Generic Messages

[peterje]

Feature Description

A generic message type allows consumers of the API to include domain-specific data on their Messages with type-safety. The current solution either require creating a custom .d.ts definition of Message or abusing the annotations field.

I propose exporting a generic Message in place of the current Message interface as follows.

type CustomFields = Record<string, JSONValue>;
export type Message<T extends CustomFields = {}> = MessageBase & T;

APIs and hooks which consume Message should be generic as well. For example,

const {append} = useChat<{filePath: string}>()
append({
  role: "user",
  content: "what is the meaning of life",
  filePath: "/files/uploaded/hitchhiker.pdf"
})

should be possible.

Use Case

The content of a message is typically just one piece of a complex LLM solution. Documents, requestIDs, and third-party tracking IDs are common requirements.

Additional context

Tagging @shuding as we briefly discussed this earlier today.

[polooner]

need this