Transforms the success value — .then(fn) that stays a Task: lazy, retryable, E kept. fn may return a value or a promise of one (they flatten), so this is andThen too.

const loadUser = (id: number) => Task(() => ({ name: 'u' + id }));

loadUser(1).map((u) => u.name).map((n) => n.toUpperCase()); // still lazy, still a Task