Google Messages has been going through major changes recently UI wise and feature wise as well. Google has completely redesigned the chat screen UI and the bottom bar which hosts all the stuff like input box, attachment, emoji buttons etc. Along with all these changes one change which Google brought was the input box redesign. I don't want to say much just look at the screenshot below how it currently looks. 

As you can see in the above screenshots, the input box was just above the attachment and emoji buttons and many people disliked it (as far as I know it). It was kind of a new UI as compared to what we are used to in other apps. But seems like Google has realised or recieved enough feedback to backtrack on this change. 

In the latest version of Google Messages beta, Google has brought back the single line input box, I mean the input box is now similar to other apps. Here are some screenshots of the new input box. It doesn't leave space below the input box and houses only the attachment (+) button.

I personally enabled it with a flag, but it looks like Google will roll out this change for sure and we will see it rolling out for people shortly. 

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