fix: honor supported_protocol_versions when negotiating initialize - #1093
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DaleSeo
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Bump to latest stable release https://github.com/modelcontextprotocol/rust-sdk/releases/tag/rmcp-v3.1.0 ``` Added classify authorization-required errors (modelcontextprotocol/rust-sdk#1056) add strict stateless protocol metadata validation (modelcontextprotocol/rust-sdk#1091) SEP-2260 stream-based enforcement of client receive-side request association (modelcontextprotocol/rust-sdk#1055) Fixed (model) decode metadata-bearing input-required results affecting mrtr (modelcontextprotocol/rust-sdk#1097) require metadata for modern HTTP requests (modelcontextprotocol/rust-sdk#1089) honor supported_protocol_versions when negotiating initialize (modelcontextprotocol/rust-sdk#1093) Other document the ping utility with examples (modelcontextprotocol/rust-sdk#1106) complete Tier 1 feature docs and finalize roadmap (modelcontextprotocol/rust-sdk#1101) (conformance) meeting requirements for tier 1 (modelcontextprotocol/rust-sdk#1087) ``` Signed-off-by: Filinto Duran <1373693+filintod@users.noreply.github.com>
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Motivation and Context
Follow-up to #1080.
ServerHandler::supported_protocol_versionsalready declares which revisions a server supports, and two paths already honor it. Inline, per-request negotiation rejects versions outside the list withunsupported_protocol_version, anddiscoveradvertises the list to clients. However, theinitializehandshake ignored it and hardcodedProtocolVersion::KNOWN_VERSIONSinsidenegotiate_protocol_version.That made the server inconsistent. For example, a server that narrows its list to exclude
2026-07-28would advertise the narrower list throughdiscoverand reject a per-request2026-07-28. Butinitializewould still return2026-07-28, and the server would then be unable to handle the follow-up requests that version requires, including SEP-2243 standard headers and discovery.KNOWN_VERSIONSonly represents the versions the SDK has constants for. It does not mean that every server supports all of them.This PR passes the server's supported list into
negotiate_protocol_version, so the handshake only agrees to versions the server actually declares.supported_protocol_versionshas been added toServicewith the same default ofKNOWN_VERSIONS. This lets both service-layer negotiation paths access it, including theserve_serverhandshake used by stdio and stateful HTTP, as well as the stateless wrapper added in #1080.How Has This Been Tested?
Added tests
Breaking Changes
None.
Types of changes
Checklist