I tried a few coding orchestrators but most of them were Electron/Tauri apps and the performance bugged me. I also just prefer the terminal since GUI orchestrators lock you into their workflow. So I built cmux as a native macOS app in Swift/AppKit. It uses libghostty for terminal rendering and reads your existing Ghostty config for themes, fonts, colors, and more.
The main additions are the sidebar and notification system. The sidebar has vertical tabs that show git branch, working directory, listening ports, and the latest notification text for each workspace. The notification system picks up terminal sequences (OSC 9/99/777) and has a CLI (cmux notify) you can wire into agent hooks for Claude Code, OpenCode, etc. When an agent is waiting, its pane gets a blue ring and the tab lights up in the sidebar, so I can tell which one needs me across splits and tabs. Cmd+Shift+U jumps to the most recent unread.
The in-app browser has a scriptable API ported from agent-browser [1]. Agents can snapshot the accessibility tree, get element refs, click, fill forms, evaluate JS, and read console logs. You can split a browser pane next to your terminal and have Claude Code interact with your dev server directly.
Everything is scriptable through the CLI and socket API – create workspaces/tabs, split panes, send keystrokes, open URLs in the browser.
Demo video: https://www.youtube.com/watch?v=i-WxO5YUTOs
Repo (AGPL): https://github.com/manaflow-ai/cmux
https://iterm2.com/3.0/documentation-preferences.html#:~:tex...
Some feedback (since you were asking for it elsewhere in the thread!). Happy to go into more detail about any of these if it's helpful:
- It's not obvious/easy to open browser dev tools (cmd-alt-i didn't work), and when I did find it (right click page -> inspect element) none of the controls were visible but I could see stuff happening when I moved my mouse over the panel
- Would be cool to borrow more of ghostty's behavior:
- hotkey overrides - I have some things explicitly unmapped / remapped in my ghostty config that conflict with some cmux keybindings and weren't respected
- command palette (cmd-shift-p) for less-often-used actions + discoverability
- cmd-z to "zoom in" to a pane is enormously useful imo> hotkey overrides - I have some things explicitly unmapped / remapped in my ghostty config that conflict with some cmux keybindings and weren't respected
We need to be better about this; right now you can modify keyboard shorcuts with cmd+, in the GUI. Planning on making it a config file in the spirit of ghostty though, not sure if we want to reuse ghostty's config file though since it might become a maintenance burden for them...
> command palette (cmd-shift-p) for less-often-used actions + discoverability
yes
> cmd-z to "zoom in" to a pane is enormously useful imo
Thinking of the right way to design this. Like hypothetically we can expand it, but what happens if you make a vertical/horizontal split, or cmd+t to make a new tab? I guess we could just "merge" it back into the original space which would be pretty cool.
if you make a new split (or navigate splits), it would zoom you back out (contract the panel) and just split/navigate the way it normally would
Currently experimenting with agent-of-empires for tmux+worktrees to parallelize code changes.
So you can make your own script that can make new panels/workspaces and just invoke it from the terminal:
git worktree add -b my-branch ../repo-my-branch
ws=$(cmux new-workspace 2>&1 | awk '{print $2}')
cmux send --workspace "$ws" "cd ../repo-my-branch && claude"
cmux send-key --workspace "$ws" Enter
Would love to hear what other features have been particularly beneficial to your dev style too. Some directions I'm interested in is having everything be programmable; so my coding agent can set up workspaces for me, click through browsers to test things, etc. And having a main Claude Code manage subagents that have their own easily visible terminal windows.
I went the similar path of going vertical tabs after having worked that way in iTerm2 for months. Here's what I currently have:
Project-based organization -- Group sessions by working directory with a visual icon strip sidebar.
Multiple session types -- Claude Code sessions, standalone terminal shells, and embedded browser tabs.
Session persistence -- Terminal output is logged and replayed on relaunch so you never lose context.
Session resume -- Claude Code sessions detect their session ID automatically and resume where you left off.
Planning mode -- Draft and refine plans in a built-in text editor, then send them to Claude with one click.
Planning templates -- Start plans from structured templates for bug reports, feature requests, code reviews, refactors, and more.
Auto-titling -- Generic session names are replaced with descriptive titles generated by Claude after the first exchange.
Theming -- Light and dark themes with full CSS variable control.
Native menus and keyboard shortcuts -- macOS-native menu bar with comprehensive shortcut coverage.
Resizable layout -- Adjustable sessions sidebar width with state persistence across restarts.
Dock badge -- macOS dock icon shows the number of actively working Claude sessions.
Pin and archive -- Pin important sessions to the top or archive completed ones to keep the list clean.
Session card view -- See all sessions in a sortable grid with activity stats, token counts, and quick actions.
File tracker -- See which files Claude creates, modifies, and deletes in a live sidebar panel.
Macros -- One-click buttons for frequently used commands like /clear or commit this work.
Remote mode -- Monitor and control sessions from your phone via an encrypted WebSocket relay.
It has become my development hub where I can iterate very quickly.
The latest release (0.57.0) should fix it.
It doesn't have built-in notifications and there's no panel to see all the open sessions, but I wonder how hard that would be to add.
I've used zmx since I ran into it a few weeks ago. Uses libghostty as well. It's great because it allows me to replace tmux completely in all my ssh sessions, and can keep one session per assistant.
Would greatly appreciate it!
Would love to be able to color the sidebar tab.
Nice work!
I have Karabiner Elements so I added it and it's amazing!
Want to fix this, how do I reproduce? Select with mouse and cmd+c seems to work for me.
https://gist.github.com/roshan/b2a073e2377f370ce83cf7c4ea6d8...
I'm on MacOS 15.7.4 on an M4 Max Macbook
cmux notify --title "Claude Code" --subtitle "Waiting" --body "Agent needs input"
One question though, have you thought about trying to upstream any of this into Ghostty instead of making an entirely different app?
osascript << 'EOF' use framework "Foundation" use framework "AppKit"
set ghosttyIconPath to "/Applications/Ghostty.app/Contents/Resources/Ghostty.icns" set cmuxAppPath to "/Applications/cmux.app"
-- Read the icon file set iconImage to current application's NSImage's alloc()'s initWithContentsOfFile:ghosttyIconPath
-- Set it as the custom icon for cmux.app current application's NSWorkspace's sharedWorkspace()'s setIcon:iconImage forFile:cmuxAppPath options:0 EOF
((The ghost pairs well with Kiro, what can I say?))