Implement MCP 2026-07-28#2286
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🦋 Changeset detectedLatest commit: f4c3ff0 The changes in this PR will be included in the next version bump. This PR includes changesets to release 9 packages
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@modelcontextprotocol/client
@modelcontextprotocol/codemod
@modelcontextprotocol/core
@modelcontextprotocol/server
@modelcontextprotocol/server-legacy
@modelcontextprotocol/express
@modelcontextprotocol/fastify
@modelcontextprotocol/hono
@modelcontextprotocol/node
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Mirrors the v1.x-2026-07-28 arrangement: pull_request triggers are unfiltered (PRs targeting the branch already get CI); this adds the branch to the push filters so post-merge state runs CI too.
… the stdio env safelist (#2281)
…op stale task artifacts (#2290)
…evision generation (#2291)
…igin validation middleware (#2304)
…ort; dual-era examples (#2305)
…nts, and the error status matrix (#2306)
…and missing envelope fields (#2311)
…streaming, and stamping scenarios (#2309)
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…ling from baseline (conformance#366) (#2366)
…ListenResult (#2953) (#2371)
…on* (spec #2891) (#2372)
Co-authored-by: Matt <77928207+mattzcarey@users.noreply.github.com> Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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Full implementation of the MCP 2026-07-28 specification revision on SDK v2. See the spec changelog for the protocol changes and the RC announcement for context.
This PR collects ~65 reviewed chunk PRs from the
v2-2026-07-28integration branch (#2281 through #2374). Each was reviewed and CI-gated individually before landing on the integration branch.SEPs implemented
Stateless protocol
initializehandshake, noMcp-Session-Id; protocol version, client identity and capabilities carried in_metaon every request;server/discoverfor up-front version selection;ping,logging/setLevel, SSE resumability removedsubscriptions/listenlong-lived stream replaces the GET endpoint andresources/subscribe/unsubscribe@deprecatedsweep on the roots/sampling/logging runtime APIs and type surfaceMulti-round-trip requests
InputRequiredResult(resultType: "input_required") replaces server-initiatedroots/list/sampling/createMessage/elicitation/create; all results carryresultTypeTransport
Mcp-Method/Mcp-Namestandard request headers on Streamable HTTP POSTs;x-mcp-headerparameter mirroringttlMs/cacheScopeon list/read results; client-side response cache_metakeys (traceparent/tracestate/baggage)Schema
inputSchema/outputSchemaaccept any 2020-12 keywords;structuredContentaccepts any JSON value; default validator isAjv2020Authorization
issvalidation infinishAuth()application_typeand registration metadata defaults403 insufficient_scope(union with challenged scopes)Removed
Backward compatibility
The SDK continues to interoperate with 2025-era peers.
versionNegotiationcontrols which era the client speaks;createMcpHandlerserves both eras from one server.Migration
npx @modelcontextprotocol/codemod v1-to-v2handles the mechanical renamesdocs/migration/upgrade-to-v2.mdcovers what the codemod can'tdocs/migration/support-2026-07-28.mdcovers adopting the 2026 wire surface once on v2Breaking Changes
This is a major-version release (v1 → v2). See the migration guide; every change carries a changeset.
Types of changes
Checklist