diff --git a/CLAUDE.md b/CLAUDE.md
index 84c1542..a7b5aa6 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -14,8 +14,6 @@ For architecture and decision rationale, see [ARCHITECTURE.md](ARCHITECTURE.md).
 - **Frameworks**: IOKit.pwr_mgt (power assertions), ServiceManagement (login items), Foundation (UserDefaults)
 - **Target**: macOS 15.6 (Sequoia), Apple Silicon + Intel
 - **Dependencies**: None. Zero third-party packages.
-- **Build**: `xcodebuild build -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS'`
-- **Test**: `xcodebuild test -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS'`
 
 ## Project Structure
 
@@ -26,7 +24,7 @@ vigil/
 ├── PRD.md                 # Product requirements
 ├── app/                   # macOS app (Xcode project)
 │   ├── Vigil.xcodeproj/
-│   ├── Vigil/             # Source + PrivacyInfo.xcprivacy
+│   ├── Vigil/             # Source + PrivacyInfo.xcprivacy + Localizable.xcstrings
 │   └── VigilTests/
 ├── appstore/              # App Store screenshots (2880×1800)
 └── website/               # Static promo site (Vercel): vigil-for-mac.vercel.app
@@ -43,6 +41,7 @@ New `.swift` files in `app/Vigil/` are auto-included in the build (PBXFileSystem
 - `// MARK: -` comments for view section organization
 - `import IOKit.pwr_mgt` (submodule import, not `import IOKit`)
 - Computed properties for view decomposition (`heroSection`, `modeSection`, etc.)
+- `LocalizedStringResource` for localizable strings in enums/models (not plain `String`) — enables auto-extraction into String Catalogs
 
 ## Testing
 
@@ -53,6 +52,37 @@ New `.swift` files in `app/Vigil/` are auto-included in the build (PBXFileSystem
 - **Integration-style**: Tests create real IOPMAssertions and verify via `findAssertions(forPid:)`, a helper that queries the kernel with `IOPMCopyAssertionsByProcess`
 - **Entry point**: `AppLauncher` (the actual `@main`) detects test runs via `NSClassFromString("XCTestCase")` and substitutes a lightweight `TestApp`. Do not add `@main` to `VigilApp` directly.
 
+## Localization
+
+- **Catalog**: Single `Localizable.xcstrings` (String Catalog) — all languages in one file
+- **Languages**: English (source), German (de), Spanish (es), Hindi (hi), Ukrainian (uk), Chinese Simplified (zh-Hans)
+- **SwiftUI views**: `Text("...")` and `Label("...")` strings are auto-extracted on build — no manual registration
+- **Enum/model strings**: Return `LocalizedStringResource` (not `String`) so Xcode auto-extracts them too
+- **Not localized**: `SleepMode.assertionReason` — intentionally English (appears in `pmset` output and Activity Monitor)
+- **Adding a new string**: Just use `Text("New string")` or return `LocalizedStringResource`. Build the project — the key appears in `Localizable.xcstrings` marked "New". Add translations there.
+- **Testing a language**: In Xcode: Edit Scheme → Run → Options → App Language. See CLI Commands below for command-line testing.
+
+## CLI Commands
+
+```bash
+# Build
+xcodebuild build -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS'
+
+# Test
+xcodebuild test -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS'
+
+# Build and run
+xcodebuild build -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS' -quiet && \
+open "$(xcodebuild -project app/Vigil.xcodeproj -scheme Vigil -showBuildSettings 2>/dev/null | grep '^ *BUILT_PRODUCTS_DIR = ' | sed 's/.*= //')/Vigil.app"
+
+# Build and run with a specific language (replace 'uk' with: de, es, hi, zh-Hans)
+xcodebuild build -project app/Vigil.xcodeproj -scheme Vigil -destination 'platform=macOS' -quiet && \
+open "$(xcodebuild -project app/Vigil.xcodeproj -scheme Vigil -showBuildSettings 2>/dev/null | grep '^ *BUILT_PRODUCTS_DIR = ' | sed 's/.*= //')/Vigil.app" --args -AppleLanguages '(uk)'
+
+# Verify sleep assertion is active
+pmset -g assertions | grep Vigil
+```
+
 ## Distribution
 
 - **App Store name**: "Vigil - Stay Awake" (managed in App Store Connect, separate from PRODUCT_NAME)
diff --git a/app/Vigil.xcodeproj/project.pbxproj b/app/Vigil.xcodeproj/project.pbxproj
index 99ef67e..a5e95d1 100644
--- a/app/Vigil.xcodeproj/project.pbxproj
+++ b/app/Vigil.xcodeproj/project.pbxproj
@@ -152,14 +152,10 @@
 				en,
 				Base,
 				de,
-				fr,
 				es,
-				"es-US",
-				uk,
-				"en-GB",
-				"en-IN",
 				hi,
-				ar,
+				uk,
+				"zh-Hans",
 			);
 			mainGroup = 8C983B4B2F634369004A6B1A;
 			minimizedProjectReferenceProxies = 1;
diff --git a/app/Vigil/Localizable.xcstrings b/app/Vigil/Localizable.xcstrings
new file mode 100644
index 0000000..9921d65
--- /dev/null
+++ b/app/Vigil/Localizable.xcstrings
@@ -0,0 +1,380 @@
+{
+  "sourceLanguage" : "en",
+  "strings" : {
+    "Display & System" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Bildschirm & System"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Pantalla y sistema"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "डिस्प्ले और सिस्टम"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Екран і система"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "显示器和系统"
+          }
+        }
+      }
+    },
+    "Launch at Login" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Bei Anmeldung starten"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Abrir al iniciar sesión"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "लॉगिन पर लॉन्च करें"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Запускати при вході"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "登录时启动"
+          }
+        }
+      }
+    },
+    "Mode" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Modus"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Modo"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "मोड"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Режим"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "模式"
+          }
+        }
+      }
+    },
+    "Quit Vigil" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Vigil beenden"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Salir de Vigil"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Vigil बंद करें"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Завершити Vigil"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "退出 Vigil"
+          }
+        }
+      }
+    },
+    "Remember Last State" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Letzten Status merken"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Recordar último estado"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "पिछली स्थिति याद रखें"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Запам'ятати останній стан"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "记住上次状态"
+          }
+        }
+      }
+    },
+    "Screen and system stay awake" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Bildschirm und System bleiben wach"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "La pantalla y el sistema permanecen activos"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "स्क्रीन और सिस्टम जागते रहेंगे"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Екран і система не засинатимуть"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "屏幕和系统保持唤醒"
+          }
+        }
+      }
+    },
+    "Screen may sleep, system stays running" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Bildschirm kann schlafen, System läuft weiter"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "La pantalla puede apagarse, el sistema sigue activo"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "स्क्रीन स्लीप हो सकती है, सिस्टम चलता रहेगा"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Екран може заснути, система працюватиме"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "屏幕可能休眠，系统保持运行"
+          }
+        }
+      }
+    },
+    "Sleep prevention is off" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Schlafsperre ist deaktiviert"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "La prevención de reposo está desactivada"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "स्लीप प्रिवेंशन बंद है"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Запобігання сну вимкнено"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "防休眠已关闭"
+          }
+        }
+      }
+    },
+    "Sleep prevention is on" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Schlafsperre ist aktiviert"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "La prevención de reposo está activada"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "स्लीप प्रिवेंशन चालू है"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Запобігання сну увімкнено"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "防休眠已开启"
+          }
+        }
+      }
+    },
+    "Stay Awake" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Wach bleiben"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Mantener activo"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "जागते रहें"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Не засинати"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "保持唤醒"
+          }
+        }
+      }
+    },
+    "System Only" : {
+      "localizations" : {
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Nur System"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Solo sistema"
+          }
+        },
+        "hi" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "केवल सिस्टम"
+          }
+        },
+        "uk" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Лише система"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "仅系统"
+          }
+        }
+      }
+    }
+  },
+  "version" : "1.0"
+}
diff --git a/app/Vigil/MenuBarView.swift b/app/Vigil/MenuBarView.swift
index 4778ed3..750bf0a 100644
--- a/app/Vigil/MenuBarView.swift
+++ b/app/Vigil/MenuBarView.swift
@@ -85,7 +85,7 @@ struct MenuBarView: View {
             .pickerStyle(.segmented)
             .labelsHidden()
 
-            Text(sleepManager.sleepMode.description)
+            Text(sleepManager.sleepMode.modeDescription)
                 .font(.caption)
                 .foregroundStyle(.secondary)
                 .frame(maxWidth: .infinity, alignment: .center)
diff --git a/app/Vigil/SleepManager.swift b/app/Vigil/SleepManager.swift
index 73e2d06..27ea310 100644
--- a/app/Vigil/SleepManager.swift
+++ b/app/Vigil/SleepManager.swift
@@ -24,14 +24,14 @@ enum SleepMode: String, CaseIterable {
         }
     }
 
-    var label: String {
+    var label: LocalizedStringResource {
         switch self {
         case .displayAndSystem: "Display & System"
         case .systemOnly: "System Only"
         }
     }
 
-    var description: String {
+    var modeDescription: LocalizedStringResource {
         switch self {
         case .displayAndSystem: "Screen and system stay awake"
         case .systemOnly: "Screen may sleep, system stays running"