I am writing a custom package wrapping Foundation Models which provides a chain-of-thought with intermittent self-evaluation among other things. At first I was designing this package with the command line in mind, but after seeing how well it augments the models and makes them more intelligent I wanted to try and build a SwiftUI wrapper around the package.
When I started I was using synchronous generation rather than streaming, but to give the best user experience (as I've seen in the WWDC sessions) it is necessary to provide constant feedback to the user that something is happening.
I have created a super simplified example of my setup so it's easier to understand.
First, there is the Reasoning conversation item, which can be converted to an XML representation which is then fed back into the model (I've found XML works best for structured input)
public typealias ConversationContext = XMLDocument
extension ConversationContext {
public func toPlainText() -> String {
return xmlString(options: [.nodePrettyPrint])
}
}
/// Represents a reasoning item in a conversation, which includes a title and reasoning content.
/// Reasoning items are used to provide detailed explanations or justifications for certain decisions or responses within a conversation.
@Generable(description: "A reasoning item in a conversation, containing content and a title.")
struct ConversationReasoningItem: ConversationItem {
@Guide(description: "The content of the reasoning item, which is your thinking process or explanation")
public var reasoningContent: String
@Guide(description: "A short summary of the reasoning content, digestible in an interface.")
public var title: String
@Guide(description: "Indicates whether reasoning is complete")
public var done: Bool
}
extension ConversationReasoningItem: ConversationContextProvider {
public func toContext() -> ConversationContext {
// <ReasoningItem title="${title}">
// ${reasoningContent}
// </ReasoningItem>
let root = XMLElement(name: "ReasoningItem")
root.addAttribute(XMLNode.attribute(withName: "title", stringValue: title) as! XMLNode)
root.stringValue = reasoningContent
return ConversationContext(rootElement: root)
}
}
Then there is the generator, which creates a reasoning item from a user query and previously generated items:
struct ReasoningItemGenerator {
var instructions: String {
"""
<omitted for brevity>
"""
}
func generate(from input: (String, [ConversationReasoningItem])) async throws -> sending LanguageModelSession.ResponseStream<ConversationReasoningItem> {
let session = LanguageModelSession(instructions: instructions)
// build the context for the reasoning item out of the user's query and the previous reasoning items
let userQuery = "User's query: \(input.0)"
let reasoningItemsText = input.1.map { $0.toContext().toPlainText() }.joined(separator: "\n")
let context = userQuery + "\n" + reasoningItemsText
let reasoningItemResponse = try await session.streamResponse(
to: context, generating: ConversationReasoningItem.self)
return reasoningItemResponse
}
}
I'm not sure if returning LanguageModelSession.ResponseStream<ConversationReasoningItem> is the right move, I am just trying to imitate what session.streamResponse returns.
Then there is the orchestrator, which I can't figure out. It receives the streamed ConversationReasoningItems from the Generator and is responsible for streaming those to SwiftUI later and also for evaluating each reasoning item after it is complete to see if it needs to be regenerated (to keep the model on-track). I want the users of the orchestrator to receive partially generated reasoning items as they are being generated by the generator. Later, when they finish, if the evaluation passes, the item is kept, but if it fails, the reasoning item should be removed from the stream before a new one is generated. So in-flight reasoning items should be outputted aggresively.
I really am having trouble figuring this out so if someone with more knowledge about asynchronous stuff in Swift, or- even better- someone who has worked on the Foundation Models framework could point me in the right direction, that would be awesome!
