coke

Disable sleep on macOS.

No root. No kernel extension. No background daemon. One binary.

Important

USE AT YOUR OWN RISK

Background

Clamshell mode is defined as running a MacBook with the lid closed, an external display connected, and AC power attached. In clamshell mode, macOS does not sleep on lid close. Idle sleep from inactivity is not disabled.

coke sets the same bit (0x02) via kPMSetClamshellSleepState, preventing sleep on lid close regardless of whether an external display or AC power is present. It also creates an idle sleep assertion (same as caffeinate -i) to prevent sleep from inactivity in any circumstance.

In clamshell mode, the mask is redundant — powerd already has the bit set. The idle sleep assertion still applies (idle sleep is independent of clamshell mode). Coke's unique value is keeping the machine awake with the lid closed when you don't have an external display or AC power.

caffeinate -i prevents idle sleep but does not prevent sleep on lid close. If you close the lid without an external display and AC power, caffeinate will not keep the machine awake. coke will.

Usage

coke             # disable sleep (foreground, Ctrl+C to stop)
coke off         # re-enable clamshell sleep (manual cleanup)
coke status      # show current lid/sleep state

While coke is running, the machine will not sleep — neither from closing the lid nor from idle timeout. On clean exit (Ctrl+C, SIGTERM, SIGHUP), the idle sleep assertion is released and normal idle sleep behavior resumes. The clamshell flag is cleared unless the system is in clamshell mode (external display + AC), in which case the flag is left intact to avoid desyncing powerd (see Behavior on exit).

Install

Homebrew

brew tap maltekliemann/coke
brew install coke

From source

make
make install

Requires Xcode command line tools (xcode-select --install).

Behavior on exit

On clean exit, coke checks whether the system is in clamshell mode (external display connected and AC power attached):

• Clamshell mode active: The mask is left intact. powerd has the same bit set and tracks it internally — clearing it would desync powerd's state. powerd only re-sends the bit on zero↔non-zero transitions of its internal tracking variable, so once desynced, it won't recover until a display or power source change.

• Clamshell mode not active: The mask is cleared. If the lid is closed at that moment, the machine sleeps immediately. This is how the XNU kernel works: IOPMrootDomain evaluates clamshell sleep policy the instant clamshellSleepDisableMask drops to zero. There is no userspace mechanism to clear the flag without triggering this evaluation. Amphetamine (CDMManager) uses the same API and has the same behavior.

How it works

coke prevents sleep through two independent mechanisms:

Clamshell sleep (lid close): IOConnectCallScalarMethod with selector kPMSetClamshellSleepState on the IOPMrootDomain user client sets the kClamshellSleepDisablePowerd bit in the kernel's clamshellSleepDisableMask. The flag is globally sticky — RootDomainUserClient::clientClose does not undo it, so it persists across IOKit connection open/close cycles. coke re-asserts the flag every second to recover if another tool clears it.

Idle sleep: An IOPMAssertion of type kIOPMAssertionTypePreventUserIdleSystemSleep prevents the system from sleeping due to inactivity. This is the same mechanism caffeinate -i uses. The assertion is per-process and automatically released by the kernel if the process dies.

No root or entitlement is required. The IOPMrootDomain user client has kIOUserClientEntitlementsKey = false and the kPMSetClamshellSleepState selector has no clientHasPrivilege gate. This is the same API that Amphetamine uses from the App Store sandbox.

Multi-instance coordination

Multiple instances coordinate via flock() on a per-user lock file. Each running instance holds LOCK_SH (shared lock) for its lifetime. On exit, an instance tries a non-blocking upgrade to LOCK_EX (exclusive). If the upgrade succeeds, it is the last instance and conditionally resets the clamshell flag (see Behavior on exit). If it fails, other instances still hold LOCK_SH, so the flag stays set.

The idle assertion needs no coordination — each process holds its own, and the kernel releases it automatically on process death.

Crash behavior

On SIGKILL or crash, the kernel closes the process's file descriptors (releasing the flock) and releases the idle assertion. The clamshell flag, however, is a global kernel flag with no process ownership — it remains set until coke off or reboot.

Safety

Important

By using coke, you accept full responsibility for any consequences.

• Clean exit (Ctrl+C, SIGTERM, SIGHUP) releases the idle assertion and conditionally clears the clamshell flag (preserved in clamshell mode)
• SIGKILL or crash leaves the clamshell flag set until coke off or reboot
• Thermal throttling and emergency shutdown (SMC) remain active
• User-initiated sleep (power button, Apple menu) still works
• State resets on reboot regardless