macOS Fan Monitor¶

???+ tip inline "The one-line summary"

**Why is my Mac hot — and what should I close?** A native macOS terminal
app that answers that at a glance, on MacBook Pros *and* fanless MacBook
Airs, without asking an LLM each time.

fm is a lazygit / yazi-style Textual TUI built for the members of the Agentic Builders Collective. It watches your Mac's real signals — fan RPM or CPU throttling, temperatures, per-core CPU, RAM breakdown, swap, and the live process list — figures out why the machine is hot, ranks the processes worth closing, and lets you terminate one with a single key. A full-screen ABC mark assembles while the first readings load, then the persistent header identifies the app as Fan Monitor - Agentic Builders Collective.

ABC boot screen

fm TUI

The core idea¶

A hot Mac comes from two very different causes, and the fix for each is different:

Regime	Signal	What's happening	Fix
CPU	load high and CPU% high	something is genuinely computing	close / wait on the CPU hog
Memory (swap thrash)	load high but CPU% low	RAM is exhausted; processes are blocked on disk, not computing	close memory hogs
Thermal	neither, but macOS is throttling	residual heat the cooling can't shed yet	let it cool, close the largest processes

The memory regime is the sneaky one — ps %cpu and Activity Monitor's "top CPU" both miss it, because a process stuck paging shows low CPU. fm infers it from the combination of swap pressure, the memory compressor, load, and how much CPU is actually being used. That inference is the heart of the tool.

MacBook Air¶

No fan? fm notices, retitles the FAN tile to COOLING, reads the CPU speed limit from pmset -g therm, and adds a 🌡️ thermal verdict. The CPU and Memory tabs show which cores are pinned and whether the machine is swapping.

fm on a fanless Mac

Get started¶

pipx install macos-fanmon
fm

See Getting Started for the full walkthrough, and User Guide for every screen and key.

Jump to¶

Getting Started — install & first run
User Guide — tiles, tabs, keys, killing
How It Works — the diagnosis logic
The Algorithm — scoring & thresholds (exact)
Watchdog Integration — correlate with your own watchdog
Troubleshooting — common issues, Air notes
Roadmap — what's next
Contributing — dev setup & tests

Safety model¶

Read-only by default. fm reads the SMC, pmset, Mach CPU counters, ps, vm_stat, and your watchdog logs. It never writes to hardware.
Nothing dies unless you say so. The k key shows a confirmation prompt and re-checks each PID is still alive before sending SIGTERM. It is never automatic.
System daemons are never killable. WindowServer, Spotlight, suggestd, and friends are symptoms, not causes — the tool explains them instead of offering to kill them.

About ABC¶

The Agentic Builders Collective is a Singapore-based community of 1,000+ people building agentic software. fm is community software: it wears ABC's wordmark and colours, and the peach → coral gradient from the logo is the heat scale on every gauge.

License¶

MIT — see LICENSE.