Agent Loop：一个循环就是一个 Agent

import anthropic

client = anthropic.Anthropic()
MODEL = "claude-opus-4-6"

SYSTEM = "你是一个 Coding Agent，可以执行 bash 命令来完成任务。"

TOOLS = [{
    "name": "bash",
    "description": "执行 shell 命令，返回输出",
    "input_schema": {
        "type": "object",
        "properties": {
            "command": {"type": "string", "description": "要执行的 shell 命令"}
        },
        "required": ["command"]
    }
}]

import subprocess

def run_bash(command: str) -> str:
    result = subprocess.run(
        command, shell=True, capture_output=True, text=True, timeout=30
    )
    return result.stdout + result.stderr


def agent_loop(query: str):
    messages = [{"role": "user", "content": query}]

    while True:
        response = client.messages.create(
            model=MODEL, system=SYSTEM,
            messages=messages, tools=TOOLS, max_tokens=8000,
        )
        messages.append({"role": "assistant", "content": response.content})

        # 没有工具调用 → 结束
        if response.stop_reason != "tool_use":
            for block in response.content:
                if hasattr(block, "text"):
                    print(block.text)
            return

        # 执行所有工具调用，收集结果
        results = []
        for block in response.content:
            if block.type == "tool_use":
                output = run_bash(block.input["command"])
                print(f"[bash] {block.input['command']}")
                print(f"  → {output[:200]}")
                results.append({
                    "type": "tool_result",
                    "tool_use_id": block.id,
                    "content": output,
                })
        messages.append({"role": "user", "content": results})


if __name__ == "__main__":
    query = input("You: ").strip()
    agent_loop(query)

# 轮次 1：用户消息
messages = [{"role": "user", "content": "列出当前目录的 Python 文件"}]

# 轮次 1：LLM 响应（包含 tool_use block）
messages.append({"role": "assistant", "content": response.content})

# 轮次 1：工具结果
messages.append({"role": "user", "content": [tool_result]})

# 轮次 2：LLM 继续推理...

{
    "role": "user",
    "content": [
        {
            "type": "tool_result",
            "tool_use_id": block.id,  # 必须和 tool_use 的 id 匹配
            "content": "命令输出..."
        }
    ]
}