In a LAN world, all OP players can use commands, but the UI and autocompletion are only accessible by the host player
Created Issue:
In a LAN world, all OP players can use commands, but the UI and autocompletion only appear to the host player
Added Linked Issues:
relates to
Probably due to tab-completion not being implemented for multiplayer yet.
Source
Is this still an issue in 18w01a?
Seems to be fixed.