The three setups
Terminal + tmux
A tool that runs inside your terminal to split the screen and keep work alive when you close it. It has been the standard for a long time and works the same way on a server you SSH into. It was built for a person typing commands, so it does not tell whether an agent is waiting for you.
Terminal + herdr
The tmux idea, rebuilt for AI agents. Every pane is marked working, blocked or idle, and herdr tells you when an agent stops and needs an answer. Agents can drive herdr themselves through its CLI and socket API to open panes or prompt other agents. Like tmux, it runs inside the terminal you already use.
Ultenix
The terminal itself. Splitting, keeping work alive, telling agent states apart and notifications all live in one app, with nothing else to add.
Side by side
| Terminal + tmux | Terminal + herdr | Ultenix | |
|---|---|---|---|
| What you install | Your terminal plus tmux | Your terminal plus herdr | Ultenix only |
| Platforms | macOS, Linux and others | macOS, Linux, Windows (beta) | macOS (driven from iPhone and iPad) |
| Agent state per pane | Not tracked | Working, blocked, idle | Working, waiting for you, done, idle |
| Told when an agent needs you | No | Yes | Mac notifications, and on your iPhone |
| Work keeps running when you close the window | Yes (detach) | Yes (background server) | Yes (background process) |
| After a restart | Not restored by default | Layout restored, supported agent sessions resumed (processes do not survive) | Layout and working directories restored (Pro) |
| Controls | Prefix keys (Ctrl+B) | Prefix keys and the mouse | Regular Mac shortcuts (⌘T, ⌘\) and the mouse |
| Telling panes apart | Status line and border colors | Themes | Per-pane colors and per-directory background images |
| Japanese and other IME input | Depends on your terminal | Depends on your terminal | Composing text flows in the line and is never overwritten mid-conversion |
| Ask the AI for a command | No | No (it hosts your agents) | Ask in your own words or by voice, and see what it does before it runs |
| Operations you cannot undo | Not stopped | Not stopped | Always stop before running, and a person presses the button |
| Driven by agents | tmux commands | CLI and socket API (open panes, prompt other agents) | Built around a person watching and deciding |
| Other machines | Run tmux on the machine you SSH into | Saved SSH machines in one window | Reach this Mac from iPhone and iPad |
| Price | Free | Free (Apache 2.0) | Free. Pro is $7 a month |
How we compared
- Scope: tools for running several agents side by side in one screen, like Ultenix. Plain terminal apps without their own splitting and session handling are not included.
- The tmux and herdr columns rely only on each project's own documentation, checked on October 11, 2026.
- Prices are for individual use.
Sources
- tmux：github.com/tmux/tmux
- tmux：man.openbsd.org/tmux.1
- herdr：github.com/herdrdev/herdr
- herdr：herdr.dev/docs/session-state
- Ultenix：Features、Pricing
Which one to pick
tmux or herdr fit you if you work on servers over SSH, want the same setup on Linux or Windows, or do not want to change the terminal you already use. If you want agents to open panes and prompt each other, herdr is the better fit.
Ultenix fits you if you run many agents side by side on a Mac and do not want to miss the one waiting for you. Panes are told apart by color and background, and you can get the call on your iPhone when you step away. Typing in Japanese and other languages without broken text, and stopping before anything you cannot undo, are built in from the start.