Cmux Settings

cmux-settings

cmux reads user settings from ~/​.config/​cmux/​cmux.json (JSONC). The app installs a file watcher; saving the file applies changes immediately, no restart needed. Legacy ~/​.config/​cmux/​settings.json is read only as a fallback for keys not present in cmux.json.

Schema: https://raw.githubusercontent.com/​manaflow-ai/​cmux/​main/​web/​data/​cmux.schema.json. The authoritative path list lives in Sources/​CmuxSettingsJSONPathSupport.swift in the cmux checkout, and the installed skill includes a generated copy in references/​all-keys.md. Top-level sections are app, terminal, notifications, sidebar, sidebarAppearance, workspaceColors, automation, browser, and shortcuts. Non-settings sections (actions, ui, commands, vault, rightSidebar) coexist in the same file.

Helper script

Use the bundled helper for every read/​write. It strips JSONC comments, writes atomically, and validates keys against the schema.

# From a cmux checkout
skills/​cmux-settings/​scripts/​cmux-settings <subcommand>

# From an installed Codex skill
~/​.codex/​skills/​cmux-settings/​scripts/​cmux-settings <subcommand>

For brevity in the rest of this doc, assume the script is on $PATH as cmux-settings. To make it so for a session from a checkout: export PATH="$PWD/​skills/​cmux-settings/​scripts:$PATH".

Subcommands:

--file <path> overrides the target file (useful for --file ~/​.config/​cmux/​settings.json when the user keeps things in the legacy file).

Workflow

1. Confirm the change. If the user named a setting in plain English (e.g. "make the sidebar tint match the terminal background"), look it up first.

   cmux-settings list-supported | rg -i 'sidebar.*terminal|terminal.*sidebar'
   

2. Set the value. JSON literals (true, false, numbers, arrays, objects) must be valid JSON. Plain words are stored as strings.

   cmux-settings set sidebarAppearance.matchTerminalBackground true
   cmux-settings set app.appearance dark
   cmux-settings set shortcuts.bindings.toggleSidebar cmd+b
   cmux-settings set shortcuts.bindings.newTab '["ctrl+b","c"]'
   cmux-settings set browser.hostsToOpenInEmbeddedBrowser '["localhost","*.internal.example"]'
   

3. Verify by reading back and validating.

   cmux-settings get sidebarAppearance.matchTerminalBackground
   cmux-settings validate
   

4. Tell the user it auto-reloaded. No app restart. If they want to revert, run cmux-settings unset <key>.

Quick reference

• Appearance: app.appearance = "system" | "light" | "dark", app.appIcon, app.menuBarOnly, app.minimalMode.
• Sidebar tint: sidebarAppearance.matchTerminalBackground, sidebarAppearance.tintColor, sidebarAppearance.tintOpacity (0..1).
• Sidebar details: sidebar.hideAllDetails, sidebar.showBranchDirectory, sidebar.showPullRequests, sidebar.showPorts, sidebar.showLog.
• Notifications: notifications.dockBadge, notifications.sound (enum incl. "none", "custom_file"), notifications.customSoundFilePath, notifications.hooks (array).
• Browser: browser.defaultSearchEngine, browser.theme, browser.openTerminalLinksInCmuxBrowser, browser.hostsToOpenInEmbeddedBrowser.
• Automation: automation.socketControlMode (off | cmuxOnly | automation | password | allowAll), automation.portBase, automation.portRange.
• Shortcuts: shortcuts.bindings.<actionId> = "cmd+b", ["ctrl+b","c"], null, or "" to unbind. See references/​shortcut-actions.md.

For the full list of settings, defaults, and descriptions, run cmux-settings list-supported or read references/​all-keys.md.

Rules

• Only edit cmux.json. Never edit settings.json unless the user explicitly asks; it is legacy and only read when the key is absent from cmux.json.
• Never tell the user to restart cmux to apply a change. The file watcher reloads on save.
• Always validate after a bulk edit: cmux-settings validate. Unknown keys mean the user pasted a key the app does not consume.
• Do not blindly overwrite top-level sections (actions, ui, commands, vault, rightSidebar). They live in the same file and contain non-settings config the user has hand-tuned.
• Shortcut action ids must match the schema enum. Look them up in references/​shortcut-actions.md before binding.
• Color values must be #RRGGBB. Opacities are 0..1.
• For settings the user expressed in app-level language (e.g. "Settings > Notifications > Dock badge"), translate to the matching JSON path first; the docs page at web/​app/[locale]/​docs/​configuration/​page.tsx mirrors the schema 1:1.