Kohana framework displays really nice and descriptive error messages, for a development environment that is. For production obviously no error reports should be shown to the user. Instead we should display a pretty “404 Not Found”, or any other error page.
Creating those custom error pages in Kohana v3.x can be a real pain in the bum. I’m hoping that below guide will help you get this done in just few minutes.

Create HTML of your custom pages

/application/views/error/
/application/views/error/404.php

<h1>My custom 404 error page!</h1>

/application/views/error/500.php

<h1>My custom 500 error page!</h1>

Following the same pattern you can create custom pages for all error codes. If you want one error page for all just create it and later point all requests to that view.

Create template if you need it

Obviously you can use the same template you’re using for your normal pages. If so, feel free to omit this step.
/application/views/error.php

<?php echo $content; ?>

Extend Kohana exception class

Create directory and file as per below and copy code into the file.

/application/classes/kohana/exception.php

<?php defined('SYSPATH') or die('No direct script access.');

class Kohana_Exception extends Kohana_Kohana_Exception {

	public static function handler(Exception $e) {
		if (Kohana :: $environment === Kohana :: DEVELOPMENT) {
			// In development show normal Kohana errors
			parent :: handler($e);
		} else {
			// In production show custom error page
			try {
				Kohana :: $log->add(Log :: ERROR, parent :: text($e));

				$attributes = array (
					'action'  => 500,
					'message' => rawurlencode($e->getMessage())
				);

				if ($e instanceof HTTP_Exception) {
					$attributes['action'] = $e->getCode();
				}

				// Error sub-request.
				echo Request::factory(Route::get('error')->uri($attributes))->execute()->send_headers()->body();

			} catch (Exception $e) {
				// Clean the output buffer if one exists
				ob_get_level() and ob_clean();

				// Display the exception text
				echo parent :: text($e);

				// Exit with an error status
				exit (1);
			}
		}
	}

}

Add route for error pages

/application/bootstrap.php

Route::set('error', 'error/<action>/(<message>)', array('action' => '[0-9]++', 'message' => '.+'))
	->defaults(array(
		'controller' => 'error',
		'action'	 => '404'
));

Finally, create controller for error pages

/application/controller/error.php

<?php defined('SYSPATH') or die('No direct script access.');

class Controller_Error extends Controller_Template {
	// if you've created your custom error template. If not use your standard template here.
	public $template = 'error';
	
	public function before() {
		parent :: before();
	}
	
	/**
	 * Serves HTTP 404 error page
	 */
	public function action_404() {
		$this->template->content = View :: factory('error/404');
	}

	/**
	 * Serves HTTP 500 error page
	 */
	public function action_500() {
		$this->template->content = View :: factory('error/500');
	}
}

That’s it. Try to access a page on your site that doesn’t exist and you should see your custom 404 error page. Remember that when working in development standard Kohana errors will be show and only on production our pretty error pages will shine. Line 6 in `exception.php` controls this behaviour.

Above is simplified and slightly modified version of Lysender post.