Does we have agency, free will, during sleep - during dreaming?
If agency is real, then the answer must be yes - because if we say no then the implication is that humans only have free will under what may be exceptional circumstances of health, alertness and at certain ages.
If we were to say that free will is absent during dreams, then we would have to say that it was absent during delirious states and during psychosis (schizophrenia, mania, psychotic depression); and also during dementia, and epilepsy, and some forms of brain damage...
And then we would have to recognize that similar conditions apply to children, and many of the elderly, and to people with mental handicap - and indeed to almost any human being for much of each day.
So we end-up with a concept of free will being regarded as something that is an exceptional state enjoyed only by exceptional people - and that at other times human choice is unfree but merely a product of circumstances and contingencies.
And this view is incompatible with Christianity.
(The above is to equate free will with strict and legalistic ideas of mental competence; rather akin to the legal concepts of fitness-to-plead and responsibility. But this is not the human condition - and these legal concepts are operationally deployed in a crude fashion based on an assumption of competence within certain age boundaries.)
So, our understanding should be that free will is something indestructible that stands behind all contingencies.
Free will is eternal and always and necessarily operative, regardless of the choices and possibilities of action - such that the brain damaged person in a coma who is 'shut-in' without movement or sensation is nonetheless assumed to have free will for as long as they are alive - they are not just 'able' to make choices among their mental contents, but necessarily will make choices among their mental contents: free will cannot be switched -off.
Since salvation depends on these choices, and since such choices may be disconnected from perceptible action, we can understand how it is intrinsically impossible for us to judge others in relation to salvation - because we can only perceive another person's actions, and indirectly infer their freely willed choices from these actions.
Yet of course the soul which chooses must be (is) in some way connected with the mind and body which enacts (or fails to enact) choices - therefore we can ask: what is the nature of this connection? - how may we conceptualize the connection between the soul which has free will, and the mind and body which are subject to circumstance?
I think one answer is the concept of empathy - the soul has empathy for the mind and body, a sympathetic resonance with the happiness and sufferings of mind and body, such that the soul feels what they feel.
Again the analogy of the parent can do the necessary work: a good Father or Mother will feel the pleasures and pains of their children, by empathy.
Somewhat likewise, the soul is connected to the mind and body by a necessary and unavoidable empathic identification - while it retains agency under any circumstance.
Yet the soul's agency, while eternal, is affected by mind and body - because empathy is necessary the soul is changed by its own choices - there are consequences to the soul from its previous choices.
Thus free will is always; but that which freely chooses is changed by its choices.
Therefore (without outside intervention) the soul will corrupt itself even after a single initial wrong choice - since the consequence of even a single wrong choice will necessarily damage and corrupt the soul to a significant degree, and make that soul significantly less good and more likely to make another bad choice.
The process is cumulative and the result may be a soul practically incapable of making a good choice even while wholly retaining agency and free will.
We may perhaps directly perceive this process in ourselves, but only indirectly - by inference - in others.