feat: expose progress_callback in ServerSession methods#2041
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BryceEWatson wants to merge 6 commits into
Open
feat: expose progress_callback in ServerSession methods#2041BryceEWatson wants to merge 6 commits into
BryceEWatson wants to merge 6 commits into
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…elicit_form() Add progress_callback parameter to ServerSession methods that send requests to clients, matching the pattern already used by ClientSession.call_tool(). This brings the Python SDK into parity with the TypeScript SDK's RequestOptions.onprogress support. The MCP spec supports bidirectional progress notifications, and BaseSession.send_request() already accepts progress_callback, but the ServerSession convenience methods were not exposing it. Fixes modelcontextprotocol#1671 Github-Issue: modelcontextprotocol#1671
The if-guards checking for progress_token in context.meta always evaluate to True when progress_callback is provided, so the false branches are never taken. Mark with pragma: no branch to satisfy 100% coverage requirement.
Merge upstream/main into fix/1671-serversession-progress-callback. Resolved import conflict in mcpserver/server.py by keeping both the new ProgressFnT import and the expanded mcp.types imports from the lowlevel Server decorator refactor (modelcontextprotocol#1985).
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Merge upstream/main which included major refactors: - Context class moved from server.py to mcpserver/context.py (modelcontextprotocol#2203) - Lowlevel Server decorators replaced with on_* kwargs (modelcontextprotocol#1985) - Docstring formatting standardized with periods (modelcontextprotocol#2095) - mcp.shared.progress module removed (modelcontextprotocol#2080) Resolved conflicts by: - Taking upstream server.py (Context class removed) - Adding progress_callback to new context.py - Keeping progress_callback docstrings with upstream period style - Restoring RequestContext import for new tests - Updating tests to use ctx: Context injection pattern
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Sync the progress_callback feature branch onto current upstream/main, which had undergone a large refactor since the branch was last updated (dispatcher extraction, ProgressFnT moved from mcp.shared.session to mcp.shared.dispatcher, removal of the experimental tasks modules, and a test reorganization). Conflict resolution: - src/mcp/server/session.py: take upstream's import block (ProgressFnT now comes from mcp.shared.dispatcher). The progress_callback pass-throughs on create_message/elicit/elicit_form/elicit_url auto-merged onto upstream's refactored send_request, which already accepts progress_callback. - src/mcp/server/mcpserver/context.py: keep both upstream's LoggingLevel import and the ProgressFnT import (relocated to mcp.shared.dispatcher). - tests/shared/test_progress_notifications.py: upstream deleted this pre-existing file in its test reorg. Re-add it containing only this PR's two feature tests (create_message and elicit_form progress_callback pass-through), adapted to the new client callback API (mcp.client.ClientRequestContext). Verified locally: ruff format/lint clean, pyright clean, full suite green (2388 passed serially), coverage 100%.
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Fixes #1671
Motivation and Context
The
ServerSessionhigh-level methods for sending requests to clients (create_message,elicit_form,elicit_url) don't expose theprogress_callbackparameter, even though the underlyingBaseSession.send_request()fully supports it. This means servers can't easily receive progress notifications from clients during sampling or elicitation requests.ClientSession.call_tool()already exposesprogress_callbackfor the client→server direction. This PR adds the same support for the server→client direction, bringing the Python SDK into parity with the TypeScript SDK'sRequestOptions.onprogress.How Has This Been Tested?
tests/shared/test_progress_notifications.py:test_server_create_message_progress_callback: verifies progress callbacks work during sampling requests viaMCPServer+Clienttest_server_elicit_form_progress_callback: verifies progress callbacks work during elicitation requests viaMCPServer+Clientmain, the full test suite passes locally (uv run pytest),uv run pyrightreports 0 errors, anduv run ruff check .is clean. CI is green on all checks.Breaking Changes
No. All new parameters default to
None, maintaining full backward compatibility.Types of changes
Checklist
Additional context
Approach: Mirrors the existing
ClientSession.call_tool()pattern — addsprogress_callback: ProgressFnT | None = Noneto each method signature and passes it through tosend_request().Files changed (4):
src/mcp/server/session.py— Core: added param tocreate_message()(all overloads + impl),elicit(),elicit_form(),elicit_url()src/mcp/server/elicitation.py— Helpers: passthrough inelicit_with_validation()andelicit_url()src/mcp/server/mcpserver/context.py— Context API: passthrough inContext.elicit()andContext.elicit_url()tests/shared/test_progress_notifications.py— 2 new E2E testsIntentionally excluded:
list_roots()andsend_ping()— these are short-lived requests where progress tracking isn't meaningful.AI assistance disclosure
I used AI assistance while writing this change. I've reviewed and tested every line, understand the mechanism (
send_requestalready acceptsprogress_callbackand maps it toon_progress; these convenience methods just weren't forwarding it), and can answer questions on it directly.