Open Canvas is an open-source web application designed for collaborative writing with agents to produce better documentation. It is inspired by OpenAI's 'Canvas,' but there are several key differences. It is fully open-source, including all the code for the front-end, content generation agents, and reflective agents, all released under the MIT license. It comes with built-in reflective agents that can remember style rules and user insights across sessions. Additionally, it allows users to start with a blank text or an existing code editor, working in the language of their choice, thus facilitating iteration on existing content.