Idlewild 1.2.3

Idlewild 1.2.3

Idlewild 1.2.2

Idlewild 1.2.2

Idlewild 1.2.1

Idlewild 1.2.1

Idlewild 1.2.0

Idlewild 1.2.0

Idlewild 1.1.1

Idlewild 1.1.1

Idlewild 1.1.0

Idlewild 1.1.0

Idlewild 1.0.1

Idlewild 1.0.1

Idlewild 1.0.0

A macOS menu bar app that notices when a process has been running away with a
CPU core, works out why, and offers to stop it.

Activity Monitor is a microscope, not a smoke alarm — you have to already suspect
something before you go look. Idlewild is the smoke alarm.

What it does

Watches for processes that hold above a threshold (default 80% of one core) for
a sustained period (default 5 minutes). When one does, it takes a stack sample,
classifies what the process is actually doing, and tells you in a sentence:

a web page stuck throwing JavaScript errors in a loop
garbage-collection thrash, usually a memory leak
regular-expression backtracking
a tight loop in the program's own code
threads look idle — the CPU time may be elsewhere

That last one matters as much as the rest: it stops the app accusing a process
whose threads are merely parked.

Then it offers three things:

• Force Quit — SIGKILL.
• Pause It — SIGSTOP. Stops the burn without losing the process's state, so
  a stuck browser tab can be resumed rather than lost.
• Ignore / Always Allow — dismiss once, or add it to the allowlist.

Cost

A monitor must never become the thing it hunts.

	CPU per hour	% of one core
Idlewild (120 s cadence, steady state)	161 ms	0.0045%
A typical menu bar CPU meter, for scale	~130,000 ms	3.6%

Measured on an M1 MacBook Air over a five-minute window with app startup
excluded. The About panel shows Idlewild's own consumption, so it stays
accountable to the standard it enforces.

Apple Silicon only

That is deliberate, and it buys real signal. rusage_info_v4 carries a per-QoS
breakdown of where a process spent its CPU time, which on Apple Silicon maps onto
physical cores: user_interactive work runs on P-cores at high clock, while
background work parks on E-cores and barely warms the die. Two processes at 100%
CPU can differ enormously in how much heat they produce, and Idlewild flags the
expensive kind with "this is what heats the machine".

Requirements

• macOS 14 or later, Apple Silicon.
• Notifications are optional — the menu bar icon turns into a flame either way.

Installing

Open the DMG and drag Idlewild to Applications. The app is signed with a
Developer ID certificate, notarized by Apple, and stapled, so it opens normally
with no right-click-to-open workaround.

Turn on Launch at login in Settings so it survives a reboot.

Not on the Mac App Store

It cannot be. Under the App Sandbox, proc_listpids, proc_pid_rusage and
kill() all return EPERM — the app can neither find, measure, nor stop a runaway
process, and no App Store entitlement lifts that. This was tested rather than
assumed; Scripts/sandbox-probe.sh reproduces it on any Mac.

Known issues

• If notifications never prompt and the app does not appear in
  System Settings → Notifications, stale LaunchServices registrations are the
  likely cause. See docs/DEVELOPMENT.md for the fix.
• Browser tabs are reported as "Safari web page" rather than by page title.
  Getting the tab title requires private API; Activity Monitor uses it, we do
  not. Force-quitting the process makes Safari name the tab in its reload notice.

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Idlewild-1.0.0.dmg

SHA-256  0631ae0e0fe5110f2df0b5139dd52a75014d1370781709157081827f27cda4d3

Signed with Developer ID, notarized by Apple, and stapled. Verified by mounting
the image and running Gatekeeper against the app inside it, so it opens with no
warning even offline.