OS X copy paste into Terminal adds fdbf bfb9 b083 to beginning and end of selection
Answered here:

https://superuser.com/questions/1045432/os-x-copy-paste-into-terminal-adds-fdbf-bfb9-b083-to-beginning-and-end-of-select/1047996#1047996

This error has to do with a feature known as bracketed pasted mode[1]. Neovim does not support it yet[2]. You get the error above if an application acts like it can support that mode, but fails to support it.

In neovim open a terminal window. With 'always' in the clipboard, run the following:

pbpaste | xxd


There should be no errors. Now run the following:

cat | xxd


Enter ⌘-v followed by Ctrl-D.

You should expect to see the errors. In the second case, input is being handled by the application, which wraps the input with special bytes. The padded bytes are sent as stdin.