fix: Add macOS platform support via Chameleon typealias pattern

Package.swift

@@ -5,7 +5,7 @@ import PackageDescription
 
 let package = Package(
   name: "ConversationKit",
-  platforms: [.iOS(.v17), .macCatalyst(.v17)],
+  platforms: [.iOS(.v17), .macCatalyst(.v17), .macOS(.v14)],
   products: [
     .library(
       name: "ConversationKit",

Sources/ConversationKit/Model/ImageAttachment.swift

@@ -20,9 +20,9 @@ import SwiftUI
 
 public struct ImageAttachment: Attachment {
   public let id = UUID()
-  public let image: UIImage
+  public let image: PlatformImage
 
-  public init(image: UIImage) {
+  public init(image: PlatformImage) {
     self.image = image
   }
 
@@ -37,7 +37,7 @@ public struct ImageAttachment: Attachment {
 
 extension ImageAttachment: View {
   public var body: some View {
-    Image(uiImage: image)
+    Image(platformImage: image)
       .resizable()
       .aspectRatio(contentMode: .fill)
       .frame(width: 100, height: 100)

Sources/ConversationKit/Platform/PlatformTypes.swift

@@ -0,0 +1,74 @@
+//
+// PlatformTypes.swift
+// ConversationKit
+//
+// Cross-platform type aliases following the Chameleon pattern:
+// centralize platform differences so view code stays clean.
+
+import SwiftUI
+
+#if canImport(UIKit)
+  import UIKit
+  public typealias PlatformImage = UIImage
+#elseif canImport(AppKit)
+  import AppKit
+  public typealias PlatformImage = NSImage
+#endif
+
+// MARK: - Platform Image Construction
+
+extension PlatformImage {
+  /// Create a platform image from an SF Symbol name.
+  static func systemSymbol(_ name: String) -> PlatformImage? {
+    #if canImport(UIKit)
+      return UIImage(systemName: name)
+    #elseif canImport(AppKit)
+      return NSImage(systemSymbolName: name, accessibilityDescription: nil)
+    #endif
+  }
+}
+
+// MARK: - Platform Image → SwiftUI Image
+
+extension Image {
+  /// Create a SwiftUI Image from a platform-native image.
+  init(platformImage: PlatformImage) {
+    #if canImport(UIKit)
+      self.init(uiImage: platformImage)
+    #elseif canImport(AppKit)
+      self.init(nsImage: platformImage)
+    #endif
+  }
+}
+
+// MARK: - Platform Colors
+
+extension Color {
+  /// Secondary system background — `.secondarySystemBackground` on iOS,
+  /// `.controlBackgroundColor` on macOS.
+  static var platformSecondaryBackground: Color {
+    #if canImport(UIKit)
+      Color(uiColor: .secondarySystemBackground)
+    #elseif canImport(AppKit)
+      Color(nsColor: .controlBackgroundColor)
+    #endif
+  }
+
+  /// System gray 4 — `.systemGray4` on iOS, `.systemGray` on macOS.
+  static var platformGray4: Color {
+    #if canImport(UIKit)
+      Color(uiColor: .systemGray4)
+    #elseif canImport(AppKit)
+      Color(nsColor: .systemGray)
+    #endif
+  }
+
+  /// Separator color — `.separator` on iOS, `.separatorColor` on macOS.
+  static var platformSeparator: Color {
+    #if canImport(UIKit)
+      Color(uiColor: .separator)
+    #elseif canImport(AppKit)
+      Color(nsColor: .separatorColor)
+    #endif
+  }
+}

Sources/ConversationKit/Views/AttachmentPreviewCard.swift

@@ -44,7 +44,7 @@ public struct AttachmentPreviewCard<AttachmentType: Attachment & View>: View {
 public struct ConcentricClipShapeModifier: ViewModifier {
   public func body(content: Content) -> some View {
 #if compiler(>=6.2)
-    if #available(iOS 26.0, *) {
+    if #available(iOS 26.0, macOS 26.0, *) {
       content
         .clipShape(.rect(corners: Edge.Corner.Style.concentric(minimum: 12), isUniform: false))
     } else {
@@ -60,13 +60,13 @@ public struct ConcentricClipShapeModifier: ViewModifier {
       .clipShape(RoundedRectangle(cornerRadius: 8))
       .overlay(
         RoundedRectangle(cornerRadius: 8)
-          .stroke(Color(.separator), lineWidth: 0.5)
+          .stroke(Color.platformSeparator, lineWidth: 0.5)
       )
   }
 }
 
 #Preview {
-  AttachmentPreviewCard(attachment: ImageAttachment(image: UIImage(systemName: "photo")!)) {
+  AttachmentPreviewCard(attachment: ImageAttachment(image: PlatformImage.systemSymbol("photo")!)) {
     print("Delete action tapped")
   }
 }

Sources/ConversationKit/Views/AttachmentPreviewScrollView.swift

@@ -40,9 +40,9 @@ struct AttachmentPreviewScrollView<AttachmentType: Attachment & View>: View {
 #Preview {
   struct PreviewWrapper: View {
     @State var attachments = [
-      ImageAttachment(image: UIImage(systemName: "photo")!),
-      ImageAttachment(image: UIImage(systemName: "camera")!),
-      ImageAttachment(image: UIImage(systemName: "mic")!)
+      ImageAttachment(image: PlatformImage.systemSymbol("photo")!),
+      ImageAttachment(image: PlatformImage.systemSymbol("camera")!),
+      ImageAttachment(image: PlatformImage.systemSymbol("mic")!)
     ]
 
     var body: some View {

Sources/ConversationKit/Views/ConversationView.swift

@@ -303,7 +303,9 @@ extension ConversationView where AttachmentType == EmptyAttachment {
         }
       }
       .navigationTitle("Chat")
+      #if os(iOS)
       .navigationBarTitleDisplayMode(.inline)
+      #endif
   }
 }
 
@@ -361,9 +363,9 @@ extension ConversationView where AttachmentType == EmptyAttachment {
             Markdown(messageContent)
               .padding()
               .background {
-                Color(uiColor: message.participant == .other
-                      ? .secondarySystemBackground
-                      : .systemGray4)
+                message.participant == .other
+                      ? Color.platformSecondaryBackground
+                      : Color.platformGray4
               }
               .roundedCorner(10, corners: .allCorners)
             if message.participant == .other {
@@ -381,6 +383,8 @@ extension ConversationView where AttachmentType == EmptyAttachment {
       }
     }
     .navigationTitle("Chat")
+    #if os(iOS)
     .navigationBarTitleDisplayMode(.inline)
+    #endif
   }
 }

Sources/ConversationKit/Views/MessageComposerView.swift

@@ -53,7 +53,7 @@ public struct MessageComposerView<AttachmentType: Attachment & View>: View {
 
   public var body: some View {
 #if compiler(>=6.2)
-    if #available(iOS 26.0, *) {
+    if #available(iOS 26.0, macOS 26.0, *) {
       GlassEffectContainer {
         HStack(alignment: .bottom) {
           if !disableAttachments, let attachmentActions {
@@ -121,7 +121,7 @@ public struct MessageComposerView<AttachmentType: Attachment & View>: View {
         .clipShape(Circle())
         .overlay(
           Circle()
-            .stroke(Color(.separator), lineWidth: 0.5)
+            .stroke(Color.platformSeparator, lineWidth: 0.5)
         )
         .padding(.trailing, 8)
       }
@@ -156,7 +156,7 @@ public struct MessageComposerView<AttachmentType: Attachment & View>: View {
       .clipShape(RoundedRectangle(cornerRadius: 22))
       .overlay(
         RoundedRectangle(cornerRadius: 22)
-          .stroke(Color(.separator), lineWidth: 0.5)
+          .stroke(Color.platformSeparator, lineWidth: 0.5)
       )
     }
     .padding(.top, 8)
@@ -174,9 +174,9 @@ extension MessageComposerView where AttachmentType == EmptyAttachment {
 #Preview("With Attachments") {
   @Previewable @State var message = "Hello, world!"
   @Previewable @State var attachments = [
-    ImageAttachment(image: UIImage(systemName: "photo")!),
-    ImageAttachment(image: UIImage(systemName: "camera")!),
-    ImageAttachment(image: UIImage(systemName: "mic")!)
+    ImageAttachment(image: PlatformImage.systemSymbol("photo")!),
+    ImageAttachment(image: PlatformImage.systemSymbol("camera")!),
+    ImageAttachment(image: PlatformImage.systemSymbol("mic")!)
   ]
 
   MessageComposerView(message: $message, attachments: $attachments)

Sources/ConversationKit/Views/MessageView.swift

@@ -20,29 +20,62 @@
 import SwiftUI
 import MarkdownUI
 
+/// Cross-platform corner specification replacing UIRectCorner.
+struct RectCorner: OptionSet, Sendable {
+  let rawValue: Int
+  static let topLeft = RectCorner(rawValue: 1 << 0)
+  static let topRight = RectCorner(rawValue: 1 << 1)
+  static let bottomLeft = RectCorner(rawValue: 1 << 2)
+  static let bottomRight = RectCorner(rawValue: 1 << 3)
+  static let allCorners: RectCorner = [.topLeft, .topRight, .bottomLeft, .bottomRight]
+}
+
+/// Cross-platform rounded corner shape using pure SwiftUI Path.
 struct RoundedCorner: Shape {
   var radius: CGFloat = .infinity
-  var corners: UIRectCorner = .allCorners
+  var corners: RectCorner = .allCorners
 
   func path(in rect: CGRect) -> Path {
-    let path = UIBezierPath(
-      roundedRect: rect,
-      byRoundingCorners: corners,
-      cornerRadii: CGSize(width: radius, height: radius)
-    )
-    return Path(path.cgPath)
+    let tl = corners.contains(.topLeft) ? radius : 0
+    let tr = corners.contains(.topRight) ? radius : 0
+    let bl = corners.contains(.bottomLeft) ? radius : 0
+    let br = corners.contains(.bottomRight) ? radius : 0
+
+    var path = Path()
+    path.move(to: CGPoint(x: rect.minX + tl, y: rect.minY))
+    path.addLine(to: CGPoint(x: rect.maxX - tr, y: rect.minY))
+    path.addArc(
+      tangent1End: CGPoint(x: rect.maxX, y: rect.minY),
+      tangent2End: CGPoint(x: rect.maxX, y: rect.minY + tr),
+      radius: tr)
+    path.addLine(to: CGPoint(x: rect.maxX, y: rect.maxY - br))
+    path.addArc(
+      tangent1End: CGPoint(x: rect.maxX, y: rect.maxY),
+      tangent2End: CGPoint(x: rect.maxX - br, y: rect.maxY),
+      radius: br)
+    path.addLine(to: CGPoint(x: rect.minX + bl, y: rect.maxY))
+    path.addArc(
+      tangent1End: CGPoint(x: rect.minX, y: rect.maxY),
+      tangent2End: CGPoint(x: rect.minX, y: rect.maxY - bl),
+      radius: bl)
+    path.addLine(to: CGPoint(x: rect.minX, y: rect.minY + tl))
+    path.addArc(
+      tangent1End: CGPoint(x: rect.minX, y: rect.minY),
+      tangent2End: CGPoint(x: rect.minX + tl, y: rect.minY),
+      radius: tl)
+    return path
   }
 }
 
 extension View {
-  func roundedCorner(_ radius: CGFloat, corners: UIRectCorner) -> some View {
+  func roundedCorner(_ radius: CGFloat, corners: RectCorner) -> some View {
     clipShape(RoundedCorner(radius: radius, corners: corners))
   }
 }
 
 public struct MessageView: View {
   @Environment(\.presentErrorAction) var presentErrorAction
-  
+
   let message: String?
   let imageURL: String?
   let fullWidth: Bool = false
@@ -97,15 +130,15 @@ public struct MessageView: View {
             Markdown(message)
           }
         }
-      } 
+      }
       .padding()
       .if(fullWidth) { view in
         view.frame(maxWidth: .infinity, alignment: .leading)
       }
       .background {
-        Color(uiColor: participant == .other
-              ? .secondarySystemBackground
-              : .systemGray4)
+        participant == .other
+          ? Color.platformSecondaryBackground
+          : Color.platformGray4
       }
       .roundedCorner(8, corners: participant == .other ? .topLeft : .topRight)
       .roundedCorner(20, corners: participant == .other ? [.topRight, .bottomLeft, .bottomRight] : [.topLeft, .bottomLeft, .bottomRight])