System Sentinel

Find out what is wrong with your Mac, why, and fix it in a click.

Formerly CPU Sentinel: installing 0.7.0 replaces it and keeps your settings and history.

System Sentinel lives in the menu bar. It opens on Checkup, which finds what is wrong on its own (running hot, memory short, battery draining fast, the disk filling, an app keeping the Mac awake or crashing) and lets you pick what feels wrong from eleven symptoms, each with fix buttons. It samples every process every 5 seconds and shows the load on a gauge, as charts and as plain-English insights. It records which apps used the most CPU over the last day and week, and explains what each macOS process is for. The Energy tab shows the Mac's power draw, which apps cost the most battery, what keeps the Mac awake and how the battery is wearing. When something gets stuck at high CPU it tells you, and it can kill that process in one click or automatically.

Install

Easiest: open Terminal (Cmd+Space, type Terminal, press Return), paste this line and press Return:

curl -fsSL https://raw.githubusercontent.com/andrewbakercloudscale/system-sentinel/main/install.sh | bash

It runs install.sh: downloads the latest release, installs it to Applications, clears the quarantine flag and opens it. Run it again any time to update. To share it, click Share with a friend in About (or Share at the bottom of the main window).

Or keep a copy of the script in your home folder. Paste this into Terminal. It downloads the latest release, installs it to Applications, clears the quarantine flag (the app is not notarised by Apple) and launches it:

cat > ~/install-system-sentinel.sh <<'EOF'
#!/bin/bash
# Installs (or updates to) the latest System Sentinel release in /Applications.
set -euo pipefail
REPO="andrewbakercloudscale/system-sentinel"
APP="${SYSTEM_SENTINEL_APP:-/Applications/System Sentinel.app}"
TMP="$(mktemp -d)"
trap 'rm -rf "$TMP"' EXIT

echo "== Downloading the latest release"
if command -v gh >/dev/null 2>&1 && gh auth status >/dev/null 2>&1; then
  gh release download --repo "$REPO" --pattern '*Sentinel-*.zip' --dir "$TMP"
else
  URL="$(curl -fsSL "https://api.github.com/repos/$REPO/releases/latest" \
    | grep -o '"browser_download_url": *"[^"]*\.zip"' | head -1 | cut -d'"' -f4 || true)"
  if [ -z "$URL" ]; then
    echo "Could not reach the release. If the repository is private, install GitHub CLI"
    echo "(brew install gh), run: gh auth login, then run this script again."
    exit 1
  fi
  curl -fL --progress-bar -o "$TMP/System-Sentinel.zip" "$URL"
fi
ZIP="$(ls "$TMP"/*.zip | head -1)"

echo "== Installing to $APP"
pkill -x SystemSentinel 2>/dev/null || true
pkill -x CPUSentinel 2>/dev/null || true        # its name before 0.7.0
rm -rf "/Applications/CPU Sentinel.app"
ditto -x -k "$ZIP" "$TMP/unzipped"
rm -rf "$APP"
ditto "$(ls -d "$TMP"/unzipped/*.app | head -1)" "$APP"
# Not notarised by Apple: clear only the download quarantine flag.
xattr -dr com.apple.quarantine "$APP"

if [ -z "${SYSTEM_SENTINEL_NO_OPEN:-}" ]; then
  echo "== Launching"
  open "$APP"
fi
echo "Done: $(defaults read "$APP/Contents/Info" CFBundleShortVersionString). Look for the red chip in the menu bar."
EOF
chmod +x ~/install-system-sentinel.sh && ~/install-system-sentinel.sh

Run ~/install-system-sentinel.sh again any time to update. You need macOS 14 or later, on an Apple chip (M1 or later) or an Intel Mac. The script checks first and says so if this Mac cannot run it; on an account that is not an administrator it installs to your own Applications folder. Look for the red chip in the menu bar.

Build from source instead (needs Xcode or its command line tools, xcode-select --install):

git clone https://github.com/andrewbakercloudscale/system-sentinel.git
cd system-sentinel
bash scripts/build-app.sh      # runs the tests, builds, installs to ~/Applications, launches

Why

On a Mac that feels slow, Activity Monitor gives you a list of numbers. It doesn't tell you:

• which processes are a problem rather than a passing spike;
• what a process is, like mediaanalysisd, knowledgeconstructiond or WindowServer;
• whether it's safe to kill a process;
• which app used the most CPU over the last day or week;
• what is draining the battery, or keeping the Mac awake with the lid open.

System Sentinel answers each of those. It was built after a macOS energy logger (PerfPowerServices) used one and a half cores for 37 hours and nothing said so.

Highlights

Checkup: what's wrong, and the fix	Found on its own, or picked from eleven symptoms (Slow or hot, Battery drains, Disk full, Wi-Fi or internet, Won't sleep, Mic or camera, App crashes or won't open, Bluetooth, Display or dock, iCloud stuck, Restarted by itself). Then the checks, performance first and security last, and the everyday restarts (sound, Bluetooth, Wi-Fi, Finder, iCloud sync). Ignore what is on purpose.
Route test	mtr-style, for a minute up to an hour: loss, delay and jitter at every hop, a chart of when it happened, and a report to send your provider.
Insights in plain English	"WindowServer is busy because the screen is being captured", "Photos is analysing your library", "3 Chrome tab processes use 40% together". Click More to see what is happening, each process involved and who started it, and numbered steps to fix it.
One-click fixes	Insights carry buttons that act, not just advise: Quit Slack, Let the Mac sleep (stop 5 caffeinate), Turn on Low Power Mode, or the exact System Settings page. A minute after you quit or kill something it tells you what changed: "power 14 W → 6 W, about 4 hours more battery".
Heat and power alerts	A pop-up when the Mac runs hot or draws more than your chosen watts (default 25 W) for your chosen minutes (default 3), naming the likely culprit with Kill and Ignore buttons.
Explain with ChatGPT	The sparkles button opens ChatGPT with a ready-made prompt: the process, its CPU history, your Mac model and its busiest processes, asking what it is and how to bring it down.
Battery and energy	Live power draw in watts and a 7 day chart, time left, energy use and idle wakeups by app with an estimate of the minutes each costs per hour on battery, sleep blockers (including caffeinate "on behalf of" a terminal tool) with a Kill button, and battery health: capacity, cycles and macOS's own verdict.
Beyond the CPU	Memory pressure and swap, graphics load, screen brightness and displays, network and disk by app, how the Mac sleeps (dark wakes and their causes, charge lost with the lid shut), battery wear over time with a projected date for 80%, and charging habits. Chrome's tabs ranked by likely energy use, with Show and Close.
Performance and efficiency cores	Per-core load on the Overview, split into the efficiency cores macOS uses for background work and the performance cores that draw most of the power.
Reports	"Today in brief" in plain sentences, comparison with your usual week, apps working far above their own usual, and a weekly report on the Events tab with an optional Monday notification. Export it as Markdown or PDF.
History from 30 minutes to a week	CPU by app over the last 30 minutes, 3, 6 or 24 hours, or 7 days, the heaviest users and when each one peaked. Kept across restarts and sleep.
Know when a process started	Every process shows its uptime, so a renderer that has been busy for 13 days is easy to spot.
Kill anything, carefully	One-click kill for your own processes, your password for root ones, a separate sudo button with a warning for core macOS processes, and Force kill (kill -9) for anything that ignores a kill. A banner says whether it worked and who relaunched it if it came back.
Rules that remember	Per app: alert (the default), ignore, ignore during work hours or overnight, auto-kill, auto-kill on battery, or auto-kill only under 30% battery. Auto-kill is limited to 3 kills an hour per app. Rules (a page on Settings) also lists every launch agent and daemon that starts by itself, with its CPU.
Dark mode, and a window you can move	Every screen is designed for light and dark. Open in window moves the panel into a normal window you can drag and resize. The menu bar can show CPU load, watts or battery beside the icon.

Screenshots

Overview

The load on a gauge, what is using the CPU now and over the last hour, cores and memory.

Processes

The top 30, each with uptime, a 15 minute trend, averages, memory and Kill.

Trends

A page on Overview. CPU by hour, stacked by app, and the heaviest users over 24 hours or 7 days.

Energy

Power draw, energy by app, what keeps the Mac awake, and battery health.

Events

Everything flagged, killed or auto-killed over 7 days.

Settings

What counts as a stuck process, and launch at login.

Dark mode

Every screen has its own dark design.

Documentation

• Online user guide: every screen with screenshots. Help (Cmd ?) in the app opens it.
• User guide: every screen, reading the charts, insights, killing processes, rules, notifications, privacy, reset, uninstall and troubleshooting.
• Process guide: what the common macOS background processes are, why they get busy, and whether to kill them.
• PLAN.md: why it was built, the design and what is next.

Safety, in short

• Core macOS processes (WindowServer, kernel_task, launchd, Finder, Dock and others) are never killed automatically and have no Kill button. Their sudo kill button warns you what will happen first.
• Root processes need your admin password and are never auto-killed.
• Auto-kill applies only to apps you opted in, at most 3 times an hour each.

Privacy

Nothing about you, your files or your apps is uploaded, and there is no tracking. History stays in ~/Library/Application Support/SystemSentinel/. To test the connection the app itself pings 1.1.1.1 every 3 minutes, looks up www.apple.com and loads captive.apple.com every 10 minutes, checks the certificates of github.com, npm and PyPI every 30 minutes, and asks GitHub for updates. The speed test, route test and DNS map contact Apple, Cloudflare, Google and Zscaler only when you run them. Explain opens ChatGPT with a prompt describing the process and your Mac, so OpenAI receives it. Details.

Uninstall

Quit it (Quit at the bottom of the panel), then in Terminal:

rm -rf "/Applications/System Sentinel.app" ~/Library/Application\ Support/SystemSentinel
defaults delete consulting.cloudscale.systemsentinel

Then remove it from System Settings, General, Login Items, and from Privacy & Security if you gave it Full Disk Access or Automation. To start fresh without uninstalling, use Settings, Diagnostics, Reset all settings….

Development

swift test                     # 229 tests, including a real CPU burner that must be flagged and killed
swift build                    # debug build
bash scripts/build-app.sh      # test, build, bundle, install, launch
bash scripts/release.sh        # zip and .dmg in dist/; signs and notarises
                               # when DEVELOPER_ID and NOTARY_PROFILE are set
bash scripts/publish-release.sh NOTES.md  # release.sh, then tag, push and publish all
                               # three files, and check the website's .dmg link serves it

To render every tab, in light and dark, to PNG files without touching your data:

"build/System Sentinel.app/Contents/MacOS/SystemSentinel" --snapshot /tmp/shots --after 600 --expand 2

--after sets how many seconds to sample before rendering (default 22). --expand opens only the first n insights (default all). The README screenshots are made this way.

The code is split into SentinelCore (sampling, detection, history, insights; tested) and SystemSentinel (the SwiftUI app).

Licence

MIT. See LICENSE.