calcom/cal.diy · error · ConflictException

Webhook with this subscriber url already exists for this use

Error message

Webhook with this subscriber url already exists for this user

What it means

UserWebhooksService.createUserWebhook calls getUserWebhookByUrl(userId, subscriberUrl); if a row exists for that user+URL it throws ConflictException (HTTP 409). The (userId, subscriberUrl) pair is unique.

Source

Thrown at apps/api/v2/src/modules/webhooks/services/user-webhooks.service.ts:23

import { WebhookTriggerEvents } from "@calcom/prisma/enums";

@Injectable()
export class UserWebhooksService {
  constructor(private readonly webhooksRepository: WebhooksRepository) {}

  async createUserWebhook(userId: number, body: PipedInputWebhookType) {
    validateWebhookUrl(body.subscriberUrl);

    if (body.eventTriggers.includes(WebhookTriggerEvents.DELEGATION_CREDENTIAL_ERROR)) {
      throw new BadRequestException(
        "DELEGATION_CREDENTIAL_ERROR trigger is only available for organization webhooks"
      );
    }

    const existingWebhook = await this.webhooksRepository.getUserWebhookByUrl(userId, body.subscriberUrl);
    if (existingWebhook) {
      throw new ConflictException("Webhook with this subscriber url already exists for this user");
    }

    return this.webhooksRepository.createUserWebhook(userId, {
      ...body,
      payloadTemplate: body.payloadTemplate ?? null,
      secret: body.secret ?? null,
    });
  }

  async getUserWebhooksPaginated(userId: number, skip: number, take: number) {
    return this.webhooksRepository.getUserWebhooksPaginated(userId, skip, take);
  }
}

View on GitHub (pinned to 176037d0af)

Solutions

List the user's webhooks and check subscriberUrl before creating.
Use unique subscriber URLs per webhook.
Handle 409 as 'already registered' idempotently.

Example fix

// before
await api.createUserWebhook(userId, { subscriberUrl, ... });
// after
const list = await api.listUserWebhooks(userId);
if (list.find(w => w.subscriberUrl === subscriberUrl)) return;
await api.createUserWebhook(userId, { subscriberUrl, ... });

Defensive patterns

Strategy: validation

Validate before calling

async function createIfMissingUser(api, userId, body) {
  const list = await api.getUserWebhooksPaginated(userId, 0, 1000);
  if (list.find(w => w.subscriberUrl === body.subscriberUrl)) return;
  return api.createUserWebhook(userId, body);
}

Type guard

const isDuplicateUrl = (list: { subscriberUrl: string }[], url: string): boolean =>
  list.some(w => w.subscriberUrl === url);

Try / catch

try { await api.createUserWebhook(userId, body); }
catch (e) { if (e.status === 409) return; else throw e; }

Prevention

Pre-list user webhooks before creating.
Use unique subscriber URLs per user webhook.
Idempotently absorb 409.

When it happens

Trigger: POSTing a user webhook with a subscriberUrl already registered for the same userId.

Common situations: Retry after a successful create; single callback endpoint reused across integrations for one user; dev URL reuse.

Related errors

AI-assisted analysis of calcom/cal.diy@176037d0af (2026-08-12). Data as JSON: /api/errors/25aa49213ee8b0e9. Report an issue: GitHub.