Harness is standalone desktop apps that talk to any AI agent through localhost APIs. Not a plugin, not a platform. Just apps on your machine. The agent reads your kanban board, respects your "don't do" list, sends you alerts, leaves async questions, and checks how much time it has left. Works with Claude Code, Codex, Cursor, or anything that can make HTTP requests. Drop a markdown file in your project and the agent knows the apps exist. No accounts, no cloud, no tracking.