Normally, agent and patient always stay the same:
The bread (patient) is eaten.
Carol (agent) ate the bread (patient).
But what if you had a causative clause, something like:
Peter made Carol eat the bread.
Is Carol
still the agent? Maybe it doesn't make much sense in English, but this question specifically came from looking at the Japanese causative:
Peter ga Carol ni pan wo tabesaseru.
I made him eat the bread.