HappyHorse-1.0 Review — The #1 Video Model That Entered Anonymously and Shook the Leaderboard

On April 7, 2026, a video model appeared on Artificial Analysis's arena under no name, no company, no affiliation. Within 48 hours it had climbed to #1 in all four categories. Three days later, Alibaba's ATH unit confirmed ownership. The model was HappyHorse-1.0 — a 15B-parameter unified Transformer built by the architect of Kling AI. We review the technology, the anonymous debut strategy, the open-source credibility gap, and what the leaderboard dominance actually means for developers and enterprises.