gistfile1.txt

add_filter('update_post_metadata', function ($check, $object_id, $meta_key, $meta_value, $prev_value) {

    if ($meta_key !== 'fave_property_id') {
        return $check;
    }

    // 1) Manual edits in wp-admin should always be allowed.
    // We treat "manual" as the classic post edit save (not AJAX/REST).
    $is_manual_admin_save =
        is_admin()
        && !wp_doing_ajax()
        && !wp_is_json_request()
        && (
            doing_action('save_post')
            || doing_action('post_updated')
            || (isset($_POST['action']) && $_POST['action'] === 'editpost')
        );

    if ($is_manual_admin_save) {
        return $check; // don't interfere with manual changes
    }

    // 2) Only apply "write once" rule if call originates from the plugin.
    $plugin_path_fragment = DIRECTORY_SEPARATOR . 'plugins' . DIRECTORY_SEPARATOR . 'houzez-property-feed' . DIRECTORY_SEPARATOR;

    $from_feed_plugin = false;
    foreach (debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, 25) as $frame) {
        if (!empty($frame['file']) && strpos($frame['file'], $plugin_path_fragment) !== false) {
            $from_feed_plugin = true;
            break;
        }
    }

    if (!$from_feed_plugin) {
        return $check; // not from that plugin => allow
    }

    // 3) From the plugin: only update if meta does not exist yet.
    if (metadata_exists('post', $object_id, $meta_key)) {
        return false; // block overwrite, keep existing value
    }

    return $check; // allow first write
}, 10, 5);