Shared State

What it demonstrates

Middleware in a chain often needs to hand data forward: a request id, timing, or accumulated metrics. Microsoft Agent Framework’s Python function-middleware signature is deliberately minimal — async def mw(context, call_next) — with no shared bag baked in. The idiomatic trick is to put both middleware on the same object and let them read and write instance attributes. That instance is the shared state.

This lesson builds a MiddlewareContainer holding a call_count. The first middleware increments it; the second reads it back to stamp each tool result with its call number.

The code

class MiddlewareContainer:
    def __init__(self) -> None:
        self.call_count: int = 0  # the shared state both methods touch

    async def call_counter_middleware(self, context, call_next):
        self.call_count += 1
        await call_next()

    async def result_enhancer_middleware(self, context, call_next):
        await call_next()  # tool runs first — result only exists after
        if context.result:
            context.result = f"[Call #{self.call_count}] {context.result}"

You wire them in by passing bound methods of one instance: middleware=[container.call_counter_middleware, container.result_enhancer_middleware].

The gotcha

Order matters, and so does when you read context.result. You must await call_next() to continue the chain, and the tool’s output only exists after that inner call runs — so read or mutate context.result after the await, not before. The counter middleware also has to run before the enhancer, or the enhancer stamps a stale count. Mutate the tool output by assigning to context.result.

Azure / MAF mapping

The container pattern is pure Python — no framework API for shared state. The framework contract is FunctionInvocationContext plus a zero-argument call_next. The agent itself is a plain Agent(client=FoundryChatClient(...)) against Azure AI Foundry with AzureCliCredential(), so the middleware runs around every tool call the model makes.

Run it

uv run tutorial/02-agents/middleware/06_shared_state.py — needs Foundry creds (az login). Three queries share the counter and it ends with Total function calls made: 3.

Next: Runtime Context