Open-Fiesta is an open-source AI chat playground that allows users to interact with multiple AI models simultaneously. Built with Next.js 14 and TypeScript, it supports providers like Gemini and OpenRouter, enabling comparison of outputs from up to 5 different models side-by-side. The platform includes features like web search integration, image attachment support, and a clean streaming interface. It offers both traditional development setup and comprehensive Docker support for development and production environments.