Oversize message causes a 400 Bad Request loop

[ashward]

Start a chat conversation.
Go to http://en.wikipedia.org/wiki/List_of_unicode_characters and CMD/CTRL+A CMD/CTRL-C to copy the entire page contents.
Open the network tab of your browser dev tools.
Paste the copied page into the chat window and send it.
Chat gets stuck in a loop sending messages that return HTTP 400s.