Item 9: Understand the Three Middleware Types¶

Middleware 在请求到达 Agent 或调用工具之前拦截处理。有三种类型：

三种 Middleware¶

类型	拦截时机	Context 类
Agent	Agent.run() 调用前后	AgentContext
Function	工具调用前后	FunctionInvocationContext
Chat	LLM Chat API 调用前后	ChatContext

Agent Middleware¶

from agent_framework import AgentMiddleware, AgentContext

class LoggingMiddleware(AgentMiddleware):
    async def process(self, context: AgentContext, call_next):
        print(f"Before agent run: {context.input_messages}")
        await call_next()
        print(f"After agent run")

Function Middleware¶

from agent_framework import FunctionMiddleware, FunctionInvocationContext

class TimingMiddleware(FunctionMiddleware):
    async def process(self, context: FunctionInvocationContext, call_next):
        import time
        start = time.time()
        await call_next()
        print(f"Tool {context.tool_name} took {time.time() - start}s")

Chat Middleware¶

from agent_framework import ChatMiddleware, ChatContext

class PromptInjectMiddleware(ChatMiddleware):
    async def process(self, context: ChatContext, call_next):
        context.messages.insert(0, Message(role="system", contents=["Always be concise."]))
        await call_next()

注册 Middleware¶

agent = Agent(
    client=client,
    middleware=[LoggingMiddleware(), TimingMiddleware()]
)

Things to Remember¶

Agent Middleware：拦截 Agent.run()，适合日志、监控
Function Middleware：拦截工具调用，适合计日志、性能追踪
Chat Middleware：拦截 LLM API 调用，适合 prompt 修改
await call_next() 继续执行链，不能忘了