ServerSession methods (create_message, elicit_form) don't expose progress_callback parameter #1671
Description
Summary
The ServerSession high-level methods for sending requests to clients (create_message, elicit_form) don't expose the progress_callback parameter, even though the underlying BaseSession.send_request() fully supports it.
This means servers can't easily receive progress notifications from clients during sampling or elicitation requests.
Current Behavior
# ServerSession.elicit_form() - no progress_callback parameter
async def elicit_form(
self,
message: str,
requestedSchema: types.ElicitRequestedSchema,
related_request_id: types.RequestId | None = None,
) -> types.ElicitResult:
return await self.send_request(...) # progress_callback not passed through
# ServerSession.create_message() - same issue
async def create_message(
self,
messages: list[types.SamplingMessage],
*,
max_tokens: int,
# ... other params ...
related_request_id: types.RequestId | None = None,
) -> types.CreateMessageResult:
return await self.send_request(...) # progress_callback not passed throughExpected Behavior
# Should be able to pass progress_callback
result = await server_session.elicit_form(
message="Please provide your details",
requestedSchema=schema,
progress_callback=lambda progress, total, msg: print(f"Progress: {progress}/{total} - {msg}")
)
result = await server_session.create_message(
messages=messages,
max_tokens=1000,
progress_callback=lambda progress, total, msg: print(f"Sampling progress: {progress}/{total}")
)Context
- The MCP spec supports bidirectional progress notifications - clients CAN send
notifications/progressback to servers during request handling BaseSession.send_request()already supportsprogress_callbackparameterClientSession.call_tool()exposesprogress_callbackfor the client→server direction- The TypeScript SDK exposes this via
RequestOptions.onprogressin bothcreateMessage()andelicitInput() - Tests in
tests/shared/test_progress_notifications.pydemonstrate the bidirectional flow works
Suggested Fix
Add progress_callback: ProgressFnT | None = None parameter to:
ServerSession.create_message()ServerSession.elicit_form()- Any other
ServerSessionmethods that send requests to clients
And pass it through to send_request().
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