Why the question tag of 'I am' is 'Aren't you?

The question tag for "I am" is actually "aren't I?" rather than "aren't you." This usage stems from the convention in English where the auxiliary verb "to be" is negated in the tag, leading to "aren't" for the subject "I." Therefore, the correct formation would be, "I am happy, aren't I?" This reflects a unique exception in English grammar.