cmux-customize

Use this skill for personal cmux configuration changes stored outside the app source tree, especially ~/.config/cmux/cmux.json and project-local .cmux/cmux.json files. It covers action registry entries, surface tab bar buttons, plus-button click and right-click menu behavior, custom workspace commands, right sidebar wiring, and related config cleanup.

Prerequisites

• Use the cmux-settings skill's cmux-settings helper script for global ~/.config/cmux/cmux.json reads and writes.
• Read the cmux-settings skill first when the task touches standard settings under app, terminal, notifications, sidebar, sidebarAppearance, workspaceColors, automation, browser, or shortcuts.

Reference

Global config:

cmux-settings path
cmux-settings dump --no-comments

Common structural sections in cmux.json:

• actions: action registry used by custom UI and commands.
• ui.surfaceTabBar.buttons: buttons shown in the surface tab bar.
• ui.newWorkspace.action: action triggered by a normal click on the plus button.
• ui.newWorkspace.contextMenu: menu items shown when right-clicking the plus button.
• commands: named workspace commands and layouts.
• rightSidebar: custom right sidebar wiring.
• vault: custom Vault agent registrations.

ui.surfaceTabBar.buttons can contain built-in action ids as strings or object references:

[
  "cmux.newTerminal",
  "cmux.newBrowser",
  "cmux.splitRight",
  "cmux.splitDown",
  { "action": "custom-action-id" }
]

Use ui.newWorkspace.contextMenu for plus-button right-click menus. ui.newWorkspace.rightClick is accepted by cmux as a legacy alias, but new edits should use contextMenu.

Workflow

Step 1: Inspect current config

Read the existing config before changing anything.

cmux-settings dump --no-comments

If the user names a visible UI surface, search for the related ids.

rg -n "surfaceTabBar|newWorkspace|rightSidebar|<action-id>|<label>" ~/.config/cmux/cmux.json

Step 2: Make the smallest config edit

Use the helper for global config edits. It parses JSONC and writes atomically.

Remove custom agent launch buttons from the surface tab bar while keeping built-in surface controls:

cmux-settings set ui.surfaceTabBar.buttons \
  '["cmux.newTerminal","cmux.newBrowser","cmux.splitRight","cmux.splitDown"]'

Remove one named action from a tab bar without deleting the action registry entry:

cmux-settings get ui.surfaceTabBar.buttons
# Edit the array to remove only { "action": "<action-id>" }, then set it back.

Delete an action entirely only when the user asks for the command itself to go away from every surface.

cmux-settings unset actions.<action-id>

Customize the plus button and its right-click menu:

cmux-settings set ui.newWorkspace.action '"workspace-new-cmux-worktree"'
cmux-settings set ui.newWorkspace.contextMenu \
  '[{"action":"workspace-new-cmux-worktree","title":"New cmux Worktree"},{"action":"workspace-terminal-browser","title":"Terminal + Browser"},{"type":"separator"},{"action":"cmux.newTerminal","title":"New Terminal"},{"action":"cmux.newBrowser","title":"New Browser"}]'

Step 3: Verify

Always read back the changed path.

cmux-settings get ui.surfaceTabBar.buttons
cmux-settings get ui.newWorkspace.contextMenu

Validate parseability. The strict supported-key validator may flag valid structural or newer app keys when the checked-out source list is older than the running app. If that happens, do not remove unrelated keys. Confirm the file parses and report the unrelated validator warning.

cmux-settings dump --no-comments >/tmp/cmux-config.json

Step 4: Report apply behavior

cmux watches ~/.config/cmux/cmux.json, so config edits apply after save without a rebuild. Do not run a tagged app reload for pure config or skill changes.

Rules

• Preserve unrelated custom actions, commands, menus, Vault entries, and right sidebar config.
• Do not delete action definitions just because their buttons were removed from the tab bar.
• Do not use defaults write for persistent product config.
• Do not edit repo/ for user config changes.
• Do not run app reloads for config-only or skill-only changes.
• Keep responses short and include the exact path or key changed.