Function handleChatResponse

frontend/src/hooks/useChatStream.ts:83–118

(targetChatId: string, message: string)

  useEffect(() => {
    setCurrentChatId(chatId);
  }, [chatId]);

  const [saveMessage] = useMutation(SAVE_MESSAGE);

  const [createChat] = useMutation(CREATE_CHAT, {
    onCompleted: async (data) => {
      const newChatId = data.createChat.id;
      setCurrentChatId(newChatId);
      await handleChatResponse(newChatId, input, pendingImagesRef.current);
      window.history.pushState({}, '', `/chat?id=${newChatId}`);
      logger.info(`new chat: ${newChatId}`);
    },
    onError: () => {
      toast.error('Failed to create chat');
      setLoadingSubmit(false);
    },
  });

  const handleChatResponse = async (
    targetChatId: string,
    message: string,
    images?: string[],
    // The first turn of a project chat arrives with its user message already
    // stored server-side (createProject saves it); re-saving would double it.
    saveUser = true,
    // The chat's own stored model. State-held selectedModel lags one render
    // behind, so the auto-started first turn passes this directly.
    model?: string
  ) => {
    const replyId = `${targetChatId}-${Date.now()}`;
    // Outside the try so the catch can tell "failed before anything streamed"
    // (safe to retry) from "died mid-turn" (retrying would rerun real work).
    const steps: TurnStep[] = [];
    try {
      setInput('');
      const userInput: ChatInputType = {
        chatId: targetChatId,
        message,
        model: model ?? selectedModel,