When a task throws an unhandled exception, any output in its print buffer will be flushed to the screen. Then the error message accompanied by a tag stack will be output to the screen and the user will be returned to the prompt.
If an unexpected error happens inside a task that is non-recoverable, do not attempt to try/catch it unless you can improve the error message to something more useful. Generally speaking, just let the error bubble up and be handled by CommandBox for consistency and simplicity.
If there are expected situations such as a file not existing, that you know might go wrong, we wholeheartedly recommend checking for these situations and using the error() method to alert the user. Errors returned from the error() method will not contain any stack traces, etc.