Clamshell vs Capsomnia: No Admin Install, No pmset Switch

Verdict: pick Clamshell for Mac to keep a MacBook awake with the lid closed. It needs no administrator at install and no privileged helper, while Capsomnia's installer needs administrator access to place a helper in /Library/PrivilegedHelperTools and add a sudoers rule. It changes lid-close sleep only, while Capsomnia switches the system-wide pmset -a disablesleep setting. Thermal protection is always on, your Caps Lock key stays a Caps Lock key, and agents can use the screen while the built-in display stays black.

No adminNo password, sudo, helper or sudoers rule

No pmsetLid-close sleep only, gone after a restart

Thermal cutoffAlways on, nothing to set up

7-day trialThen $9.99 once, 14-day refund

Clamshell for Mac keeps a MacBook awake with the lid closed, on power or battery. No admin password, no helper, no monitor. Free for 7 days, then $9.99 once.

Download free trial

Apple Silicon, macOS 14+. Notarized by Apple. 3.6 MB. Or buy now, $9.99

Same closed lid, no installer password.Clamshell overrides lid sleep with an unprivileged control only while you have it armed. Capsomnia gets there by switching a system-wide sleep setting through a helper that an administrator installs.

Capsomnia and Clamshell both keep a MacBook running with the lid shut and no external display. Capsomnia is a free, open-source menu bar app that, in its README's words, "turns Caps Lock into a physical keep-awake switch for closed-lid MacBook work". Caps Lock on disables sleep. Caps Lock off restores it. Clamshell for Mac is the app this site makes: you arm it, close the lid, and it restores normal lid sleep when you disarm, quit or open the lid after a one-close arm.

The two reach the closed lid by different routes, and that is what this page compares. Clamshell does it as an ordinary app. Capsomnia does it with an installer that needs an administrator, a root-owned helper and a system-wide setting.

Side-by-side comparison

Capsomnia cells come from its GitHub README, changelog, security policy and website, checked October 12, 2026. "Not stated" means we could not find it there; it does not mean the feature is missing.

	Clamshell Recommended	Capsomnia
Admin rights	None. No sudo, admin password, kernel extension, driver or privileged helper.	The README lists "Administrator access during installation". The uninstaller may also ask for administrator authentication.
What gets installed	A normal menu bar app.	The app in `/Applications`, a privileged helper at `/Library/PrivilegedHelperTools/capsomnia-pmset`, a sudoers rule limited to six exact helper commands, and a LaunchAgent.
How lid-closed works	Unprivileged IOKit lid sleep-state control plus an idle-sleep assertion while armed. Never changes `pmset` settings.	The helper runs `pmset -a disablesleep 1` and `0` through passwordless `sudo`. The app checks `SleepDisabled` after every change and every ten seconds.
Scope of the change	Lid-close sleep only, while armed.	System-wide. Its website says of Caps Lock on: "sleep is disabled."
The switch	Menu bar menu, right-click, Option while closing the lid on supported Macs, URL scheme or Shortcuts. Caps Lock is not used.	The Caps Lock key, or a custom shortcut. The Caps Lock light shows the state.
Extra permissions and system flags	No sudo or admin rights. Does not change `SleepDisabled`.	Accessibility permission, only if the optional "Prevent all-caps typing" is on. Optional "Hide the Caps Lock indicator" uses an undocumented system-wide macOS feature flag and needs a restart.
When it ends	Menu and Option-close arming end when the lid opens. Right-click and Shortcuts arming last until you disarm. Normal lid sleep returns on disarm or quit.	When Caps Lock is turned off, the app is quit, or an optional auto-off timer expires. The README says to turn Caps Lock off after use and confirm normal sleep has returned.
After a crash or force quit	The lid change is never saved across a restart. The direct edition can relaunch after an unexpected exit when its crash-recovery agent is permitted.	A LaunchAgent restarts the app. If it is force-killed while crash recovery is disabled or unavailable, "the last system sleep setting can remain active". Manual fix: `sudo pmset -a disablesleep 0`.
Thermal safeguard	Always on. Serious or critical thermal pressure disarms toward normal lid sleep and blocks arming until cooled.	Not stated. The README advises: "Ensure sufficient airflow and use a stable power source."
Battery safeguard	Optional low-battery disarm at a level you choose, off by default.	Not stated. An optional auto-off timer sleeps the Mac when it expires with the lid closed.
Screen for agents, lid closed	On by default. Agents can use the screen while the built-in display stays black. The Mac locks when the lid opens.	Off by default: closing the lid puts the display to sleep. Opt-in "Keep display awake" keeps the display session available and lowers the built-in display to minimum brightness while closed.
Agent detection	No. It does not detect agents.	Not stated. The README describes a manual switch.
Automation	`clamshell://arm`, `disarm`, `toggle`, and four Shortcuts actions (Arm, Disarm, Toggle, Status).	Optional `cpsm` command-line tool and agent Skill, installed as a separate package after macOS authentication. A URL scheme and Shortcuts actions are not stated.
External display connected	Pauses instead of arming.	Skips its forced display sleep, per the 1.0.2 changelog entry. External displays are not changed.
Price	7-day free trial, then $9.99 once for 1 Mac or $19.99 for 3 Macs. 14-day money-back guarantee. Also on Setapp.	Free.
Source code	Closed source.	Open source, MIT license.
Platform	Apple Silicon Mac laptops, macOS 14 or later.	Signed package: Apple silicon, macOS 14 or later. Building from source also supports Intel on macOS 13.5 or later.
Distribution	Notarized download from clamshell.dev, and Setapp.	Developer ID signed, notarized `.pkg` installer on GitHub Releases. Version 4.2.4, released October 7, 2026.

How each app keeps a closed MacBook awake

A MacBook has two separate reasons to sleep. Idle sleep happens when nobody touches it. Lid sleep happens the moment the lid closes, and a power assertion of the kind caffeinate holds does not stop it. How keep-awake apps keep a closed MacBook awake lays out the four methods apps use.

Clamshell overrides lid sleep with an IOKit control that macOS lets an ordinary app call, and holds an idle-sleep assertion while armed. Nothing asks for a password. It never touches pmset or the SleepDisabled setting.

Capsomnia uses the pmset route. Its README says: "System sleep settings require elevated privileges, so Capsomnia uses a small fixed native helper through passwordless sudo." The installer places that helper at /Library/PrivilegedHelperTools/capsomnia-pmset and adds a sudoers rule, which is why installation needs an administrator. The README is careful about the limits: the rule covers six exact commands, the helper is a compiled executable that does not invoke a shell, and the menu bar app itself does not run as root. The sleep commands the helper runs are /usr/bin/pmset -a disablesleep 1 and 0. That is the same setting as typing the command yourself, and it turns sleep off for the whole system, not only at the lid. Our guide to what pmset disablesleep does explains it.

No administrator anywhere on the left. Clamshell installs and arms as an ordinary app and changes lid sleep only while armed. Capsomnia needs an administrator once, at install, to place its helper and sudoers rule. On a managed work Mac that step can be a blocker.

What can be left switched on

Because disablesleep is a system setting, the question with any pmset app is what happens when the app is not there to switch it back. Capsomnia handles the usual cases: quitting restores normal sleep, and a LaunchAgent restarts the app after a crash and reapplies the setting that matches the Caps Lock state. Its README is also plain about the gap: "If Capsomnia is force-killed while crash recovery is disabled or unavailable, the last system sleep setting can remain active." The recovery it documents is a Terminal command with sudo:

pmset -g | grep SleepDisabled
sudo pmset -a disablesleep 0

Its usage notes add: "Turn Caps Lock off after use and confirm that normal sleep behavior has returned." Our guide to undoing pmset disablesleep walks through that check.

Clamshell has no such setting to check. It never sets SleepDisabled. Normal lid-close sleep is restored when you disarm or quit, and the lid change is never saved across a restart, so restarting always restores it.

Your Caps Lock key becomes the switch

Capsomnia's idea is that the Caps Lock light tells you the state at a glance. The cost is that the key now does two jobs. Left alone, turning sleep prevention on also turns capitals on. Capsomnia answers that with optional settings, each with its own requirement, all described in its README:

Prevent all-caps typing. Stops Caps Lock from forcing uppercase while Capsomnia is on. It needs macOS Accessibility permission, which Capsomnia uses for a local event filter that removes the Caps Lock modifier from keyboard events. The README says it does not store or send keyboard input.
Hide the Caps Lock indicator. The README says this "uses an undocumented system-wide macOS feature flag, may affect other text-cursor indicators, and takes effect after restarting the Mac". The helper edits a file in /Library/Preferences/FeatureFlags and keeps a backup so the previous value can be restored.
Custom toggle shortcut. For people who already use Caps Lock for something else. The Caps Lock light still shows the state.

Clamshell does not use the Caps Lock key. On a MacBook with a lid angle sensor you hold Option while closing the lid, and that session ends by itself when the lid opens. Arming from the menu bar menu also covers the next lid close only. There is no key to remember to turn off.

Agents, and the screen they need

Neither app detects whether an agent is running, as far as Capsomnia's README says. With both, you decide when it is on.

Clamshell is armed from the menu bar, or from a script with open "clamshell://arm" and open "clamshell://disarm", or with its Shortcuts actions. The URL request is asynchronous, so check the menu bar state before closing the lid. The Claude Code lid-closed guide has a full setup.

Capsomnia offers an optional command-line tool, cpsm, and an agent Skill. You install them from Advanced Settings as a separate package after macOS authentication, and the Skill is placed in ~/.agents/skills/ with a Claude Code link. The cpsm README says the Skill teaches agents the commands, such as setting a one-shot timer, and notes that cpsm off also puts the Mac to sleep.

The screen is the larger difference. Computer use and the iOS Simulator need a display session to work with. In Clamshell, agents can use the screen during an armed lid-closed session while the built-in display stays black, and that setting is on by default. In Capsomnia the default is the opposite: "closing the lid puts the display to sleep while work keeps running". You opt in to "Keep display awake", which keeps the display session available and lowers the built-in display to minimum brightness while the lid is closed, then restores the previous brightness when it opens.

Why Clamshell is the better pick

No administrator at install. Capsomnia's README lists administrator access during installation as a requirement. Clamshell asks for none, so it also works on Macs where you are not an admin.
No root helper and no sudoers rule. Capsomnia installs a privileged helper in /Library/PrivilegedHelperTools and a rule that lets it run through passwordless sudo. Clamshell has no helper, driver or kernel extension.
Lid-close sleep only. Capsomnia switches pmset -a disablesleep, which covers the whole system. Clamshell changes what happens at the lid, while armed, and leaves the rest of macOS sleep alone.
Nothing persists across a restart. Capsomnia's README says the last sleep setting can remain active if the app is force-killed while crash recovery is unavailable, and gives a sudo command to fix it. Clamshell's lid change is never saved across a restart.
Thermal safety you cannot switch off. Serious or critical thermal pressure disarms Clamshell toward normal lid sleep and blocks arming until the Mac cools. We found no automatic thermal cutoff in Capsomnia's README, changelog, security policy or website. Its README asks you to ensure airflow.
Caps Lock stays Caps Lock. No Accessibility permission to keep your typing lowercase, and no undocumented feature flag to hide an indicator.
Option-close ends by itself. Hold Option, close the lid, and the session ends when you open it. With Capsomnia, sleep stays disabled until Caps Lock is turned off, a timer you set expires, or the app quits.
Agents keep a screen by default. The built-in display stays black while agents can still use the screen, and the Mac locks when the lid opens.
Try it first. Free for 7 days, then $9.99 once, with a 14-day money-back guarantee on direct purchases.

Close the lid without an installer password. Clamshell is free for 7 days, then $9.99 once for one Mac.

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Apple Silicon, macOS 14+. Notarized by Apple. 3.6 MB. Or buy now, $9.99

Looking at other options? Clamshell vs Insomnia covers another free tool, and the best keep-awake apps for a closed lid compares the wider field.

Frequently asked questions

Does Capsomnia need an admin password?

Yes, at install. Capsomnia's README lists administrator access during installation as a requirement. The package installs a privileged sleep-control helper in /Library/PrivilegedHelperTools and adds a sudoers rule, so the app can later run that helper through passwordless sudo. Clamshell for Mac needs no sudo, admin rights or helper at any point.

Is Capsomnia free?

Yes. Capsomnia is free and open source under the MIT license, with a signed and notarized package on GitHub. Clamshell for Mac is free for 7 days, then $9.99 once for one Mac or $19.99 for up to 3 Macs, with a 14-day money-back guarantee on direct purchases.

What does Capsomnia do to the Caps Lock key?

It turns Caps Lock into the keep-awake switch. Caps Lock on disables sleep and Caps Lock off restores it. An optional setting stops Caps Lock from typing capitals while Capsomnia is on, and that setting needs macOS Accessibility permission. Clamshell does not use the Caps Lock key. You arm it from the menu bar, by holding Option while closing the lid on supported Macs, or from a script.

What happens if Capsomnia is force-killed while it is on?

Capsomnia's README says that if it is force-killed while crash recovery is disabled or unavailable, the last system sleep setting can remain active, and it gives sudo pmset -a disablesleep 0 as the manual recovery command. Its LaunchAgent normally restarts the app after a crash. Clamshell never sets SleepDisabled, and its lid change is never saved across a restart.

Does Capsomnia detect Claude Code or Codex?

Its README does not say so. It describes a manual switch, with an optional command-line tool and agent Skill that let an agent run Capsomnia commands. Clamshell does not detect agents either. Scripts arm and disarm it with clamshell://arm and clamshell://disarm or Shortcuts actions.

Can agents use the screen with the lid closed in each app?

In Clamshell, yes by default: agents can use the screen during an armed lid-closed session while the built-in display stays black. In Capsomnia the default is that closing the lid puts the display to sleep. Its opt-in Keep display awake setting keeps the display session available and lowers the built-in display to minimum brightness while the lid is closed.

Is there a Capsomnia alternative that needs no admin rights?

Clamshell for Mac. It keeps an Apple Silicon MacBook awake with the lid closed without pmset, sudo, an admin password or a privileged helper, and restores normal lid sleep when you disarm or quit. It costs $9.99 once after a 7-day free trial.

If you want a free, open-source tool and like a physical Caps Lock switch with an auto-off timer, Capsomnia covers that.

Ready to close the lid? Clamshell keeps your MacBook awake with no admin rights. Free for 7 days, then $9.99 once.

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Apple Silicon, macOS 14+. Notarized by Apple. 3.6 MB. Or buy now, $9.99

Related guides

Sources checked October 12, 2026: Capsomnia's GitHub README, changelog, security policy, 4.2.4 release, the cpsm README and capsomnia.com. Capsomnia was not installed or run for this page, so nothing here is a hands-on test of it. Projects change; check the repository before deciding. Clamshell is the publisher of this comparison and is not affiliated with Capsomnia, Anthropic or OpenAI. Product names belong to their respective owners.