Function handleSubmit

frontend/src/hooks/useChatStream.ts:120–154

(e: React.FormEvent<HTMLFormElement>)

      const userInput: ChatInputType = {
        chatId: targetChatId,
        message,
        model: model ?? selectedModel,
        role: 'user',
      };
      if (saveUser) {
        saveMessage({
          variables: {
            input: userInput as ChatInputType,
          },
        });
      }

      // The agent loop runs on the backend, against the project's real files.
      // The bubble appears with the first text delta rather than up front, so a
      // failed turn does not leave an empty message behind.
      // The turn is built as steps, not as one growing string: the agent
      // narrates, runs a tool, narrates again, and only its last words are the
      // answer. `content` still holds the joined text so everything that reads
      // a message as plain text keeps working.
      const flush = () =>
        setMessages((prev) => {
          const next: Message = {
            id: replyId,
            role: 'assistant',
            content: steps
              .filter(
                (s): s is Extract<TurnStep, { kind: 'text' }> =>
                  s.kind === 'text'
              )
              .map((s) => s.text)
              .join(''),
            createdAt: new Date().toISOString(),
            steps: [...steps],
          };
          return prev.some((m) => m.id === replyId)
            ? prev.map((m) => (m.id === replyId ? { ...m, ...next } : m))
            : [...prev, next];
        });