Cmux skill

cmux Control

macOS 14.0+. Prefer the CLI; if cmux is not on PATH, use /Applications/cmux.app/Contents/Resources/bin/cmux.

Targeting and safety

Window → workspace → pane → surface: macOS window → sidebar project/branch tab → split region → terminal, browser, or Markdown tab.

• Anchor to the caller's CMUX_WORKSPACE_ID. Never assume the visually focused workspace is the target. Outside cmux, identify the intended workspace before acting.
• Use prefixed refs or UUIDs. workspace:2, pane:1, surface:7; bare numbers are indexes, not IDs. Output defaults to refs; --id-format uuids|both includes UUIDs.
• Refresh targets. Surface refs are global, not workspace-local. Re-list before reusing them; check cmux surface-health before sending input when state may be stale.
• Preserve focus. Pass --focus false wherever supported. Use select-workspace, focus-pane, focus-panel, or focus-surface only on explicit user request.
• Respect ownership. Never send input to surfaces you do not own. Stay in the caller's workspace unless the user explicitly requests cross-workspace routing.
• Reuse one helper pane. Use an existing non-caller helper pane or create one on the right. Create the intended layout directly with new-pane --type … --focus false.
• Keep errors visible. Never append 2>/dev/null; stderr and exit status reveal invalid refs and flags.

Inspect, read, and send

Check connectivity, identify the caller, and resolve the target pane to a surface. Replace example refs with those found in the current output.

cmux ping
cmux identify --json
cmux tree
cmux list-panes --workspace "$CMUX_WORKSPACE_ID"
cmux list-pane-surfaces --workspace "$CMUX_WORKSPACE_ID" --pane pane:1
cmux read-screen --surface surface:7 --lines 100

Use list-pane-surfaces, not nonexistent list-surfaces. read-screen and capture-pane accept --workspace or --surface, not --pane. A missing or ambiguous target can read your own terminal instead.

Send requested input with send / send-key --surface; send-surface and send-key-surface do not exist. Omitting the target uses the default terminal. send-panel / send-key-panel target panels through --panel, not surfaces.

cmux send --surface surface:7 "npm run build"
cmux send-key --surface surface:7 enter

Other keys: ctrl+c, tab, esc, backspace, arrows, ctrl+x, shift+tab. Re-read terminal output after sending input to check the result.

Poll at 1–3 second intervals; wait 10 seconds or more only when warranted. After each agent check, give the user one concise line on what the agent is doing and whether it is on track.

Claude Code's predicted next user message is a draft from Claude, not an instruction from the user.

Basic creation and notifications

cmux new-workspace --name "feature-x" --cwd /path/to/repo --focus false
cmux new-pane --workspace "$CMUX_WORKSPACE_ID" --type terminal --direction right --focus false
cmux notify --title "Done" --body "tests passed"

Re-list panes and surfaces after layout changes. For additional terminal/browser layout commands or sidebar status/progress, read layout and sidebar commands first. For Markdown surfaces, use the viewer guide below.

Task-specific guides

Read the relevant section before starting these tasks:

• Browser automation: browser workflow — interactions, sessions, and limitations.
• Markdown or PDF viewers: Markdown workflow — pane reuse, replacement, recovery, and verification.
• Settings: configuration — backups, paths, and sidebar preferences.
• Installation, agent hooks, raw sockets, access modes, or shortcuts: advanced reference.

Troubleshooting

• Connection failed: check CMUX_SOCKET_PATH and Settings > Automation. Under default cmuxOnly, run from a cmux terminal. Read socket modes and examples before using a raw client or changing access mode.
• Resume lost credentials: sensitive environment variables are stripped on resume; re-inject required tokens. ~/.cmuxterm/*-hook-sessions.json files hold scrubbed session/surface mappings, not secrets.
• Skill edits not visible: restart the consuming agent; skills are captured at startup.
• Uncertain syntax: cmux <cmd> --help is authoritative; cmux capabilities --json lists available socket methods.