tl;dr: Tencent has open-sourced Hy4 preview, a 770B-parameter MoE model (49B active) with a 1M+ token context window, targeting coding, office, and research tasks. In internal blind evaluations, it slightly outperformed GLM-5.3 and Kimi K3, and Tencent claims it participated in its own training optimization, improving inference throughput by 31.8%. API pricing is $0.834/M input tokens and $2.501/M output tokens, with free access via WorkBuddy and CodeBuddy for two weeks.