Hi. I noticed the same problem, so I made a pull request. I hope you find it helpful.
However, if you write it simply, the following writing style is implicit, but it is easy.
def create
message = Message.create!(params.require(:message).permit(:content))
respond_to do |format|
format.turbo_stream do
render turbo_stream: turbo_stream.append(:messages, message)
end
format.html { redirect_to messages_url }
end
end