Markus is a local-first markdown editor for developers and AI-native builders. It opens your existing folders as workspaces and edits the .md files in place. No import, no proprietary format, no cloud, no account, no telemetry. Keyboard-first, native (Tauri + Rust, ~12 MB), with handcrafted themes. €39 one-time license, lifetime, 14-day free trial.