const stream = await this.anthropic.messages.stream({
  model: 'claude-sonnet-4-20250514',
  max_tokens: 4096,
  system: SYSTEM_PROMPT,
  tools: this.anthropicTools,
  messages,
});for await (const event of stream) {
  if (event.type === 'content_block_delta') {
    const delta = event.delta as any;
    if (delta.type === 'text_delta' && delta.text) {
      onToken(delta.text);
    }
  }
}
const finalMessage = await stream.finalMessage();