Some changes to adventofcode this year, will only have 12-days of puzzles, and no longer have global leaderboard according to the faq:

Why did the number of days per event change?

It takes a ton of my free time every year to run Advent of Code, and building the puzzles accounts for the majority of that time. After keeping a consistent schedule for ten years(!), I needed a change. The puzzles still start on December 1st so that the day numbers make sense (Day 1 = Dec 1), and puzzles come out every day (ending mid-December).

Scaling it a bit down rather than completely burning out is nice i think.

What happened to the global leaderboard?

The global leaderboard was one of the largest sources of stress for me, for the infrastructure, and for many users. People took things too seriously, going way outside the spirit of the contest; some people even resorted to things like DDoS attacks. Many people incorrectly concluded that they were somehow worse programmers because their own times didn't compare. What started as a fun feature in 2015 became an ever-growing problem, and so, after ten years of Advent of Code, I removed the global leaderboard. (However, I've made it so you can share a read-only view of your private leaderboard. Please don't use this feature or data to create a "new" global leaderboard.)

While trying to get a fast time on a private leaderboard, may I use AI / watch streamers / check the solution threads / ask a friend for help / etc?

If you are a member of any private leaderboards, you should ask the people that run them what their expectations are of their members. If you don't agree with those expectations, you should find a new private leaderboard or start your own! Private leaderboards might have rules like maximum runtime, allowed programming language, what time you can first open the puzzle, what tools you can use, or whether you have to wear a silly hat while working.

Probably the most positive change here, it's a bit of shame we can't have nice things, a no real way to police stuff like people using AI for leaderboard times. Still keeping the private one, for smaller groups of people, that can set expectations is unfortunately the only pragmatic thing to do.

Should I use AI to solve Advent of Code puzzles?

No. If you send a friend to the gym on your behalf, would you expect to get stronger? Advent of Code puzzles are designed to be interesting for humans to solve - no consideration is made for whether AI can or cannot solve a puzzle. If you want practice prompting an AI, there are almost certainly better exercises elsewhere designed with that in mind.

It's nice to know the creator (Eric Wastl) has a good head on his shoulders.