Got a problem using final_answer tool

[th0x11]

Hey guys, I'm using this route.ts code

`import { anthropic, AnthropicProviderOptions } from '@ai-sdk/anthropic';
import { convertToModelMessages, hasToolCall, streamText, tool, UIMessage, smoothStream, stepCountIs } from 'ai';
import { get_company_info } from './tools';
import z from 'zod';

const webSearchTool = anthropic.tools.webSearch_20250305({
maxUses: 5,
});

export async function POST(req: Request) {
try {
const { messages }: { messages: UIMessage[] } = await req.json();

const result = streamText({
  model: anthropic('claude-sonnet-4-20250514'),
  providerOptions: {
    anthropic: {
      thinking: { type: 'enabled', budgetTokens: 12000 },
    } as AnthropicProviderOptions,
  },
  system: 'You are a helpful financial analyst assistant. Answer concise and to the point. Dont hesitate to ask the user for confirmation or details when confused or not sure. USE THE FINAL_ANSWER TO PROVIDE THE FINAL ANSWER TO THE USER.',
  headers: {
    "anthropic-beta": "interleaved-thinking-2025-05-14",
  },
  tools: {
    get_company_info,
    web_search: webSearchTool,
    final_answer: {
      description: 'Provide the final answer to the user.',
      inputSchema: z.object({
        answer: z.string().describe('The final answer to show tothe user.'),
      }),
      execute: async ({ answer }) => {
        return answer;
      }
    },
  },
  stopWhen: [
    stepCountIs(100),
  ],
  messages: convertToModelMessages(messages),
  experimental_transform: smoothStream({
    delayInMs: 70,
    chunking: 'word',
  }),
});

return result.toUIMessageStreamResponse();

} catch (error) {
console.error('Chat API error:', error);
return new Response(
JSON.stringify({ error: 'An error occurred while processing your request.' }),
{
status: 500,
headers: { 'Content-Type': 'application/json' },
}
);
}
}`

for my AI agent and using useChat to handle the frontend, i don't understand why the tool call to final_answer isn't streamed but only appear when the tool-call is finished.

i've also tried using final_answer as the stopWhen condition with hasToolCall but i get the same behaviour.

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