OpenMAIC (Open Multi-Agent Interactive Classroom) is an AI education platform developed by Tsinghua University's THU-MAIC research team that transforms any topic or document into a rich, interactive classroom experience. Powered by multi-agent orchestration via LangGraph 1.1, it generates slides, quizzes, interactive HTML simulations, and project-based learning activities delivered by AI teachers and AI classmates who can speak, draw on a whiteboard, and engage in real-time discussions. The architecture consists of four pillars: a two-stage generation pipeline for outline and scene content creation, multi-agent orchestration managing agent interactions, a playback engine state machine controlling classroom presentation, and an action engine executing 28+ action types including speech, whiteboard operations, and visual effects. Built on Next.js 16, React 19, and Tailwind CSS 4, it supports OpenAI, Anthropic, Google Gemini, DeepSeek, and Grok as LLM providers. Validated with over 700 students at Tsinghua University, it supports English and Chinese with export capabilities to PowerPoint and interactive HTML.