I have the following requirements for url patterns:

1. /CPT/ (archive of custom post type)
2. /CPT/post-name (single post in custom post type)
3. /CPT/category-name (archive of cpt category)
4. /CPT/category-name/post-name (single post in custom post type category)

Those are the structures I need. So far 1, 3, and 4 are working properly - but I cannot get 2 to do anything but throw a 404.

When I modify the rewrite rules to accommodate #2, 3 or 4 breaks and either throws 404 or redirects to the home page. Is this possible to correct so all four permalinks are functional?

I tried using the CPT permalinks plugin - but I was unsuccessful at getting the /CPT/post-name to work in conjunction with the other permalink structures I need (3 & 4).

I read through and attempted the use of another solution here - but again, these ignored the need for the structure of /cpt/post-name.

Basically, I need to ensure that the slug for the custom post type and the slug for the custom post type custom category is the same - here are some specific examples of meaningful urls:

• /services (archive of custom post type)
• /services/botox (single post of custom post type)
• /services/injectables (archive of custom post type custom taxonomy)
• /services/injectables/botox (single post of custom post type custom taxonomy)

Below is the code I currently have in place that is working with the exception of #2 structure:

// Register the Custom Post Type
function register_custom_post_type() {
    $args = array(
        'labels' => array(
            'name' => 'Services',
            'singular_name' => 'Service',
        ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array(
            'slug' => 'services', // Base slug for your CPT
            'with_front' => false,
            'hierarchical' => true, // Allows for /services/category/post
        ),
        'show_in_rest' => true, // Enable Gutenberg editor if needed
        'supports' => array( 'title', 'editor', 'excerpt', 'author', 'thumbnail', 'comments', 'revisions', 'custom-fields' ),
        'taxonomies' => array('services_category'), // Attach custom taxonomy if needed
    );

    register_post_type('services', $args);
}
add_action('init', 'register_custom_post_type');

// Register Custom Taxonomy for the Custom Post Type
function register_custom_taxonomy() {
    $args = array(
        'labels' => array(
            'name' => 'Services Categories',
            'singular_name' => 'Services Category',
        ),
        'public' => true,
        'rewrite' => array(
            'slug' => 'services', // This will make the taxonomy appear under /services/category-name/
            'with_front' => false,
            'hierarchical' => true, // Ensure categories are hierarchical (like regular categories)
        ),
        'hierarchical' => true,
    );

    register_taxonomy('services_category', 'services', $args);
}
add_action('init', 'register_custom_taxonomy');

**// Custom Rewrite Rules to Match the Permalink Structure
function custom_rewrite_rules($rules) {
    $new_rules = array(
        // CPT Archive: /services/
        'services/?$' => 'index.php?post_type=services',

        // Single CPT Post: /services/post-name/
        'services/([^/]+)/?$' => 'index.php?post_type=services&name=$matches[1]',

        // Custom Taxonomy Archive: /services/category-name/
        // This rule should be placed *after* the CPT single post rule to avoid conflicts
        'services/([^/]+)/?$' => 'index.php?taxonomy=services_category&term=$matches[1]',

        // Single CPT Post within a Category: /services/category-name/post-name/
        'services/([^/]+)/([^/]+)/?$' => 'index.php?post_type=services&services_category=$matches[1]&name=$matches[2]',
    );

    return $new_rules + $rules;
}
add_filter('rewrite_rules_array', 'custom_rewrite_rules');

// Add rewrite tag for custom taxonomy (to ensure taxonomy permalinks work)
function add_custom_rewrite_tags() {
    add_rewrite_tag('%services_category%', '([^&]+)');
}
add_action('init', 'add_custom_rewrite_tags');