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Authentication Delivery Hooks

Beta

This feature is in beta. Core behavior is stable and ready to try, but some APIs or configuration may still evolve before general availability.

Transactional authentication delivery hooks live under:

  • auth.handlers.email.onSend
  • auth.handlers.sms.onSend

Use them to modify or block verification emails, password reset emails, magic links, email OTP, email change messages, and phone OTP/SMS login messages.

Email Hook​

import { defineConfig } from '@edge-base/shared';

export default defineConfig({
  email: {
    provider: 'resend',
    apiKey: process.env.EMAIL_API_KEY!,
    from: 'noreply@myapp.com',
  },
  auth: {
    handlers: {
      email: {
        onSend: async (type, to, subject, html, ctx, locale) => {
          if (to.endsWith('@disposable.test')) {
            throw new Error('Disposable email addresses are not allowed.');
          }

          return {
            subject,
            html: `<div data-locale="${locale ?? 'en'}">${html}</div>`,
          };
        },
      },
    },
  },
});

Signature​

type MailType =
  | 'verification'
  | 'passwordReset'
  | 'magicLink'
  | 'emailOtp'
  | 'emailChange';

type EmailOnSend = (
  type: MailType,
  to: string,
  subject: string,
  html: string,
  ctx: { waitUntil(promise: Promise<unknown>): void },
  locale?: string,
) => Promise<{ subject?: string; html?: string } | void>
  | { subject?: string; html?: string }
  | void;

SMS Hook​

export default defineConfig({
  sms: {
    provider: 'twilio',
    accountSid: process.env.TWILIO_ACCOUNT_SID!,
    authToken: process.env.TWILIO_AUTH_TOKEN!,
    from: '+15551234567',
  },
  auth: {
    handlers: {
      sms: {
        onSend: async (type, to, body) => {
          if (type === 'phoneOtp') {
            return { body: `[MyApp] ${body}` };
          }
        },
      },
    },
  },
});

Signature​

type SmsType = 'phoneOtp' | 'phoneLink';

type SmsOnSend = (
  type: SmsType,
  to: string,
  body: string,
  ctx: { waitUntil(promise: Promise<unknown>): void },
) => Promise<{ body?: string } | void>
  | { body?: string }
  | void;

Behavior​

  • Blocking hooks
  • Timeout is 5s
  • Throw to reject delivery
  • Return partial overrides to rewrite the outbound message
  • ctx.waitUntil(...) is available for background side effects

See Also​