Is it your brain deceiving you or it is the magician deceiving you?

I'd say it is your brain that is deceiving you.
Like if you agree.
Comment if you disagree with the questions validity or my answer.

I think it depends on the specifics of the magic and the distinction will often be a bit nitpicky. If the trick is "clean" in the sense that it couldn't be spotted with the aid of a recording from multiple camera angles, then I'd lean more towards to magician doing the deception. In the other case, if the trick depends on some perceptual error or misremembering exactly how something happened or was worded, then that is more on the brain.