Set throwExceptions() in the front controller:

$front->throwExceptions(true);

Set renderExceptions() in the response object:

$response->renderExceptions(true);
$front->setResponse($response);
$front->dispatch();

// or:
$front->returnResponse(true);
$response = $front->dispatch();
$response->renderExceptions(true);
echo $response;

The constructor now accepts exactly three arguments, Zend_Controller_Request_Abstract $request, Zend_Controller_Response_Abstract $response, and array $params (optional). Zend_Controller_Action::__construct() uses these to set the request, response, and invokeArgs properties of the object, and if overriding the constructor, you should do so as well. Better yet, use the init() method to do any instance configuration, as this method is called as the final action of the constructor.

run() is no longer defined as final, but is also no longer used by the front controller; it's sole purpose is for using the class as a page controller. It now takes two optional arguments, a Zend_Controller_Request_Abstract $request and a Zend_Controller_Response_Abstract $response.

indexAction() no longer needs to be defined, but is encouraged as the default action. This allows using the RewriteRouter and action controllers to specify different default action methods.

__call() should be overridden to handle any undefined actions automatically.

_redirect() now takes an optional second argument, the HTTP code to return with the redirect, and an optional third argument, $prependBase, that can indicate that the base URL registered with the request object should be prepended to the url specified.

The _action property is no longer set. This property was a Zend_Controller_Dispatcher_Token, which no longer exists in the current incarnation. The sole purpose of the token was to provide information about the requested controller, action, and URL parameters. This information is now available in the request object, and can be accessed as follows:

// Retrieve the requested controller name
// Access used to be via: $this->_action->getControllerName().
// The example below uses getRequest(), though you may also directly access the
// $_request property; using getRequest() is recommended as a parent class may
// override access to the request object.
$controller = $this->getRequest()->getControllerName();

// Retrieve the requested action name
// Access used to be via: $this->_action->getActionName().
$action = $this->getRequest()->getActionName();

// Retrieve the request parameters
// This hasn't changed; the _getParams() and _getParam() methods simply proxy to
// the request object now.
$params = $this->_getParams();
$foo = $this->_getParam('foo', 'default'); // request 'foo' parameter, using
                                           // 'default' as default value if not found

noRouteAction() has been removed. The appropriate way to handle non-existent action methods should you wish to route them to a default action is using __call():

public function __call($method, $args)
{
    // If an unmatched 'Action' method was requested, pass on to the default
    // action method:
    if ('Action' == substr($method, -6)) {
        return $this->defaultAction();
    }
    
    throw new Zend_Controller_Exception('Invalid method called');
}