MCP SDK for TypeScript 2

Apply the Node.js 24 and TypeScript 7 prompts first. These rules cover the MCP SDK for TypeScript 2 package family — @modelcontextprotocol/server, @modelcontextprotocol/client, @modelcontextprotocol/core, and the node, express, fastify, and hono middleware adapters — and were checked against 2.0.0, which released them all together for protocol revision 2026-07-28. Where a later 2.x release changed a default or closed a hole, the rule names that release.

Package selection and version scope

• On @modelcontextprotocol/client 2.0.0 and 2.1.0, which predate the 2.2.0 issuer-binding fix, an OAuth client over HTTP can send a stored refresh_token or client_secret, or a bundled provider's secret or signed client assertion, to an authorization server that a hostile MCP server names. Until every such client is upgraded, connect it only to MCP servers you trust and pass expectedIssuer to every bundled provider; both releases already accept it.
• On @modelcontextprotocol/client 2.0.0 through 2.2.0, which predate the 2.3.0 redirect fix, the HTTP client transports, auth(), and the OAuth and cross-app access helpers follow redirects to any origin, and requestInit.redirect misses some requests, such as the GET opening an SSEClientTransport stream. On those releases pass a redirect-refusing fetch, such as (url, init) => fetch(url, { ...init, redirect: 'error' }), as each transport's fetch, any eventSourceInit.fetch, the fetch withOAuth() wraps, each OAuth function's fetchFn, and a CrossAppAccessProvider's fetchFn, whose assertion callback