Messages API 响应现在包含 usage.output_tokens_details.thinking_tokens，报告计费输出令牌中有多少是扩展思考令牌。

Messages API 响应现在包含 usage.output_tokens_details.thinking_tokens，用于报告计费输出令牌中有多少是扩展思考令牌。在流式传输时，该细分仅出现在最终的 message_delta 事件中。无需 beta 标头。

The Messages API response now includes usage.output_tokens_details.thinking_tokens, reporting how many of the billed output tokens were extended thinking. When streaming, the breakdown appears only on the final message_delta event. No beta header is required.