CRM does not call Drupal civicrm_post hook when adding Individuals to Groups via API

Using CRM 1.3 with CivicSpace 0.8.3RC3 –

Using the CRM "Add members to groups page" (eg. /civicrm/group/search?reset=1&force=1&context=smog&gid=3), the individual is added successfully to the group, but the drupal hook_civicrm_post is never called by the framework.

working in the debugger, it appears the problem is on the CiviCRM side, since the actual call to add the group (CRM_Contact_BAO_GroupContact::addContactsToGroup) occurs in CRM_Contact_Form_Task_AddToGroup::postProcess; somewhere down here the hooks need to get called, and they are not.

This will need to get fixed before Organic Group integration will work.