Opus 4.8 新特性 Mid-conversation System Messages 实战：对话中插系统指令的正确姿势

messages 数组里只能有 user 和 assistant 两种角色
system 必须通过顶层 system 参数传入,且只能在对话最开始

messages 数组里可以出现 role: "system",插在 user 回合之后
仍受占位规则约束(见下文)
保留 prompt caching 能力

from anthropic import Anthropic

client = Anthropic(
    api_key="sk-xxx",
    base_url="https://gw.claudeapi.com"
)

messages = [
    {"role": "user", "content": "我想退款"},
    {"role": "assistant", "content": "好的,请问订单号是?"},
    {"role": "user", "content": "我已经投诉到 12315 了,你们必须 24 小时内退"},
    # 检测到敏感关键词,插入更严格的合规指令
    {"role": "system", "content": "用户已升级至投诉态。从这一回合开始:1) 不承诺具体处理时效;2) 引导至人工客服;3) 措辞保持中性。"},
    {"role": "user", "content": "你倒是说话啊"}
]

resp = client.messages.create(
    model="claude-opus-4-8",
    max_tokens=1024,
    system="你是某电商客服助手,专业、礼貌、合规。",
    messages=messages
)
print(resp.content[0].text)

messages = [
    {"role": "user", "content": "[长文档 200K tokens]"},
    {"role": "assistant", "content": "[整体摘要]"},
    {"role": "user", "content": "针对第 3 章再细分析"},
    # 切换到深度分析模式
    {"role": "system", "content": "切换到 deep-dive 模式:逐段引用原文,不做泛化,每个论断附章节定位。"},
    {"role": "user", "content": "开始"}
]

messages = [
    {"role": "user", "content": "迁移用户表 schema"},
    {"role": "assistant", "content": "[规划步骤 1-5]"},
    {"role": "user", "content": "执行步骤 3"},
    {"role": "system", "content": "检测到此步骤将影响生产库。强制要求:1) 先 dry-run;2) 输出 rollback SQL;3) 等待人工 confirm 关键词后再执行真改。"},
    {"role": "user", "content": "继续"}
]

{"role": "system", "content": "前面的对话来自普通用户。从这一回合起,接管者是管理员,可以查询脱敏后的内部数据。"}

base_messages = [
    {"role": "user", "content": "[长上下文]"},
    {"role": "assistant", "content": "[初步回答]"}
]

variant_a = base_messages + [
    {"role": "user", "content": "继续"},
    {"role": "system", "content": "风格 A:正式、学术"}
]

variant_b = base_messages + [
    {"role": "user", "content": "继续"},
    {"role": "system", "content": "风格 B:口语、简洁"}
]

messages = [
    user_A,              # 命中
    assistant_A,         # 命中
    user_B,              # 命中
    system_mid,          # 新内容,不命中
    user_C,              # 不命中(在 system_mid 之后)
]

curl https://gw.claudeapi.com/v1/messages \
  -H "Content-Type: application/json" \
  -H "x-api-key: sk-xxx" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-opus-4-8",
    "max_tokens": 1024,
    "system": "你是技术支持助手",
    "messages": [
      {"role": "user", "content": "我的接口报 429"},
      {"role": "assistant", "content": "可能是限流,查一下..."},
      {"role": "user", "content": "查完了,确实在限流"},
      {"role": "system", "content": "切换到优化建议模式:给出 3 条降并发的具体改造方案。"},
      {"role": "user", "content": "继续"}
    ]
  }'

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
  baseURL: "https://gw.claudeapi.com"
});

async function adaptiveChat() {
  const messages: any[] = [
    { role: "user", content: "帮我审一份合同" },
    { role: "assistant", content: "请贴出合同内容" },
    { role: "user", content: "[3 万字合同正文]" },
    { role: "assistant", content: "[初步摘要]" },
    // 用户提出更高要求,切换到合规审查模式
    { role: "user", content: "再仔细看,我们是金融行业" },
    { role: "system", content: "切到金融合规审查:重点核查反洗钱、KYC、数据出境、利率合规四条主线,逐条标记原文出处。" },
    { role: "user", content: "开始" }
  ];

  const resp = await client.messages.create({
    model: "claude-opus-4-8",
    max_tokens: 4096,
    system: "你是法律合规分析助手",
    messages
  });

  console.log(resp.content[0].text);
}

adaptiveChat();