Summary

ChangeStream leaks `error` listeners when used with `events.once(...,

{ signal: AbortSignal.timeout(...) }

)`.

Environment

• Node.js: 24.x (also reproduced on 25.x)
• mongodb driver: current latest in project setup
• MongoDB: 8.x replica set

Repro

```js
import

{ once }

from 'node:events';
import

{ MongoClient }

from 'mongodb';

const client = new MongoClient('mongodb://localhost:27017/agent?replicaSet=travel');
await client.connect();

const chats = client.db('agent').collection('chats');
const stream = chats.watch();

setInterval(() => {
once(stream, 'change',

{ signal: AbortSignal.timeout(50) }

).catch(() => {});
}, 100);
```

Actual Result

```txt
MaxListenersExceededWarning: Possible EventEmitter memory leak detected.
11 error listeners added to [ReadableCursorStream].
```

Control Case (works as expected)

```js
import

{ once, EventEmitter }

from 'node:events';

const ee = new EventEmitter();

setInterval(() => {
once(ee, 'change',

{ signal: AbortSignal.timeout(50) }

).catch(() => {});
}, 100);
```

No warning in the same scenario.

Why this looks driver-specific

With `--trace-warnings`, stack points to `ChangeStream._streamEvents` adding `stream.on('error', ...)` repeatedly.

Expected

Using `events.once` repeatedly with timeout-abort should not accumulate internal listeners in `ChangeStream`/`ReadableCursorStream` until warning threshold.

Actual

`error` listeners on internal cursor stream accumulate and trigger `MaxListenersExceededWarning`.

Additional Notes

If needed, I can provide a minimal runnable repo.