Remindian is a mature macOS menu-bar application that provides bidirectional synchronization between Obsidian markdown vaults and multiple task management services including Apple Reminders, Things 3, Todoist, TickTick, Asana, Linear, and calendar feeds. The core architecture uses a protocol-based adapter pattern (TaskSource/TaskDestination) enabling pluggable sources and destinations. The sync engine performs surgical edits on vault files, preserving surrounding content and supporting recurrence rules, natural-language quick-add, and per-profile configurations. The codebase is well-structured with extensive tests (40+ test files), security hardening (AppleScript injection protection, OAuth CSRF validation, file permission enforcement), and features like safe mode crash recovery, mass-deletion guard, and backup/restore. It is actively maintained with a version history up to v5.32.0 and demonstrates strong engineering practices with modular design and comprehensive error handling.
FluidCalendar is a full-stack Next.js 15 calendar and task-management application intended as an open-source alternative to Motion. In production, it lets users manage tasks and calendar events in a local PostgreSQL-backed store, connect external calendars via Google, Outlook, and CalDAV, and synchronize tasks bidirectionally with Google Tasks, Outlook Tasks, and CalDAV VTODO providers. The application also includes an auto-scheduling engine that finds open time slots and scores them by deadline proximity, energy level, project grouping, and buffer constraints, plus dedicated focus mode, board/list task views, recurring event handling, and rich settings/admin screens. It is not a data-research repository, though its multi-provider synchronization layer has meaningful data-engineering depth.