PenEcho
A shared canvas application for thinking with AI beyond a chat window, where a hand sketch, equation or note can be turned by a built-in agent or a connected MCP client such as Codex or Claude Code into a diagram, document or small interactive widget next to the original sketch.
PenEcho is an infinite canvas for handwriting, equations, text and images that an AI can act on directly rather than through a separate chat window. Sketching and pausing triggers an automatic AI answer, and requests can turn a sketch into architecture, sequence or workflow diagrams with automatic layout, exportable as SVG or PNG, or into small working widgets such as calculators, quizzes and prototypes that run on the canvas and can be saved or shared.
An MCP connection lets an agent such as Codex, Claude Code or Kimi draw directly onto a canvas the user has explicitly turned on, read handwritten feedback on its next turn, and keep working in the same place as the user's own notes; local MCP stays on the user's machine, while cloud canvases use a separate signed-in connection.
It runs as a desktop app for macOS and Windows, installs as a Node.js command-line tool, or runs from source, and can use a signed-in Codex, Claude Code or Kimi CLI, a user's own model API key, or a hosted PenEcho model.