diff --git a/src/browser/tests/event/message.html b/src/browser/tests/event/message.html
index 88be4650..55153c8b 100644
--- a/src/browser/tests/event/message.html
+++ b/src/browser/tests/event/message.html
@@ -161,6 +161,32 @@
 }
 </script>
 
+<script id=postMessageTransfersPorts>
+{
+  // window.postMessage(data, targetOrigin, [port]) must deliver the transferred
+  // MessagePort as event.ports[0] (regression: ports used to always be empty,
+  // so receivers doing `e.ports[0].onmessage = ...` threw on undefined).
+  const channel = new MessageChannel();
+  let received = null;
+  let echoed = null;
+
+  channel.port1.onmessage = (e) => { echoed = e.data; };
+
+  const handler = (e) => {
+    received = e.ports[0];
+    received.postMessage('pong');
+  };
+  window.addEventListener('message', handler, { once: true });
+
+  window.postMessage('ping', '*', [channel.port2]);
+
+  testing.onload(() => {
+    testing.expectEqual(true, received instanceof MessagePort);
+    testing.expectEqual('pong', echoed);
+  });
+}
+</script>
+
 <script id=messageEventOriginFromLocation>
 {
   let receivedOrigin = null;
diff --git a/src/browser/tests/navigator/navigator.html b/src/browser/tests/navigator/navigator.html
index 92f33bab..09419d69 100644
--- a/src/browser/tests/navigator/navigator.html
+++ b/src/browser/tests/navigator/navigator.html
@@ -27,6 +27,36 @@
   testing.expectEqual('Gecko', navigator.product);
   testing.expectEqual(false, navigator.javaEnabled());
   testing.expectEqual(false, navigator.webdriver);
+
+  testing.expectEqual(null, navigator.doNotTrack);
+
+  // Every Navigator attribute must be a native accessor on the prototype
+  for (const name of [
+    'userAgent', 'appName', 'appCodeName', 'appVersion', 'platform',
+    'language', 'languages', 'onLine', 'cookieEnabled', 'hardwareConcurrency',
+    'deviceMemory', 'maxTouchPoints', 'vendor', 'product', 'webdriver',
+    'plugins', 'doNotTrack', 'globalPrivacyControl',
+  ]) {
+    const desc = Object.getOwnPropertyDescriptor(Navigator.prototype, name);
+    testing.expectEqual('function', typeof desc.get); // accessor on prototype
+    testing.expectEqual(undefined, desc.value);        // not a data property
+    testing.expectEqual(undefined, Object.getOwnPropertyDescriptor(navigator, name)); // not own
+    testing.expectEqual(true, desc.get.toString().includes('[native code]'));
+  }
+</script>
+
+<script id=navigator_native_descriptor_walk>
+  // Mirror the bot-detection fingerprint: read every navigator property's
+  // descriptor and call toString() on its value/getter. This must not throw.
+  let obj = navigator;
+  do {
+    for (const name of Object.getOwnPropertyNames(obj)) {
+      const d = Object.getOwnPropertyDescriptor(obj, name);
+      if (d.value !== undefined) { d.value.toString(); }
+      else if (d.get !== undefined) { d.get.toString(); }
+    }
+  } while (obj = Object.getPrototypeOf(obj));
+  testing.expectEqual(null, navigator.doNotTrack);
 </script>
 
 <script id=permission_query type=module>
diff --git a/src/browser/webapi/Navigator.zig b/src/browser/webapi/Navigator.zig
index c51e3da2..958fd109 100644
--- a/src/browser/webapi/Navigator.zig
+++ b/src/browser/webapi/Navigator.zig
@@ -48,6 +48,62 @@ pub fn getLanguages(_: *const Navigator) [2][]const u8 {
     return .{ "en-US", "en" };
 }
 
+pub fn getDoNotTrack(_: *const Navigator) ?[]const u8 {
+    return null;
+}
+
+pub fn getAppName(_: *const Navigator) []const u8 {
+    return "Netscape";
+}
+
+pub fn getAppCodeName(_: *const Navigator) []const u8 {
+    return "Mozilla";
+}
+
+pub fn getAppVersion(_: *const Navigator) []const u8 {
+    return "1.0";
+}
+
+pub fn getLanguage(_: *const Navigator) []const u8 {
+    return "en-US";
+}
+
+pub fn getOnLine(_: *const Navigator) bool {
+    return true;
+}
+
+pub fn getCookieEnabled(_: *const Navigator) bool {
+    return true;
+}
+
+pub fn getHardwareConcurrency(_: *const Navigator) u32 {
+    return 4;
+}
+
+pub fn getDeviceMemory(_: *const Navigator) f64 {
+    return 8.0;
+}
+
+pub fn getMaxTouchPoints(_: *const Navigator) u32 {
+    return 0;
+}
+
+pub fn getVendor(_: *const Navigator) []const u8 {
+    return "";
+}
+
+pub fn getProduct(_: *const Navigator) []const u8 {
+    return "Gecko";
+}
+
+pub fn getWebdriver(_: *const Navigator) bool {
+    return false;
+}
+
+pub fn getGlobalPrivacyControl(_: *const Navigator) bool {
+    return true;
+}
+
 pub fn getPlatform(_: *const Navigator) []const u8 {
     return switch (builtin.os.tag) {
         .macos => "MacIntel",
@@ -166,25 +222,27 @@ pub const JsApi = struct {
         pub const empty_with_no_proto = true;
     };
 
-    // Read-only properties
+    // Read-only properties. All are accessors (not data properties) so they
+    // present as native getters on Navigator.prototype, matching real browsers
+    // — see the getter definitions above for why.
     pub const userAgent = bridge.accessor(Navigator.getUserAgent, null, .{});
-    pub const appName = bridge.property("Netscape", .{ .template = false });
-    pub const appCodeName = bridge.property("Mozilla", .{ .template = false });
-    pub const appVersion = bridge.property("1.0", .{ .template = false });
+    pub const appName = bridge.accessor(Navigator.getAppName, null, .{});
+    pub const appCodeName = bridge.accessor(Navigator.getAppCodeName, null, .{});
+    pub const appVersion = bridge.accessor(Navigator.getAppVersion, null, .{});
     pub const platform = bridge.accessor(Navigator.getPlatform, null, .{});
-    pub const language = bridge.property("en-US", .{ .template = false });
+    pub const language = bridge.accessor(Navigator.getLanguage, null, .{});
     pub const languages = bridge.accessor(Navigator.getLanguages, null, .{});
-    pub const onLine = bridge.property(true, .{ .template = false });
-    pub const cookieEnabled = bridge.property(true, .{ .template = false });
-    pub const hardwareConcurrency = bridge.property(4, .{ .template = false });
-    pub const deviceMemory = bridge.property(@as(f64, 8.0), .{ .template = false });
-    pub const maxTouchPoints = bridge.property(0, .{ .template = false });
-    pub const vendor = bridge.property("", .{ .template = false });
-    pub const product = bridge.property("Gecko", .{ .template = false });
-    pub const webdriver = bridge.property(false, .{ .template = false });
+    pub const onLine = bridge.accessor(Navigator.getOnLine, null, .{});
+    pub const cookieEnabled = bridge.accessor(Navigator.getCookieEnabled, null, .{});
+    pub const hardwareConcurrency = bridge.accessor(Navigator.getHardwareConcurrency, null, .{});
+    pub const deviceMemory = bridge.accessor(Navigator.getDeviceMemory, null, .{});
+    pub const maxTouchPoints = bridge.accessor(Navigator.getMaxTouchPoints, null, .{});
+    pub const vendor = bridge.accessor(Navigator.getVendor, null, .{});
+    pub const product = bridge.accessor(Navigator.getProduct, null, .{});
+    pub const webdriver = bridge.accessor(Navigator.getWebdriver, null, .{});
     pub const plugins = bridge.accessor(Navigator.getPlugins, null, .{});
-    pub const doNotTrack = bridge.property(null, .{ .template = false });
-    pub const globalPrivacyControl = bridge.property(true, .{ .template = false });
+    pub const doNotTrack = bridge.accessor(Navigator.getDoNotTrack, null, .{});
+    pub const globalPrivacyControl = bridge.accessor(Navigator.getGlobalPrivacyControl, null, .{});
     pub const registerProtocolHandler = bridge.function(Navigator.registerProtocolHandler, .{ .dom_exception = true });
     pub const unregisterProtocolHandler = bridge.function(Navigator.unregisterProtocolHandler, .{ .dom_exception = true });
 
diff --git a/src/browser/webapi/Window.zig b/src/browser/webapi/Window.zig
index 6e8be504..ced64548 100644
--- a/src/browser/webapi/Window.zig
+++ b/src/browser/webapi/Window.zig
@@ -39,6 +39,7 @@ const Event = @import("Event.zig");
 const EventTarget = @import("EventTarget.zig");
 const ErrorEvent = @import("event/ErrorEvent.zig");
 const MessageEvent = @import("event/MessageEvent.zig");
+const MessagePort = @import("MessagePort.zig");
 const MediaQueryList = @import("css/MediaQueryList.zig");
 const storage = @import("storage/storage.zig");
 const Element = @import("Element.zig");
@@ -561,7 +562,7 @@ pub fn close(self: *Window) void {
     };
 }
 
-pub fn postMessage(self: *Window, message: js.Value.Temp, target_origin: ?[]const u8, frame: *Frame) !void {
+pub fn postMessage(self: *Window, message: js.Value.Temp, target_origin: ?[]const u8, transfer: ?[]const *MessagePort, frame: *Frame) !void {
     // For now, we ignore targetOrigin checking and just dispatch the message
     // In a full implementation, we would validate the origin
     _ = target_origin;
@@ -581,6 +582,7 @@ pub fn postMessage(self: *Window, message: js.Value.Temp, target_origin: ?[]cons
         .frame = target_frame,
         .source = source_window,
         .origin = try arena.dupe(u8, origin),
+        .ports = if (transfer) |t| try arena.dupe(*MessagePort, t) else &.{},
     };
 
     try target_frame.js.scheduler.add(callback, PostMessageCallback.run, 0, .{
@@ -788,6 +790,7 @@ const PostMessageCallback = struct {
     arena: Allocator,
     origin: []const u8,
     message: js.Value.Temp,
+    ports: []const *MessagePort,
 
     fn deinit(self: *PostMessageCallback) void {
         self.frame.releaseArena(self.arena);
@@ -811,6 +814,7 @@ const PostMessageCallback = struct {
                 .data = .{ .value = self.message },
                 .origin = self.origin,
                 .source = self.source,
+                .ports = self.ports,
                 .bubbles = false,
                 .cancelable = false,
             }, frame._page)).asEvent();
@@ -987,8 +991,8 @@ pub const JsApi = struct {
 const CrossOriginWindow = struct {
     window: *Window,
 
-    pub fn postMessage(self: *CrossOriginWindow, message: js.Value.Temp, target_origin: ?[]const u8, frame: *Frame) !void {
-        return self.window.postMessage(message, target_origin, frame);
+    pub fn postMessage(self: *CrossOriginWindow, message: js.Value.Temp, target_origin: ?[]const u8, transfer: ?[]const *MessagePort, frame: *Frame) !void {
+        return self.window.postMessage(message, target_origin, transfer, frame);
     }
 
     pub fn getTop(self: *CrossOriginWindow, frame: *Frame) Access {
diff --git a/src/browser/webapi/event/MessageEvent.zig b/src/browser/webapi/event/MessageEvent.zig
index d4a649e3..2bd07147 100644
--- a/src/browser/webapi/event/MessageEvent.zig
+++ b/src/browser/webapi/event/MessageEvent.zig
@@ -35,11 +35,13 @@ _proto: *Event,
 _data: ?Data = null,
 _origin: []const u8 = "",
 _source: ?*Window = null,
+_ports: []const *MessagePort = &.{},
 
 const MessageEventOptions = struct {
     data: ?Data = null,
     origin: ?[]const u8 = null,
     source: ?*Window = null,
+    ports: []const *MessagePort = &.{},
 };
 
 pub const Data = union(enum) {
@@ -75,6 +77,7 @@ fn initWithTrusted(arena: Allocator, typ: String, opts_: ?Options, trusted: bool
             ._data = opts.data,
             ._origin = if (opts.origin) |str| try arena.dupe(u8, str) else "",
             ._source = opts.source,
+            ._ports = if (opts.ports.len == 0) &.{} else try arena.dupe(*MessagePort, opts.ports),
         },
     );
 
@@ -117,8 +120,8 @@ pub fn getSource(self: *const MessageEvent) ?*Window {
     return self._source;
 }
 
-pub fn getPorts(_: *const MessageEvent) []*MessagePort {
-    return &.{};
+pub fn getPorts(self: *const MessageEvent) []const *MessagePort {
+    return self._ports;
 }
 
 pub const JsApi = struct {