Remnant characters when tab completing with ohmyzsh

I found my way to fix it :
Modify the last line of the .oh-my-zsh/themes/agnoster.zsh-theme file

PROMPT='%{%f%b%k%}$(build_prompt) '

to

PROMPT='%{%f%b%k%}$(build_prompt)%{ %}'

It works. (@^0^@)/
See GitHub #10598