[Python] Session_id is always null in fastmcp (https://github.com/jlowin/fastmcp)

am exploring the new fastmcp framework(https://github.com/jlowin/fastmcp). i have write a server and a client, and i want to have access to the session_id in the server side(am thinking of using it as key for my cache), but i always git a null value for the session id

here is the server code:

from fastmcp import FastMCP, Context


# Initialize FastMCP server
mcp = FastMCP("test mcp server")


@mcp.tool()
async def request_info(ctx: Context) -> dict:
"""Return information about the current request."""
return {
"request_id": ctx.request_id,
"client_id": ctx.client_id or "Unknown client",
"session_id": ctx.session_id
}


# Basic dynamic resource returning a string
@mcp.resource("resource://greeting")
def get_greeting() -> str:
"""Provides a simple greeting message."""
return "Hello from FastMCP Resources!"



if __name__ == "__main__":
# Initialize and run the server
transport = "streamable"
if transport == "streamable":
print("Running server with streamable-http transport ...")
mcp.run(transport="http")
elif transport == "sse":
print("Running server with sse transport ...")
mcp.run(transport="sse", port=8001, path="/sse")


and here is the client code:

from fastmcp import Client
from contextlib import AsyncExitStack
import asyncio


class MCP_ChatBot:
def __init__(self):
# Initialize client and Azure OpenAI objects
self.client = Client("http://127.0.0.1:8000/mcp")
self.available_tools = []
self.available_prompts = []
self.exit_stack=AsyncExitStack()
self.message_history=[]

async def connect_to_server_and_run(self):
async with self.client:
print(f"Client connected: {self.client.is_connected()}")

# List available tools
tools = await self.client.list_tools()
print("\nConnected to server with tools:", len(tools))
print('--- tool names ---')
for tool in tools:
print(tool.name)
print('---------------')
try:
print('--- request info ---')
result = await self.client.call_tool('request_info')
print(result)
except Exception as e:
print(e)

async def cleanup(self):
await self.exit_stack.aclose()
async def main():
chatbot = MCP_ChatBot()
try:
await chatbot.connect_to_server_and_run()
finally:
await chatbot.cleanup()

if __name__ == "__main__":
asyncio.run(main())


and here the output of the client:

Client connected: True

Connected to server with tools: 1

--- Tool Names ---
- request_info

--- Request Info ---
[TextContent(
type='text',
text='{
"request_id": "2",
"client_id": "Unknown client",
"session_id": null
}',
annotations=None,
meta=None
)]


I'm wondering why the session_id is null. Did I miss something in my implementation, or is it that FastMCP does not handle session_id properly?

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