For the purposes of res judicata, is appellant permitted to add new causes of action to the first action?

For the same reasons, the fact that appellant has added causes of action to the instant complaint that were not alleged in the first action does not compel a different analysis. It is well-established that the doctrine of res judicata applies to claims that not only were litigated, but also could have been litigated. (Pollock v. University of Southern California, supra, 112 Cal.App.4th at p. 1427 [noting that the doctrine applies to a matter that the party had an opportunity to litigate in a prior lawsuit, "`and should not be permitted to litigate [] again to the harassment and vexation of [the party's] opponent'"].) Because all claims alleged in both the first action and the instant action arise out of the same facts, any purportedly new causes of action could have been litigated previously and are thus barred.

Second, the prior proceeding resulted in a final judgment on the merits.