Keep a clamshell Mac awake reliably: caffeinate -is LaunchAgent + toggle script + 97-line Swift menu bar app that shows the live pmset assertion state (truth, not config)

awake.sh

#!/bin/bash
# awake — toggle the keep-awake LaunchAgent (fi.dui.keepawake, caffeinate -is).
# The -s (PreventSystemSleep) is what survives monitor-pull with the lid closed
# on AC (A/B isolated 2026-08-15; idle-class apps lose that pull 4/4).
# AC-only by design: on battery the Mac sleeps normally regardless.
#
#   awake          show status (assertion truth, not config)
#   awake on       load the agent, verify the assertion appears
#   awake off      unload the agent, verify the assertion is gone
set -u
PLIST="$HOME/Library/LaunchAgents/fi.dui.keepawake.plist"
LABEL="fi.dui.keepawake"
UID_N=$(id -u)

held() { pmset -g assertions | grep -q "PreventSystemSleep named: \"caffeinate"; }

status() {
  if held; then
    pid=$(launchctl print "gui/$UID_N/$LABEL" 2>/dev/null | awk '/pid =/{print $3}')
    echo "AWAKE — PreventSystemSleep held (agent pid ${pid:-?}). Survives monitor-pull, lid closed, on AC."
  else
    echo "SLEEPY — no PreventSystemSleep assertion. Monitor-pull with lid closed will sleep the Mac."
  fi
}

case "${1:-status}" in
  on)
    launchctl bootstrap "gui/$UID_N" "$PLIST" 2>/dev/null
    sleep 1
    held && status || { echo "FAILED: agent loaded but no assertion appeared — check: launchctl print gui/$UID_N/$LABEL"; exit 1; }
    ;;
  off)
    launchctl bootout "gui/$UID_N/$LABEL" 2>/dev/null
    sleep 1
    held && { echo "FAILED: assertion still present after unload"; exit 1; } || status
    ;;
  status|*)
    status
    ;;
esac

AwakeMenubar.swift

// AwakeMenubar — menu-bar truth indicator + toggle for the fi.dui.keepawake
// LaunchAgent (caffeinate -is). Shows the live assertion state, never config:
//   cup (filled)  = PreventSystemSleep held (survives monitor-pull, lid closed, on AC)
//   zzz           = not held (that pull will sleep the Mac)
//   dotted circle = unknown (before the first read, or while toggling)
// Icons are SF Symbols template images, so they match the menu bar's own
// monochrome and adapt to light/dark. Left-click toggles via
// ~/.local/bin/awake on|off. Polls every 5s, reads off the main thread.
// Built locally with swiftc; no third-party code.
import AppKit

enum AwakeState { case unknown, awake, sleepy }

@discardableResult
func run(_ cmd: String, _ args: [String]) -> (Int32, String) {
    let p = Process()
    p.executableURL = URL(fileURLWithPath: cmd)
    p.arguments = args
    let pipe = Pipe()
    p.standardOutput = pipe
    p.standardError = Pipe()
    do { try p.run() } catch { return (127, "") }
    p.waitUntilExit()
    let data = pipe.fileHandleForReading.readDataToEndOfFile()
    return (p.terminationStatus, String(data: data, encoding: .utf8) ?? "")
}

func readState() -> AwakeState {
    let (code, out) = run("/usr/bin/pmset", ["-g", "assertions"])
    guard code == 0, !out.isEmpty else { return .unknown }
    return out.contains("PreventSystemSleep named: \"caffeinate") ? .awake : .sleepy
}

func symbol(_ name: String, _ desc: String) -> NSImage? {
    let img = NSImage(systemSymbolName: name, accessibilityDescription: desc)
    img?.isTemplate = true
    return img
}

let awakePath = NSString(string: "~/.local/bin/awake").expandingTildeInPath

final class App: NSObject, NSApplicationDelegate {
    var item: NSStatusItem!
    var busy = false
    let iconAwake = symbol("cup.and.saucer.fill", "awake")
    let iconSleepy = symbol("zzz", "sleepy")
    let iconUnknown = symbol("circle.dotted", "unknown")

    func applicationDidFinishLaunching(_ n: Notification) {
        item = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
        item.button?.action = #selector(clicked)
        item.button?.target = self
        show(.unknown)
        poll()
        Timer.scheduledTimer(withTimeInterval: 5, repeats: true) { _ in self.poll() }
    }

    func show(_ state: AwakeState) {
        switch state {
        case .awake:
            item.button?.image = iconAwake
            item.button?.toolTip = "AWAKE — PreventSystemSleep held. Monitor-pull safe (AC, lid closed). Click to disable."
        case .sleepy:
            item.button?.image = iconSleepy
            item.button?.toolTip = "SLEEPY — monitor-pull with lid closed will sleep the Mac. Click to enable."
        case .unknown:
            item.button?.image = iconUnknown
            item.button?.toolTip = "Reading keep-awake state…"
        }
    }

    func poll() {
        guard !busy else { return }
        DispatchQueue.global().async {
            let state = readState()
            DispatchQueue.main.async { if !self.busy { self.show(state) } }
        }
    }

    @objc func clicked() {
        guard !busy else { return }
        busy = true
        show(.unknown)
        DispatchQueue.global().async {
            let target = readState() == .awake ? "off" : "on"
            run("/bin/bash", [awakePath, target])
            let state = readState()
            DispatchQueue.main.async { self.busy = false; self.show(state) }
        }
    }
}

let app = NSApplication.shared
app.setActivationPolicy(.accessory)
let delegate = App()
app.delegate = delegate
app.run()

fi.dui.keepawake.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>fi.dui.keepawake</string>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/bin/caffeinate</string>
		<string>-is</string>
	</array>
	<key>RunAtLoad</key>
	<true/>
	<key>KeepAlive</key>
	<true/>
</dict>
</plist>