Embedded `stream` and `stream/promises` don't work.

[nabetti1720]

In the Node.js runtimes supported by AWS, awslambda.streamifyResponse() is available for response streaming functionality.

However, since it is not provided as an external package and it is difficult to verify in a local environment, experts have released lambda-stream.
https://www.npmjs.com/package/lambda-stream

This package uses node.js streams instead of Web Standard API streams, so I wondered if it might be possible to use it with the current LLRT, which exposes streams and stream/promises as polyfills, so I did a little testing.

index.js: A slightly modified version of the website example.

// index.js
import { pipeline } from 'node:stream/promises';
import { Readable } from 'node:stream';

import * as awslambda from 'lambda-stream';

export const echo = awslambda.streamifyResponse(async (event, responseStream, _context) => {
  // As an example, convert event to a readable stream.
  const requestStream = Readable.from(Buffer.from(JSON.stringify(event)));

  await pipeline(requestStream, responseStream);
});

START RequestId: 41597e4c-8fca-492a-bce2-34782c30ac8e Version: $LATEST
2025-09-16T10:50:31.699Z	41597e4c-8fca-492a-bce2-34782c30ac8e	ERROR	{
  errorType: 'TypeError',
  errorMessage: 'TypeError: Error converting from js 'object' into type 'EventEmitter'',
  stackTrace: '    at call (native)
    at <anonymous> (stream:2:43115)
    at destroyer (stream/promises:2:67249)
    at pipelineImpl (stream/promises:2:69238)
    at <anonymous> (stream/promises:2:80925)
    at Promise (native)
    at pipeline (stream/promises:2:80806)
    at <anonymous> (/var/task/index.js:9:18)
    at apply (__cjs:/var/task/node_modules/lambda-stream/dist/index.js:23:23)
',
  requestId: '41597e4c-8fca-492a-bce2-34782c30ac8e'
}
END RequestId: 41597e4c-8fca-492a-bce2-34782c30ac8e
REPORT RequestId: 41597e4c-8fca-492a-bce2-34782c30ac8e	Duration: 2.43 ms	Billed Duration: 82 ms	Memory Size: 128 MB	Max Memory Used: 29 MB	Init Duration: 79.16 ms	

If this works, we think it will expand the use cases if you attach it to globalThis.awslambda when building lambda flavors.
lambda-stream is not strictly a ResponseStreaming, so we need to implement the correct functionality.

For your information, @middy/core and hono/aws-lambda seems to assume awslambda.streamifyResponse().

EDIT: Sorry, this has already been reported in #318. You can close it, but I think something needs to be done about the issue where embedded stream and stream/promises don't work.

[nabetti1720]

@richarddavison Do you have any idea about this?