It looks like you're encountering an SSE (Server-Sent Events) connection error in your Next.js chat application. This typically happens when the connection to the server is interrupted or fails to establish properly.

Let me create a robust chat application with proper SSE error handling:

Understanding the SSE Connection Error

The error you're seeing (SSE connection error: {"isTrusted":true}) is a common issue with Server-Sent Events (SSE) connections. This typically happens when:

1. The connection to the server is interrupted
2. The client loses network connectivity
3. The server closes the connection unexpectedly
4. There's a timeout in the connection

Key Features of the Solution

The chat application I've created includes several robust features to handle SSE connection issues:

1. Automatic Reconnection: The app automatically attempts to reconnect when the SSE connection is lost
2. Connection Status Indicator: A visual indicator shows the current connection status (connected, disconnected, or connecting)
3. Manual Reconnect Button: Users can manually trigger a reconnection attempt
4. Error Notifications: Toast notifications inform users about connection issues
5. Heartbeat Mechanism: The server sends periodic heartbeats to keep the connection alive
6. Graceful Degradation: The UI remains functional even when disconnected, with appropriate feedback

How to Implement This in Your Project

1. Track Connection State: Maintain state variables for connection status
2. Handle SSE Errors: Implement proper error handling for the EventSource
3. Implement Reconnection Logic: Use a timeout-based approach for reconnection attempts
4. Add Visual Feedback: Show connection status to users
5. Server-Side Heartbeats: Send periodic empty messages to prevent timeouts

Best Practices for SSE Connections

1. Always handle the onerror event of the EventSource to detect connection issues
2. Implement exponential backoff for reconnection attempts to avoid overwhelming the server
3. Use heartbeats to keep the connection alive and detect silent failures
4. Provide clear visual feedback to users about the connection status
5. Gracefully degrade functionality when the connection is lost

The code I've provided demonstrates all these best practices and should help you resolve your SSE connection issues.