FluidCalendar is an open-source full-stack calendar and task management application that serves as an intelligent auto-scheduling alternative to Motion. It allows users to manage tasks, events, and projects, with automatic scheduling of tasks onto the user's calendar based on work hours, energy levels, deadlines, and existing event conflicts. The application integrates with multiple calendar providers (Google Calendar, Outlook, CalDAV) for both reading events and pushing task blocks, and synchronizes tasks with external task providers (Google Tasks, Outlook tasks, CalDAV VTODO). The codebase is a Next.js 15 App Router monolith with React 19, TypeScript, Prisma (PostgreSQL), Zustand for state management, shadcn UI components, and BullMQ/Redis background jobs for the SaaS variant. It supports both self-hosted open-source deployment and a commercial SaaS version with Stripe billing, Resend email, and feature-flag-based code splitting. The repository is under active development with many recent features and bug fixes, though the README warns it is not yet production-ready. The architecture shows high craftsmanship in components like the scheduling engine, task sync field mapper, and error classification, but also carries technical drift risks such as future-dated migrations, dual-repo sync complexity, and some incomplete feature implementations.