How to allow ClientSessionGroup to pass additional parameters to ClientSession (_establish_session method)？

[raychen911]

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

session_group

When I use ClientSessionGroup, I expect mcp.ClientSession to support the elicitation_callback parameter. However, I found that there is no way to pass this parameter through the initialization of ClientSessionGroup.

Example Code

async def _establish_session(
        self, server_params: ServerParameters
    ) -> tuple[types.Implementation, mcp.ClientSession]:
        """Establish a client session to an MCP server."""

        
            # This does not allow passing other arguments supported by ClientSession, such as: elicitation_callback
            await self._exit_stack.enter_async_context(session_stack)
            # ...

Python & MCP Python SDK

1.13.0

[felixweinberger]

This seems legit if true, we should make sure this core protocol feature is supported.

[maxisbey]

This was fixed in #1576. ClientSessionGroup.connect_to_server() now accepts a session_params: ClientSessionParameters argument that lets you pass elicitation_callback and other callbacks (sampling_callback, list_roots_callback, logging_callback, message_handler, client_info) through to ClientSession: https://github.com/modelcontextprotocol/python-sdk/blob/c0328540c97d/src/mcp/client/session_group.py#L73-L82

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