# Cmux

> End-user control of cmux topology and routing (windows, workspaces, panes/surfaces, focus, moves, reorder, identify, trigger flash). Use when automation needs deterministic placement and navigation in a multi-pane cmux layout.

- Skill: `jasonkneen/cmux` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add jasonkneen/cmux`
- Raw SKILL.md: https://api.skillmd.com/api/skills/jasonkneen/cmux/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: jasonkneen (https://skillmd.com/u/jasonkneen)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/jasonkneen/cmux

---


# cmux Core Control

Non-browser cmux topology and routing.

- **Window**: top-level macOS cmux window.
- **Workspace**: tab-like group within a window.
- **Pane**: split container in a workspace.
- **Surface**: a tab within a pane (terminal or browser panel).

## Fast start

```bash
cmux identify --json                              # current caller context
cmux list-windows / list-workspaces / list-panes
cmux list-pane-surfaces --pane pane:1
cmux new-workspace
cmux new-split right --panel pane:1
cmux new-split down --command "npm run dev"       # new terminal runs the command in a live shell
cmux move-surface --surface surface:7 --pane pane:2 --focus true
cmux split-off --surface surface:7 right
cmux reorder-surface --surface surface:7 --before surface:3

# workspace context-menu actions (color, description, rename, pin, ...)
cmux workspace-action --action set-color --color Blue
cmux workspace-action --action set-description --description "Ship checklist"

# attention cue
cmux trigger-flash --surface surface:7
```

## Handle model

Output defaults to short refs (`window:N`, `workspace:N`, `pane:N`, `surface:N`). UUIDs are accepted as input; request UUID output only when needed with `--id-format uuids|both`.

## Initial command on new terminals

`new-workspace`, `new-split`, `new-pane`, and `new-surface` accept `--command <text>`. cmux starts the terminal's normal interactive shell and delivers the text plus one Enter at spawn time, so the command runs immediately and the shell stays alive after it exits. No follow-up `send` or `send-key enter` is needed, and the text is passed literally (quoting, `&&`, pipes, and `$VARS` are interpreted by the new shell). The flag is terminal-only: it is rejected with `--type browser|simulator|agent-session`, blank text is ignored, and `new-workspace --layout` ignores it because layout surfaces define their own commands. Details: [references/panes-surfaces.md](references/panes-surfaces.md).

## Settings

cmux-owned settings live in `~/.config/cmux/cmux.json`. `cmux docs settings` prints the docs URL, schema URL, raw GitHub resources, cmux.json paths, and reload command. `cmux settings`, `cmux settings cmux-json`, and `cmux settings shortcuts` open the UI.

`cmux reload-config` reloads both `cmux.json` and `~/.config/ghostty/config`, refreshing terminals in place with no app restart.

Terminal rendering (font, cursor style, theme, scrollback, `background-opacity`, `background-blur`) belongs in Ghostty config, not cmux settings. Everything else (app behavior, sidebar, notifications, browser behavior, automation, workspace colors, cmux-owned shortcuts) is cmux settings. Before editing, copy any existing `cmux.json` to a timestamped `.bak` next to it. Legacy `~/.config/cmux/settings.json` and `~/Library/Application Support/com.cmuxterm.app/settings.json` are read only as fallback for missing keys.

For a completed download, the CLI can inspect the bounded history owned by the
target browser surface without consuming a waiter:

```bash
cmux browser --surface <surface> download list
cmux browser --surface <surface> download list --limit 5 --json
```

Use the browser skill for the full response fields and wait/path compatibility
details.

## Deep-dive references

| Reference | When to Use |
|-----------|-------------|
| [references/handles-and-identify.md](references/handles-and-identify.md) | Handle syntax, self-identify, caller targeting |
| [references/windows-workspaces.md](references/windows-workspaces.md) | Window/workspace lifecycle, reorder/move, and context-menu actions (color, description, rename) |
| [references/panes-surfaces.md](references/panes-surfaces.md) | Splits, surfaces, move/reorder, focus routing |
| [references/trigger-flash-and-health.md](references/trigger-flash-and-health.md) | Flash cue and surface health checks |
| [../cmux-workspace/SKILL.md](../cmux-workspace/SKILL.md) | Current caller workspace rules and non-disruptive automation |
| [../cmux-settings/SKILL.md](../cmux-settings/SKILL.md) | Safe cmux.json settings edits and validation |
| [../cmux-browser/SKILL.md](../cmux-browser/SKILL.md) | Browser automation on surface-backed webviews |
| [../cmux-markdown/SKILL.md](../cmux-markdown/SKILL.md) | Markdown viewer panel with live file watching |