Setup with Cloudflare Workers

// lovablehtml-prerender.js (Cloudflare Worker)
export default {
  async fetch(req, env) {
    // Only handle public GET navigations
    if (req.method !== 'GET') return fetch(req);

    const isHtmlRequest = (req.headers.get('accept') || '').includes('text/html');
    if (!isHtmlRequest) return fetch(req);

    const headers = new Headers();
    headers.set('x-lovablehtml-api-key', env.LOVABLEHTML_API_KEY);
    headers.set('accept', 'text/html');
    const forward = [
      'accept-language',
      'sec-fetch-mode',
      'sec-fetch-site',
      'sec-fetch-dest',
      'sec-fetch-user',
      'upgrade-insecure-requests',
      'referer',
      'user-agent',
    ];
    for (const name of forward) {
      const v = req.headers.get(name);
      if (v) headers.set(name, v);
    }

    const r = await fetch('https://lovablehtml.com/api/prerender/render?url=' + encodeURIComponent(req.url), { headers });

    // 304 = not pre-rendered, pass through to origin
    if (r.status === 304) {
      return fetch(req);
    }
    if ((r.headers.get('content-type') || '').includes('text/html')) {
      return new Response(await r.text(), { headers: { 'content-type': 'text/html; charset=utf-8' } });
    }
    return fetch(req);
  },
};