The app is capable of offering a reboot, but in this instance it didn’t. Is there a reason why the app and notification can get out of sync?
(Ignore me highlighting “service reboot” text, which is not the same as a “system reboot”)
The terminal output is from a flatpak update, they usually do not require a reboot. The notification you get at the bottom is from you updating the core system packages with pacman -Syu that most of the time require a reboot.
What do you mean ‘out-of-sync’ here?
Your screenshot clearly shows a “Reboot recommended!” notification.
Cachy-Update has given me the option to reboot the system in previous times, but now it only showed the notification.
Cachy-Update will give an option to reboot if it updates a kernel, if other core packages are updated it just gives the notification. There may be other package updates that will trigger a reboot option instead of just the notification.
all related to core update (especially kernels) need to restart the system for taking effect
as to why there is prompt “Reboot now or not [y/n]” because the prompt there giving you an options, in case you in the process doing something big like rendering file for example in blender
Why the devs think that the user wouldn’t want that same option to reboot when something that it’s not the kernel requires it? The [N] is in uppercase, so there wouldn’t by any additional [Enter] needing to be pressed.
well if you know it needs a reboot, then reboot. You need a prompt to hit y to do that?
Then why there’s a prompt to begin with?
Someone felt the need to half-implement this feature.
Cachy-Update doesn’t show a reboot notification. The notification you are seeing doesn’t come from Cachy-Update, it comes from something else 
Technically speaking, the kernel is the only package that *strictly* requires a reboot on update and is therefore the only thing Cachy-Update is taking care of on that front. The rest is either already handled via the services restart step or up to the user’s discretion.
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For the record, the notification you’re seeing comes from (which is not part of Cachy-Update): cachyos-hooks/cachyos-reboot-required at master · CachyOS/cachyos-hooks · GitHub
There’s no inconsistency on the Cachy-Update side nor “half-implemented feature”, it’s just two different things.