BullMQ: Flow parent job's 'failed' event not triggered when child jobs fail

[Crismon96]

I'm implementing a job flow using BullMQ (latest version) with NestJS, and I've encountered an issue with error handling in flow jobs.

The setup

I have a parent flow job and multiple child jobs. The flow is set up like this:

const children = buildingImports.map((jobData) => ({
  name: buildingImportQueueName,
  queueName: buildingImportQueueName,
  data: {
    data: jobData,
    title,
  },
  opts: {
    failParentOnFailure: false, // I've tried both true and false
  },
}));

const flow = await flowProducer.add({
  name: `${FLOW_JOB_PREFIX}-${uuidv4()}`,
  queueName: buildingImportFlowQueueName, // Separate queue for flow jobs
  data: {
    title,
    description,
    targetOrgId,
  },
  children,
  opts: {
    jobId: asyncJob.id.toString(),
    ...jobCleanupConfig,
  },
});

I've created separate processors for the flow job and child jobs:

@Processor(buildingImportFlowQueueName)
export class BuildingImportFlowProcessor extends WorkerProcessorBase<BuildingImportFlowJobData> {
  // Process method works fine
  async process({ id, data }: Job<AsyncJobData<BuildingImportFlowJobData>>) {
    logger.info('Processing parent flow job', { flowId: id, flowData: data });
    return;
  }

  // This works when all children complete successfully
  @OnWorkerEvent('completed')
  async onCompleted(job: Job<AsyncJobData<BuildingImportFlowJobData>>) {
    // This handler works correctly
  }

  // This is never called when child jobs fail
  @OnWorkerEvent('failed')
  async onFailed(job: Job<AsyncJobData<BuildingImportFlowJobData>>, error: Error) {
    logger.error('Building import flow failed event handler triggered', {
      flowId: job.id || 'unknown',
      error: error.message,
    });
    // Additional handling...
  }
}

The problem

When all child jobs complete successfully, the parent job's process method is called and the completed event handler works as expected.

However, when any child job fails, neither the parent job's process method nor its failed event handler is called. There's no logging or indication that the parent job is aware of the child failure.

What I've tried

1. Using separate queues for flow jobs and child jobs
2. Setting failParentOnFailure: true and failParentOnFailure: false
3. Adding extensive logging in both child and parent job handlers
4. Added event handlers in the child processor to confirm child failures are happening
5. Checked that child jobs have correct parent keys

According to the BullMQ documentation on Flows, parent jobs should be notified when children fail, but this isn't happening in my case.

Question

How can I ensure that when a child job fails, the parent flow job's failed event handler is triggered? Is there a specific configuration I'm missing for failure propagation in BullMQ flows?