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Lifespan does not execute on startup streamable-http #1300
Description
Initial Checks
- I confirm that I'm using the latest version of MCP Python SDK
- I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue
Description
With stdio protocol, the lifespan runs on server start up as expected. However, with streamable-http the lifespan does not execute on server start up.
Example Code
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager
from dataclasses import dataclass
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.session import ServerSession
# Mock database class for example
class Database:
"""Mock database class for example."""
@classmethod
async def connect(cls) -> "Database":
"""Connect to database."""
return cls()
async def disconnect(self) -> None:
"""Disconnect from database."""
pass
def query(self) -> str:
"""Execute a query."""
return "Query result"
@dataclass
class AppContext:
"""Application context with typed dependencies."""
db: Database
@asynccontextmanager
async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
"""Manage application lifecycle with type-safe context."""
# Initialize on startup
print("Enter lifespan")
db = await Database.connect()
try:
yield AppContext(db=db)
finally:
# Cleanup on shutdown
await db.disconnect()
# Pass lifespan to server
mcp = FastMCP("My App", lifespan=app_lifespan)
# Access type-safe lifespan context in tools
@mcp.tool()
def query_db(ctx: Context[ServerSession, AppContext]) -> str:
"""Tool that uses initialized resources."""
db = ctx.request_context.lifespan_context.db
return db.query()
mcp.run(transport="streamable-http") # on server startup, the lifespan does not runPython & MCP Python SDK
1.13.1
Activity
jpoehnelt commentedon Aug 27, 2025
Why was this closed? Link to PR?
savvaki commentedon Aug 28, 2025
I can reopen if you're able to reproduce?
zeyugao commentedon Sep 29, 2025
I experience this problem also, do not know if I have missed something?
saved your code to t.py
beginor commentedon Oct 14, 2025
The same issue still exits with mcp 1.17.0 😂
Arnab-cloud commentedon Oct 22, 2025
This is my observation:
When using
transport=streamable-http, the lifespan context does not execute on server startup. Instead, it runs only when a new client connects and a session is created. I don't know if this is the expected behavior.This is when I ran the server without connecting with a client:
After connecting with a client:
I have tried with both mcp-inspector and
ClientSession. Works in both cases.OS: Windows 11Code for client:
Client Output:
fernando-torres-blip-ai commentedon Jan 13, 2026
Still facing this problem, any solution ?
maxisbey commentedon Feb 19, 2026
Subsumed by #2113 which redesigns lifespan with proper server-scoped vs session-scoped lifetimes.
feat(server): integrate server lifespan into Starlette app lifespan
docs(migration): add lifespan redesign migration guide for Option B