I have fitted a simple ar1 model with poisson outcome in brms.

As far as I know an ARMA model assumes that the “shocks” (the “error term” in the ARMA process) is iid gaussian.

I don’t see a way to extract these from my brms model for assumption checking. Am I missing something? How can I check my model?

A a side note/question:

I also didn’t find a way to get fitted or predicted values utilizing the fitted ARMA process. It seems the choices are either to set the ARMA process to zero or to simulate new draws of the ARMA process. The same also applies to GP models