Reactive Resume is a full-stack, open-source resume builder and job application tracker. It provides a rich web interface for creating, editing, and managing resumes with real-time preview, multi-format export (PDF, DOCX, Markdown, JSON), and ATS compatibility analysis. The system includes an AI-powered assistant for resume tailoring and cover letter drafting, an MCP server for LLM integration, and a semantic CSS stylesheet system for fine-grained PDF styling. The architecture is a monorepo with a React frontend (TanStack Router, Zustand, Lingui i18n), a Node.js API layer (oRPC, Drizzle ORM, PostgreSQL), and dedicated packages for PDF generation, DOCX export, authentication, and UI components. Key entry points include the resume builder interface, public resume sharing pages, an AI agent chat, and a job application board with stage tracking and CSV import/export. External dependencies include PostgreSQL, Redis, AI provider APIs (OpenAI, Anthropic, Gemini), and cloud storage (Vercel Blob or S3). The codebase is well-structured with extensive unit and integration tests, a reusable UI component library, and a modular package architecture that supports self-hosting via Docker or Vercel.