Clamshell
Keeps your MacBook running with the lid shut, then stands down at your battery cutoff.
About
Clamshell keeps a MacBook running with the lid shut, on battery or plugged in. Downloads finish, builds compile, backups complete, and a Mac you reach remotely stays reachable while it rides in a bag or sits on a shelf. It lives in the menu bar and runs on macOS 26 with Apple silicon.
One dial sets the battery level where Clamshell stands down, anywhere from 0 to 100 percent. A forecast turns that cutoff into hours and minutes, measured from your own Mac's closed-lid runs, so you can see what 20 percent versus 50 percent costs before you shut the lid.
Choose a hold for one time or until you turn it off. A battery at 45°C ends the hold, charger or not, and a lid shut on battery for eight hours stands down. Low Power Mode switches on during a battery hold, and Finish up keeps the Mac working for 20 minutes, then sleeps it.
A forecast measured on your Mac
The big number is hours and minutes to your cutoff, measured from your own closed-lid runs. Drag the dial and the forecast moves with it, so the cutoff becomes a time you can plan around.
One cutoff dial
Stand down anywhere from 0 percent, run it flat, to 100 percent, charger only. The dial starts at 20 percent, applies on battery, and changes without a password.
Two modes
For one time ends when you next open the lid or restart. Until I turn it off survives a restart and resumes by itself at boot.
Heat and bag safeguards
A battery at 45°C ends the hold, on the charger too, so a Mac sealed in a bag gets to sleep and cool. A lid shut on battery for eight hours stands down as well.
Finish up, then sleep
One menu item, or Control-Option-Command-P from any app: keep working with the lid shut for 20 minutes, then the Mac sleeps by itself.
A headless Mac on the charger
Plugged in with the lid shut and no display, the hold continues for as long as the battery stays under 45°C. That is the setup for a home server or a Mac you reach by screen sharing or SSH.