What’s New

MCP TypeScript SDK 2.0.0-beta.5

2.0.0-beta.5Pre-release
Added 2
  • Export the Protocol base class and mergeCapabilities from the @modelcontextprotocol/client and @modelcontextprotocol/server package roots
  • Add public constant SERVER_INFO_META_KEY with value 'io.modelcontextprotocol/serverInfo'
Changed 5
  • The codemod now rewrites Protocol and mergeCapabilities imports from shared/protocol.js to the client or server package root instead of dropping them
  • Align the 2026-07-28 wire with the final revision: serverInfo moves from the DiscoverResult body to the result _meta, and the per-request envelope's clientInfo demotes from required to optional
  • Servers now stamp _meta['io.modelcontextprotocol/serverInfo'] on every 2026-era response including subscriptions/listen graceful-close results
  • Clients keep sending clientInfo and read server identity from the discover result's _meta only, with anonymous servers returning undefined from getServerVersion()
  • DiscoverResult no longer declares serverInfo and RequestMetaEnvelope's clientInfo is optional
Minor Changes

  • #2501 1480241 Thanks @felixweinberger! - Export the Protocol base class and mergeCapabilities from the @modelcontextprotocol/client and @modelcontextprotocol/server package roots, restoring the v1 import for consumers that subclass Protocol (e.g. the MCP Apps SDK). The client and server packages each bundle their own compiled copy of the class, so import it from one package consistently within a process.

    The codemod now rewrites Protocol and mergeCapabilities imports from shared/protocol.js to the client or server package root, like the module's other symbols, instead of dropping them with an action-required marker.

  • #2513 f413763 Thanks @felixweinberger! - Align the 2026-07-28 wire with the final revision (spec PR #3002): serverInfo moves from the DiscoverResult body to the result _meta, and the per-request envelope's clientInfo demotes from required to SHOULD.

    Before this change the SDK shipped the pre-#3002 shape in both directions: the client hard-rejected a conforming server's DiscoverResult (missing body serverInfo failed parse, so the probe misclassified the server as legacy and attempted an initialize handshake against it — a hard connect failure against a modern-only server such as go-sdk v1.7.0-pre.3), and the server rejected conforming clients that omit clientInfo.

    Now:

    • The 2026 wire schemas are the final revision exactly: no body serverInfo on DiscoverResult, envelope clientInfo optional (a present-but-malformed value still fails validation).
    • Servers stamp _meta['io.modelcontextprotocol/serverInfo'] on every 2026-era response (spec SHOULD; a handler-authored value wins, the 2025-era wire is untouched). This includes the entry-built subscriptions/listen graceful-close results — the spec's SubscriptionsListenResultMeta extends ResultMetaObject.
    • Clients keep sending clientInfo and read server identity from the discover result's _meta only. A server that stamps no identity is anonymous: getServerVersion() is undefined and the response cache partitions under a per-connection surrogate. A malformed _meta serverInfo value is treated as absent on receive (the spec marks the field self-reported, unverified, and display-only).
    • Breaking type changes: DiscoverResult no longer declares serverInfo; RequestMetaEnvelope's clientInfo is optional. New public constant SERVER_INFO_META_KEY ('io.modelcontextprotocol/serverInfo').
Patch Changes
  • Updated dependencies [f413763]:
    • @modelcontextprotocol/core@2.0.0-beta.5
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