Google released an exciting update for its assistant iOS app today, which supports Siri shortcuts and for the first time opening lines for communication between the two competing assistants.
Siri and Google Assistant have historically been unable to collaborate in any way, but thanks to the opening of Siri via shortcuts in iOS 12, which changes now. With the latest update, you can set up a shortcut in iOS for immediate, via Siri, trigger a command you want to provide Google's assistant.
The shortcut you want to set up immediately for the assistant is one that only launches the app and triggers the voice recognition. This shortcut will be available to set up as a suggestion in Settings, and if you want consistency with other Google devices, you can create your custom trigger phrase like "Ok Google" or "Hi Google." That way, when you say the phrase via Siri, the assistant will start and immediately start listening to your command ̵
In addition to setting up a default shortcut for triggering the assistant, the Google app views each command you give the assistant as a shortcut option in IOS Settings. Because of this, for all requests you regularly make by the assistant, you can set up individual shortcuts for each individual, complete with its own custom trigger statements. The limitation of your device being unlocked means that these shortcuts can never run in the background, but in addition to the disadvantage, the possibilities of integrating the assistant with Siri are extremely wide now.
Google has unfortunately not built any kind of settings screen into the Assistant app to get shortcuts, but since all recent commands you've made are available from Settings ⇾ Assistant ⇾ Siri & Search ⇾ Shortcuts, it's not a big problem for those who know what they are doing.  Google Assistant's resolution of Siri shortcuts is simply the last proof of what we already knew: the shortcuts are a game exchange for Siri. No shortcuts do not solve Apple's assistant reliability issues, but it's quite remarkable that I can now set up custom Siri sentences that trigger Google's own assistant and even specific assistant requests. Perhaps for a few days, the app can handle these requests in the background, but at least I'm happy with what we have here.
Google Assistant is available on the App Store.