Neuralink wants to upgrade a brain chip while it’s still in someone’s head.

As children across the country drop letters to Santa into mailboxes this week, postal workers are gearing up for one of their busiest times of the year — and one Bay Area letter carrier is embracing the rush with a smile that residents say rivals Santa’s. On a cool December morning, USPS letter carrier Chyanne Thomas moved along her Saratoga route, delivering mail with a cheerful energy and a contagious smile that has endeared her to the community.