"Vouchsafe" defined as to give in a gracious or condescending manner

Solution 1:

Aren't gracious and condescending antonyms?

Not originally. Indeed, it remains that one meaning of to condescend is to forgo rank or privilege and join people "below" you as equals.

This was so often used ironically, of someone acting as if they were talking to an inferior, that it became the predominant sense.

Vouchsafe underwent the same partial change, and can mean either bestowing something from a superior position (which would be a graceful act), or else as if from a superior position. So it can be used both to match the old sense of condescend, or the new.

The really confusing sense, is that sometimes people talk of "vouchsafing prayers to God", which matches neither sense. My guess is that it's a matter of people only knowing vouchsafe from religious contexts (God is often vouchsafing, or being asked to vouchsafe something, in religious writing) understanding that it means "give", but not understanding the implied imbalance of the transaction.

Edit: Or another possibility is it was originally from asking saints to vouchsafe to intercede with God, on the matter of the prayer, among those denominations that believe in intercession of saints. Still no more than a guess.

Solution 2:

Yes they are. The difference here is in how vouchsafe is used. If something were vouchsafed to you by a king, it would be in a gracious manner. If it were vouchsafed to you by one of your peers, use of vouchsafe would indicate condescension.

Essentially, the word means that something was granted to you. If it were granted by someone who obviously has more power than you, than it will be understood to have been done in a graceful manner. If you use the word to refer to someone who is at the same social, economic or power level as you, then it would be taken as ironic and suggest a condescending manner.