Valet Driver for Craft 3

Craft3ValetDriver.php

<?php

class Craft3ValetDriver extends ValetDriver
{
    /**
     * Determine if the driver serves the request.
     *
     * @param  string  $sitePath
     * @param  string  $siteName
     * @param  string  $uri
     * @return bool
     */
    public function serves($sitePath, $siteName, $uri)
    {
        return file_exists($sitePath . '/craft');
    }

    /**
     * Determine if the incoming request is for a static file.
     *
     * @param  string  $sitePath
     * @param  string  $siteName
     * @param  string  $uri
     * @return string|false
     */
    public function isStaticFile($sitePath, $siteName, $uri)
    {
        if (file_exists($staticFilePath = $sitePath.'/web/'.$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)
    {
        return $sitePath.'/web/index.php';
    }
}

Install this to ~/.valet/Drivers/Craft3ValetDriver.php