How to disable the assist input when the home button is long pressed? I have removed Google Now in order to assign long press on home button to open another app. But recently it comes back with a different interface I'm familiar with. I guess the phone just has updated it. 

However I'm unable to disable or uninstall it. In Google Play I can't find which app has just been updated. In the setting of the app there is no option to disable it. 

These are some system Google apps that's under my suspicion: Google Services Framework, Google Partner Setup, Google One Time Init, Google Play Store and Google Play services. But I find no evidence to against them.
It turns out that it's actually from Firefox, not Google. To disable this, go to Setting › Apps › Configure apps (the gear button) › Default Apps › Assist &amp; voice input and change to none: