301 redirect instead of 404 when URL is a prefix of a post or page name? in WordPress

This isrmal, it is because redirect_canonical() , which makes sure you are always at a "canonical" URL (conforming to your permalink structure), executes redirect_guess_404_permalink() to make a best guess at a post when the URL is incomplete . If you want to prevent this, I think the best way is to hook into the redirect_canonical filter , and return false if it is a 404. Something like this:

add_filter('redirect_canonical', 'no_redirect_on_404');
function_redirect_on_404($redirect_url)
{ if (is_404()) { return false; } return $redirect_url;
}