diff --git a/CHANGELOG.md b/CHANGELOG.md
index f7d8410..ddea5e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,15 @@
 
 ## Unreleased
 
+### Provisional iPhone Duo support
+
+- Add `Device.iPhoneDuo` with the A20 Pro chip and `isFoldable`, true only for iPhone Duo and its simulator.
+- Recognize the `iPhone19,4` hardware identifier and omit the image. Display metrics remain unknown (`-1` for diagonal/ratio, `nil` for PPI); other unconfirmed capabilities use false/empty defaults.
+
+### Bug fixes
+
+- Make `isSimulator` return `true` for simulators of unknown devices, so detecting a simulator does not require support for its model.
+
 ## Version 5.9.0
 
 Releasedate: 2026-09-22
diff --git a/Source/Device.generated.swift b/Source/Device.generated.swift
index 1fc5534..d54aacb 100644
--- a/Source/Device.generated.swift
+++ b/Source/Device.generated.swift
@@ -236,6 +236,8 @@ public enum Device {
     case iPhone18Pro
     /// Device is an [iPhone 18 Pro Max](https://support.apple.com/en-us/148591)
     case iPhone18ProMax
+    /// Provisional iPhone Duo; display metrics and other capabilities await verification.
+    case iPhoneDuo
     /// Device is an [iPad 2](https://support.apple.com/kb/SP622)
     ///
     /// ![Image](https://support.apple.com/library/APPLE/APPLECARE_ALLGEOS/SP622/SP622_01-ipad2-mul.png)
@@ -638,6 +640,7 @@ public enum Device {
       case "iPhone18,5": return iPhone17e
       case "iPhone19,2": return iPhone18Pro
       case "iPhone19,3", "iPhone19,7": return iPhone18ProMax
+      case "iPhone19,4": return iPhoneDuo
       case "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4": return iPad2
       case "iPad3,1", "iPad3,2", "iPad3,3": return iPad3
       case "iPad3,4", "iPad3,5", "iPad3,6": return iPad4
@@ -744,6 +747,19 @@ public enum Device {
     #endif
   }
 
+  /// Returns whether the device has a foldable display, including simulators.
+  public var isFoldable: Bool {
+    #if os(iOS)
+    switch self {
+    case .iPhoneDuo: return true
+    case .simulator(let model): return model.isFoldable
+    default: return false
+    }
+    #else
+    return false
+    #endif
+  }
+
   /// Get the real device from a device.
   /// If the device is a an iPhone8Plus simulator this function returns .iPhone8Plus (the real device).
   /// If the parameter is a real device, this function returns just that passed parameter.
@@ -818,6 +834,7 @@ public enum Device {
         case .iPhone17e: return 6.1
         case .iPhone18Pro: return 6.3
         case .iPhone18ProMax: return 6.9
+        case .iPhoneDuo: return -1
         case .iPad2: return 9.7
         case .iPad3: return 9.7
         case .iPad4: return 9.7
@@ -969,6 +986,7 @@ public enum Device {
       case .iPhone17e: return (width: 9, height: 19.5)
       case .iPhone18Pro: return (width: 9, height: 19.5)
       case .iPhone18ProMax: return (width: 9, height: 19.5)
+      case .iPhoneDuo: return (width: -1, height: -1)
       case .iPad2: return (width: 3, height: 4)
       case .iPad3: return (width: 3, height: 4)
       case .iPad4: return (width: 3, height: 4)
@@ -1073,7 +1091,7 @@ public enum Device {
 
     /// All iPhones
     public static var allPhones: [Device] {
-      return [.iPhone4, .iPhone4s, .iPhone5, .iPhone5c, .iPhone5s, .iPhone6, .iPhone6Plus, .iPhone6s, .iPhone6sPlus, .iPhone7, .iPhone7Plus, .iPhoneSE, .iPhone8, .iPhone8Plus, .iPhoneX, .iPhoneXS, .iPhoneXSMax, .iPhoneXR, .iPhone11, .iPhone11Pro, .iPhone11ProMax, .iPhoneSE2, .iPhone12, .iPhone12Mini, .iPhone12Pro, .iPhone12ProMax, .iPhone13, .iPhone13Mini, .iPhone13Pro, .iPhone13ProMax, .iPhoneSE3, .iPhone14, .iPhone14Plus, .iPhone14Pro, .iPhone14ProMax, .iPhone15, .iPhone15Plus, .iPhone15Pro, .iPhone15ProMax, .iPhone16, .iPhone16Plus, .iPhone16Pro, .iPhone16ProMax, .iPhone16e, .iPhone17, .iPhone17Pro, .iPhone17ProMax, .iPhoneAir, .iPhone17e, .iPhone18Pro, .iPhone18ProMax]
+      return [.iPhone4, .iPhone4s, .iPhone5, .iPhone5c, .iPhone5s, .iPhone6, .iPhone6Plus, .iPhone6s, .iPhone6sPlus, .iPhone7, .iPhone7Plus, .iPhoneSE, .iPhone8, .iPhone8Plus, .iPhoneX, .iPhoneXS, .iPhoneXSMax, .iPhoneXR, .iPhone11, .iPhone11Pro, .iPhone11ProMax, .iPhoneSE2, .iPhone12, .iPhone12Mini, .iPhone12Pro, .iPhone12ProMax, .iPhone13, .iPhone13Mini, .iPhone13Pro, .iPhone13ProMax, .iPhoneSE3, .iPhone14, .iPhone14Plus, .iPhone14Pro, .iPhone14ProMax, .iPhone15, .iPhone15Plus, .iPhone15Pro, .iPhone15ProMax, .iPhone16, .iPhone16Plus, .iPhone16Pro, .iPhone16ProMax, .iPhone16e, .iPhone17, .iPhone17Pro, .iPhone17ProMax, .iPhoneAir, .iPhone17e, .iPhone18Pro, .iPhone18ProMax, .iPhoneDuo]
     }
 
     /// All iPads
@@ -1379,10 +1397,13 @@ public enum Device {
     return allRealDevices.map(Device.simulator)
   }
 
-  /// Returns whether the device is any of the simulator
+  /// Returns whether the device is a simulator, including simulators of unknown devices.
   /// Useful when there is a need to check and skip running a portion of code (location request or others)
   public var isSimulator: Bool {
-    return isOneOf(Device.allSimulators)
+    if case .simulator = self {
+      return true
+    }
+    return false
   }
 
   /**
@@ -1551,6 +1572,7 @@ public enum Device {
       case .iPhone17e: return 460
       case .iPhone18Pro: return 460
       case .iPhone18ProMax: return 460
+      case .iPhoneDuo: return nil
       case .iPad2: return 132
       case .iPad3: return 264
       case .iPad4: return 264
@@ -1734,6 +1756,7 @@ extension Device: CustomStringConvertible {
       case .iPhone17e: return "iPhone 17e"
       case .iPhone18Pro: return "iPhone 18 Pro"
       case .iPhone18ProMax: return "iPhone 18 Pro Max"
+      case .iPhoneDuo: return "iPhone Duo"
       case .iPad2: return "iPad 2"
       case .iPad3: return "iPad (3rd generation)"
       case .iPad4: return "iPad (4th generation)"
@@ -1904,6 +1927,7 @@ extension Device: CustomStringConvertible {
       case .iPhone17e: return "iPhone 17e"
       case .iPhone18Pro: return "iPhone 18 Pro"
       case .iPhone18ProMax: return "iPhone 18 Pro Max"
+      case .iPhoneDuo: return "iPhone Duo"
       case .iPad2: return "iPad 2"
       case .iPad3: return "iPad (3rd generation)"
       case .iPad4: return "iPad (4th generation)"
@@ -2634,6 +2658,7 @@ extension Device {
       case .iPhone17e: return .a19
       case .iPhone18Pro: return .a20Pro
       case .iPhone18ProMax: return .a20Pro
+      case .iPhoneDuo: return .a20Pro
       case .iPad2: return .a5
       case .iPad3: return .a5X
       case .iPad4: return .a6X
diff --git a/Source/Device.swift.gyb b/Source/Device.swift.gyb
index 63b4348..e878903 100644
--- a/Source/Device.swift.gyb
+++ b/Source/Device.swift.gyb
@@ -32,6 +32,7 @@ class Device:
       has5gSupport=False,
       hasEsimSupport=False,
       hasDualEsimSupport=False,
+      isFoldable=False,
   ):
     self.caseName = caseName
     self.comment = comment
@@ -61,6 +62,7 @@ class Device:
     self.has5gSupport = has5gSupport
     self.hasEsimSupport = hasEsimSupport
     self.hasDualEsimSupport = hasDualEsimSupport
+    self.isFoldable = isFoldable
 
 # iOS
 iPods = [
@@ -284,6 +286,10 @@ iPhones = [
                 hasDynamicIsland=True, cameras=123, hasLidarSensor=True, hasUSBCConnectivity=True,
                 has5gSupport=True,
                 hasEsimSupport=True, hasDualEsimSupport=True),
+
+            # Duo capabilities other than its chip and foldability are unconfirmed (false/empty defaults).
+            Device("iPhoneDuo", "Provisional iPhone Duo; display metrics and other capabilities await verification.", "", ["iPhone19,4"], -1, (-1, -1), "iPhone Duo", "iPhone Duo", "nil",
+                cpu="a20Pro", isFoldable=True),
           ]
 
 iPads = [
@@ -828,6 +834,23 @@ public enum Device {
     #endif
   }
 
+  /// Returns whether the device has a foldable display, including simulators.
+  public var isFoldable: Bool {
+    #if os(iOS)
+    switch self {
+% for device in iOSDevices:
+%   if device.isFoldable:
+    case .${device.caseName}: return true
+%   end
+% end
+    case .simulator(let model): return model.isFoldable
+    default: return false
+    }
+    #else
+    return false
+    #endif
+  }
+
   /// Get the real device from a device.
   /// If the device is a an iPhone8Plus simulator this function returns .iPhone8Plus (the real device).
   /// If the parameter is a real device, this function returns just that passed parameter.
@@ -1205,10 +1228,13 @@ public enum Device {
     return allRealDevices.map(Device.simulator)
   }
 
-  /// Returns whether the device is any of the simulator
+  /// Returns whether the device is a simulator, including simulators of unknown devices.
   /// Useful when there is a need to check and skip running a portion of code (location request or others)
   public var isSimulator: Bool {
-    return isOneOf(Device.allSimulators)
+    if case .simulator = self {
+      return true
+    }
+    return false
   }
 
   /**
diff --git a/Tests/Tests.swift b/Tests/Tests.swift
index ce99bbc..74e298f 100644
--- a/Tests/Tests.swift
+++ b/Tests/Tests.swift
@@ -16,6 +16,43 @@ class DeviceKitTests: XCTestCase {
 
   let device = Device.current
 
+  func testIsFoldable() {
+    for model in Device.allRealDevices {
+      #if os(iOS)
+      let expected = model == .iPhoneDuo
+      #else
+      let expected = false
+      #endif
+      XCTAssertEqual(model.isFoldable, expected, model.description)
+      XCTAssertEqual(Device.simulator(model).isFoldable, expected, model.description)
+    }
+    XCTAssertFalse(Device.unknown("unrecognized").isFoldable)
+    XCTAssertFalse(Device.simulator(.unknown("unrecognized")).isFoldable)
+  }
+
+  #if os(iOS)
+  func testProvisionalIPhoneDuo() {
+    let model = Device.iPhoneDuo
+    XCTAssertEqual(Device.mapToDevice(identifier: "iPhone19,4"), model)
+    XCTAssertEqual(Device.mapToDevice(identifier: "placeholder:iPhoneDuo"), .unknown("placeholder:iPhoneDuo"))
+    XCTAssertEqual(model.description, "iPhone Duo")
+    XCTAssertEqual(model.safeDescription, "iPhone Duo")
+    XCTAssertTrue(Device.allPhones.contains(model))
+    XCTAssertTrue(Device.allRealDevices.contains(model))
+    XCTAssertTrue(Device.allSimulators.contains(.simulator(model)))
+    for variant in [model, .simulator(model)] {
+      XCTAssertTrue(variant.isPhone)
+      XCTAssertFalse(variant.isPad)
+      XCTAssertTrue(variant.isFoldable)
+      XCTAssertEqual(variant.cpu, .a20Pro)
+      XCTAssertEqual(variant.diagonal, -1)
+      XCTAssertEqual(variant.screenRatio.width, -1)
+      XCTAssertEqual(variant.screenRatio.height, -1)
+      XCTAssertNil(variant.ppi)
+    }
+  }
+  #endif
+
   #if os(iOS) || os(watchOS)
   func testSeptember2026Devices() {
     struct ExpectedDevice {
@@ -32,8 +69,8 @@ class DeviceKitTests: XCTestCase {
     ]
     let chip = Device.CPU.a20Pro
     XCTAssertEqual(chip.description, "A20 Pro")
-    // The deferred model and unverified identifiers must remain unknown.
-    for identifier in ["iPhone19,1", "iPhone19,4", "iPhone19,5", "iPhone19,6", "placeholder:iPhone18Pro", "placeholder:iPhone18ProMax"] {
+    // Unverified identifiers must remain unknown.
+    for identifier in ["iPhone19,1", "iPhone19,5", "iPhone19,6", "placeholder:iPhone18Pro", "placeholder:iPhone18ProMax"] {
       XCTAssertEqual(Device.mapToDevice(identifier: identifier), .unknown(identifier))
     }
     #else
@@ -91,6 +128,36 @@ class DeviceKitTests: XCTestCase {
     #endif
   }
 
+  func testIsSimulatorForKnownAndUnknownDevices() {
+    for model in Device.allRealDevices + [.unknown("unrecognized")] {
+      XCTAssertFalse(model.isSimulator, model.description)
+      XCTAssertTrue(Device.simulator(model).isSimulator, model.description)
+    }
+  }
+
+  #if os(iOS) && targetEnvironment(simulator)
+  func testCurrentSimulatorWithKnownAndUnknownModels() {
+    let originalModelIdentifier = ProcessInfo.processInfo.environment["SIMULATOR_MODEL_IDENTIFIER"]
+    defer {
+      if let originalModelIdentifier = originalModelIdentifier {
+        setenv("SIMULATOR_MODEL_IDENTIFIER", originalModelIdentifier, 1)
+      } else {
+        unsetenv("SIMULATOR_MODEL_IDENTIFIER")
+      }
+    }
+
+    let models: [(String, Device)] = [
+      ("iPhone19,4", .iPhoneDuo),
+      ("iPhone999,1", .unknown("iPhone999,1"))
+    ]
+    for (identifier, model) in models {
+      setenv("SIMULATOR_MODEL_IDENTIFIER", identifier, 1)
+      XCTAssertEqual(Device.current, .simulator(model), identifier)
+      XCTAssertTrue(Device.current.isSimulator, identifier)
+    }
+  }
+  #endif
+
   func testDeviceDescription() {
     #if os(macOS)
     #else