fix(client): accept the draft protocol version the json-schema-ref-no-deref mock advertises#398
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…-deref mock advertises The scenario's hand-rolled server/discover handler advertises supportedVersions: ['2026-07-28'], but every other method is delegated to StreamableHTTPServerTransport from the pinned SDK (^1.29.0), whose version whitelist tops out at 2025-11-25. A SEP-2575 client that honors the negotiated version then gets HTTP 400 on tools/list, and the sep-2106-no-network-ref-deref check can never run. Extend the existing server/discover workaround to the version check: rewrite an incoming MCP-Protocol-Version: 2026-07-28 header to the SDK's LATEST_PROTOCOL_VERSION before delegating (patching rawHeaders too, since the SDK's Node adapter rebuilds its web-standard Request from rawHeaders). Add a stateless-draft-client regression test. Fixes #397 Co-Authored-By: Claude Fable 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01N4TdyLB13XSsPwNScYHf4C
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pcarleton
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Jul 8, 2026
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Requested by Paul Carleton · Slack thread
Fixes #397
Before / After
Before: the
json-schema-ref-no-derefmock's hand-rolledserver/discoverhandler advertisessupportedVersions: ["2026-07-28"], but every other method is delegated toStreamableHTTPServerTransportfrom the pinned@modelcontextprotocol/sdk@^1.29.0, whose version whitelist tops out at2025-11-25. A SEP-2575 client that probesserver/discoverand then honors the negotiated version gotHTTP 400 Bad Request: Unsupported protocol version: 2026-07-28ontools/list, so thesep-2106-no-network-ref-derefcheck always reported FAILURE ("Client did not call tools/list...") for a fully conformant client.After: the same client's
tools/listsucceeds (HTTP 200 with the tool schema), the client can be evaluated on the actual SEP-2106 behavior, and the check passes/fails on$refhandling as intended. Clients sending an already-SDK-supported version (e.g.2025-11-25) or a genuinely bogus version are unaffected.How
Extends the existing
server/discoverworkaround (the pattern from #347) to the version whitelist the pinned transport enforces: before delegating a POST to the SDK transport, an incomingMCP-Protocol-Version: 2026-07-28header — exactly the version the scenario's ownserver/discoveradvertises — is rewritten to the SDK'sLATEST_PROTOCOL_VERSION. Bothreq.headersandreq.rawHeadersare patched, because the SDK's Node adapter (@hono/node-server) rebuilds its web-standardRequestfromrawHeaders. A regression test drives the scenario with a stateless SEP-2575 client (via the harness'ssendStatelessRequest) that negotiates viaserver/discoverand then callstools/listwith the draft version header; it fails with HTTP 400 without the fix and passes with it.Local verification:
npm run check(typecheck + eslint + prettier),npm test(355 passed), andnpm run buildall pass.🤖 Generated with Claude Code
https://claude.ai/code/session_01N4TdyLB13XSsPwNScYHf4C
Generated by Claude Code