I dinked around on this but for the life of me, can't find where it's getting the URI from. I did learn how paging works in EditEngine though.

Yeah, this is a little obscure since I was trying not to build more than we needed. The URI comes from DiffusionRepositoryManagementPanel->newEditEnginePage(), which does this:

$key = $this->getManagementPanelKey();
$label = $this->getManagementPanelLabel();
$panel_uri = $this->getPanelURI();

return id(new PhabricatorEditPage())
  ->setKey($key)
  ->setLabel($label)
  ->setViewURI($panel_uri)
  ->setFieldKeys($field_keys);

getPanelURI() has an implementation above:

final public function getPanelURI() {
  $repository = $this->getRepository();
  $key = $this->getManagementPanelKey();
  return $repository->getPathURI("manage/{$key}/");
}

The problem is that this URI is being generated before you do your edit, and the URI contains the (old) callsign.

A hacky approach would probably be to override getEffectiveObjectEditDoneURI($object) in DiffusionRepositoryEditEngine, and do something like this:

$page = $this->getSelectedPage();
if ($page) {
  $key = $page->getKey();
  
  return $object->getURI("manage/{$key}/");
}
 
return parent::getEffectiveObjectEditDoneURI($object);

I think that will fix it? I'm really not happy with how these methods are working right now and plan to clean them up a bit -- I probably made the behavior too simple in Diffusion, and then kind of weird in Settings.

+1 it's very confusing

Heh, just ran into this today