How to add persistence sessions when working with langgraph

I have a super simple example that I use with `langgraph dev` where my config is: ```json { "dependencies": ["."], "graphs": { "agent": "./src/agent/graph.py:make_graph" }, "env": ".env" } ``` where `agent` invokes the `make_graph` function. ```py """MCP client.""" import os from langchain_mcp_adapters.client import MultiServerMCPClient from langgraph.prebuilt import create_react_agent SERVER_CONFIGS = { "playwright": { "command": "npx", "args": ["-y", "@playwright/mcp@latest"], "transport": "stdio", }, } client = MultiServerMCPClient(SERVER_CONFIGS) async def make_graph(): """make_graph.""" tools = await client.get_tools() agent = create_react_agent( "google_genai:gemini-2.5-pro-preview-05-06", tools, ) return agent ``` However, when running playwright, the session gets cut off as each new tool call creates a new session. I have read here and there that the recommended solution is to add a session: ```py """MCP client.""" import os from langchain_mcp_adapters.client import MultiServerMCPClient from langchain_mcp_adapters.tools import load_mcp_tools from langgraph.prebuilt import create_react_agent SERVER_CONFIGS = { "playwright": { "command": "npx", "args": ["-y", "@playwright/mcp@latest"], "transport": "stdio", }, } client = MultiServerMCPClient(SERVER_CONFIGS) async def make_graph(): """make_graph.""" agent = None async with client.session("playwright") as session: tools = await load_mcp_tools(session) agent = create_react_agent( "google_genai:gemini-2.5-pro-preview-05-06", tools, ) return agent ``` But I consistently get this error when the LLM attempts to run any of the tools in playwright: ``` Error: ClosedResourceError() Please fix your mistakes. ``` Am I doing something wrong here or am I missing something fundamental?