AG-UI Protocol: Where should I set user_id?

[weimch]

The current protocol sepcification define RunAgentInput below:

class RunAgentInput(ConfiguredBaseModel):
    thread_id: str
    run_id: str
    state: Any
    messages: List[Message]
    tools: List[Tool]
    context: List[Context]
    forwarded_props: Any

As it states, the thread_id is ID of the conversation thread and the run_id ID of the current run. There is no place to set user_id in RunAgentInput.

I also found the Message specifion below:

type UserMessage = {
  id: string
  role: "user"
  content: string
  name?: string
}

As it states, the name is Optional name of the sender. But it seems not reasonable to set user_id here, because one user may trigger multipe threads and in one thread, there is only one user. Put user_id here looks like multiple user in one thread.

Should the sepcification consider add user_id to RunAgentInput?