It could be because: rewrite rules may not be updated correctly If any other plugin or theme feature might conflict with your rewrite rules or custom post types, deactivate them temporarily to ensure no conflicts. Ensure that your permalink settings are set to "Post Name" in the WordPress setting Here's your adjusted code with the potential improvements: // Remove slug from 'project' post type URLs function na_remove_slug( $post_link, $post, $leavename ) { if ( 'project' != $post->post_type || 'publish' != $post->post_status ) { return $post_link; } $post_link = str_replace( '/' . $post->post_type . '/', '/', $post_link ); return $post_link; } add_filter( 'post_type_link', 'na_remove_slug', 10, 3 ); function na_parse_request( $query ) { if ( ! $query->is_main_query() || ! isset( $query->query['name'] ) ) { return; } // Debugging line error_log( 'Project post type detected!' ); if ( ! empty( $query->query['name'] ) ) { $query->set( 'post_type', array( 'post', 'project', 'page' ) ); } } add_action( 'pre_get_posts', 'na_parse_request' ); // Temporarily flush rewrite rules (remove after testing) function na_flush_rewrite_rules() { flush_rewrite_rules(); } add_action( 'after_switch_theme', 'na_flush_rewrite_rules' );

thx for you help I did what I wanted with this type of function function custom_post_type_projects() { $args = array( 'public' => true, 'label' => 'Projects', 'rewrite' => array( 'slug' => 'pisanie-prac', 'with_front' => false ), ); register_post_type('project', $args); } add_action('init', 'custom_post_type_projects'); there is no /blog/ and I added my subpage in structure of URLs, it works perfectly also with YOAST SEO breadcrumbs, showing the exact structure I wanted.