Why Insomniac is like this

What was broken

A build, an export, a large upload, an agent working through a task: they all die the moment the machine decides nobody is around. The tools that prevent that, caffeinate and the apps wrapped around it, do exactly one thing and consider the job done.

It is not done. A laptop held awake with the display off, in a bag, on a bed, vents against a desk, gets hot. Nothing in those tools is watching, which means the user is being asked to make a thermal judgement they have no instruments for.

And then there is the myth, which is the single most requested feature in this category: keeping a Mac running with the lid closed and nothing attached. On Apple Silicon the lid sensor forces sleep and no software overrides it. Not pmset disablesleep, not caffeinate, not an IOKit assertion. Every tool promising otherwise is either wrong or quietly relying on clamshell mode.

Who it’s for

• Developers running long builds, exports, uploads or agents who need the machine to stay up
• People who leave a Mac working while they are elsewhere and would rather it not overheat
• People who want one switch and a timer, not a scripting environment

Who it isn’t for

• People who want schedules, triggers and scripted rules. Amphetamine is better at that and our comparison says so
• Anyone expecting closed-lid operation on Apple Silicon with nothing attached. The hardware does not allow it

Rules we don’t break

Decided once, so they never have to be argued about again.

• Never promise what the hardware will not do. An earlier version of this project's own README claimed closed-lid keep-awake with nothing attached. It was wrong, it was corrected in public, and the app now states in its own interface which behaviour your particular Mac supports.
• Safety is the feature, not a setting. The thermal layer is always watching. Keeping a Mac awake without watching the heat is the thing this app exists to replace.
• It should switch itself off. Auto-off timers, live cutoffs, crash recovery. “On until I remember” is how a Mac stays awake all night.
• Advise, don't just report. A temperature reading is useless to most people. How long staying awake is safe right now is not.
• One switch, and free. It lives in the menu bar and does one job, which is also why it costs nothing.

What it actually does

• Keep-awake with a timer. Blocks idle sleep for a duration you choose, with a countdown, safe restore of the previous state, and recovery if the app or the machine crashes.
• Thermal advisory and live cutoff. Reads the thermal state, advises a safe duration from it, and stops on its own before it becomes unsafe.
• Ambient awareness. Local weather, fetched keylessly, adjusts the advice and degrades gracefully when it is unavailable.
• Silent toggling. A privileged helper installed through SMAppService, driven over XPC, so switching it on does not ask for your password every time.
• Honest lid behaviour. Rock-solid lid-open keep-awake, the option to turn the display off, and a clear statement of what a closed lid does on your specific Mac.

What it refuses to do

The most useful part of any note like this. Every line has a reason attached.

• Scripting, schedules and triggers. A different product for a different person, and Amphetamine already does it properly.
• Overriding the lid sensor. Not a decision. A fact. Nothing in software does this on Apple Silicon, so nothing here pretends to.
• Charging for it. A single-switch utility. A price would not survive its own comparison page.

How we’ll know it worked

• A long job finishes unattended, and the Mac is cool when you come back.
• The suggested duration gets accepted rather than overridden, which means the advice is trusted.
• The safety cutoff fires occasionally. If it never fires, either nobody pushes their machine or the threshold is wrong.
• Nobody is surprised by what a closed lid does, because the app told them first.

Where it could go wrong

• Marketing drifting ahead of the hardware. The category's standard failure, and this project has already made it once. Every page describing the app has to keep matching what the app says in its own UI.
• Thermal state is coarse. The advice is built on the state macOS exposes, not per-sensor readings. A conservative guide, not an instrument.
• A privileged helper is a serious component. Silent toggling means an installed helper and XPC. It removes a password prompt and raises the bar for correctness and signing.
• Apple Silicon and Intel genuinely differ. The closed-lid answer is different on each, which makes the honest explanation longer than the marketing sentence people expect.

On the recordThis project shipped a README claiming something the hardware will not do, and then corrected itself in public rather than quietly. That correction is the reason the lid question gets four sentences on this page instead of one confident clause.

What’s next

• Keep the lid explanation in front of people rather than in a footnote.
• Nothing dated. All four planned milestones are built and shipped.