MCP TypeScript SDK v2 released, split into separate server and client packages

v2 is the current stable line, implementing the 2026-07-28 MCP spec and running on Node.js, Bun, and Deno. Releases are split into @modelcontextprotocol/server (for building MCP servers) and @modelcontextprotocol/client (for building MCP clients). Tool and prompt schema definitions now use Standard Schema, supporting compatible libraries like Zod v4, Valibot, and ArkType. Four thin adapter packages—@modelcontextprotocol/node, express, fastify, and hono—handle only transport and framework wiring, adding no new MCP features or business logic, and ship with runnable example directories. For developers building MCP servers and clients with this SDK, upgrading isn't just a version bump: dependency names, import paths, and tool schema syntax all change, and the maintainers provide a dedicated migration guide. v1.x (@modelcontextprotocol/sdk) stays on the v1.x branch and will receive bug fixes and security updates for at least six months after v2's release, giving teams still on v1 a buffer—but they should schedule migration ahead for the split-package dependency management.