f.lux not working on M5 Pro or M5 Max? Here's why, and what works.

This page is our own test, with dates and sources. We make Atapa, so read the parts about Atapa as a vendor’s words. Everything else here you can check on your own Mac in a minute.

Which Macs are affected?

Apple’s thread 819331 names the M5 Pro and M5 Max MacBook Pros, on the built-in display and on external displays, and the MacBook Neo on an external display. Reports for the base M5 conflict, and we have not tested one, so this page does not claim either way. On Intel Macs and on M1 through M4, gamma tables still apply and f.lux works as before.

Atapa runs on any Apple silicon Mac with macOS 14 or later. Intel Macs are not supported in 1.0.

How do I confirm it on my Mac in one minute?

1. Open f.lux preferences and drag the Daytime slider all the way to the left. In version 42.2 it reads 2700K (Tungsten).
2. Look at a white window, for example an empty Finder window. If it stays white while f.lux says it is on, you are in the bug.
3. Open System Settings, Displays, Night Shift. Turn on “Turn on until tomorrow” and move Color temperature to More Warm. The screen should turn mildly orange.

That is the whole test. Night Shift uses a different path and still moves the color. The gamma-table control does not. Do not use a screenshot to judge it: macOS composites captures separately, so a capture can look tinted while the panel in front of you is not.

Why does the app say it succeeded?

The call that sets a gamma table returns success. Reading the table back returns exactly the table that was just set. The display pipeline never applies it. So the app has no way to know; every value it can check agrees with it.

On our 14-inch M5 Pro on 26 October 2026, macOS 27.2 (build 26B123), we set a deep-red 256-entry table on the built-in display. The result code was 0. The readback matched at 0, 3 and 6 seconds. The panel did not change. The result was the same on macOS 27.0.1.

This is also why Atapa does not try to detect the bug from code. During setup it shows a method check and asks you to look at the screen, because the screen is the only honest readout.

What still works today?

Three things, in order of effort.

Night Shift. Built into macOS, nothing to install. On our M5 Pro at More Warm on 29 October 2026 it was mildly orange, never red. Apple does not publish a kelvin number; independent measurements put the warmest step around 2700 to 3000K.

Atapa. Atapa is a Mac menu bar app that warms and dims the screen from daylight (6500K) to deep red (500K) through the evening. It works on M5 Pro and M5 Max MacBook Pros, where apps that tint through a gamma table do nothing. It costs $12 once for all of your own Macs, with a 14-day trial and a 14-day refund. It has no account and no network code. It requires macOS 14 or later on Apple silicon. Kevin Hofmann makes it at SOULRISE LLC. It tints in the display pipeline, not through the gamma table, so the bug does not touch it.

BetterDisplay’s non-gamma path. Its maintainer wrote on 13 October 2026 that image adjustments now go through a compositor filter instead of the color table. That is display configuration and brightness work, not an evening schedule, and it is the right tool for that job.

Does Sundown work on this bug?

Sundown’s own app answers. On our 14-inch M5 Pro, macOS 27.2, on 29 October 2026, Sundown 1.6.4 showed this at the top of its window:

“Warming isn’t available on this Mac yet. Your Mac’s display ignores the usual way apps warm the screen, so for now Sundown leaves your screen’s color, brightness, Night Shift and True Tone as they are. We’re working on it.”

Sundown’s blog describes its flicker-free mode as dimming through the gamma table, which is the mechanism this bug ignores. They say they are working on it. We recheck after each Sundown update and date the line under What changed.

Credit where it is due: Sundown has a large guide library, a Windows build in progress, and far more customization than Atapa, including key pop-up styles, a Sound Studio, panel backgrounds, ambient-light dimming and room adaptation. If you are on an M1 to M4 Mac and want those, it is a fair choice. Its 7-day trial asked for a card at checkout on 2026-10-29 (“$39/year after your 7-day trial”); Atapa’s 14-day trial does not.

Will Apple fix it?

Apple’s Developer Technical Support reproduced the bug. It is filed as FB22273730, with duplicates FB22273782 and FB23444164. BetterDisplay’s maintainer wrote on 13 October 2026 that it was still with Apple engineering. It is open on macOS 27.0.1 and on 27.2.

We retest after each macOS update, with a 10-minute look at the panel, and add a dated line under What changed at the bottom of this page. When Apple fixes it, f.lux will work on these Macs again. Atapa does not depend on the fix either way.

Will the tint show in screenshots or on a call?

Not in screenshots. With the color matrix, a capture taken during the tint shows true color: tested on 2026-10-28 on the M5 Pro, macOS 27.2, with a capture before and during a visible orange tint. The tint is applied after the point where macOS captures the image.

Screen sharing uses the same capture path, so it should show true color to the other side as well. One FaceTime check is still open, and the result will be dated here. On older Macs where Atapa falls back to an overlay layer, captures do include the tint.

Transcript of the demo video

The video is still to be filmed. The words below are what it will say, and they match this page.