Quill. A little room for your own words.

Quill is a Markdown writing app for Mac that lets writers revise drafts with AI without copying text between apps. Hold the right Option key and describe a change, type a request with Command-K, or ask a question; the co-writer edits directly in the draft. Notes remain plain .md files in a chosen folder, and each change can be kept or reverted. Quill supports Claude Code, Codex, Cursor, Gemini CLI and other co-writers, can read linked pages as briefs, and maintains a Voice.md file for writing preferences. It requires macOS 26 or later.