[BUG] lifespan context manager not triggered when using mount_http() in fastapi-mcp 0.4.0

Environment

fastapi-mcp version: 0.4.0 FastAPI version: 0.125.0 Python version: 3.14.2

Description

When using FastApiMCP.mount_http() with a FastAPI application that defines a lifespan context manager, the lifespan events are not triggered. The server logs indicate that the ASGI lifespan protocol is unsupported:

INFO: ASGI 'lifespan' protocol appears unsupported. This prevents proper initialization and cleanup of resources (database connections, cache, background tasks, etc.) which is critical for production applications.

from fastapi import FastAPI from fastapi_mcp import FastApiMCP from contextlib import asynccontextmanager import logging

logging.basicConfig(level=logging.INFO) logger = logging.getLogger(name)

Lifespan context manager

@asynccontextmanager async def lifespan(app: FastAPI): # Startup logger.info(" Application starting up...") logger.info("Initializing database connections...") logger.info("Loading cache...") yield # Shutdown logger.info(" Application shutting down...") logger.info("Closing database connections...") logger.info("Clearing cache...")

FastAPI app with lifespan

app = FastAPI( title="MCP Service", description="", version="1.0.0", openapi_url="/openapi.json", docs_url="/docs", redoc_url="/redoc", lifespan=lifespan )

@app.get("/health") async def health(): return {"status": "healthy"}

MCP setup

mcp = FastApiMCP(app) mcp.mount_http()

Actual Behavior

Console output:

INFO: Started server process [37181] INFO: Waiting for application startup. INFO: ASGI 'lifespan' protocol appears unsupported. INFO: Application startup complete. INFO: Uvicorn running on http://0.0.0.0:8000