Skip to main content
sunpeak API

​
Overview

The useHostContext hook subscribes to the full host context object, which contains theme, display mode, locale, safe area insets, container dimensions, and more. It updates reactively whenever the host changes any value. In addition to providing reactive state, useHostContext automatically applies host-provided styles and fonts to the iframe document. This includes CSS style variables, document theme (light/dark), and @font-face rules for host-provided fonts — all applied on initial context and updated whenever the host context changes.

Wraps onhostcontextchanged

MCP Apps SDK reference
Most apps should use the convenience hooks instead of accessing the full context directly: useTheme, useDisplayMode, useLocale, useTimeZone, useUserAgent, usePlatform, useDeviceCapabilities, useSafeArea, useViewport, useStyles, and useToolInfo.

​
Import

import { useHostContext } from 'sunpeak';

​
Signature

function useHostContext(): McpUiHostContext | null

​
Returns

Returns the full McpUiHostContext object, or null before the first update. 
interface McpUiHostContext {
  toolInfo?: { id?: RequestId; tool: Tool };
  theme?: 'light' | 'dark';
  styles?: McpUiHostStyles;
  displayMode?: 'inline' | 'pip' | 'fullscreen';
  availableDisplayModes?: ('inline' | 'pip' | 'fullscreen')[];
  containerDimensions?: { height?: number; maxHeight?: number; width?: number; maxWidth?: number };
  locale?: string;
  timeZone?: string;
  userAgent?: string;
  platform?: 'mobile' | 'desktop' | 'web';
  deviceCapabilities?: { hover?: boolean; touch?: boolean };
  safeAreaInsets?: { top: number; bottom: number; left: number; right: number };
}

​
Usage

import { useHostContext } from 'sunpeak';

function MyResource() {
  const context = useHostContext();

  return (
    <div>
      <p>Theme: {context?.theme}</p>
      <p>Display: {context?.displayMode}</p>
      <p>Locale: {context?.locale}</p>
    </div>
  );
}