Coolstead
Built a native macOS menu-bar app that monitors thermal conditions and applies a gradual, safety-bounded fan curve without replacing macOS thermal protection.
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Project notes
Active project
Designing steadier cooling for a Mac
- Estimated reading time
- About 2 minutes
- In this project story
- 6 sections
Coolstead is a native macOS menu-bar experiment that begins cooling earlier than the default fan policy without treating maximum fan speed as the answer. It reads thermal state and sensor data, applies a gradual fan curve, and gives control back to macOS whenever active cooling is disabled.
The product is deliberately conservative. Fan control touches hardware behavior, so every feature is designed around limits, invalid-data handling, and a reliable return to automatic mode.
Outcomes
Returns every controlled fan to automatic mode when cooling stops or the app quits
Caps requested speed at 75% of each fan's reported range
Supports fanless Macs with a monitoring-only experience
Goals
Respond before heat becomes uncomfortable with a smooth curve instead of an abrupt maximum-speed switch.
Keep safety visible in the architecture rather than leaving it to interface copy.
Support different Mac hardware including fanless devices that can still benefit from monitoring.
Remain reversible so quitting, disconnecting, or losing trustworthy sensor data restores automatic control.
What I built
A native menu-bar app
for current thermal state, temperature readings, fan monitoring, and balanced-cooling controls.
A privileged helper path
for the narrow set of operations that require elevated permission.
A bounded control model
that clamps requests to the fan’s reported range and never asks for more than 75% of that range.
Gradual target ramping
so fan requests move toward the curve instead of jumping directly to it.
Monitoring-only behavior
for unsupported or fanless hardware.
Technical highlights
- Native platform work
Swift,SwiftUI, macOS app packaging, menu-bar behavior, and a bundled helper.- Hardware integration
reverse-engineered SMC behavior through the MIT-licensed
macos-smc-fanpackage.- Failure handling
missing or invalid readings disable writes, and lifecycle events return controlled fans to automatic mode.
- Workspace tooling
a small
pnpmandTurboreposhell keeps build, test, type-check, and desktop-bundling commands consistent.
Results
- A safety-first thermal loopwhere guardrails are part of the control path.
- A quieter product philosophyfocused on earlier, gradual cooling rather than aggressive fan behavior.
- A native foundationthat can be tested in monitoring-only mode before privileged control is approved.
Why it matters
System utilities earn trust through what they refuse to do.
Coolstead is an exercise in making a small hardware-facing tool useful while keeping its limits explicit.
De este proyecto
Dentro del trabajo.
Product story
Coolstead: Safety-first cooling for a Mac
What it takes to design a native fan-control utility around bounded requests, invalid sensor data, reversible behavior, and macOS as the final safety layer.
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