Stops a batch: every job still pending or processing becomes cancelled. A cancelled job is final and is not charged; a render already under way may finish, but its result is discarded. Jobs that already rendered keep their output and their charge. Cancelled jobs cannot be resumed; to render them again, create_batch a new batch with those rows. get_batch shows the cancelled count, and repeating the call cancels nothing more. Needs batches:create on the connection and renders:create in the user's workspace role.