Excalidraw is an open-source virtual whiteboard and diagramming application, published both as a hosted PWA (excalidraw-app) and as an npm library (@excalidraw/excalidraw). The system provides an infinite canvas with hand-drawn-style rendering, supporting a wide range of shapes (rectangles, ellipses, arrows, lines, freedraw, text, sticky notes, images, frames, embeddables) and tools (laser pointer, eraser, bucket fill, lasso selection, shape recognition). It features real-time collaboration via WebSocket (socket.io) and Firebase, with end-to-end encryption, cursor sharing, and follow/unfollow. The architecture is a React-based single-page application with a modular monorepo structure: the core editor logic resides in packages/excalidraw, element manipulation in packages/element, geometry utilities in packages/math, shared constants and data structures in packages/common, and export helpers in packages/utils. State management uses Jotai atoms and a custom action registration system (ActionManager). The editor renders to an HTML5 canvas with a separate SVG overlay for interactive elements. Key entry points include packages/excalidraw/index.tsx (library export) and excalidraw-app/index.tsx (hosted app bootstrap). Data flows from user interactions through actions to element mutations, scene updates, and canvas re-rendering. External dependencies include Firebase (Firestore, Storage), socket.io, Radix UI, Jotai, roughjs, and various build tools. The codebase also includes an AI-assisted text-to-diagram feature (TTD dialog) that converts Mermaid syntax into Excalidraw elements via streaming SSE and auto-fix logic.

This repository implements an MCP (Model Context Protocol) server that renders Excalidraw diagrams with hand-drawn style animations. It provides two primary tools: `read_me` (returns a cheat sheet with element format and color palettes) and `create_view` (renders diagrams from Excalidraw JSON elements with streaming draw-on animations). The architecture is a Node.js server supporting both Streamable HTTP and stdio transports, with a React-based widget that uses Excalidraw's `exportToSvg` for SVG rendering (not the full canvas component). Key features include: progressive element streaming with morphdom DOM diffing, smooth viewport camera animation, interactive fullscreen editing with checkpoint/restore persistence (file, memory, or Redis backends), pencil stroke audio feedback, and one-click export to excalidraw.com. The server is deployable on Vercel via serverless functions. The codebase demonstrates strong engineering practices with clean abstractions, well-documented design decisions, and a focus on performance (no blink on final render, efficient SVG diffing).