mcp: reject discover when transport lacks version#1108
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Use the session transport-filtered supportedVersions in ServerSession.handle so stateful Streamable HTTP servers return UnsupportedProtocolVersionError instead of a DiscoverResult that omits the probed protocol version.
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Problem
On a stateful Streamable HTTP server,
ServerSession.handlegates new-protocol requests against the globalsupportedProtocolVersionslist. The transport-filtered list (viafilterSupportedVersions/SupportsProtocolVersion) can omit2026-07-28, yetserver/discoverstill returned HTTP 200 with aDiscoverResultthat excluded the probed version instead ofUnsupportedProtocolVersionError.Approach
Align the version gate in
handlewith the session's transport-filteredsupportedVersions, matching whatserver/discoveradvertises. Rename and update the stateful regression test to expect HTTP 400 withCodeUnsupportedProtocolVersion.Test plan
go test ./...go test -race ./...TestStreamableStateful_DiscoverRejectsUnsupportedVersionFixes #1025