HTTP/1.1 200 OK
Content-Type: image/png
Cache-Control: public, max-age=259200, immutable

<binary image data>

{
  "error": {
    "code": 404,
    "type": "not_found_error",
    "message": "素材不存在、已过期或已被自动清理",
    "details": {
      "upstream_code": "ASSET_NOT_FOUND"
    }
  },
  "request_id": "req_xxx"
}

{
  "error": {
    "code": 500,
    "type": "internal_error",
    "message": "素材存储读取失败",
    "details": {
      "upstream_code": "STORAGE_READ_FAILED"
    },
    "retryable": true
  },
  "request_id": "req_xxx"
}

{
  "error": {
    "code": 503,
    "type": "service_unavailable_error",
    "message": "当前环境未配置素材存储",
    "details": {
      "upstream_code": "STORAGE_NOT_CONFIGURED"
    },
    "retryable": true
  },
  "request_id": "req_xxx"
}