mongodb/node-mongodb-native · error · MongoUnexpectedServerResponseError

Cursor document did not contain a batch

Error message

Cursor document did not contain a batch

What it means

Thrown by CursorResponse.encryptedBatch getter when, in a CSFLE/Queryable Encryption flow, the encrypted cursor document has neither a 'firstBatch' nor a 'nextBatch' array. The driver expects cursor responses to carry one of these batch fields; their absence means the (encrypted) server response is malformed. Surfaced as MongoUnexpectedServerResponseError.

Source

Thrown at src/cmap/wire_protocol/responses.ts:277

    if (namespace != null) return ns(namespace);
    return null;
  }

  public get length() {
    return Math.max(this.batchSize - this.iterated, 0);
  }

  private _encryptedBatch: OnDemandDocument | null = null;
  get encryptedBatch() {
    if (this.encryptedResponse == null) return null;
    if (this._encryptedBatch != null) return this._encryptedBatch;

    const cursor = this.encryptedResponse?.get('cursor', BSONType.object);
    if (cursor?.has('firstBatch'))
      this._encryptedBatch = cursor.get('firstBatch', BSONType.array, true);
    else if (cursor?.has('nextBatch'))
      this._encryptedBatch = cursor.get('nextBatch', BSONType.array, true);
    else throw new MongoUnexpectedServerResponseError('Cursor document did not contain a batch');

    return this._encryptedBatch;
  }

  private get batch() {
    if (this._batch != null) return this._batch;
    const cursor = this.cursor;
    if (cursor.has('firstBatch')) this._batch = cursor.get('firstBatch', BSONType.array, true);
    else if (cursor.has('nextBatch')) this._batch = cursor.get('nextBatch', BSONType.array, true);
    else throw new MongoUnexpectedServerResponseError('Cursor document did not contain a batch');
    return this._batch;
  }

  public get batchSize() {
    return this.batch?.size();
  }

  public get postBatchResumeToken() {

View on GitHub (pinned to 3366c21a63)

Solutions

1. Ensure `mongodb-client-encryption` (and its bundled libmongocrypt) versions are compatible with the driver version.
2. Confirm the MongoDB server supports CSFLE/Queryable Encryption for the operation being run.
3. Remove any proxy/LB that may alter encrypted responses.
4. Upgrade driver and encryption library to matching current versions.

try {
  await encryptedCollection.find({}).toArray();
} catch (err) {
  if (err instanceof MongoUnexpectedServerResponseError && /did not contain a batch/.test(err.message)) {
    // encrypted response malformed; verify mongodb-client-encryption / libmongocrypt versions
  }
  throw err;
}

When it happens

Trigger: Client-side encryption is in use; the encrypted response from the server is parsed, its cursor subdocument is read, and neither firstBatch nor nextBatch is present. Happens with a malformed encrypted response, a server/proxy stripping batch fields, or a driver/encryption-library version mismatch that mis-parses the response.

Common situations: Using Queryable Encryption or CSFLE with an incompatible `mongodb-client-encryption` version, a server that does not support the encryption protocol, or an intermediary altering encrypted responses. Triggered on find/aggregate/getMore over an encrypted collection.

Related errors

• Unable to create collection: ${cause.message}
• Malformed JSON body in GET request.
• Unable to complete request.
• Malformed response body - missing field `access_token`.
• Malformed response body - missing field `expires_in`.

AI-assisted analysis of mongodb/node-mongodb-native@3366c21a63 (2026-08-04). Data as JSON: /data/errors/292704aeafdd89d8.json. Report an issue: GitHub.