Lesson 11: PresidentStep + Concurrent Fan-Out

Optional Mini-Flow

When config.isPresident is true, BasicFlow can spawn concurrent trivia runs using PresidentStep.

public onCrossing(...) {
  const nth = this.getContext<string>('config.nth');
  this.sessionCompleted();
  return new HumanMessageEx(this, `Who is the ${nth} President of United State`);
}

Uses its own memory namespace (president).
Marks the session complete immediately inside each spawned run.

Spawning Concurrent Runs

protected async spawnSteps(): Promise<string> {
  const step = await this.activate(PresidentStep);
  const nths = ['10th','11th','12th','13th','14th','15th','16th'];
  await this.concurrentSteps<string>({
    items: nths,
    batchSize: 3,
    onConfig: (item) => ({ nth: item, isPresident: true }),
    onBotResponse(item, response) {
      step.saveState({ [item]: response['message'] });
    },
  });
  new SessionLogger(this.getSessionDoc()).log(`Finished concurrent flow: ${this.name}`);
  step.sessionCompleted();
  return 'done';
}

batchSize throttles parallelism.
onConfig injects per-run context.
onBotResponse aggregates answers back into the parent.

Triggering It Over HTTP

To force the concurrent path from outside the UI, hit the flow runner directly:

curl -X POST http://localhost:8000/ai/run \
  -H "Content-Type: application/json" \
  -H "CHAT_SESSION_ID: <uuid>" \
  -d '{ 
        "flowName": "BasicFlow",
        "config": { "_concurrent": true }
      }'

_concurrent: true tells BasicFlow to activate the PresidentStep fan‑out.
Add a CHAT_SESSION_ID header to keep runs isolated if you are issuing multiple requests.

When to Use

Batch evaluations or trivia fan-out.
Large document scoring or summarization.
Stress-testing flows with controlled concurrency.

With this, every step in BasicFlow now has a dedicated lesson following the real transition order.