Horizon is a Windows desktop workspace built around a user-selected folder of plain Markdown. The same material can open as an Obsidian vault, so the interface adds structure without taking ownership of the work.
Calendar, project planning, research, file navigation, rapid capture, and focus sessions live in one environment. The research space adds spatial arrangement, search, connections, reading, and local or Zotero-linked PDFs.
The boundary is intentionally local: Horizon runs against the selected workspace, listens only on the local computer, and includes no analytics or telemetry service.