聊天完成块对象

chat.completion.chunk 是流式返回（stream: true）时每个 SSE 数据块的格式。

对象示例

{
  "id": "chatcmpl-abc123",
  "object": "chat.completion.chunk",
  "created": 1677652288,
  "model": "gpt-4o",
  "system_fingerprint": "fp_44709d6fcb",
  "choices": [
    {
      "index": 0,
      "delta": {
        "role": "assistant",
        "content": "你好"
      },
      "finish_reason": null
    }
  ]
}

最后一个块（finish_reason 不为 null）

{
  "id": "chatcmpl-abc123",
  "object": "chat.completion.chunk",
  "created": 1677652288,
  "model": "gpt-4o",
  "choices": [
    {
      "index": 0,
      "delta": {},
      "finish_reason": "stop"
    }
  ]
}

字段说明

字段	类型	说明
id	string	本次请求的唯一 ID（与所有块相同）
object	string	固定为 "chat.completion.chunk"
created	integer	创建时间（Unix 时间戳）
model	string	实际使用的模型 ID
system_fingerprint	string	系统配置指纹
choices[].index	integer	候选结果索引（通常为 0）
choices[].delta.role	string	仅第一个 chunk 包含，值为 "assistant"
choices[].delta.content	string/null	当前块的文本内容增量
choices[].delta.tool_calls	array	工具调用增量（工具调用时出现）
choices[].finish_reason	string/null	结束原因；生成中为 null，结束时为 "stop" 等

完整流响应格式

data: {"id":"chatcmpl-abc","object":"chat.completion.chunk","model":"gpt-4o","choices":[{"index":0,"delta":{"role":"assistant","content":""},"finish_reason":null}]}

data: {"id":"chatcmpl-abc","object":"chat.completion.chunk","model":"gpt-4o","choices":[{"index":0,"delta":{"content":"你"},"finish_reason":null}]}

data: {"id":"chatcmpl-abc","object":"chat.completion.chunk","model":"gpt-4o","choices":[{"index":0,"delta":{"content":"好"},"finish_reason":null}]}

data: {"id":"chatcmpl-abc","object":"chat.completion.chunk","model":"gpt-4o","choices":[{"index":0,"delta":{},"finish_reason":"stop"}]}

data: [DONE]

流结束的标志是 data: [DONE]，收到此事件后停止读取。