEST_CACHE_DIR.with(|cell| cell.borrow().clone()) {
+      return dir;
+    }
+  }
+
+  if let Ok(dir) = std::env::var("DONUTBROWSER_CACHE_DIR") {
+    return PathBuf::from(dir);
+  }
+
+  base_dirs().cache_dir().join(app_name())
+}
+
+pub fn profiles_dir() -> PathBuf {
+  data_dir().join("profiles")
+}
+
+pub fn binaries_dir() -> PathBuf {
+  data_dir().join("binaries")
+}
+
+pub fn data_subdir() -> PathBuf {
+  data_dir().join("data")
+}
+
+pub fn settings_dir() -> PathBuf {
+  data_dir().join("settings")
+}
+
+pub fn proxies_dir() -> PathBuf {
+  data_dir().join("proxies")
+}
+
+#[cfg(test)]
+thread_local! {
+  static TEST_DATA_DIR: std::cell::RefCell<Option<PathBuf>> = const { std::cell::RefCell::new(None) };
+  static TEST_CACHE_DIR: std::cell::RefCell<Option<PathBuf>> = const { std::cell::RefCell::new(None) };
+}
+
+#[cfg(test)]
+pub struct TestDirGuard {
+  kind: TestDirKind,
+}
+
+#[cfg(test)]
+enum TestDirKind {
+  Data,
+  Cache,
+}
+
+#[cfg(test)]
+impl Drop for TestDirGuard {
+  fn drop(&mut self) {
+    match self.kind {
+      TestDirKind::Data => TEST_DATA_DIR.with(|cell| *cell.borrow_mut() = None),
+      TestDirKind::Cache => TEST_CACHE_DIR.with(|cell| *cell.borrow_mut() = None),
+    }
+  }
+}
+
+#[cfg(test)]
+pub fn set_test_data_dir(dir: PathBuf) -> TestDirGuard {
+  TEST_DATA_DIR.with(|cell| *cell.borrow_mut() = Some(dir));
+  TestDirGuard {
+    kind: TestDirKind::Data,
+  }
+}
+
+#[cfg(test)]
+pub fn set_test_cache_dir(dir: PathBuf) -> TestDirGuard {
+  TEST_CACHE_DIR.with(|cell| *cell.borrow_mut() = Some(dir));
+  TestDirGuard {
+    kind: TestDirKind::Cache,
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_app_name() {
+    let name = app_name();
+    assert!(
+      name == "DonutBrowser" || name == "DonutBrowserDev",
+      "app_name should be DonutBrowser or DonutBrowserDev, got: {name}"
+    );
+  }
+
+  #[test]
+  fn test_data_dir_returns_path() {
+    let dir = data_dir();
+    assert!(
+      dir.to_string_lossy().contains(app_name()),
+      "data_dir should contain app_name"
+    );
+  }
+
+  #[test]
+  fn test_cache_dir_returns_path() {
+    let dir = cache_dir();
+    assert!(
+      dir.to_string_lossy().contains(app_name()),
+      "cache_dir should contain app_name"
+    );
+  }
+
+  #[test]
+  fn test_subdirectory_helpers() {
+    assert!(profiles_dir().ends_with("profiles"));
+    assert!(binaries_dir().ends_with("binaries"));
+    assert!(data_subdir().ends_with("data"));
+    assert!(settings_dir().ends_with("settings"));
+    assert!(proxies_dir().ends_with("proxies"));
+  }
+
+  #[test]
+  fn test_set_test_data_dir() {
+    let tmp = PathBuf::from("/tmp/test-donut-data");
+    let _guard = set_test_data_dir(tmp.clone());
+    assert_eq!(data_dir(), tmp);
+    assert_eq!(profiles_dir(), tmp.join("profiles"));
+    assert_eq!(binaries_dir(), tmp.join("binaries"));
+  }
+
+  #[test]
+  fn test_set_test_cache_dir() {
+    let tmp = PathBuf::from("/tmp/test-donut-cache");
+    let _guard = set_test_cache_dir(tmp.clone());
+    assert_eq!(cache_dir(), tmp);
+  }
+
+  #[test]
+  fn test_guard_cleanup() {
+    let original_data = data_dir();
+    let original_cache = cache_dir();
+
+    {
+      let _guard = set_test_data_dir(PathBuf::from("/tmp/test-cleanup-data"));
+      assert_eq!(data_dir(), PathBuf::from("/tmp/test-cleanup-data"));
+    }
+    assert_eq!(data_dir(), original_data);
+
+    {
+      let _guard = set_test_cache_dir(PathBuf::from("/tmp/test-cleanup-cache"));
+      assert_eq!(cache_dir(), PathBuf::from("/tmp/test-cleanup-cache"));
+    }
+    assert_eq!(cache_dir(), original_cache);
+  }
+}
diff --git a/src-tauri/src/browser_runner.rs b/src-tauri/src/browser_runner.rs
index c26dd4d..0434e52 100644
--- a/src-tauri/src/browser_runner.rs
+++ b/src-tauri/src/browser_runner.rs
@@ -6,13 +6,11 @@ use crate::platform_browser;
 use crate::profile::{BrowserProfile, ProfileManager};
 use crate::proxy_manager::PROXY_MANAGER;
 use crate::wayfern_manager::{WayfernConfig, WayfernManager};
-use directories::BaseDirs;
 use serde::Serialize;
 use std::path::PathBuf;
 use std::time::{SystemTime, UNIX_EPOCH};
 use sysinfo::System;
 pub struct BrowserRunner {
-  base_dirs: BaseDirs,
   pub profile_manager: &'static ProfileManager,
   pub downloaded_browsers_registry: &'static DownloadedBrowsersRegistry,
   auto_updater: &'static crate::auto_updater::AutoUpdater,
@@ -23,7 +21,6 @@ pub struct BrowserRunner {
 impl BrowserRunner {
   fn new() -> Self {
     Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
       profile_manager: ProfileManager::instance(),
       downloaded_browsers_registry: DownloadedBrowsersRegistry::instance(),
       auto_updater: crate::auto_updater::AutoUpdater::instance(),
@@ -37,14 +34,7 @@ impl BrowserRunner {
   }
 
   pub fn get_binaries_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("binaries");
-    path
+    crate::app_dirs::binaries_dir()
   }
 
   /// Get the executable path for a browser profile
diff --git a/src-tauri/src/camoufox_manager.rs b/src-tauri/src/camoufox_manager.rs
index 1d8609f..ba9d35c 100644
--- a/src-tauri/src/camoufox_manager.rs
+++ b/src-tauri/src/camoufox_manager.rs
@@ -1,7 +1,6 @@
 use crate::browser_runner::BrowserRunner;
 use crate::camoufox::{CamoufoxConfigBuilder, GeoIPOption, ScreenConstraints};
 use crate::profile::BrowserProfile;
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::path::PathBuf;
@@ -74,7 +73,6 @@ struct CamoufoxManagerInner {
 
 pub struct CamoufoxManager {
   inner: Arc<AsyncMutex<CamoufoxManagerInner>>,
-  base_dirs: BaseDirs,
 }
 
 impl CamoufoxManager {
@@ -83,7 +81,6 @@ impl CamoufoxManager {
       inner: Arc::new(AsyncMutex::new(CamoufoxManagerInner {
         instances: HashMap::new(),
       })),
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
     }
   }
 
@@ -92,14 +89,7 @@ impl CamoufoxManager {
   }
 
   pub fn get_profiles_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("profiles");
-    path
+    crate::app_dirs::profiles_dir()
   }
 
   /// Generate Camoufox fingerprint configuration during profile creation
diff --git a/src-tauri/src/downloaded_browsers_registry.rs b/src-tauri/src/downloaded_browsers_registry.rs
index 75d03dd..2290202 100644
--- a/src-tauri/src/downloaded_browsers_registry.rs
+++ b/src-tauri/src/downloaded_browsers_registry.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::fs;
@@ -71,16 +70,7 @@ impl DownloadedBrowsersRegistry {
   }
 
   fn get_registry_path() -> Result<PathBuf, Box<dyn std::error::Error + Send + Sync>> {
-    let base_dirs = BaseDirs::new().ok_or("Failed to get base directories")?;
-    let mut path = base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("data");
-    path.push("downloaded_browsers.json");
-    Ok(path)
+    Ok(crate::app_dirs::data_subdir().join("downloaded_browsers.json"))
   }
 
   pub fn add_browser(&self, info: DownloadedBrowserInfo) {
@@ -128,19 +118,7 @@ impl DownloadedBrowsersRegistry {
     };
     let browser_instance = create_browser(browser_type.clone());
 
-    // Get binaries directory
-    let binaries_dir = if let Some(base_dirs) = directories::BaseDirs::new() {
-      let mut path = base_dirs.data_local_dir().to_path_buf();
-      path.push(if cfg!(debug_assertions) {
-        "DonutBrowserDev"
-      } else {
-        "DonutBrowser"
-      });
-      path.push("binaries");
-      path
-    } else {
-      return false;
-    };
+    let binaries_dir = crate::app_dirs::binaries_dir();
 
     let files_exist = browser_instance.is_version_downloaded(version, &binaries_dir);
 
@@ -535,15 +513,7 @@ impl DownloadedBrowsersRegistry {
     browser: &str,
     version: &str,
   ) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
-    // Get binaries directory path
-    let base_dirs = directories::BaseDirs::new().ok_or("Failed to get base directories")?;
-    let mut binaries_dir = base_dirs.data_local_dir().to_path_buf();
-    binaries_dir.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    binaries_dir.push("binaries");
+    let binaries_dir = crate::app_dirs::binaries_dir();
 
     let version_dir = binaries_dir.join(browser).join(version);
 
@@ -830,19 +800,7 @@ impl DownloadedBrowsersRegistry {
 
       let browser = create_browser(browser_type.clone());
 
-      // Get binaries directory
-      let binaries_dir = if let Some(base_dirs) = directories::BaseDirs::new() {
-        let mut path = base_dirs.data_local_dir().to_path_buf();
-        path.push(if cfg!(debug_assertions) {
-          "DonutBrowserDev"
-        } else {
-          "DonutBrowser"
-        });
-        path.push("binaries");
-        path
-      } else {
-        return Err("Failed to get base directories".into());
-      };
+      let binaries_dir = crate::app_dirs::binaries_dir();
 
       log::info!(
         "binaries_dir: {binaries_dir:?} for profile: {}",
diff --git a/src-tauri/src/downloader.rs b/src-tauri/src/downloader.rs
index a89edb5..d9db2f9 100644
--- a/src-tauri/src/downloader.rs
+++ b/src-tauri/src/downloader.rs
@@ -681,21 +681,7 @@ impl Downloader {
 
     // Use injected registry instance
 
-    // Get binaries directory - we need to get it from somewhere
-    // This is a bit tricky since we don't have access to BrowserRunner's get_binaries_dir
-    // We'll need to replicate this logic
-    let binaries_dir = if let Some(base_dirs) = directories::BaseDirs::new() {
-      let mut path = base_dirs.data_local_dir().to_path_buf();
-      path.push(if cfg!(debug_assertions) {
-        "DonutBrowserDev"
-      } else {
-        "DonutBrowser"
-      });
-      path.push("binaries");
-      path
-    } else {
-      return Err("Failed to get base directories".into());
-    };
+    let binaries_dir = crate::app_dirs::binaries_dir();
 
     // Check if registry thinks it's downloaded, but also verify files actually exist
     if self.registry.is_browser_downloaded(&browser_str, &version) {
diff --git a/src-tauri/src/group_manager.rs b/src-tauri/src/group_manager.rs
index 8fef804..625bcc6 100644
--- a/src-tauri/src/group_manager.rs
+++ b/src-tauri/src/group_manager.rs
@@ -1,8 +1,6 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::fs;
-use std::path::{Path, PathBuf};
 use std::sync::Mutex;
 
 use crate::events;
@@ -33,48 +31,15 @@ struct GroupsData {
   groups: Vec<ProfileGroup>,
 }
 
-pub struct GroupManager {
-  base_dirs: BaseDirs,
-  data_dir_override: Option<PathBuf>,
-}
+pub struct GroupManager;
 
 impl GroupManager {
   pub fn new() -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: std::env::var("DONUTBROWSER_DATA_DIR")
-        .ok()
-        .map(PathBuf::from),
-    }
+    Self
   }
 
-  // Helper for tests to override data directory without global env var
-  #[allow(dead_code)]
-  pub fn with_data_dir_override(dir: &Path) -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: Some(dir.to_path_buf()),
-    }
-  }
-
-  fn get_groups_file_path(&self) -> PathBuf {
-    if let Some(dir) = &self.data_dir_override {
-      let mut override_path = dir.clone();
-      // Ensure the directory exists before returning the path
-      let _ = fs::create_dir_all(&override_path);
-      override_path.push("groups.json");
-      return override_path;
-    }
-
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("data");
-    path.push("groups.json");
-    path
+  fn get_groups_file_path(&self) -> std::path::PathBuf {
+    crate::app_dirs::data_subdir().join("groups.json")
   }
 
   fn load_groups_data(&self) -> Result<GroupsData, Box<dyn std::error::Error>> {
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 3bf5b2c..8a682c1 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -11,6 +11,7 @@ static PENDING_URLS: Mutex<Vec<String>> = Mutex::new(Vec::new());
 mod api_client;
 mod api_server;
 mod app_auto_updater;
+pub mod app_dirs;
 mod auto_updater;
 mod browser;
 mod browser_runner;
@@ -706,12 +707,7 @@ pub fn run() {
     pending.push(url.clone());
   }
 
-  // Configure logging plugin with separate logs for dev and production
-  let log_file_name = if cfg!(debug_assertions) {
-    "DonutBrowserDev"
-  } else {
-    "DonutBrowser"
-  };
+  let log_file_name = app_dirs::app_name();
 
   tauri::Builder::default()
     .plugin(
diff --git a/src-tauri/src/profile/manager.rs b/src-tauri/src/profile/manager.rs
index 04e5189..3245b2d 100644
--- a/src-tauri/src/profile/manager.rs
+++ b/src-tauri/src/profile/manager.rs
@@ -6,13 +6,11 @@ use crate::events;
 use crate::profile::types::{get_host_os, BrowserProfile};
 use crate::proxy_manager::PROXY_MANAGER;
 use crate::wayfern_manager::WayfernConfig;
-use directories::BaseDirs;
 use std::fs::{self, create_dir_all};
 use std::path::{Path, PathBuf};
 use sysinfo::{Pid, System};
 
 pub struct ProfileManager {
-  base_dirs: BaseDirs,
   camoufox_manager: &'static crate::camoufox_manager::CamoufoxManager,
   wayfern_manager: &'static crate::wayfern_manager::WayfernManager,
 }
@@ -20,7 +18,6 @@ pub struct ProfileManager {
 impl ProfileManager {
   fn new() -> Self {
     Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
       camoufox_manager: crate::camoufox_manager::CamoufoxManager::instance(),
       wayfern_manager: crate::wayfern_manager::WayfernManager::instance(),
     }
@@ -31,25 +28,11 @@ impl ProfileManager {
   }
 
   pub fn get_profiles_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("profiles");
-    path
+    crate::app_dirs::profiles_dir()
   }
 
   pub fn get_binaries_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("binaries");
-    path
+    crate::app_dirs::binaries_dir()
   }
 
   #[allow(clippy::too_many_arguments)]
diff --git a/src-tauri/src/proxy_manager.rs b/src-tauri/src/proxy_manager.rs
index 87f5b99..98fbf76 100644
--- a/src-tauri/src/proxy_manager.rs
+++ b/src-tauri/src/proxy_manager.rs
@@ -1,5 +1,4 @@
 use chrono::Utc;
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 use std::collections::HashMap;
@@ -149,18 +148,15 @@ pub struct ProxyManager {
   // Track active proxy IDs by profile name for targeted cleanup
   profile_active_proxy_ids: Mutex<HashMap<String, String>>, // Maps profile name to proxy id
   stored_proxies: Mutex<HashMap<String, StoredProxy>>,      // Maps proxy ID to stored proxy
-  base_dirs: BaseDirs,
 }
 
 impl ProxyManager {
   pub fn new() -> Self {
-    let base_dirs = BaseDirs::new().expect("Failed to get base directories");
     let manager = Self {
       active_proxies: Mutex::new(HashMap::new()),
       profile_proxies: Mutex::new(HashMap::new()),
       profile_active_proxy_ids: Mutex::new(HashMap::new()),
       stored_proxies: Mutex::new(HashMap::new()),
-      base_dirs,
     };
 
     // Load stored proxies on initialization
@@ -171,27 +167,12 @@ impl ProxyManager {
     manager
   }
 
-  // Get the path to the proxies directory
   fn get_proxies_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("proxies");
-    path
+    crate::app_dirs::proxies_dir()
   }
 
-  // Get the path to the proxy check cache directory
   fn get_proxy_check_cache_dir(&self) -> Result<PathBuf, Box<dyn std::error::Error>> {
-    let mut path = self.base_dirs.cache_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("proxy_checks");
+    let path = crate::app_dirs::cache_dir().join("proxy_checks");
     fs::create_dir_all(&path)?;
     Ok(path)
   }
diff --git a/src-tauri/src/proxy_storage.rs b/src-tauri/src/proxy_storage.rs
index f8cda0d..4cfb132 100644
--- a/src-tauri/src/proxy_storage.rs
+++ b/src-tauri/src/proxy_storage.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::fs;
 use std::path::PathBuf;
@@ -35,15 +34,7 @@ impl ProxyConfig {
 }
 
 pub fn get_storage_dir() -> PathBuf {
-  let base_dirs = BaseDirs::new().expect("Failed to get base directories");
-  let mut path = base_dirs.data_local_dir().to_path_buf();
-  path.push(if cfg!(debug_assertions) {
-    "DonutBrowserDev"
-  } else {
-    "DonutBrowser"
-  });
-  path.push("proxies");
-  path
+  crate::app_dirs::proxies_dir()
 }
 
 pub fn save_proxy_config(config: &ProxyConfig) -> Result<(), Box<dyn std::error::Error>> {
diff --git a/src-tauri/src/settings_manager.rs b/src-tauri/src/settings_manager.rs
index d7eb2e7..e850df5 100644
--- a/src-tauri/src/settings_manager.rs
+++ b/src-tauri/src/settings_manager.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::fs::{self, create_dir_all};
 use std::path::PathBuf;
@@ -91,27 +90,11 @@ impl Default for AppSettings {
   }
 }
 
-pub struct SettingsManager {
-  base_dirs: BaseDirs,
-  data_dir_override: Option<PathBuf>,
-}
+pub struct SettingsManager;
 
 impl SettingsManager {
-  fn new() -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: std::env::var("DONUTBROWSER_DATA_DIR")
-        .ok()
-        .map(PathBuf::from),
-    }
-  }
-
-  #[cfg(test)]
-  fn with_data_dir_override(dir: &std::path::Path) -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: Some(dir.to_path_buf()),
-    }
+  pub(crate) fn new() -> Self {
+    Self
   }
 
   pub fn instance() -> &'static SettingsManager {
@@ -119,18 +102,7 @@ impl SettingsManager {
   }
 
   pub fn get_settings_dir(&self) -> PathBuf {
-    if let Some(dir) = &self.data_dir_override {
-      return dir.join("settings");
-    }
-
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("settings");
-    path
+    crate::app_dirs::settings_dir()
   }
 
   pub fn get_settings_file(&self) -> PathBuf {
@@ -950,16 +922,16 @@ mod tests {
   use super::*;
   use tempfile::TempDir;
 
-  fn create_test_settings_manager() -> (SettingsManager, TempDir) {
+  fn create_test_settings_manager() -> (SettingsManager, TempDir, crate::app_dirs::TestDirGuard) {
     let temp_dir = TempDir::new().expect("Failed to create temp directory");
-    let manager = SettingsManager::with_data_dir_override(temp_dir.path());
-    (manager, temp_dir)
+    let guard = crate::app_dirs::set_test_data_dir(temp_dir.path().to_path_buf());
+    let manager = SettingsManager::new();
+    (manager, temp_dir, guard)
   }
 
   #[test]
   fn test_settings_manager_creation() {
-    let (_manager, _temp_dir) = create_test_settings_manager();
-    // Test passes if no panic occurs
+    let (_manager, _temp_dir, _guard) = create_test_settings_manager();
   }
 
   #[test]
@@ -992,7 +964,7 @@ mod tests {
 
   #[test]
   fn test_load_settings_nonexistent_file() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let result = manager.load_settings();
     assert!(
@@ -1010,7 +982,7 @@ mod tests {
 
   #[test]
   fn test_save_and_load_settings() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let test_settings = AppSettings {
       set_as_default_browser: true,
@@ -1029,11 +1001,9 @@ mod tests {
       language: None,
     };
 
-    // Save settings
     let save_result = manager.save_settings(&test_settings);
     assert!(save_result.is_ok(), "Should save settings successfully");
 
-    // Load settings back
     let load_result = manager.load_settings();
     assert!(load_result.is_ok(), "Should load settings successfully");
 
@@ -1050,7 +1020,7 @@ mod tests {
 
   #[test]
   fn test_load_table_sorting_nonexistent_file() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let result = manager.load_table_sorting();
     assert!(
@@ -1065,18 +1035,16 @@ mod tests {
 
   #[test]
   fn test_save_and_load_table_sorting() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let test_sorting = TableSortingSettings {
       column: "browser".to_string(),
       direction: "desc".to_string(),
     };
 
-    // Save sorting
     let save_result = manager.save_table_sorting(&test_sorting);
     assert!(save_result.is_ok(), "Should save sorting successfully");
 
-    // Load sorting back
     let load_result = manager.load_table_sorting();
     assert!(load_result.is_ok(), "Should load sorting successfully");
 
@@ -1093,45 +1061,37 @@ mod tests {
 
   #[test]
   fn test_should_show_launch_on_login_prompt() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let result = manager.should_show_launch_on_login_prompt();
     assert!(result.is_ok(), "Should not fail");
 
-    // By default, should show prompt (not declined, autostart not enabled)
     let _should_show = result.unwrap();
-    // Note: The actual value depends on system autostart state, so we just test it doesn't fail
   }
 
   #[test]
   fn test_decline_launch_on_login() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
-    // Initially not declined
     let settings = manager.load_settings().unwrap();
     assert!(!settings.launch_on_login_declined);
 
-    // Decline
     manager.decline_launch_on_login().unwrap();
 
-    // Should be declined now
     let settings = manager.load_settings().unwrap();
     assert!(settings.launch_on_login_declined);
   }
 
   #[test]
   fn test_load_corrupted_settings_file() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
-    // Create settings directory
     let settings_dir = manager.get_settings_dir();
     fs::create_dir_all(&settings_dir).expect("Should create settings directory");
 
-    // Write corrupted JSON
     let settings_file = manager.get_settings_file();
     fs::write(&settings_file, "{ invalid json }").expect("Should write corrupted file");
 
-    // Should handle corrupted file gracefully
     let result = manager.load_settings();
     assert!(
       result.is_ok(),
@@ -1151,7 +1111,7 @@ mod tests {
 
   #[test]
   fn test_settings_file_paths() {
-    let (manager, _temp_dir) = create_test_settings_manager();
+    let (manager, _temp_dir, _guard) = create_test_settings_manager();
 
     let settings_dir = manager.get_settings_dir();
     let settings_file = manager.get_settings_file();
diff --git a/src-tauri/src/tag_manager.rs b/src-tauri/src/tag_manager.rs
index 7577d6e..5b53207 100644
--- a/src-tauri/src/tag_manager.rs
+++ b/src-tauri/src/tag_manager.rs
@@ -1,56 +1,22 @@
 use crate::profile::BrowserProfile;
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeSet;
 use std::fs;
-use std::path::{Path, PathBuf};
 
 #[derive(Debug, Serialize, Deserialize, Default, Clone)]
 struct TagsData {
   tags: Vec<String>,
 }
 
-pub struct TagManager {
-  base_dirs: BaseDirs,
-  data_dir_override: Option<PathBuf>,
-}
+pub struct TagManager;
 
 impl TagManager {
   pub fn new() -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: std::env::var("DONUTBROWSER_DATA_DIR")
-        .ok()
-        .map(PathBuf::from),
-    }
+    Self
   }
 
-  // Helper for tests to override data directory without global env var
-  #[allow(dead_code)]
-  pub fn with_data_dir_override(dir: &Path) -> Self {
-    Self {
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
-      data_dir_override: Some(dir.to_path_buf()),
-    }
-  }
-
-  fn get_tags_file_path(&self) -> PathBuf {
-    if let Some(dir) = &self.data_dir_override {
-      let mut override_path = dir.clone();
-      let _ = fs::create_dir_all(&override_path);
-      override_path.push("tags.json");
-      return override_path;
-    }
-
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("data");
-    path.push("tags.json");
-    path
+  fn get_tags_file_path(&self) -> std::path::PathBuf {
+    crate::app_dirs::data_subdir().join("tags.json")
   }
 
   fn load_tags_data(&self) -> Result<TagsData, Box<dyn std::error::Error>> {
diff --git a/src-tauri/src/traffic_stats.rs b/src-tauri/src/traffic_stats.rs
index 3d4416a..e7c52a1 100644
--- a/src-tauri/src/traffic_stats.rs
+++ b/src-tauri/src/traffic_stats.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::fs;
@@ -328,17 +327,8 @@ fn acquire_file_lock(lock_path: &PathBuf) -> Result<FileLockGuard, Box<dyn std::
   Ok(FileLockGuard { _file: file })
 }
 
-/// Get the traffic stats storage directory
 pub fn get_traffic_stats_dir() -> PathBuf {
-  let base_dirs = BaseDirs::new().expect("Failed to get base directories");
-  let mut path = base_dirs.cache_dir().to_path_buf();
-  path.push(if cfg!(debug_assertions) {
-    "DonutBrowserDev"
-  } else {
-    "DonutBrowser"
-  });
-  path.push("traffic_stats");
-  path
+  crate::app_dirs::cache_dir().join("traffic_stats")
 }
 
 /// Get the storage key for traffic stats (profile_id if available, otherwise proxy_id)
diff --git a/src-tauri/src/version_updater.rs b/src-tauri/src/version_updater.rs
index ff943f7..d672ed1 100644
--- a/src-tauri/src/version_updater.rs
+++ b/src-tauri/src/version_updater.rs
@@ -1,4 +1,3 @@
-use directories::BaseDirs;
 use serde::{Deserialize, Serialize};
 use std::fs;
 use std::path::PathBuf;
@@ -67,13 +66,7 @@ impl VersionUpdater {
   }
 
   fn get_cache_dir() -> Result<PathBuf, Box<dyn std::error::Error>> {
-    let base_dirs = BaseDirs::new().ok_or("Failed to get base directories")?;
-    let app_name = if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    };
-    let cache_dir = base_dirs.cache_dir().join(app_name).join("version_cache");
+    let cache_dir = crate::app_dirs::cache_dir().join("version_cache");
     fs::create_dir_all(&cache_dir)?;
     Ok(cache_dir)
   }
diff --git a/src-tauri/src/wayfern_manager.rs b/src-tauri/src/wayfern_manager.rs
index 69f4aa6..81a7f16 100644
--- a/src-tauri/src/wayfern_manager.rs
+++ b/src-tauri/src/wayfern_manager.rs
@@ -1,6 +1,5 @@
 use crate::browser_runner::BrowserRunner;
 use crate::profile::BrowserProfile;
-use directories::BaseDirs;
 use reqwest::Client;
 use serde::{Deserialize, Serialize};
 use serde_json::json;
@@ -72,8 +71,6 @@ struct WayfernManagerInner {
 
 pub struct WayfernManager {
   inner: Arc<AsyncMutex<WayfernManagerInner>>,
-  #[allow(dead_code)]
-  base_dirs: BaseDirs,
   http_client: Client,
 }
 
@@ -91,7 +88,6 @@ impl WayfernManager {
       inner: Arc::new(AsyncMutex::new(WayfernManagerInner {
         instances: HashMap::new(),
       })),
-      base_dirs: BaseDirs::new().expect("Failed to get base directories"),
       http_client: Client::new(),
     }
   }
@@ -102,26 +98,12 @@ impl WayfernManager {
 
   #[allow(dead_code)]
   pub fn get_profiles_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("profiles");
-    path
+    crate::app_dirs::profiles_dir()
   }
 
   #[allow(dead_code)]
   fn get_binaries_dir(&self) -> PathBuf {
-    let mut path = self.base_dirs.data_local_dir().to_path_buf();
-    path.push(if cfg!(debug_assertions) {
-      "DonutBrowserDev"
-    } else {
-      "DonutBrowser"
-    });
-    path.push("binaries");
-    path
+    crate::app_dirs::binaries_dir()
   }
 
   async fn find_free_port() -> Result<u16, Box<dyn std::error::Error + Send + Sync>> {
diff --git a/src-tauri/tests/donut_proxy_integration.rs b/src-tauri/tests/donut_proxy_integration.rs
index 4469127..cfb9403 100644
--- a/src-tauri/tests/donut_proxy_integration.rs
+++ b/src-tauri/tests/donut_proxy_integration.rs
@@ -516,13 +516,7 @@ async fn test_traffic_tracking() -> Result<(), Box<dyn std::error::Error + Send
   // Wait for traffic stats to be flushed (happens every second)
   sleep(Duration::from_secs(2)).await;
 
-  // Verify traffic was tracked by checking traffic stats file exists
-  // Note: Traffic stats are stored in the cache directory
-  let cache_dir = directories::BaseDirs::new()
-    .expect("Failed to get base directories")
-    .cache_dir()
-    .to_path_buf();
-  let traffic_stats_dir = cache_dir.join("DonutBrowserDev").join("traffic_stats");
+  let traffic_stats_dir = donutbrowser_lib::app_dirs::cache_dir().join("traffic_stats");
   let stats_file = traffic_stats_dir.join(format!("{}.json", proxy_id));
 
   if stats_file.exists() {