spacezephyr/cowrite

Cowrite is a writing tool that runs entirely on your own computer. It gives you a browser window where you write and edit articles, while an AI coding assistant like Codex or Claude Code reads and writes the same document through a connection called MCP. The two sides share one file, so you can keep typing while the assistant works on the same page. The main idea is that you type a request inside the assistant's chat, and the article grows and updates inside the browser. You can start a new page by filling in a title and instructions, or by importing an existing Markdown file. You can paste images straight into the editor and Cowrite stores them in a local folder instead of turning them into long text strings that would slow the page down. Once a page is open, a floating toolbar lets you select text and ask for an illustration, an HTML diagram, a rewrite of just that passage, or a conversation about the content. There are also buttons for turning an article into a slide deck (an editable PPTX file plus a browser viewable PDF), for formatting it for WeChat's official account style or Xiaohongshu, a Chinese social platform, and for sending the finished piece out through Feishu, a document tool. Sending to WeChat and Zhihu is marked as not finished yet. All image generation goes through a built in tool inside Codex, so no separate image API key is needed, and the project does not switch to other image services if that tool is unavailable. Cowrite needs Node.js 20.19 or newer (or 22.12 or newer) and npm, plus a working Codex CLI or Claude Code install. Setup happens automatically the first time the plugin loads: it installs dependencies, builds the front end, and starts a local service that only listens on your own machine, so nothing is uploaded anywhere. It also ships as a plugin for both Codex and Claude Code with a marketplace listing you can add directly. The license is MIT.