Supported iPhones have now started getting the iOS 18 software update, and alongside many of the interesting changes that the update brings, iPhone users are also getting RCS support to improve the Android-iPhone messaging experience. However, support is not yet enabled for all carriers, including Google Fi Wireless.
Google has stated that only the Cupertino tech giant has the ability to enable RCS interoperability for iPhone users that are on Google Fi. The Google MVNO has completed all the necessary work to support iPhone RCS on its end, and it's now waiting on Apple.
With the official iOS 18 launch, Apple enabled RCS on the big US carriers AT&T, T-Mobile, and Verizon. It's currently not enabled for all MVNO networks though, including Google Fi and Mint Mobile.
Apple has added "RCS messaging" to the "Wireless carrier support and features for iPhone" help article. You can see there which carrier in the United States supports this interoperability on the iPhone as of now, and I suppose Apple will continue updating this article with more carriers quite soon.
Meanwhile, a Google spokesperson told 9toGoogle that right now, Fi users with an Android phone will be able to communicate over RCS with iPhone users that have RCS interoperability enabled. Of course, the spokesperson underlined that Apple has to enable RCS interoperability for iPhone users on Fi, and hopefully, the Cupertino tech giant will do so in the near future.
RCS stands for Rich Communication Services. Basically, it's a communication protocol standard for instant messaging on mobile phones. It replaces SMS and MMS on cellular networks with a more modern and richer communication system.
The fact that Apple has now integrated RCS with iPhones means a more seamless texting experience between an iPhone and an Android phone. The tech works alongside Apple's iMessage and allows you to send high-quality pictures and videos, chat over Wi-Fi and cellular data, receive 'read' receipts and other features.
I personally think that given how Apple has been known to keep a closed ecosystem, this step is a very welcome improvement. Although not every carrier is currently graced by Apple with RCS, this is bound to happen quite soon and make the texting experience between different OSes a more pleasant and enjoyable one for many people.