add_filter('robots_txt', function ($output, $public) {
    if (!$public) {
        return $output;
    }

    // ClaudeBot: targeted — kill the calendar crawl, keep the site crawlable.
    $rules  = "\n# i4a crawler policy\n";
    $rules .= "User-agent: ClaudeBot\n";
    $rules .= "Disallow: /wp-admin/\n";
    $rules .= "Allow: /wp-admin/admin-ajax.php\n";
    $rules .= "Disallow: /events/\n";

    // SEO / data-broker crawlers we turn away entirely.
    $blocked = [
        'AhrefsBot',
        'SemrushBot',
        'SemrushBot-BM',
        'MJ12bot',
        'DotBot',      // Moz
        'rogerbot',    // Moz (older)
        'BLEXBot',
        'PetalBot',
        'ZoominfoBot',
        'PiplBot',
    ];

    foreach ($blocked as $bot) {
        $rules .= "\nUser-agent: {$bot}\nDisallow: /\n";
    }

    return $output . $rules;
}, 10, 2);