Claude Agent SDK

import anthropic

# --- RAW API: you own every part of the agentic loop ---
client = anthropic.Anthropic()
messages = []

def raw_loop(user_prompt: str, tools: list) -> str:
    messages.append({"role": "user", "content": user_prompt})
    while True:
        resp = client.messages.create(
            model="claude-opus-4-8", max_tokens=4096,
            tools=tools, messages=messages
        )
        messages.append({"role": "assistant", "content": resp.content})
        if resp.stop_reason == "end_turn":
            return next(b.text for b in resp.content if b.type == "text")
        # Manually dispatch each tool_use block
        tool_results = []
        for block in resp.content:
            if block.type == "tool_use":
                output = dispatch_tool(block.name, block.input)  # your code
                tool_results.append({
                    "type": "tool_result",
                    "tool_use_id": block.id,  # must match exactly
                    "content": output,
                })
        messages.append({"role": "user", "content": tool_results})


# --- AGENT SDK: SDK owns the loop; you write hooks and definitions ---
from claude_agent_sdk import Agent, AgentDefinition, Session
from claude_agent_sdk.hooks import PreToolUseHook

def block_writes(tool_name: str, tool_input: dict) -> dict | None:
    if tool_name in ("write_file", "delete_file"):
        raise PermissionError(f"{tool_name} blocked")
    return None  # proceed unchanged

defn = AgentDefinition(
    model="claude-opus-4-8",
    system="You are a read-only code reviewer.",
    tools=["read_file", "search_code"],
)
agent = Agent(definition=defn, hooks=[PreToolUseHook(block_writes)])

with Session() as session:
    result = agent.run("Review src/auth.py for issues", session=session)
    print(result.final_message)