Cometchat Native Core

Purpose

This is the foundational skill for every CometChat React Native UI Kit v5 integration. It teaches Claude HOW CometChat works on RN — initialization order, provider wrapper chain, login, env vars, auth tokens, and the anti-patterns that break real apps.

Read this skill first, before any framework (cometchat-native-expo-patterns / cometchat-native-bare-patterns) or placement skill.

Ground-truth sources: docs/ui-kit/react-native/overview.mdx, react-native-cli-integration.mdx, expo-integration.mdx, methods.mdx, and @cometchat/chat-uikit-react-native@5.3.3's src/index.ts.

1. The init-login-render order

CometChat has exactly one valid lifecycle on React Native:

CometChatUIKit.init(settings)   →   CometChatUIKit.login({ uid })   →   render <CometChat*> components

Breaking this order produces a blank screen, a "CometChat is not initialized" runtime error, or a hung login. No exceptions.

UIKitSettings — the init object

The v5 RN UI Kit's init() takes a flat UIKitSettings object (NOT a UIKitSettingsBuilder like the web kit). Pass fields directly:

import { CometChatUIKit } from "@cometchat/chat-uikit-react-native";

await CometChatUIKit.init({
  appId: APP_ID,                  // Required — from the CometChat dashboard
  region: REGION,                 // Required — "us" | "eu" | "in"
  authKey: AUTH_KEY,              // Required for dev mode. Omit in production.
  subscriptionType: "ALL_USERS",  // Optional — "NONE" | "ALL_USERS" | "ROLES" | "FRIENDS"
});

⚠️ UIKitSettingsBuilder does NOT exist in the v5 React Native UI Kit. That's a web-kit pattern. RN expects the flat object. If an agent imports UIKitSettingsBuilder from @cometchat/chat-uikit-react-native, the import resolves to undefined and new UIKitSettingsBuilder() throws at runtime.

Other valid UIKitSettings fields (all optional): autoEstablishSocketConnection, overrideAdminHost, overrideClientHost, disableCalling, extensions, roles, callingExtension. The full type is exported from the package as UIKitSettings; check the installed kit's type defs (node_modules/@cometchat/chat-uikit-react-native) if you need the exact shape.

Init must happen once

Use a module-level flag to prevent double-init. React re-mounts in dev (strict mode, fast refresh, and navigation nesting all trigger effect re-fires):

let initialized = false;

async function initCometChat(): Promise<void> {
  if (initialized) return;
  initialized = true;

  await CometChatUIKit.init({
    appId: APP_ID,
    region: REGION,
    authKey: AUTH_KEY,
    subscriptionType: "ALL_USERS",
  });
}

Init must run before first render

Put the init call in a top-level useEffect (preferred — the provider pattern in section 6 does this) or in App.tsx before the initial navigator mounts. Avoid calling init() in a screen's effect — by the time the screen mounts, the app has already tried to render components that expect init to be done.

2. Login

Development mode

const user = await CometChatUIKit.getLoggedInUser();
if (!user) {
  await CometChatUIKit.login({ uid: "cometchat-uid-1" });  // note: OBJECT form
}

⚠️ login() takes an object { uid: "..." } on React Native, not a bare string like on the web. Passing "cometchat-uid-1" directly silently fails.

Every new CometChat app ships 5 pre-seeded test users — cometchat-uid-1 through cometchat-uid-5. Use one for development.

⚠️ login() is safe sequentially, NOT concurrently

A second login() call fired while the first is in-flight throws "Please wait until the previous login request ends." Classic trap in React Native because:

• React strict mode double-mounts effects
• react-navigation remounts screens on tab switches
• Fast Refresh triggers effect re-runs in dev

Guard with a module-level in-flight promise, same pattern as the web skill:

let loginInFlight: Promise<unknown> | null = null;

async function ensureLoggedIn(uid: string, authToken?: string): Promise<void> {
  const existing = await CometChatUIKit.getLoggedInUser();
  if (existing) return;
  if (loginInFlight) {
    await loginInFlight;   // reuse the pending promise
    return;
  }
  loginInFlight = authToken
    ? CometChatUIKit.login({ authToken })
    : CometChatUIKit.login({ uid });
  try {
    await loginInFlight;
  } finally {
    loginInFlight = null;
  }
}

Call ensureLoggedIn() from the provider / effect. Both mounts resolve against the same promise; only one login request hits the server.

Production mode

Use CometChatUIKit.login({ authToken }) with a token from your backend. The backend generates the token with the CometChat REST API using the server-only REST API Key (not the client-side Auth Key). See cometchat-native-production for the server-side token endpoint patterns.

Logout

await CometChatUIKit.logout();

Clears the local CometChat session. Call from your app's sign-out handler.

3. Provider wrapper chain (mandatory order)

Every CometChat RN app has this wrapper chain at the root. Missing wrappers cause silent layout breakage, broken gestures, or hard crashes — each wrapper is required by a specific RN ecosystem piece the UI Kit depends on.

// App.tsx (bare) or the root of your Expo app
import "react-native-gesture-handler";   // MUST be the first import
import { GestureHandlerRootView } from "react-native-gesture-handler";
import { SafeAreaProvider } from "react-native-safe-area-context";
import { CometChatThemeProvider } from "@cometchat/chat-uikit-react-native";

export default function App() {
  return (
    <GestureHandlerRootView style={{ flex: 1 }}>
      <SafeAreaProvider>
        <CometChatThemeProvider>
          <CometChatProvider>    {/* your own init/login provider — see section 6 */}
            <AppNavigator />
          </CometChatProvider>
        </CometChatThemeProvider>
      </SafeAreaProvider>
    </GestureHandlerRootView>
  );
}

Why each wrapper is mandatory:

The cometchat-native-expo-patterns and cometchat-native-bare-patterns skills show framework-specific nuances (Expo adds expo-splash-screen, bare adds pod setup), but the four-wrapper chain is fixed.

Localizing to a non-English audience? Add <CometChatI18nProvider> as a fifth wrapper, above <CometChatThemeProvider>. See cometchat-native-theming § 9 for the full five-wrapper chain (gesture → safe-area → i18n → theme → provider) and localization config.

4. Environment variables

Values to set

Where they live

• Bare RN: .env at project root + a runtime reader like react-native-config or babel-plugin-dotenv-import. Access: Config.APP_ID.
• Expo managed: app.json extra section + read via Constants.expoConfig?.extra?.APP_ID from expo-constants. Or use .env with expo-dotenv / expo-router's built-in support depending on SDK version. The cometchat-native-expo-patterns skill covers this in detail.

Do NOT bundle the REST_API_KEY into the client — RN bundles everything visible. Server endpoints live outside the RN app (Express / Hono / Cloud Functions); see cometchat-native-production.

.env / extra example

# client-side (safe to ship in the RN bundle for dev mode)
APP_ID=your_app_id
REGION=us
AUTH_KEY=your_auth_key

# server-only (NEVER ship — used by your token endpoint)
# REST_API_KEY=your_rest_api_key

5. Android + iOS platform notes

The UI Kit is cross-platform, but a few concerns only apply to one target:

The framework skills (cometchat-native-expo-patterns, cometchat-native-bare-patterns) apply these platform settings with the right syntax for each workflow.

6. Provider pattern

Instead of inlining init + login in every component, create a reusable CometChatProvider that gates rendering on isReady. Drop it below <CometChatThemeProvider> in the wrapper chain.

// CometChatProvider.tsx
import React, { createContext, useContext, useEffect, useState, type ReactNode } from "react";
import { CometChatUIKit } from "@cometchat/chat-uikit-react-native";

interface CometChatContextValue {
  isReady: boolean;
  error: string | null;
}

const CometChatContext = createContext<CometChatContextValue>({
  isReady: false,
  error: null,
});

export const useCometChat = () => useContext(CometChatContext);

// Module-level state — shared across all mounts
let initialized = false;
let loginInFlight: Promise<unknown> | null = null;

async function ensureLoggedIn(uid: string, authToken?: string): Promise<void> {
  const existing = await CometChatUIKit.getLoggedInUser();
  if (existing) return;
  if (loginInFlight) {
    await loginInFlight;
    return;
  }
  loginInFlight = authToken
    ? CometChatUIKit.login({ authToken })
    : CometChatUIKit.login({ uid });
  try {
    await loginInFlight;
  } finally {
    loginInFlight = null;
  }
}

interface CometChatProviderProps {
  appId: string;
  region: string;
  authKey?: string;
  authToken?: string;
  uid?: string;
  children: ReactNode;
}

export function CometChatProvider({
  appId,
  region,
  authKey,
  authToken,
  uid = "cometchat-uid-1",
  children,
}: CometChatProviderProps) {
  const [isReady, setIsReady] = useState(false);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    async function setup() {
      try {
        if (!initialized) {
          initialized = true;
          await CometChatUIKit.init({
            appId,
            region,
            authKey,
            subscriptionType: "ALL_USERS",
          });
        }
        await ensureLoggedIn(uid, authToken);
        setIsReady(true);
      } catch (e) {
        setError(String(e));
      }
    }
    setup();
  }, [appId, region, authKey, authToken, uid]);

  if (error) {
    return null;  // or your app's error boundary — don't render CometChat components
  }
  if (!isReady) {
    return null;  // or a splash / loading screen
  }

  return (
    <CometChatContext.Provider value={{ isReady, error }}>
      {children}
    </CometChatContext.Provider>
  );
}

Children of <CometChatProvider> can use useCometChat() to check isReady — useful if some UI wants to render before chat is ready.

7. Anti-patterns

1. Do NOT call CometChatUIKit.init() during render. Init is async with side effects; calling during render triggers infinite re-renders. Always inside useEffect or before createRoot equivalent.

2. Do NOT call login("uid") with a string. RN's login() expects an object: login({ uid: "..." }). Passing a string silently no-ops.

3. Do NOT skip the four-wrapper chain (GestureHandlerRootView → SafeAreaProvider → CometChatThemeProvider → your provider). Each wrapper is required.

4. Guard concurrent login() with a module-level in-flight promise. login() is only safe sequentially. Two calls racing (React strict mode, tab remount, Fast Refresh) throw "Please wait until the previous login request ends."

5. Do NOT hardcode AUTH_KEY in source files. Use env vars for dev. Use login({ authToken }) in production.

6. Do NOT render CometChat components before isReady. The provider's isReady: false branch should return null (or a splash), not try to render children.

7. Do NOT re-initialize on navigation. Init and login belong at app root, not per-screen. Re-init causes WebSocket churn and lost messages mid-switch.

8. Do NOT invent component names. Only use components exported from @cometchat/chat-uikit-react-native. See cometchat-native-components for the catalog.

9. Do NOT forget import "react-native-gesture-handler" at the top of the entry file (App.tsx or index.js). Without it, swipe gestures in the composer and bottom sheets silently disable.

10. Do NOT bundle the REST API key. It's server-only. Token generation happens on your backend; the RN client never sees it.

8. Docs MCP (recommended, not required)

The CometChat docs MCP gives runtime access to the most current RN UI Kit docs. Install:

claude mcp add --transport http cometchat-docs https://www.cometchat.com/docs/mcp

Use the MCP to verify prop signatures, callback names, theme token names, or error message meanings before writing any non-obvious code. Everything the skills describe here is grounded in the docs — the MCP is how you double-check during generation.

Not required to install. The skills ship with the current truth baked in. The MCP is the fallback for edge cases and for upstream changes between skill releases.

9. Package dependencies

Minimum peer deps to install before the UI Kit works:

npm install \
  @cometchat/chat-sdk-react-native \
  @cometchat/chat-uikit-react-native \
  react-native-gesture-handler \
  react-native-safe-area-context \
  react-native-reanimated

Expo adds expo-av / expo-image-picker depending on which features you enable. Calls require the separate package:

npm install @cometchat/calls-sdk-react-native

See cometchat-native-features for when to add the calls SDK.

Skill routing reference