Anti-Sleep (macOS caffeinate)

When to Use

• Use when the user wants the Mac to stay awake during a long supervised task.
• Use when a build, download, or automation run should not be interrupted by sleep.

Keep the Mac awake using the built-in caffeinate command. No install needed.

Quick start — the standard command

caffeinate -d -i -t 7200    # full power: screen stays on + no idle sleep, for 2 hours

Duration is -t <seconds>: 2h = 7200, 7h = 25200, overnight (9h) = 32400.

Aggressiveness levels

Flags	Effect
-i	prevents idle system sleep only (screen may still dim/lock)
-d	prevents display sleep (screen stays on)
-d -i	default choice — screen on + system awake
-d -i -s	adds -s: prevents sleep even on AC power semantics; -s only works when plugged in
-u -t 1	simulates user activity — wakes the display right now

Default to -d -i -t <seconds> unless the user says otherwise.

Tie to a process instead of a timer

caffeinate -d -i -w <PID>          # stays awake until that process exits (great for builds)
caffeinate -i npm run build       # wraps a command; exits when the command finishes

Run it in a visible terminal (cmux pane)

Prefer running it in the user's own terminal pane so it's visible and easy to Ctrl+C. In cmux (read the cmux skill first if interacting with panes):

cmux send --surface surface:<N> "caffeinate -d -i -t 25200\n"

Otherwise run it as a background Bash task. Never block your own foreground shell with it.

Verify and monitor

pgrep -fl caffeinate                       # is it running? shows exact flags
ps -o etime= -p <PID>                      # how long it's been running
pmset -g assertions    # inspect PreventUserIdleSystemSleep / PreventUserIdleDisplaySleep        # confirm sleep assertions are active

Gotcha: caffeinate prints nothing and holds the prompt — it looks "stuck" or like Enter wasn't pressed. It isn't stuck. Verify with pgrep, not by looking at the terminal.

Expiry: with -t it exits silently when time runs out — no notification. If the user asks "is it still on?" after hours, check pgrep first; it may simply have expired.

Keyboard backlight

caffeinate cannot keep the keyboard backlight on — it has its own inactivity timer with no CLI/API on Apple Silicon (researched 2026-07). Fix is manual, one-time: System Settings > Keyboard > "Turn keyboard backlight off after inactivity" > Never.

Stop early

kill <recorded-caffeinate-PID>    # or Ctrl+C in the pane running this task

Record the PID of the process started for this task; verify its command before stopping it. Do not stop unrelated caffeinate sessions by a broad pattern.

After starting: confirm to the user the PID, the flags, and the wall-clock time it will expire.

Limitations

• Adapted from davidondrej/skills; verify local paths, tools, credentials, and agent features before acting.
• For commands, remote access, scheduling, browser automation, or file-changing workflows, get explicit user approval and confirm the target environment first.