Implementing client-side message history pagination and optimistic UI updates for Genesys Cloud Web Messaging using React Query and the Client SDK

How-To-Articles
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Implementing client-side message history pagination and optimistic UI updates for Genesys Cloud Web Messaging using React Query and the Client SDK

What You Will Build

  • A React component that fetches, paginates, and renders historical web messaging conversations using cursor-based pagination.
  • An optimistic message composer that updates the UI instantly upon submission, then reconciles with the Genesys Cloud Web Messaging Client SDK.
  • Implementation covers React, TypeScript, and @tanstack/react-query for cache management, background refetching, and mutation handling.

Prerequisites

  • Genesys Cloud organization with Web Messaging enabled and a published integration
  • Client SDK: @gencloud/web-messaging-client-sdk@^3.0.0
  • State management: @tanstack/react-query@^5.0.0
  • Runtime: Node.js 18+ with npm or yarn
  • Dependencies: npm install @gencloud/web-messaging-client-sdk @tanstack/react-query axios

Authentication Setup

The Genesys Cloud Web Messaging Client SDK abstracts the OAuth2 client credentials flow. You initialize the client with an organizationId and integrationId. The SDK handles token acquisition, caching, and silent refresh internally. Underlying REST calls require the webmessaging:read scope for history retrieval and webmessaging:write scope for message submission.

// src/lib/genesys-client.ts
import { createClient } from '@gencloud/web-messaging-client-sdk';
import type { Client } from '@gencloud/web-messaging-client-sdk';

let cachedClient: Client | null = null;

export function getWebMessagingClient(
  organizationId: string,
  integrationId: string
): Client {
  if (cachedClient) {
    return cachedClient;
  }

  cachedClient = createClient({
    organizationId,
    integrationId,
    logLevel: 'warn',
  });

  return cachedClient;
}

The client initialization does not require manual token management. If the integration lacks the required scopes, the SDK throws a 403 Forbidden during the first API call. Store credentials securely using environment variables or a secure vault. Never embed them in client-side source control.

Implementation

Step 1: Initialize Client SDK & React Query Provider

React Query manages the data fetching lifecycle. You must wrap your application in a QueryClientProvider. The client SDK instance should be created once and reused across components to prevent duplicate WebSocket connections and token refresh cycles.

// src/providers/query-provider.tsx
import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
import { ReactNode } from 'react';

const queryClient = new QueryClient({
  defaultOptions: {
    queries: {
      staleTime: 1000 * 60 * 5,
      retry: 3,
      retryDelay: (attemptIndex) => Math.min(1000 * 2 ** attemptIndex, 30000),
    },
  },
});

export function QueryProvider({ children }: { children: ReactNode }) {
  return (
    <QueryClientProvider client={queryClient}>
      {children}
    </QueryClientProvider>
  );
}

The staleTime prevents unnecessary refetches while the user reads history. The exponential backoff retry handles transient network failures. The client SDK emits its own connection state events, which you will subscribe to in later steps.

Step 2: Fetch Message History with Pagination

The Genesys Cloud REST API for web messaging history uses cursor-based pagination at /api/v2/webmessaging/conversations/{conversationId}/messages. The Client SDK exposes this via client.messages.getHistory(). You must track the nextCursor to fetch older messages. React Query caches each page, but for a unified chat view, you will append results to a single query key using structuralSharing and manual cache manipulation.

// src/hooks/use-message-history.ts
import { useQuery, useQueryClient } from '@tanstack/react-query';
import { getWebMessagingClient } from '../lib/genesys-client';
import type { Message, PaginationResponse } from '@gencloud/web-messaging-client-sdk';

interface HistoryParams {
  organizationId: string;
  integrationId: string;
  conversationId: string;
  limit?: number;
}

export function useMessageHistory({
  organizationId,
  integrationId,
  conversationId,
  limit = 25,
}: HistoryParams) {
  const queryClient = useQueryClient();

  return useQuery({
    queryKey: ['webmessaging', 'history', conversationId],
    queryFn: async ({ signal }) => {
      const client = getWebMessagingClient(organizationId, integrationId);
      
      // Initial fetch
      const initialResponse: PaginationResponse<Message> = await client.messages.getHistory({
        conversationId,
        limit,
        signal,
      });

      let allMessages = [...initialResponse.items];
      let cursor = initialResponse.nextPage?.cursor;

      // Fetch additional pages if cursor exists
      while (cursor) {
        const response: PaginationResponse<Message> = await client.messages.getHistory({
          conversationId,
          limit,
          cursor,
          signal,
        });

        allMessages = [...allMessages, ...response.items];
        cursor = response.nextPage?.cursor;
      }

      // Store cursor for infinite scroll if needed
      queryClient.setQueryData(
        ['webmessaging', 'history', conversationId, 'cursor'],
        cursor
      );

      return allMessages.sort((a, b) => a.timestamp.localeCompare(b.timestamp));
    },
    enabled: !!conversationId,
  });
}

The signal parameter enables React Query to abort in-flight requests when the component unmounts or the query key changes. The loop fetches all available pages up to the SDK’s maximum offset limit. If the conversation spans years, you should implement a load-more button instead of fetching all pages at mount. The required scope for this call is webmessaging:read.

Step 3: Send Message with Optimistic UI Updates

Optimistic updates require a mutation that modifies the cache immediately, then reconciles with the server response. You will add a temporary message object with a status: 'sending' flag. On success, you replace the temporary object with the server-confirmed message. On failure, you revert the cache and display an error state.

// src/hooks/use-send-message.ts
import { useMutation, useQueryClient } from '@tanstack/react-query';
import { getWebMessagingClient } from '../lib/genesys-client';
import type { Message, SendMessagePayload } from '@gencloud/web-messaging-client-sdk';

interface SendParams {
  organizationId: string;
  integrationId: string;
  conversationId: string;
  payload: SendMessagePayload;
}

export function useSendMessage({
  organizationId,
  integrationId,
  conversationId,
}: Omit<SendParams, 'payload'>) {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: async (payload: SendMessagePayload) => {
      const client = getWebMessagingClient(organizationId, integrationId);
      // Underlying REST: POST /api/v2/webmessaging/conversations/{conversationId}/messages
      // Required scope: webmessaging:write
      return client.messages.send({
        conversationId,
        payload,
      });
    },
    onMutate: async (payload) => {
      // Cancel outgoing refetches to avoid overwriting optimistic data
      await queryClient.cancelQueries({
        queryKey: ['webmessaging', 'history', conversationId],
      });

      // Snapshot previous value
      const previousMessages = queryClient.getQueryData<Message[]>([
        'webmessaging',
        'history',
        conversationId,
      ]);

      // Create optimistic message
      const optimisticMessage: Message = {
        id: `temp-${Date.now()}`,
        conversationId,
        from: { id: 'client', name: 'You' },
        text: payload.text,
        timestamp: new Date().toISOString(),
        status: 'sending',
        type: 'text',
      };

      // Add to cache
      queryClient.setQueryData(
        ['webmessaging', 'history', conversationId],
        (old: Message[] = []) => [...old, optimisticMessage]
      );

      return { previousMessages };
    },
    onSuccess: (serverMessage, _variables, context) => {
      // Replace optimistic message with server response
      queryClient.setQueryData(
        ['webmessaging', 'history', conversationId],
        (old: Message[] = []) =>
          old.map((msg) =>
            msg.id.startsWith('temp-') ? serverMessage : msg
          )
      );
    },
    onError: (_error, _variables, context) => {
      // Rollback on failure
      if (context?.previousMessages) {
        queryClient.setQueryData(
          ['webmessaging', 'history', conversationId],
          context.previousMessages
        );
      }
    },
    onSettled: () => {
      // Refetch to ensure cache consistency
      queryClient.invalidateQueries({
        queryKey: ['webmessaging', 'history', conversationId],
      });
    },
  });
}

The onMutate hook runs before the network request. It cancels background refetches, snapshots the cache, and injects the temporary message. The onSuccess hook replaces the temporary ID with the authoritative server ID. The onError hook restores the snapshot. The onSettled hook triggers a background validation fetch to catch race conditions or duplicate messages.

Step 4: Subscribe to Real-Time Events & Cache Reconciliation

The Client SDK maintains a WebSocket connection and emits events for incoming messages, status changes, and disconnections. You must listen to onMessage and onStatusChange to keep the UI synchronized without polling.

// src/hooks/use-realtime-sync.ts
import { useEffect } from 'react';
import { useQueryClient } from '@tanstack/react-query';
import { getWebMessagingClient } from '../lib/genesys-client';
import type { Client, Message, ClientStatus } from '@gencloud/web-messaging-client-sdk';

export function useRealtimeSync(
  organizationId: string,
  integrationId: string,
  conversationId: string
) {
  const queryClient = useQueryClient();

  useEffect(() => {
    const client = getWebMessagingClient(organizationId, integrationId);

    const handleMessage = (message: Message) => {
      if (message.conversationId !== conversationId) return;

      queryClient.setQueryData(
        ['webmessaging', 'history', conversationId],
        (old: Message[] = []) => {
          // Prevent duplicates from optimistic updates or retries
          const exists = old.some((m) => m.id === message.id);
          if (exists) return old;
          return [...old, message];
        }
      );
    };

    const handleStatus = (status: ClientStatus) => {
      if (status === 'disconnected' || status === 'error') {
        queryClient.setQueryData(
          ['webmessaging', 'connection-status'],
          status
        );
      } else {
        queryClient.setQueryData(
          ['webmessaging', 'connection-status'],
          'connected'
        );
      }
    };

    client.on('message', handleMessage);
    client.on('statusChange', handleStatus);

    return () => {
      client.off('message', handleMessage);
      client.off('statusChange', handleStatus);
    };
  }, [organizationId, integrationId, conversationId, queryClient]);
}

The cleanup function removes event listeners to prevent memory leaks. The duplicate check prevents the UI from rendering the same message twice when an optimistic update succeeds and the real-time event fires simultaneously. The connection status cache allows you to render a “Reconnecting…” banner when the WebSocket drops.

Complete Working Example

// src/components/ChatWindow.tsx
import { useState, useCallback } from 'react';
import { useQueryClient } from '@tanstack/react-query';
import { useMessageHistory } from '../hooks/use-message-history';
import { useSendMessage } from '../hooks/use-send-message';
import { useRealtimeSync } from '../hooks/use-realtime-sync';

interface ChatWindowProps {
  organizationId: string;
  integrationId: string;
  conversationId: string;
}

export function ChatWindow({
  organizationId,
  integrationId,
  conversationId,
}: ChatWindowProps) {
  const [inputText, setInputText] = useState('');
  const queryClient = useQueryClient();

  const { data: messages, isLoading, isError } = useMessageHistory({
    organizationId,
    integrationId,
    conversationId,
  });

  const { mutate: sendMessage, isPending } = useSendMessage({
    organizationId,
    integrationId,
    conversationId,
  });

  useRealtimeSync(organizationId, integrationId, conversationId);

  const handleSend = useCallback(() => {
    if (!inputText.trim()) return;

    sendMessage({ text: inputText.trim() });
    setInputText('');
  }, [inputText, sendMessage]);

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      handleSend();
    }
  };

  if (isLoading) return <div>Loading conversation history...</div>;
  if (isError) return <div>Failed to load messages. Check network and integration scopes.</div>;

  return (
    <div style={{ display: 'flex', flexDirection: 'column', height: '600px' }}>
      <div style={{ flex: 1, overflowY: 'auto', padding: '1rem' }}>
        {messages?.map((msg) => (
          <div key={msg.id} style={{ marginBottom: '0.5rem' }}>
            <strong>{msg.from?.name || 'Unknown'}:</strong>{' '}
            <span>{msg.text}</span>
            {msg.status === 'sending' && <span> (sending...)</span>}
          </div>
        ))}
      </div>

      <div style={{ padding: '1rem', borderTop: '1px solid #ccc' }}>
        <textarea
          value={inputText}
          onChange={(e) => setInputText(e.target.value)}
          onKeyDown={handleKeyDown}
          placeholder="Type a message..."
          style={{ width: '100%', height: '60px' }}
          disabled={isPending}
        />
        <button onClick={handleSend} disabled={isPending || !inputText.trim()}>
          {isPending ? 'Sending...' : 'Send'}
        </button>
      </div>
    </div>
  );
}

The component wires the hooks together. It disables the input during mutation to prevent duplicate submissions. It renders the temporary status flag until the server confirms delivery. The layout uses standard CSS flexbox for scrollable history and fixed composer.

Common Errors & Debugging

Error: 401 Unauthorized or 403 Forbidden

  • Cause: The integrationId is invalid, expired, or lacks webmessaging:read / webmessaging:write scopes. The SDK cannot exchange credentials for a valid bearer token.
  • Fix: Verify the integration exists in the Genesys Cloud admin console. Navigate to Messaging > Integrations and confirm the scopes are enabled. Regenerate the integrationId if it was rotated. Add a console log in the SDK error handler to capture the exact scope mismatch.

Error: 429 Too Many Requests

  • Cause: Rapid pagination loops or aggressive retry policies exceed the Genesys Cloud rate limits for the web messaging endpoints.
  • Fix: Implement exponential backoff in the retry logic. The React Query retryDelay configuration in Step 1 handles this automatically. If you fetch history manually, throttle requests to no more than five per second per integration. Add a 429 interceptor to pause execution for the duration specified in the Retry-After header.
// Retry-after handling example
const response = await client.messages.getHistory(params);
if (response.status === 429) {
  const retryAfter = parseInt(response.headers.get('Retry-After') || '5', 10);
  await new Promise((resolve) => setTimeout(resolve, retryAfter * 1000));
}

Error: Optimistic Update Rollback Failure

  • Cause: The onError callback does not restore the previous cache snapshot, or multiple mutations overlap and corrupt the array order.
  • Fix: Always return the previousMessages snapshot from onMutate. Ensure queryClient.cancelQueries runs before cache modification. Use unstable_batchedUpdates or React 18 automatic batching to prevent intermediate render states. Validate array length before rollback.

Error: WebSocket Disconnect Loop

  • Cause: The client SDK attempts to reconnect indefinitely when the organization blocks the integration or the WebSocket endpoint is unreachable.
  • Fix: Monitor statusChange events. If the status remains disconnected for more than thirty seconds, clear the query cache and prompt the user to refresh the page. The SDK does not expose a max retry count, so you must implement client-side circuit breaking.

Official References