My impression of the 2023 AoC was that Wastl has spent considerable effort on making it less LLM-friendly this year. Some days, this seems to have been done by adding extra conditions and complications which make the task more difficult for LLMs to parse. Other tasks required studying the input data which is difficult to achieve with an unsupervised LLM. Finally, the first couple of days seemed a lot more difficult this year than previous years, possibly to deter chatgpt users from filling up the leaderboard right away (though this year December started with a weekend which could also be a contributing factor).