mcp-response-overriding-using-modelcontextprotocol-sdk-v1-25-x-with-next-j-5baa94b1

THEN Downgrade to MCP SDK <1.25.0, or avoid using StreamableHTTPServerTransport. If you must use v1.25.x, configure @hono/node-server with overrideGlobalObjects: false (if the SDK exposes that option) or switch to a different transport that does not rely on hono. Monitor for a SDK patch that fixes this behavior.

// Avoid instantiating StreamableHTTPServerTransport in a Next.js App Router context.
// Use a different transport, e.g., StdioServerTransport or a custom HTTP transport without hono.
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
const transport = new StdioServerTransport();