A macOS terminal written from scratch in Swift. It has its own GPU renderer, persistent sessions, split panes, workspaces, and enough agent awareness to tell you when a coding agent needs attention.
Get it
$ git clone https://github.com/robzilla1738/harness-cli.git harness$ cd harness && make release$ open Harness.appFree and open source · macOS 14+ · full setup in the docs
One stack, end to end
Plenty of terminals are a UI wrapped around parts from somewhere else. Harness is one Swift codebase: renderer, multiplexer, workspace model, and agent layer. swift build pulls in no package dependencies, so the pieces can behave like one system.
Harness has its own VT parser and Metal renderer, with a CoreText glyph atlas on the GPU. Box drawing and block characters are drawn in code, so they line up at any font size. Ligatures, inline images, and 24-bit color are built in.
Harness watches the process tree for Claude Code, Codex, Cursor, OpenCode, Aider, Gemini, Goose, and more. Panes are marked automatically, and you can add hooks when you want cleaner, explicit notifications.
Split panes, close the window, and keep the session alive. attach-window can paint the whole split layout in a plain terminal over SSH. The multiplexer runs through HarnessDaemon, not a tmux server.
Workspaces, sessions, tabs, and splits live in one sidebar, so active work stays visible instead of getting lost in a stack of similar windows.