OpenAI launches an urgent search for a new Head of Preparedness as CEO Sam Altman admits 2025 brought "real challenges" with AI's mental health impact. Plus, Google quietly rolls out the ability to change your Gmail address after years of requests, LG unveils AI-powered 5K gaming monitors that could help you skip GPU upgrades, and scientists discover water ice just beneath Mars' surface at the ideal landing site for future human missions. We're covering the biggest stories from the final week of 2025.