import error for CJS

[henrytsuicsa]

Describe the bug
i have a cjs project which need to use @modelcontextprotocol/sdk, it is fine to import mcp server's things.

However, when i mcp client code, like
import { SSEClientTransport } from "@modelcontextprotocol/sdk/client/sse.js";

the error happen:

Logs
/home/myproject/node_modules/@modelcontextprotocol/sdk/dist/cjs/client/auth.js:315
undefined
^

Error [ERR_REQUIRE_ESM]: require() of ES Module /home/myproject/node_modules/pkce-challenge/dist/index.node.js from /home/myproject/node_modules/@modelcontextprotocol/sdk/dist/cjs/client/auth.js not supported.
index.node.js is treated as an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which declares all .js files in that package scope as ES modules.
Instead either rename index.node.js to end in .cjs, change the requiring code to use dynamic import() which is available in all CommonJS modules, or change "type": "module" to "type": "commonjs" in /home/myproject/node_modules/pkce-challenge/package.json to treat all .js files as CommonJS (using .mjs for all ES modules instead).

at TracingChannel.traceSync (node:diagnostics_channel:315:14)
at Object.<anonymous> (/home/myproject/node_modules/@modelcontextprotocol/sdk/dist/cjs/client/auth.js:13:42) {

code: 'ERR_REQUIRE_ESM'
}

Additional context
Node.js v22.6.0

[anandrewfiserv]

For node 23, I am getting a ERR_REQUIRE_ASYNC_MODULE error

[wictorwilen]

I used this as a workaround in the an async function, instead of having a top-level import for it:

const SSEClientTransport = (await import('@modelcontextprotocol/sdk/client/sse.js')).SSEClientTransport;