calcom/cal.diy · error · ConflictException

Webhook with this subscriber url already exists for this oAu

Error message

Webhook with this subscriber url already exists for this oAuth client

What it means

OAuthClientWebhooksService.createOAuthClientWebhook queries getOAuthClientWebhookByUrl(platformOAuthClientId, subscriberUrl); if a row already exists it throws ConflictException (HTTP 409). The (platformOAuthClientId, subscriberUrl) pair is unique per OAuth client.

Source

Thrown at apps/api/v2/src/modules/webhooks/services/oauth-clients-webhooks.service.ts:18

import { PipedInputWebhookType } from "@/modules/webhooks/pipes/WebhookInputPipe";
import { validateWebhookUrl } from "@/modules/webhooks/utils/validate-webhook-url";
import { WebhooksRepository } from "@/modules/webhooks/webhooks.repository";
import { ConflictException, Injectable } from "@nestjs/common";

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

  async createOAuthClientWebhook(platformOAuthClientId: string, body: PipedInputWebhookType) {
    validateWebhookUrl(body.subscriberUrl);

    const existingWebhook = await this.webhooksRepository.getOAuthClientWebhookByUrl(
      platformOAuthClientId,
      body.subscriberUrl
    );
    if (existingWebhook) {
      throw new ConflictException("Webhook with this subscriber url already exists for this oAuth client");
    }

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

  async getOAuthClientWebhooksPaginated(platformOAuthClientId: string, skip: number, take: number) {
    return this.webhooksRepository.getOAuthClientWebhooksPaginated(platformOAuthClientId, skip, take);
  }

  async deleteAllOAuthClientWebhooks(platformOAuthClientId: string): Promise<{ count: number }> {
    return this.webhooksRepository.deleteAllOAuthClientWebhooks(platformOAuthClientId);
  }
}

View on GitHub (pinned to 176037d0af)

Solutions

List the client's existing webhooks and check the subscriberUrl before creating.
Make subscriber URLs unique per registration.
Handle 409 as success-when-duplicate.

Example fix

// before
await api.createOAuthClientWebhook(clientId, { subscriberUrl, ... });
// after
const list = await api.listOAuthClientWebhooks(clientId);
if (list.find(w => w.subscriberUrl === subscriberUrl)) return;
await api.createOAuthClientWebhook(clientId, { subscriberUrl, ... });

Defensive patterns

Strategy: validation

Validate before calling

async function createIfMissingOAuthClient(api, clientId, body) {
  const list = await api.getOAuthClientWebhooksPaginated(clientId, 0, 1000);
  if (list.find(w => w.subscriberUrl === body.subscriberUrl)) return;
  return api.createOAuthClientWebhook(clientId, body);
}

Type guard

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

Try / catch

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

Prevention

Use distinct callback URLs per OAuth client registration.
Deduplicate retries by subscriberUrl.
Idempotently absorb 409 responses.

When it happens

Trigger: POSTing a webhook for an OAuth client whose subscriberUrl is already registered for that same client. Unlike event-type/user webhooks, there is no DELEGATION_CREDENTIAL_ERROR guard here — only the duplicate check.

Common situations: Re-registering a callback after a transient failure that actually succeeded; two OAuth flows for the same client using one callback URL; replayed webhooks.

Related errors

AI-assisted analysis of calcom/cal.diy@176037d0af (2026-08-12). Data as JSON: /api/errors/b0e79ca59f8b7772. Report an issue: GitHub.