asResponder method

AgentResponder asResponder({ List<ChatMessage> history()?, })

Adapts this provider to AgentResponder, for ChatController's managed send().

Tool calls are dropped in this mode — a Stream<String> cannot represent them. Use sendMessage when the model may call tools.

Pass history (typically () => controller.messages) so the provider sees prior turns.

Implementation

AgentResponder asResponder({List<ChatMessage> Function()? history}) {
  return (userMessage) {
    final base = history != null ? history() : const <ChatMessage>[];
    // ChatController.send() calls beginAssistantMessage() -- which appends
    // an *empty* streaming placeholder -- before invoking the responder, so
    // `base` already ends with that placeholder by the time this closure
    // runs. Strip empty assistant messages so the provider sees the user's
    // message as the true last turn, not an empty stub.
    final conversation = [
      for (final m in base)
        if (!(m.role == ChatRole.assistant && m.isEmpty)) m,
    ];
    // Stream has no whereType() (that's an Iterable method) -- narrow with
    // where()+cast() instead.
    return streamEvents(conversation)
        .where((event) => event is TextDelta)
        .cast<TextDelta>()
        .map((event) => event.text);
  };
}