server {
  listen 80;

  location / {
    root /usr/share/nginx/html;
    index index.html;
    try_files $uri /index.html;
  }

  location /api/ {
    # Keep the /api prefix when forwarding (Flask routes are /api/*).
    proxy_pass http://backend:3001;
    proxy_http_version 1.1;

    # SSE support (important for your EventSource)
    proxy_set_header Connection '';
    proxy_buffering off;
    chunked_transfer_encoding off;
  }
}