A message to a working chat queues at once, and provider errors stay off the header
A message sent with rpc prompt to a chat that is already working is queued as a follow-up at once, and provider error text never shows in the header.
Sending a message with bandicot rpc prompt to a chat that was still working used to wait about thirty seconds and then fail as busy. The message is now queued as a follow-up straight away, and the answer says which run took it. If that chat takes no more input, the answer says so at once and points to follow_up.
When a model provider turned a request down, the header could show the provider's own reply, which can be long or quote a key. It now shows the same plain sentence as the note in the chat.