I’m trying to filter the posts on a CPT by one or more categories.

Here’s what I have so far:

$args = array(
    'post_type'         => 'cpt-name',
    'posts_per_page'    => -1,
);

// cat_term_id have been registered as a custom query var
$categories = get_query_var( "cat_term_id" );

if ( !empty( $categories ) ) {    
    $args['tax_query'] = array(
        array(
            'taxonomy'          => 'category',
            'field'             => 'term_id',
            'terms'             => $categories,
            'include_children'  => false,
        ),
    );
}

$filtered_posts = get_posts( args );

The query works, the problem is that is bringing all the posts on the CPT, and what I want is to only get the posts using the categories passed by cat_term_id.

Am I missing something?