landing/worker/index.js

function withFreshHtml(response) {
    if (!response.headers.get('content-type')?.includes('text/html')) {
        return response;
    }

    const headers = new Headers(response.headers);
    headers.set('Cache-Control', 'no-cache');

    return new Response(response.body, {
        status: response.status,
        statusText: response.statusText,
        headers,
    });
}

const worker = {
    async fetch(request, env) {
        const response = await env.ASSETS.fetch(request);

        if (
            response.status !== 404 ||
            request.method !== 'GET' ||
            !request.headers.get('accept')?.includes('text/html')
        ) {
            return withFreshHtml(response);
        }

        const indexUrl = new URL('/index.html', request.url);
        const indexResponse = await env.ASSETS.fetch(new Request(indexUrl, request));
        return withFreshHtml(indexResponse);
    },
};

export default worker;