modelcontextprotocol/typescript-sdk @modelcontextprotocol/client@2.0.0-beta.4

on GitHub

Minor Changes

• #2468 5db6e38 Thanks @felixweinberger! - The response cache now stores results as JSON-serialized documents (serialize on write, parse on read) instead of live object graphs isolated with structuredClone. Same mutation isolation, but no dependency on the structuredClone global — whose absence (jest+jsdom, Node < 17) previously made every cache write throw into the store-error swallow, silently disabling caching and output-schema lookups for the session. A value without a JSON representation now fails the write loudly to the error sink, and an undecodable document in an external store is reported, dropped, and read as a miss.

  Migration for custom ResponseCacheStore implementations: CacheEntry.value (and the set() entry value) is now string — persist and return it verbatim, JSON.parse to inspect. Entries persisted by a previous SDK version fail decode once (reported, dropped) and are rewritten on the next fetch.

• #2477 8e1d2e9 Thanks @felixweinberger! - Move the schema source modules (spec schemas, OAuth schemas, protocol constants) into @modelcontextprotocol/core and resolve them from there as a regular runtime dependency instead of bundling a private copy into each package. An application importing more than one of the packages now evaluates a single shared schema graph with shared object identity. @modelcontextprotocol/core gains a ./internal subpath (SDK-internal contract; may change in any release) and the four packages now version together.

• #2483 3f07a32 Thanks @felixweinberger! - Add preloadSchemas(), an explicit opt-in to eager wire-schema construction, and call it automatically in the Cloudflare Workers builds. The wire schemas are built lazily by default, which is the right trade on process-per-invocation runtimes — but on isolate platforms that bill request CPU while module evaluation runs during isolate warm-up, laziness moves construction into the first request each fresh isolate serves. Calling preloadSchemas() at module scope (it is synchronous and idempotent) moves that one-time cost back to module evaluation; the packages' workerd export condition now does this automatically, while the Node and browser builds stay lazy. The server package gains a dedicated browser shim for this (its browser condition previously reused the workerd shim), so browser bundles keep lazy construction.

Patch Changes

• #2458 7c49b47 Thanks @felixweinberger! - Construct the default Ajv validation engine lazily on first validation. Creating a Client or Server no longer pays the ajv + ajv-formats instantiation cost at startup when no JSON Schema validation ever runs.

• #2476 e0a0ab7 Thanks @felixweinberger! - Build protocol-revision wire schemas lazily on first validation instead of at import. Each revision's schema set is now constructed by a module-level memoized factory, so importing the client or server package no longer pays the construction cost of both frozen wire-schema graphs up front. Method membership in the revision registries stays static, the schemas themselves are unchanged, and registry lookups keep returning reference-identical schema objects.

• Updated dependencies [8e1d2e9]:

  • @modelcontextprotocol/core@2.0.0-beta.4