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Title: Client auto-resolves InputRequiredResult via existing callbacks (SEP-2322) by maxisbey · Pull Request #2998 · modelcontextprotocol/python-sdk · GitHub

Open Graph Title: Client auto-resolves InputRequiredResult via existing callbacks (SEP-2322) by maxisbey · Pull Request #2998 · modelcontextprotocol/python-sdk

X Title: Client auto-resolves InputRequiredResult via existing callbacks (SEP-2322) by maxisbey · Pull Request #2998 · modelcontextprotocol/python-sdk

Description: Client.call_tool / get_prompt / read_resource now resolve InputRequiredResult automatically: each entry in input_requests is dispatched to the same sampling_callback / elicitation_callback / list_roots_callback that already serve legacy server-to-client RPCs, the responses are collected, and the call is retried with input_responses + the echoed request_state until a terminal result arrives. allow_input_required is removed from Client; for manual control (inspecting rounds, persisting request_state across processes) use client.session.call_tool(..., allow_input_required=True) which still returns the raw union. Motivation and Context Client half of SEP-2322 / #2898. The server side and the manual ClientSession surface landed in #2974; this adds the policy-layer driver so a high-level Client user never sees InputRequiredResult directly. Shape client/_input_required.py (new): pure, method-agnostic driver. run_input_required_driver(first, *, dispatch, retry, max_rounds) loops until non-IIR. Concurrent dispatch via anyio.create_task_group(). State-only legs (server returned request_state with no input_requests) back off exponentially: 50ms doubling to a 250ms cap, counter reset by any leg with input requests. request_state is a byte-exact str | None pass-through, never inspected. max_rounds default 10 (matches typescript-sdk; csharp/go use the same constant). InputRequiredRoundsExceededError on cap; MCPError when a callback returns ErrorData. ClientSession._dispatch_input_request: extracted from the existing _on_request match-case so the legacy RPC path and the driver share one dispatch table. ClientRequestContext.request_id carries the input_requests key (a str, fits the existing RequestId = str | int). ClientSession.get_prompt / read_resource: gain the same input_responses / request_state / allow_input_required overload set that call_tool already has, with union TypeAdapters alongside _CallToolResultAdapter. Client: input_required_max_rounds: int = 10 dataclass field; shared _drive_input_required helper; call_tool / get_prompt / read_resource collapse to one signature returning the bare result type. Also: examples/stories/mrtr/ promoted from deferred stub; docs/advanced/multi-round-trip.md + docs_src/mrtr/tutorial003.py rewritten; conformance fixture sep-2322-client-request-state rewritten to drive the same five wire-shape checks via the auto-loop with a registered elicitation_callback. How Has This Been Tested? 9 driver unit tests in tests/client/test_input_required.py (single/multi-round, max-rounds cap, ErrorData raises, byte-exact request_state, backoff sequence, concurrent dispatch with event-gate, state-only counter reset). 7 integration tests in tests/client/test_client.py against in-memory MCPServer (all three callback types, multi-round with evolving state, no-callback-registered raises, get_prompt/read_resource happy path). tests/client/test_session.py covers the widened get_prompt/read_resource. tests/docs_src/test_mrtr.py exercises the new tutorial. Conformance sep-2322-client-request-state (CI). Breaking Changes Alpha-only API removal: Client.call_tool / get_prompt / read_resource no longer accept allow_input_required. Use client.session.(..., allow_input_required=True) for the manual surface. Noted in docs/migration.md. Types of changes New feature (non-breaking change which adds functionality) Breaking change (fix or feature that would cause existing functionality to change) Documentation update Checklist I have read the MCP Documentation My code follows the repository's style guidelines New and existing tests pass locally I have added appropriate error handling I have added or updated documentation as needed Additional context Open for review: ClientSessionGroup.call_tool is left at the mechanics layer (still forwards allow_input_required). read_timeout_seconds applies per round, not to the whole loop. No conformance scenario exercises the auto-loop's input-gathering directly; the existing scenario only checks wire shapes (which the auto-loop produces correctly). Worth a conformance-repo issue. Part of #2898. AI Disclaimer

Open Graph Description: Client.call_tool / get_prompt / read_resource now resolve InputRequiredResult automatically: each entry in input_requests is dispatched to the same sampling_callback / elicitation_callback / list_r...

X Description: Client.call_tool / get_prompt / read_resource now resolve InputRequiredResult automatically: each entry in input_requests is dispatched to the same sampling_callback / elicitation_callback / list_r...

Opengraph URL: https://github.com/modelcontextprotocol/python-sdk/pull/2998

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