diff --git a/sdk/generated/host.window.d.ts b/sdk/generated/host.window.d.ts
new file mode 100644
index 0000000..71ba7c2
--- /dev/null
+++ b/sdk/generated/host.window.d.ts
@@ -0,0 +1,310 @@
+// Auto-generated TypeScript definitions for host:window module
+// Generated from ext_window/build.rs - do not edit manually
+
+declare module "host:window" {
+  // ============================================================================
+  // Window Types
+  // ============================================================================
+
+  /** Options for creating a new window */
+  export interface WindowOptions {
+    /** URL to load (default: "app://index.html") */
+    url?: string;
+    /** Window width in pixels */
+    width?: number;
+    /** Window height in pixels */
+    height?: number;
+    /** Window title */
+    title?: string;
+    /** Whether window is resizable (default: true) */
+    resizable?: boolean;
+    /** Whether window has decorations (default: true) */
+    decorations?: boolean;
+    /** Whether window is visible on creation (default: true) */
+    visible?: boolean;
+    /** Whether window is transparent */
+    transparent?: boolean;
+    /** Whether window is always on top */
+    alwaysOnTop?: boolean;
+    /** Initial X position */
+    x?: number;
+    /** Initial Y position */
+    y?: number;
+    /** Minimum window width */
+    minWidth?: number;
+    /** Minimum window height */
+    minHeight?: number;
+    /** Maximum window width */
+    maxWidth?: number;
+    /** Maximum window height */
+    maxHeight?: number;
+    /** Channel allowlist for IPC - only these channels can be used */
+    channels?: string[];
+  }
+
+  /** Window position */
+  export interface Position {
+    x: number;
+    y: number;
+  }
+
+  /** Window size */
+  export interface Size {
+    width: number;
+    height: number;
+  }
+
+  /** Native window handle (platform-specific) */
+  export interface NativeHandle {
+    /** Platform type: "windows", "macos", "linux-x11", "linux-wayland", or "linux" (placeholder) */
+    platform: string;
+    /**
+     * Raw handle value (HWND on Windows, NSView* on macOS, X11 window ID on Linux).
+     * Note: On Linux without X11/Wayland detection, returns 0 as a placeholder.
+     * Typed as number since Rust u64 serializes to JS number (safe for values up to 2^53).
+     */
+    handle: number;
+  }
+
+  /** Window system event */
+  export interface WindowSystemEvent {
+    /** The window that emitted the event */
+    windowId: string;
+    /** Event type */
+    type: "close" | "focus" | "blur" | "resize" | "move" | "minimize" | "maximize" | "restore";
+    /** Event payload (e.g., size for resize, position for move) */
+    payload: unknown;
+  }
+
+  /** Window handle with methods for manipulating the window */
+  export interface Window {
+    /** Unique window identifier */
+    readonly id: string;
+
+    // Lifecycle
+    /** Close this window */
+    close(): Promise<boolean>;
+    /** Minimize this window */
+    minimize(): Promise<void>;
+    /** Maximize this window */
+    maximize(): Promise<void>;
+    /** Restore from maximized state */
+    unmaximize(): Promise<void>;
+    /** Restore from minimized state */
+    restore(): Promise<void>;
+    /** Focus this window */
+    focus(): Promise<void>;
+
+    // Position & Size
+    /** Get window position */
+    getPosition(): Promise<Position>;
+    /** Set window position */
+    setPosition(x: number, y: number): Promise<void>;
+    /** Get window size */
+    getSize(): Promise<Size>;
+    /** Set window size */
+    setSize(width: number, height: number): Promise<void>;
+
+    // Title
+    /** Get window title */
+    getTitle(): Promise<string>;
+    /** Set window title */
+    setTitle(title: string): Promise<void>;
+
+    // State queries
+    /** Check if fullscreen */
+    isFullscreen(): Promise<boolean>;
+    /** Set fullscreen mode */
+    setFullscreen(fullscreen: boolean): Promise<void>;
+    /** Check if focused */
+    isFocused(): Promise<boolean>;
+    /** Check if maximized */
+    isMaximized(): Promise<boolean>;
+    /** Check if minimized */
+    isMinimized(): Promise<boolean>;
+    /** Check if visible */
+    isVisible(): Promise<boolean>;
+    /** Check if resizable */
+    isResizable(): Promise<boolean>;
+    /** Check if has decorations */
+    hasDecorations(): Promise<boolean>;
+    /** Check if always on top */
+    isAlwaysOnTop(): Promise<boolean>;
+
+    // Configuration
+    /** Set whether window is resizable */
+    setResizable(resizable: boolean): Promise<void>;
+    /** Set whether window has decorations */
+    setDecorations(decorations: boolean): Promise<void>;
+    /** Set whether window is always on top */
+    setAlwaysOnTop(alwaysOnTop: boolean): Promise<void>;
+    /** Set window visibility */
+    setVisible(visible: boolean): Promise<void>;
+    /** Show window (alias for setVisible(true)) */
+    show(): Promise<void>;
+    /** Hide window (alias for setVisible(false)) */
+    hide(): Promise<void>;
+
+    // Native
+    /** Get native window handle */
+    getNativeHandle(): Promise<NativeHandle>;
+
+    // Events
+    /** Async iterator for events from this window */
+    events(): AsyncGenerator<WindowSystemEvent, void, unknown>;
+  }
+
+  // ============================================================================
+  // Dialog Types
+  // ============================================================================
+
+  /** File filter for open/save dialogs */
+  export interface FileFilter {
+    /** Display name for the filter (e.g., "Images") */
+    name: string;
+    /** File extensions without dots (e.g., ["png", "jpg"]) */
+    extensions: string[];
+  }
+
+  /** Options for file open dialog */
+  export interface FileDialogOptions {
+    /** Dialog title */
+    title?: string;
+    /** Default starting path */
+    defaultPath?: string;
+    /** File type filters */
+    filters?: FileFilter[];
+    /** Allow selecting multiple files */
+    multiple?: boolean;
+    /** Select directories instead of files */
+    directory?: boolean;
+  }
+
+  /** Options for message dialog */
+  export interface MessageDialogOptions {
+    /** Dialog title */
+    title?: string;
+    /** Message to display */
+    message: string;
+    /** Dialog kind: "info", "warning", or "error" */
+    kind?: "info" | "warning" | "error";
+    /** Custom button labels */
+    buttons?: string[];
+  }
+
+  // ============================================================================
+  // Menu Types
+  // ============================================================================
+
+  /** Menu item definition */
+  export interface MenuItem {
+    /** Unique identifier for this menu item */
+    id?: string;
+    /** Display label */
+    label: string;
+    /** Keyboard accelerator (e.g., "CmdOrCtrl+S") */
+    accelerator?: string;
+    /** Whether the item is enabled (default: true) */
+    enabled?: boolean;
+    /** Whether the item is checked (for checkbox items) */
+    checked?: boolean;
+    /** Submenu items */
+    submenu?: MenuItem[];
+    /** Item type: "normal", "checkbox", or "separator" */
+    type?: "normal" | "checkbox" | "separator";
+  }
+
+  /** Event emitted when a menu item is clicked */
+  export interface MenuEvent {
+    /** Source of the event: "app", "context", or "tray" */
+    menuId: string;
+    /** The id of the clicked menu item */
+    itemId: string;
+    /** The label of the clicked menu item */
+    label: string;
+  }
+
+  // ============================================================================
+  // Tray Types
+  // ============================================================================
+
+  /** Options for creating a system tray icon */
+  export interface TrayOptions {
+    /** Path to icon file */
+    icon?: string;
+    /** Tooltip text shown on hover */
+    tooltip?: string;
+    /** Context menu for the tray icon */
+    menu?: MenuItem[];
+  }
+
+  /** Tray handle with methods for manipulating the tray */
+  export interface TrayHandle {
+    /** Unique tray identifier */
+    readonly id: string;
+    /** Update tray options */
+    update(options: TrayOptions): Promise<boolean>;
+    /** Destroy this tray */
+    destroy(): Promise<boolean>;
+  }
+
+  // ============================================================================
+  // Window Functions
+  // ============================================================================
+
+  /** Create a new window and return a Window handle */
+  export function createWindow(options?: WindowOptions): Promise<Window>;
+
+  /** Close a window by ID */
+  export function closeWindow(windowId: string): Promise<boolean>;
+
+  /** Async iterator for window system events from all windows */
+  export function windowEvents(): AsyncGenerator<WindowSystemEvent, void, unknown>;
+
+  // ============================================================================
+  // Dialog Namespace
+  // ============================================================================
+
+  export const dialog: {
+    /** Show an open file dialog. Returns null if cancelled. */
+    open(options?: FileDialogOptions): Promise<string[] | null>;
+    /** Show a save file dialog. Returns null if cancelled. */
+    save(options?: FileDialogOptions): Promise<string | null>;
+    /** Show a message dialog. Returns the index of the clicked button. */
+    message(options: MessageDialogOptions | string): Promise<number>;
+    /** Show an alert dialog (convenience wrapper) */
+    alert(message: string, title?: string): Promise<number>;
+    /** Show a confirm dialog (convenience wrapper) */
+    confirm(message: string, title?: string): Promise<boolean>;
+    /** Show an error dialog (convenience wrapper) */
+    error(message: string, title?: string): Promise<number>;
+    /** Show a warning dialog (convenience wrapper) */
+    warning(message: string, title?: string): Promise<number>;
+  };
+
+  // ============================================================================
+  // Menu Namespace
+  // ============================================================================
+
+  export const menu: {
+    /** Set the application menu bar */
+    setAppMenu(items: MenuItem[]): Promise<boolean>;
+    /** Show a context menu at the current cursor position */
+    showContextMenu(items: MenuItem[], windowId?: string): Promise<string | null>;
+    /** Async iterator for menu events */
+    events(): AsyncGenerator<MenuEvent, void, unknown>;
+    /** Register a callback for menu events. Returns unsubscribe function. */
+    onMenu(callback: (event: MenuEvent) => void): () => void;
+  };
+
+  // ============================================================================
+  // Tray Namespace
+  // ============================================================================
+
+  export const tray: {
+    /** Create a system tray icon */
+    create(options?: TrayOptions): Promise<TrayHandle>;
+    /** Destroy a tray by ID */
+    destroy(trayId: string): Promise<boolean>;
+  };
+}
diff --git a/sdk/host.d.ts b/sdk/host.d.ts
index fcc5c78..3e228b0 100644
--- a/sdk/host.d.ts
+++ b/sdk/host.d.ts
@@ -488,3 +488,226 @@ declare module "host:wasm" {
     grow(instanceId: string, pages: number): Promise<number>;
   };
 }
+
+declare module "host:window" {
+  /** Options for creating a new window */
+  export interface WindowOptions {
+    url?: string;
+    width?: number;
+    height?: number;
+    title?: string;
+    resizable?: boolean;
+    decorations?: boolean;
+    visible?: boolean;
+    transparent?: boolean;
+    alwaysOnTop?: boolean;
+    x?: number;
+    y?: number;
+    minWidth?: number;
+    minHeight?: number;
+    maxWidth?: number;
+    maxHeight?: number;
+    channels?: string[];
+  }
+
+  /** Window position */
+  export interface Position {
+    x: number;
+    y: number;
+  }
+
+  /** Window size */
+  export interface Size {
+    width: number;
+    height: number;
+  }
+
+  /** Native window handle (platform-specific) */
+  export interface NativeHandle {
+    /** Platform type: "windows", "macos", "linux-x11", "linux-wayland", or "linux" (placeholder) */
+    platform: string;
+    /**
+     * Raw handle value (HWND on Windows, NSView* on macOS, X11 window ID on Linux).
+     * Note: On Linux without X11/Wayland detection, returns 0 as a placeholder.
+     * Typed as number since Rust u64 serializes to JS number (safe for values up to 2^53).
+     */
+    handle: number;
+  }
+
+  /** Window system event */
+  export interface WindowSystemEvent {
+    windowId: string;
+    type: "close" | "focus" | "blur" | "resize" | "move" | "minimize" | "maximize" | "restore";
+    payload: unknown;
+  }
+
+  /** File filter for dialogs */
+  export interface FileFilter {
+    name: string;
+    extensions: string[];
+  }
+
+  /** Options for file open/save dialog */
+  export interface FileDialogOptions {
+    title?: string;
+    defaultPath?: string;
+    filters?: FileFilter[];
+    multiple?: boolean;
+    directory?: boolean;
+  }
+
+  /** Options for message dialog */
+  export interface MessageDialogOptions {
+    title?: string;
+    message: string;
+    kind?: "info" | "warning" | "error";
+    /**
+     * Button labels to display.
+     * NOTE: The underlying rfd library only supports preset button configurations
+     * (Ok, OkCancel, YesNo, etc.). Custom button labels may be ignored or mapped
+     * to the closest preset. For reliable cross-platform behavior, use convenience
+     * methods like dialog.alert(), dialog.confirm(), dialog.error(), dialog.warning().
+     */
+    buttons?: string[];
+  }
+
+  /** Menu item definition */
+  export interface MenuItem {
+    id?: string;
+    label: string;
+    accelerator?: string;
+    enabled?: boolean;
+    checked?: boolean;
+    submenu?: MenuItem[];
+    type?: "normal" | "checkbox" | "separator";
+  }
+
+  /** Menu event */
+  export interface MenuEvent {
+    menuId: string;
+    itemId: string;
+    label: string;
+  }
+
+  /** Tray options */
+  export interface TrayOptions {
+    icon?: string;
+    tooltip?: string;
+    menu?: MenuItem[];
+  }
+
+  /** Tray handle */
+  export interface TrayHandle {
+    readonly id: string;
+    update(options: TrayOptions): Promise<boolean>;
+    destroy(): Promise<boolean>;
+  }
+
+  /** Window handle */
+  export interface Window {
+    readonly id: string;
+    close(): Promise<boolean>;
+    minimize(): Promise<void>;
+    maximize(): Promise<void>;
+    unmaximize(): Promise<void>;
+    restore(): Promise<void>;
+    focus(): Promise<void>;
+    getPosition(): Promise<Position>;
+    setPosition(x: number, y: number): Promise<void>;
+    getSize(): Promise<Size>;
+    setSize(width: number, height: number): Promise<void>;
+    getTitle(): Promise<string>;
+    setTitle(title: string): Promise<void>;
+    isFullscreen(): Promise<boolean>;
+    setFullscreen(fullscreen: boolean): Promise<void>;
+    isFocused(): Promise<boolean>;
+    isMaximized(): Promise<boolean>;
+    isMinimized(): Promise<boolean>;
+    isVisible(): Promise<boolean>;
+    isResizable(): Promise<boolean>;
+    hasDecorations(): Promise<boolean>;
+    isAlwaysOnTop(): Promise<boolean>;
+    setResizable(resizable: boolean): Promise<void>;
+    setDecorations(decorations: boolean): Promise<void>;
+    setAlwaysOnTop(alwaysOnTop: boolean): Promise<void>;
+    setVisible(visible: boolean): Promise<void>;
+    show(): Promise<void>;
+    hide(): Promise<void>;
+    getNativeHandle(): Promise<NativeHandle>;
+    events(): AsyncGenerator<WindowSystemEvent, void, unknown>;
+  }
+
+  /** Create a new window */
+  export function createWindow(options?: WindowOptions): Promise<Window>;
+
+  /** Close a window by ID */
+  export function closeWindow(windowId: string): Promise<boolean>;
+
+  /** Async iterator for window system events */
+  export function windowEvents(): AsyncGenerator<WindowSystemEvent, void, unknown>;
+
+  /** Dialog functions */
+  export const dialog: {
+    open(options?: FileDialogOptions): Promise<string[] | null>;
+    save(options?: FileDialogOptions): Promise<string | null>;
+    message(options: MessageDialogOptions | string): Promise<number>;
+    alert(message: string, title?: string): Promise<number>;
+    confirm(message: string, title?: string): Promise<boolean>;
+    error(message: string, title?: string): Promise<number>;
+    warning(message: string, title?: string): Promise<number>;
+  };
+
+  /** Menu functions */
+  export const menu: {
+    setAppMenu(items: MenuItem[]): Promise<boolean>;
+    showContextMenu(items: MenuItem[], windowId?: string): Promise<string | null>;
+    events(): AsyncGenerator<MenuEvent, void, unknown>;
+    onMenu(callback: (event: MenuEvent) => void): () => void;
+  };
+
+  /** Tray functions */
+  export const tray: {
+    create(options?: TrayOptions): Promise<TrayHandle>;
+    destroy(trayId: string): Promise<boolean>;
+  };
+}
+
+declare module "host:ipc" {
+  /** IPC event from renderer */
+  export interface IpcEvent {
+    windowId: string;
+    channel: string;
+    payload: unknown;
+    type?: "close" | "focus" | "blur" | "resize" | "move";
+  }
+
+  /** Callback for IPC events */
+  export type IpcEventCallback = (event: IpcEvent) => void;
+
+  /** Callback for channel-specific events */
+  export type ChannelCallback = (payload: unknown, windowId: string) => void;
+
+  /** Send message to a window's renderer */
+  export function sendToWindow(windowId: string, channel: string, payload?: unknown): Promise<void>;
+
+  /** Receive next IPC event */
+  export function recvWindowEvent(): Promise<IpcEvent | null>;
+
+  /** Async iterator for IPC events */
+  export function windowEvents(): AsyncGenerator<IpcEvent, void, unknown>;
+
+  /** Filter events for a specific window */
+  export function windowEventsFor(windowId: string): AsyncGenerator<IpcEvent, void, unknown>;
+
+  /** Filter events for a specific channel */
+  export function channelEvents(channel: string): AsyncGenerator<IpcEvent, void, unknown>;
+
+  /** Register callback for all IPC events */
+  export function onEvent(callback: IpcEventCallback): () => void;
+
+  /** Register callback for specific channel */
+  export function onChannel(channel: string, callback: ChannelCallback): () => void;
+
+  /** Broadcast to multiple windows */
+  export function broadcast(windowIds: string[], channel: string, payload?: unknown): Promise<void>;
+}
diff --git a/sdk/host.window.ts b/sdk/host.window.ts
new file mode 100644
index 0000000..888b9a0
--- /dev/null
+++ b/sdk/host.window.ts
@@ -0,0 +1,750 @@
+// host:window module - Deno API for native window operations
+// This is the single source of truth for the host:window SDK
+
+// ============================================================================
+// Type Definitions
+// ============================================================================
+
+/** Options for creating a new window */
+export interface WindowOptions {
+  /** URL to load (default: "app://index.html") */
+  url?: string;
+  /** Window width in pixels */
+  width?: number;
+  /** Window height in pixels */
+  height?: number;
+  /** Window title */
+  title?: string;
+  /** Whether window is resizable (default: true) */
+  resizable?: boolean;
+  /** Whether window has decorations (default: true) */
+  decorations?: boolean;
+  /** Whether window is visible on creation (default: true) */
+  visible?: boolean;
+  /** Whether window is transparent */
+  transparent?: boolean;
+  /** Whether window is always on top */
+  alwaysOnTop?: boolean;
+  /** Initial X position */
+  x?: number;
+  /** Initial Y position */
+  y?: number;
+  /** Minimum window width */
+  minWidth?: number;
+  /** Minimum window height */
+  minHeight?: number;
+  /** Maximum window width */
+  maxWidth?: number;
+  /** Maximum window height */
+  maxHeight?: number;
+  /** Channel allowlist for IPC - only these channels can be used */
+  channels?: string[];
+}
+
+/** Window position */
+export interface Position {
+  x: number;
+  y: number;
+}
+
+/** Window size */
+export interface Size {
+  width: number;
+  height: number;
+}
+
+/** Native window handle (platform-specific) */
+export interface NativeHandle {
+  /** Platform type: "windows", "macos", "linux-x11", "linux-wayland", or "linux" (placeholder) */
+  platform: string;
+  /**
+   * Raw handle value (HWND on Windows, NSView* on macOS, X11 window ID on Linux).
+   * Note: On Linux without X11/Wayland detection, returns 0 as a placeholder.
+   * Typed as number since Rust u64 serializes to JS number (safe for values up to 2^53).
+   */
+  handle: number;
+}
+
+/** Window system event */
+export interface WindowSystemEvent {
+  /** The window that emitted the event */
+  windowId: string;
+  /** Event type */
+  type: "close" | "focus" | "blur" | "resize" | "move" | "minimize" | "maximize" | "restore";
+  /** Event payload (e.g., size for resize, position for move) */
+  payload: unknown;
+}
+
+/** File filter for open/save dialogs */
+export interface FileFilter {
+  /** Display name for the filter (e.g., "Images") */
+  name: string;
+  /** File extensions without dots (e.g., ["png", "jpg"]) */
+  extensions: string[];
+}
+
+/** Options for file open/save dialog */
+export interface FileDialogOptions {
+  /** Dialog title */
+  title?: string;
+  /** Default starting path */
+  defaultPath?: string;
+  /** File type filters */
+  filters?: FileFilter[];
+  /** Allow selecting multiple files */
+  multiple?: boolean;
+  /** Select directories instead of files */
+  directory?: boolean;
+}
+
+/** Options for message dialog */
+export interface MessageDialogOptions {
+  /** Dialog title */
+  title?: string;
+  /** Message to display */
+  message: string;
+  /** Dialog kind: "info", "warning", or "error" */
+  kind?: "info" | "warning" | "error";
+  /** Custom button labels */
+  buttons?: string[];
+}
+
+/** Menu item definition */
+export interface MenuItem {
+  /** Unique identifier for this menu item */
+  id?: string;
+  /** Display label */
+  label: string;
+  /** Keyboard accelerator (e.g., "CmdOrCtrl+S") */
+  accelerator?: string;
+  /** Whether the item is enabled (default: true) */
+  enabled?: boolean;
+  /** Whether the item is checked (for checkbox items) */
+  checked?: boolean;
+  /** Submenu items */
+  submenu?: MenuItem[];
+  /** Item type: "normal", "checkbox", or "separator" */
+  type?: "normal" | "checkbox" | "separator";
+}
+
+/** Event emitted when a menu item is clicked */
+export interface MenuEvent {
+  /** Source of the event: "app", "context", or "tray" */
+  menuId: string;
+  /** The id of the clicked menu item */
+  itemId: string;
+  /** The label of the clicked menu item */
+  label: string;
+}
+
+/** Options for creating a system tray icon */
+export interface TrayOptions {
+  /** Path to icon file */
+  icon?: string;
+  /** Tooltip text shown on hover */
+  tooltip?: string;
+  /** Context menu for the tray icon */
+  menu?: MenuItem[];
+}
+
+/** Tray handle with methods for manipulating the tray */
+export interface TrayHandle {
+  /** Unique tray identifier */
+  readonly id: string;
+  /** Update tray options */
+  update(options: TrayOptions): Promise<boolean>;
+  /** Destroy this tray */
+  destroy(): Promise<boolean>;
+}
+
+/** Window handle with methods for manipulating the window */
+export interface Window {
+  /** Unique window identifier */
+  readonly id: string;
+  // Lifecycle
+  close(): Promise<boolean>;
+  minimize(): Promise<void>;
+  maximize(): Promise<void>;
+  unmaximize(): Promise<void>;
+  restore(): Promise<void>;
+  focus(): Promise<void>;
+  // Position & Size
+  getPosition(): Promise<Position>;
+  setPosition(x: number, y: number): Promise<void>;
+  getSize(): Promise<Size>;
+  setSize(width: number, height: number): Promise<void>;
+  // Title
+  getTitle(): Promise<string>;
+  setTitle(title: string): Promise<void>;
+  // State
+  isFullscreen(): Promise<boolean>;
+  setFullscreen(fullscreen: boolean): Promise<void>;
+  isFocused(): Promise<boolean>;
+  isMaximized(): Promise<boolean>;
+  isMinimized(): Promise<boolean>;
+  isVisible(): Promise<boolean>;
+  isResizable(): Promise<boolean>;
+  hasDecorations(): Promise<boolean>;
+  isAlwaysOnTop(): Promise<boolean>;
+  // Configuration
+  setResizable(resizable: boolean): Promise<void>;
+  setDecorations(decorations: boolean): Promise<void>;
+  setAlwaysOnTop(alwaysOnTop: boolean): Promise<void>;
+  setVisible(visible: boolean): Promise<void>;
+  show(): Promise<void>;
+  hide(): Promise<void>;
+  // Native
+  getNativeHandle(): Promise<NativeHandle>;
+  // Events
+  events(): AsyncGenerator<WindowSystemEvent, void, unknown>;
+}
+
+/** Callback function for menu event handlers */
+export type MenuCallback = (event: MenuEvent) => void;
+
+// ============================================================================
+// Deno Core Ops Declaration
+// ============================================================================
+
+declare const Deno: {
+  core: {
+    ops: {
+      // Window Lifecycle (10 ops)
+      op_window_create(opts: WindowOptions): Promise<string>;
+      op_window_close(windowId: string): Promise<boolean>;
+      op_window_minimize(windowId: string): Promise<void>;
+      op_window_maximize(windowId: string): Promise<void>;
+      op_window_unmaximize(windowId: string): Promise<void>;
+      op_window_restore(windowId: string): Promise<void>;
+      op_window_set_fullscreen(windowId: string, fullscreen: boolean): Promise<void>;
+      op_window_is_fullscreen(windowId: string): Promise<boolean>;
+      op_window_focus(windowId: string): Promise<void>;
+      op_window_is_focused(windowId: string): Promise<boolean>;
+      // Window Properties (16 ops)
+      op_window_get_position(windowId: string): Promise<Position>;
+      op_window_set_position(windowId: string, x: number, y: number): Promise<void>;
+      op_window_get_size(windowId: string): Promise<Size>;
+      op_window_set_size(windowId: string, width: number, height: number): Promise<void>;
+      op_window_get_title(windowId: string): Promise<string>;
+      op_window_set_title(windowId: string, title: string): Promise<void>;
+      op_window_set_resizable(windowId: string, resizable: boolean): Promise<void>;
+      op_window_is_resizable(windowId: string): Promise<boolean>;
+      op_window_set_decorations(windowId: string, decorations: boolean): Promise<void>;
+      op_window_has_decorations(windowId: string): Promise<boolean>;
+      op_window_set_always_on_top(windowId: string, alwaysOnTop: boolean): Promise<void>;
+      op_window_is_always_on_top(windowId: string): Promise<boolean>;
+      op_window_set_visible(windowId: string, visible: boolean): Promise<void>;
+      op_window_is_visible(windowId: string): Promise<boolean>;
+      op_window_is_maximized(windowId: string): Promise<boolean>;
+      op_window_is_minimized(windowId: string): Promise<boolean>;
+      // Dialogs (3 ops)
+      op_window_dialog_open(opts: FileDialogOptions): Promise<string[] | null>;
+      op_window_dialog_save(opts: FileDialogOptions): Promise<string | null>;
+      op_window_dialog_message(opts: MessageDialogOptions): Promise<number>;
+      // Menus (3 ops)
+      op_window_set_app_menu(items: MenuItem[]): Promise<boolean>;
+      op_window_show_context_menu(windowId: string | null, items: MenuItem[]): Promise<string>;
+      op_window_menu_recv(): Promise<MenuEvent | null>;
+      // Tray (3 ops)
+      op_window_create_tray(opts: TrayOptions): Promise<string>;
+      op_window_update_tray(trayId: string, opts: TrayOptions): Promise<boolean>;
+      op_window_destroy_tray(trayId: string): Promise<boolean>;
+      // Events & Native (2 ops)
+      op_window_events_recv(): Promise<WindowSystemEvent | null>;
+      op_window_get_native_handle(windowId: string): Promise<NativeHandle>;
+    };
+  };
+};
+
+const core = Deno.core;
+
+// ============================================================================
+// Window Functions
+// ============================================================================
+
+/**
+ * Create a new window and return a Window handle.
+ *
+ * @param opts - Window options
+ * @returns A Window handle for controlling the window
+ *
+ * @example
+ * ```ts
+ * import { createWindow } from "host:window";
+ *
+ * const win = await createWindow({
+ *   url: "app://index.html",
+ *   width: 1200,
+ *   height: 800,
+ *   title: "My App"
+ * });
+ *
+ * // Later, manipulate the window
+ * await win.setTitle("Updated Title");
+ * const { width, height } = await win.getSize();
+ * ```
+ */
+export async function createWindow(opts: WindowOptions = {}): Promise<Window> {
+  const windowId = await core.ops.op_window_create(opts);
+
+  const handle: Window = {
+    id: windowId,
+
+    // Lifecycle
+    async close(): Promise<boolean> {
+      return await core.ops.op_window_close(windowId);
+    },
+    async minimize(): Promise<void> {
+      return await core.ops.op_window_minimize(windowId);
+    },
+    async maximize(): Promise<void> {
+      return await core.ops.op_window_maximize(windowId);
+    },
+    async unmaximize(): Promise<void> {
+      return await core.ops.op_window_unmaximize(windowId);
+    },
+    async restore(): Promise<void> {
+      return await core.ops.op_window_restore(windowId);
+    },
+    async focus(): Promise<void> {
+      return await core.ops.op_window_focus(windowId);
+    },
+
+    // Position & Size
+    async getPosition(): Promise<Position> {
+      return await core.ops.op_window_get_position(windowId);
+    },
+    async setPosition(x: number, y: number): Promise<void> {
+      return await core.ops.op_window_set_position(windowId, x, y);
+    },
+    async getSize(): Promise<Size> {
+      return await core.ops.op_window_get_size(windowId);
+    },
+    async setSize(width: number, height: number): Promise<void> {
+      return await core.ops.op_window_set_size(windowId, width, height);
+    },
+
+    // Title
+    async getTitle(): Promise<string> {
+      return await core.ops.op_window_get_title(windowId);
+    },
+    async setTitle(title: string): Promise<void> {
+      return await core.ops.op_window_set_title(windowId, title);
+    },
+
+    // State
+    async isFullscreen(): Promise<boolean> {
+      return await core.ops.op_window_is_fullscreen(windowId);
+    },
+    async setFullscreen(fullscreen: boolean): Promise<void> {
+      return await core.ops.op_window_set_fullscreen(windowId, fullscreen);
+    },
+    async isFocused(): Promise<boolean> {
+      return await core.ops.op_window_is_focused(windowId);
+    },
+    async isMaximized(): Promise<boolean> {
+      return await core.ops.op_window_is_maximized(windowId);
+    },
+    async isMinimized(): Promise<boolean> {
+      return await core.ops.op_window_is_minimized(windowId);
+    },
+    async isVisible(): Promise<boolean> {
+      return await core.ops.op_window_is_visible(windowId);
+    },
+    async isResizable(): Promise<boolean> {
+      return await core.ops.op_window_is_resizable(windowId);
+    },
+    async hasDecorations(): Promise<boolean> {
+      return await core.ops.op_window_has_decorations(windowId);
+    },
+    async isAlwaysOnTop(): Promise<boolean> {
+      return await core.ops.op_window_is_always_on_top(windowId);
+    },
+
+    // Configuration
+    async setResizable(resizable: boolean): Promise<void> {
+      return await core.ops.op_window_set_resizable(windowId, resizable);
+    },
+    async setDecorations(decorations: boolean): Promise<void> {
+      return await core.ops.op_window_set_decorations(windowId, decorations);
+    },
+    async setAlwaysOnTop(alwaysOnTop: boolean): Promise<void> {
+      return await core.ops.op_window_set_always_on_top(windowId, alwaysOnTop);
+    },
+    async setVisible(visible: boolean): Promise<void> {
+      return await core.ops.op_window_set_visible(windowId, visible);
+    },
+    async show(): Promise<void> {
+      return await core.ops.op_window_set_visible(windowId, true);
+    },
+    async hide(): Promise<void> {
+      return await core.ops.op_window_set_visible(windowId, false);
+    },
+
+    // Native
+    async getNativeHandle(): Promise<NativeHandle> {
+      return await core.ops.op_window_get_native_handle(windowId);
+    },
+
+    // Events - filter for this window
+    async *events(): AsyncGenerator<WindowSystemEvent, void, unknown> {
+      for await (const event of windowEvents()) {
+        if (event.windowId === windowId) {
+          yield event;
+        }
+      }
+    }
+  };
+
+  return handle;
+}
+
+/**
+ * Close a window by ID.
+ *
+ * @param windowId - The window ID to close
+ * @returns true if closed successfully
+ *
+ * @example
+ * ```ts
+ * import { closeWindow } from "host:window";
+ *
+ * await closeWindow("main-window");
+ * ```
+ */
+export async function closeWindow(windowId: string): Promise<boolean> {
+  return await core.ops.op_window_close(windowId);
+}
+
+/**
+ * Receive the next window system event (blocking).
+ * Returns null when no more events are available.
+ *
+ * @returns The next window event or null
+ */
+async function recvWindowEvent(): Promise<WindowSystemEvent | null> {
+  return await core.ops.op_window_events_recv();
+}
+
+/**
+ * Async generator for window system events from all windows.
+ * Use in a for-await loop to process events as they arrive.
+ *
+ * @example
+ * ```ts
+ * import { windowEvents } from "host:window";
+ *
+ * for await (const event of windowEvents()) {
+ *   console.log(`Window ${event.windowId}: ${event.type}`);
+ *   if (event.type === "close") {
+ *     console.log("Window closed");
+ *   }
+ * }
+ * ```
+ */
+export async function* windowEvents(): AsyncGenerator<WindowSystemEvent, void, unknown> {
+  while (true) {
+    const event = await recvWindowEvent();
+    if (event === null) break;
+    yield event;
+  }
+}
+
+// ============================================================================
+// Dialog Namespace
+// ============================================================================
+
+/**
+ * Dialog functions for file and message dialogs.
+ *
+ * @example
+ * ```ts
+ * import { dialog } from "host:window";
+ *
+ * // Open file dialog
+ * const files = await dialog.open({
+ *   title: "Select Images",
+ *   filters: [{ name: "Images", extensions: ["png", "jpg"] }],
+ *   multiple: true
+ * });
+ *
+ * // Show confirmation
+ * const confirmed = await dialog.confirm("Are you sure?");
+ * ```
+ */
+export const dialog = {
+  /**
+   * Show an open file dialog.
+   *
+   * @param opts - Dialog options
+   * @returns Array of selected file paths, or null if cancelled
+   */
+  async open(opts: FileDialogOptions = {}): Promise<string[] | null> {
+    return await core.ops.op_window_dialog_open(opts);
+  },
+
+  /**
+   * Show a save file dialog.
+   *
+   * @param opts - Dialog options
+   * @returns Selected file path, or null if cancelled
+   */
+  async save(opts: FileDialogOptions = {}): Promise<string | null> {
+    return await core.ops.op_window_dialog_save(opts);
+  },
+
+  /**
+   * Show a message dialog.
+   *
+   * @param opts - Dialog options or message string
+   * @returns Index of the clicked button
+   */
+  async message(opts: MessageDialogOptions | string): Promise<number> {
+    const options: MessageDialogOptions = typeof opts === "string" ? { message: opts } : opts;
+    return await core.ops.op_window_dialog_message(options);
+  },
+
+  /**
+   * Show an alert dialog.
+   *
+   * @param message - Message to display
+   * @param title - Dialog title
+   * @returns Index of clicked button (always 0 for OK)
+   */
+  async alert(message: string, title: string = "Alert"): Promise<number> {
+    return await core.ops.op_window_dialog_message({
+      title,
+      message,
+      kind: "info",
+      buttons: ["OK"]
+    });
+  },
+
+  /**
+   * Show a confirmation dialog.
+   *
+   * @param message - Message to display
+   * @param title - Dialog title
+   * @returns true if OK clicked, false if cancelled
+   */
+  async confirm(message: string, title: string = "Confirm"): Promise<boolean> {
+    const result = await core.ops.op_window_dialog_message({
+      title,
+      message,
+      kind: "info",
+      buttons: ["Cancel", "OK"]
+    });
+    return result === 1;
+  },
+
+  /**
+   * Show an error dialog.
+   *
+   * @param message - Error message to display
+   * @param title - Dialog title
+   */
+  async error(message: string, title: string = "Error"): Promise<number> {
+    return await core.ops.op_window_dialog_message({
+      title,
+      message,
+      kind: "error",
+      buttons: ["OK"]
+    });
+  },
+
+  /**
+   * Show a warning dialog.
+   *
+   * @param message - Warning message to display
+   * @param title - Dialog title
+   */
+  async warning(message: string, title: string = "Warning"): Promise<number> {
+    return await core.ops.op_window_dialog_message({
+      title,
+      message,
+      kind: "warning",
+      buttons: ["OK"]
+    });
+  }
+};
+
+// ============================================================================
+// Menu Namespace
+// ============================================================================
+
+/**
+ * Receive the next menu event (blocking).
+ * Returns null when no more events are available.
+ */
+async function recvMenuEvent(): Promise<MenuEvent | null> {
+  return await core.ops.op_window_menu_recv();
+}
+
+/**
+ * Async generator for menu events.
+ */
+async function* menuEvents(): AsyncGenerator<MenuEvent, void, unknown> {
+  while (true) {
+    const event = await recvMenuEvent();
+    if (event === null) break;
+    yield event;
+  }
+}
+
+let menuListenerActive = false;
+const menuCallbacks: MenuCallback[] = [];
+
+/**
+ * Register a callback for menu events.
+ *
+ * @param callback - Function called for each menu event
+ * @returns Unsubscribe function
+ */
+function onMenu(callback: MenuCallback): () => void {
+  menuCallbacks.push(callback);
+
+  if (!menuListenerActive) {
+    menuListenerActive = true;
+    (async () => {
+      for await (const event of menuEvents()) {
+        for (const cb of menuCallbacks) {
+          try {
+            cb(event);
+          } catch (e) {
+            console.error("Error in menu callback:", e);
+          }
+        }
+      }
+      menuListenerActive = false;
+    })();
+  }
+
+  return () => {
+    const index = menuCallbacks.indexOf(callback);
+    if (index !== -1) {
+      menuCallbacks.splice(index, 1);
+    }
+  };
+}
+
+/**
+ * Menu functions for application and context menus.
+ *
+ * @example
+ * ```ts
+ * import { menu } from "host:window";
+ *
+ * // Set application menu
+ * await menu.setAppMenu([
+ *   {
+ *     label: "File",
+ *     submenu: [
+ *       { id: "open", label: "Open", accelerator: "CmdOrCtrl+O" },
+ *       { id: "save", label: "Save", accelerator: "CmdOrCtrl+S" },
+ *       { type: "separator", label: "" },
+ *       { id: "quit", label: "Quit", accelerator: "CmdOrCtrl+Q" }
+ *     ]
+ *   }
+ * ]);
+ *
+ * // Listen for menu events
+ * const unsub = menu.onMenu((event) => {
+ *   console.log("Menu clicked:", event.itemId);
+ * });
+ * ```
+ */
+export const menu = {
+  /**
+   * Set the application menu bar.
+   *
+   * @param items - Menu items to display
+   * @returns true if successful
+   */
+  async setAppMenu(items: MenuItem[]): Promise<boolean> {
+    return await core.ops.op_window_set_app_menu(items);
+  },
+
+  /**
+   * Show a context menu at the current cursor position.
+   *
+   * @param items - Menu items to display
+   * @param windowId - Optional window to show menu in
+   * @returns ID of clicked item, or null if cancelled
+   */
+  async showContextMenu(items: MenuItem[], windowId?: string): Promise<string | null> {
+    const result = await core.ops.op_window_show_context_menu(windowId ?? null, items);
+    return result === "" ? null : result;
+  },
+
+  /** Async generator for menu events */
+  events: menuEvents,
+
+  /** Register a callback for menu events */
+  onMenu
+};
+
+// ============================================================================
+// Tray Namespace
+// ============================================================================
+
+/**
+ * Create a system tray icon.
+ *
+ * @param opts - Tray options
+ * @returns TrayHandle for controlling the tray
+ */
+async function createTray(opts: TrayOptions = {}): Promise<TrayHandle> {
+  const trayId = await core.ops.op_window_create_tray(opts);
+
+  return {
+    id: trayId,
+
+    async update(newOpts: TrayOptions): Promise<boolean> {
+      return await core.ops.op_window_update_tray(trayId, newOpts);
+    },
+
+    async destroy(): Promise<boolean> {
+      return await core.ops.op_window_destroy_tray(trayId);
+    }
+  };
+}
+
+/**
+ * Destroy a tray by ID.
+ *
+ * @param trayId - The tray ID to destroy
+ * @returns true if destroyed successfully
+ */
+async function destroyTray(trayId: string): Promise<boolean> {
+  return await core.ops.op_window_destroy_tray(trayId);
+}
+
+/**
+ * System tray functions.
+ *
+ * @example
+ * ```ts
+ * import { tray } from "host:window";
+ *
+ * const myTray = await tray.create({
+ *   icon: "assets/icon.png",
+ *   tooltip: "My App",
+ *   menu: [
+ *     { id: "show", label: "Show Window" },
+ *     { type: "separator", label: "" },
+ *     { id: "quit", label: "Quit" }
+ *   ]
+ * });
+ *
+ * // Later, update or destroy
+ * await myTray.update({ tooltip: "Updated!" });
+ * await myTray.destroy();
+ * ```
+ */
+export const tray = {
+  /** Create a system tray icon */
+  create: createTray,
+
+  /** Destroy a tray by ID */
+  destroy: destroyTray
+};