Keep Mac Awake During Long Tasks Using Caffeinate

Anti-Sleep keeps a Mac awake for a long supervised task using the built-in caffeinate command - no install needed. The standard invocation is:

caffeinate -d -i -t 7200

where -t <seconds> sets the duration (7200 for 2 hours, 25200 for 7 hours, 32400 for an overnight 9-hour run). Flag combinations control aggressiveness: -i alone only prevents idle system sleep (the screen may still dim or lock), -d alone keeps the display on, -d -i together (the default choice) keeps the screen on and the system awake, -d -i -s adds sleep prevention that only applies while plugged into AC power, and -u -t 1 simulates user activity to wake the display immediately. Instead of a fixed timer, it can tie to a process: caffeinate -d -i -w <PID> stays awake until that process exits, or caffeinate -i npm run build wraps a command and exits when it finishes - well suited to a build that runs an unpredictable length of time.

Use it whenever a build, download, or supervised automation run on a Mac should not be interrupted by sleep. It runs preferably in the user's own visible terminal pane (a cmux surface, via cmux send) so it can be watched and Ctrl+C'd, or as a background Bash task - never blocking the agent's own foreground shell.

Input is a duration or a PID/command to tie the wake state to. Output is a running caffeinate process with no terminal output at all - it silently holds the prompt, which looks stuck but is not, and it exits with no notification once a -t timer expires. Verification is done separately: pgrep -fl caffeinate confirms it is running and shows its exact flags, ps -o etime= -p <PID> shows elapsed time, and pmset -g assertions | grep -i deny confirms the sleep assertions are actually active. pkill -f "caffeinate -d -i" or Ctrl+C in its pane stops it early.

macOS's built-in caffeinate, pmset, and pgrep/ps utilities only - no external dependency. It cannot keep the keyboard backlight on, since that has its own inactivity timer with no CLI or API on Apple Silicon as of the source's research; the only fix is a one-time manual change in System Settings > Keyboard > "Turn keyboard backlight off after inactivity" > Never.

Anyone running a long, unattended build, download, or automation task on a Mac who needs the machine to stay awake for the duration without buying or installing a separate utility.