Keep AI coding agents running overnight on a MacBook.

Overnight agent runs on a MacBook usually fail for one of six reasons: the lid closed and the Mac slept, idle sleep kicked in, the network dropped, the agent stopped to ask for permission, the battery ran out, or the Mac got too hot. Keep the Mac awake with the lid shut, pre-approve what the agent needs, plug in on a hard surface, and log a heartbeat so you can check the run in the morning. For the lid, Clamshell for Mac is a menu bar app that keeps an Apple Silicon MacBook awake with the lid closed, without an external monitor or sudo.

Quick answer

What stops an overnight run

Agents can also stop for reasons no keep-awake tool can touch: a usage or rate limit, an API error, a crashed process, or a task the agent decided was done. The heartbeat and log below help you tell these apart from sleep.

Local or cloud: check where the agent runs

Keep the Mac awake with the lid closed

• Apple's closed-display mode needs an external display, keyboard and mouse, and power. It is supported and works well if you already have that desk setup.
• sudo pmset -a disablesleep 1 works with no hardware, but it is global, needs admin rights, has no timer, and applies on battery. The risk is forgetting it. How to check and undo it.
• Clamshell changes lid behavior only while armed, shows its state in the menu bar, needs no admin rights, and never persists across a restart. Arm it from the menu, with Option held while closing the lid on Macs with a lid angle sensor, from Shortcuts, or with clamshell://arm.

Clamshell for Mac keeps your agents running with the lid closed. Free for 7 days, then $9.99 once for one Mac.

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Pre-flight checklist

1. Commit or branch first. Start the run from a clean state so the morning diff shows only the agent's work.
2. Decide the permissions up front. Claude Code's non-interactive mode takes -p with --allowedTools or --permission-mode, and recent versions add --permission-prompts none for unattended runs. codex exec is read-only by default; --sandbox workspace-write allows edits in the workspace. For other tools, find their equivalent. Grant the narrowest access that lets the task finish.
3. Write output to a file. Terminal scrollback is not a record. Log the agent's output and a timestamp heartbeat.
4. Plug in. A long run on battery is a gamble. If you must use battery, set a cutoff (see below).
5. Pick the surface. A hard, flat desk with open air around the vents. Not a bed, sofa, closed drawer or bag.
6. Disconnect external displays if you are relying on Clamshell. It pauses instead of arming while an external display is connected.
7. Arm and confirm. Check the menu bar shows armed. A URL request or shortcut is not confirmation.
8. Run a two-minute proof. Start the heartbeat, close the lid for two minutes, open it, and confirm the timestamps kept arriving.

A wrapper with a heartbeat

This zsh wrapper requests arming, writes a timestamp every minute, runs the agent, and requests disarming on exit. Swap the agent line for Codex, a build, or any other command.

#!/bin/zsh
set -e
LOG="$HOME/agent-night-$(date +%Y%m%d).log"

open "clamshell://arm"
( while true; do date -u '+beat %Y-%m-%dT%H:%M:%SZ' >> "$LOG"; sleep 60; done ) &
HB=$!
trap 'kill $HB 2>/dev/null; open "clamshell://disarm" || true' EXIT

claude -p "Run the test suite and fix any failures" \
  --allowedTools "Bash,Read,Edit" >> "$LOG" 2>&1
date -u '+done %Y-%m-%dT%H:%M:%SZ' >> "$LOG"

Power, heat and ventilation

With the lid closed, the built-in display is off, which removes a large part of a laptop's normal power draw. The rest depends on the work. A mostly idle agent waiting on API responses is light. Local builds, test suites and especially local models are heavy, and they draw the same power and make the same heat as they would with the lid open, with less room for air to move if the Mac sits on something soft.

• Plug in for overnight runs. On battery, a heavy workload can empty it well before morning.
• Leave the vents clear. Closed-lid MacBooks still need airflow. Never run a heavy job in a bag or under a blanket.
• Thermal safety is always on in Clamshell. If macOS reports serious or critical thermal pressure, Clamshell disarms toward normal lid sleep and refuses to arm until the Mac cools. That pauses your run on purpose. If it happens, cut parallel jobs or move the Mac.
• Low battery cutoff. Clamshell's Disarm on low battery is off by default. Turn it on in General settings and choose a level so an unplugged run lets the Mac sleep instead of draining flat.

Check the run in the morning

1. Read the heartbeat. Timestamps a minute apart all night mean the Mac stayed awake. A gap marks when it stopped.
2. Match gaps to sleep. pmset -g log lists sleep and wake events with timestamps. A sleep entry at the gap points to sleep; no sleep entry points to the agent, the network or a limit.
3. Read the agent's last output in the log. A question, a permission denial, or an API error explains most stops.
4. Review the diff with git status and git diff before accepting anything.
5. Disarm. If the wrapper did not, disarm from the menu bar before the Mac goes into a bag.

What Clamshell does and does not do

Frequently asked questions

Related guides

• Keep Claude Code running with the lid closed
• Keep Codex running when you close your MacBook lid
• Keep a MacBook awake with the lid closed on battery
• Why caffeinate does not work with the lid closed
• Compare Clamshell, Amphetamine, pmset and Apple's setup

Sources checked September 29, 2026: Anthropic's Claude Code cloud sessions and non-interactive mode docs, OpenAI's Codex Cloud and non-interactive mode docs, Apple's external display guidance for a closed laptop, and the macOS pmset(1) manual. Clamshell behavior is described from its app source and FAQ. No new hardware testing was done for this page. Clamshell is an independent app, not affiliated with Anthropic, OpenAI, Cursor or Ollama. Product names belong to their owners.