推論モデルが空のコンテンツを返すのはなぜですか？

{
  "error": {
    "message": "上游返回了空响应。",
    "type": "shell_api_error",
    "code": "empty_response"
  }
}

{
  "choices": [
    {
      "index": 0,
      "message": { "role": "assistant", "content": "" },
      "finish_reason": "length"
    }
  ],
  "usage": {
    "prompt_tokens": 1500,
    "completion_tokens": 300,
    "completion_tokens_details": { "reasoning_tokens": 300, "text_tokens": 0 }
  }
}

import json
from openai import OpenAI

client = OpenAI(api_key="YOUR_API_KEY", base_url="https://api.apiyi.com/v1")

resp = client.chat.completions.create(
    model="gpt-6.1-sol",
    messages=[{"role": "user", "content": "your question"}],
    max_tokens=2000,
)

choice = resp.choices[0]
usage = resp.usage
print("finish_reason:", choice.finish_reason)
print("content:", repr(choice.message.content)[:100])
print("completion_tokens:", usage.completion_tokens)
print("reasoning_tokens:", getattr(usage.completion_tokens_details, "reasoning_tokens", None))