calcom/cal.diy · error · BadRequestException

Cannot reserve a slot for a team event without any hosts

Error message

Cannot reserve a slot for a team event without any hosts

What it means

A NestJS BadRequestException (HTTP 400) from SlotsService_2024_09_04.reserveSlot. The event type is a team event (no eventType.userId) and eventType.hosts[0] is undefined — the team event has zero hosts assigned. The reserve flow needs a host to attach the slot to, so it refuses.

Source

Thrown at apps/api/v2/src/modules/slots/slots-2024-09-04/services/slots.service.ts:187

    }

    const reservationDuration = input.reservationDuration ?? DEFAULT_RESERVATION_DURATION;

    if (eventType.userId) {
      const slot = await this.slotsRepository.createSlot(
        eventType.userId,
        eventType.id,
        startDate.toISO(),
        endDate.toISO(),
        eventType.seatsPerTimeSlot !== null,
        reservationDuration
      );
      return this.slotsOutputService.getReservationSlotCreated(slot, reservationDuration);
    }

    const host = eventType.hosts[0];
    if (!host) {
      throw new BadRequestException("Cannot reserve a slot for a team event without any hosts");
    }

    const slot = await this.slotsRepository.createSlot(
      host.userId,
      eventType.id,
      startDate.toISO(),
      endDate.toISO(),
      eventType.seatsPerTimeSlot !== null,
      reservationDuration
    );

    return this.slotsOutputService.getReservationSlotCreated(slot, reservationDuration);
  }

  private async checkSlotOverlap(eventTypeId: number, startDate: string, endDate: string) {
    const overlappingReservation = await this.slotsRepository.getOverlappingSlotReservation(
      eventTypeId,
      startDate,

View on GitHub (pinned to 176037d0af)

Solutions

1. Assign at least one host to the team event type in the Cal.com dashboard before reserving.
2. Verify via GET /v2/event-types that hosts.length > 0 before calling reserve.
3. Surface a 'no hosts available' message and ask the event owner to add members.
4. If hosts exist in the DB but are not loaded, check the repository includes hosts in the query.

Example fix

// before
await reserve(teamEventTypeId, slotStart); // hosts: []

// after
const et = await calApi.eventTypes.getById(teamEventTypeId);
if (!et.hosts?.length) throw new ClientError('Team event has no hosts — ask owner to add members');
await reserve(teamEventTypeId, slotStart);

async function assertTeamEventHasHosts(eventTypeId: number) {
  const et = await cal.eventTypes.getById(eventTypeId);
  if (!et) throw new ClientError('Event type not found');
  if (et.teamId && !(et.hosts?.length)) {
    throw new UserFacingError('Team event has no hosts — ask the owner to add members.');
  }
  return et;
}
await assertTeamEventHasHosts(eventTypeId);

function teamEventHasHosts(et: { teamId?: number | null; hosts?: unknown[] }): boolean {
  return !et.teamId || (Array.isArray(et.hosts) && et.hosts.length > 0);
}

try {
  await cal.slots.reserve({ eventTypeId, slotStart });
} catch (e) {
  if (e instanceof HttpError && e.statusCode === 400 && /without any hosts/i.test(e.message)) {
    throw new UserFacingError('This team event has no hosts yet — please contact the organizer.');
  }
  throw e;
}

When it happens

Trigger: POST /v2/slots/reserve for a team event type whose hosts array is empty — all members were removed, or the event type was created without assigning hosts.

Common situations: Team event configured but no members added; hosts transferred out of the team; race between team setup and a reserve call; misconfigured round-robin event with an empty host list.

Related errors

• Invalid start date
• Invalid end date
• Could not adjust timezone for slot ${slot.time} with timezon
• Could not adjust timezone for slot end time ${slot.time} wit
• Could not create UTC time for slot ${slot.time}

AI-assisted analysis of calcom/cal.diy@176037d0af (2026-08-12). Data as JSON: /api/errors/a96be27ac551fc41. Report an issue: GitHub.