Fixes the Responsive Filemanager when running a Coaster project locally with Laravel Valet.

CoasterValetDriver.php

<?php

class CoasterValetDriver extends ValetDriver
{
    /**
     * Determine if the driver serves the request.
     *
     * @param string $sitePath
     * @param string $siteName
     * @param string $uri
     * @return void
     */
    public function serves($sitePath, $siteName, $uri)
    {
        return is_dir($sitePath.'/public/coaster');
    }
    /**
     * Determine if the incoming request is for a static file.
     *
     * @param string $sitePath
     * @param string $siteName
     * @return string|false
     */
    public function isStaticFile($sitePath, $siteName, $uri)
    {
        if (file_exists($staticFilePath = $sitePath.'/public'.$uri)) {
            return $staticFilePath;
        }
        return false;
    }
    /**
     * Get the fully resolved path to the application's front controller.
     *
     * @param string $sitePath
     * @param string $siteName
     * @param string $uri
     * @return string
     */
    public function frontControllerPath($sitePath, $siteName, $uri)
    {
        if (strpos($uri, '/coaster/filemanager') !== false) {
            return $sitePath.'/public'.$uri;
        }
        return $sitePath.'/public/index.php';
    }
}

Worked like a champ! I copied this file into my ~/.valet/Drivers folder, then ran valet restart to fix the 404 Coaster responsive file manager error.