Minecraft 17w48a, Minecraft 17w50a, Minecraft 18w01a, Minecraft 18w02a, Minecraft 18w05a, Minecraft 18w06a, Minecraft 18w08b, Minecraft 18w11a, Minecraft 18w19a, Minecraft 1.13-pre2, Minecraft 1.13-pre3, Minecraft 1.13-pre4, Minecraft 1.13-pre5, Minecraft 1.13-pre6
The command autocompletion tries too much to be helpful and overrides going back and forth in the chat history.
Example: command key, give @p stone, Enter, command key, up arrow
Expected: Getting a stone, then having chat open with "/give @p stone" in the text box.
Actual result: Getting a stone, then having chat open with "/" and a suggested "xp" in it.
This prevents quickly going back a few entries in the last executed commands list.