Option 1

Speak to your parents directly and calmly before the event, explaining how important your partner is to you and asking them to reconsider their stance, even if just for a brief introduction.

Option 2

Tell your parents you will not attend the anniversary if your partner is not welcome, or threaten to bring your partner regardless of their disapproval.

Option 3

Attend the anniversary alone, avoiding any discussion about your partner with your family, and later apologize to your partner for not including them.