multiple people on a singleplayer world without lan

Today me and my brother were playing minecraft on the newest snapshot. We were both on separate worlds. But, when he used commands, i was able to see them. When I used commands, however, he could not see what i did. Also, when he placed a command block with the command "/say @a" it said mine and my brother's usernames. Also, when he talked in chat, I could see it, but when I talked in chat, he could not see what I had said. In the attachment, I am pressing TAB.