feat: welcome email via Vercel API route + DB trigger

[orveth]

Summary

• Adds a React Router resource route (/api/welcome-email) that sends welcome emails via Resend when called by a Supabase DB trigger
• Replaces the previous Edge Function approach with a Vercel-hosted endpoint for unified deployment and monitoring
• Includes idempotency (Resend Idempotency-Key header) to prevent duplicate sends

Files

• app/routes/api.welcome-email.ts — POST endpoint, validates webhook secret, calls Resend API
• supabase/migrations/20260410120000_welcome_email_webhook.sql — DB trigger on wallet.users INSERT

Configuration needed

Vercel env vars (all environments)

• WEBHOOK_SECRET — shared secret for authenticating DB trigger calls
• RESEND_API_KEY — Resend API key (use per-environment keys)
• RESEND_WELCOME_TEMPLATE_ID — Resend template ID (51320094-3fc9-416f-9c4a-de4fff0fc5e2)

Supabase vault secrets (per environment)

After applying the migration, run in the SQL editor:

select vault.create_secret('https://your-app-url.vercel.app', 'webhook_base_url');
select vault.create_secret('your-webhook-secret-value', 'webhook_secret');

Resend

• Domain emails.agi.cash must be verified (already done)
• Template must be published (already done — bob updated it)

How it works

1. New user inserted into wallet.users (with email)
2. Postgres trigger fires wallet.handle_new_user()
3. Trigger reads vault secrets and calls POST /api/welcome-email via pg_net
4. API route validates the webhook secret, then calls Resend API with idempotency key
5. User receives welcome email

Guest signups (no email) are skipped. Upsert-updates don't trigger (INSERT ON CONFLICT DO UPDATE fires UPDATE, not INSERT).

Supersedes

This replaces PR #980 (Edge Function approach). That PR can be closed after this merges.

🤖 Generated with Claude Code

[vercel]

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Project	Deployment	Actions	Updated (UTC)
agicash	Ready	Preview, Comment	Apr 10, 2026 11:18pm

[supabase]

Updates to Preview Branch (feat/welcome-email-api) ↗︎

Deployments	Status	Updated
Database	✅	Fri, 10 Apr 2026 23:17:40 UTC
Services	✅	Fri, 10 Apr 2026 23:17:40 UTC
APIs	✅	Fri, 10 Apr 2026 23:17:40 UTC

Tasks are run on every commit but only new migration files are pushed.
Close and reopen this PR if you want to apply changes from existing seed or migration files.

Tasks	Status	Updated
Configurations	⚠️	Fri, 10 Apr 2026 23:19:59 UTC
Migrations	✅	Fri, 10 Apr 2026 23:20:02 UTC
Seeding	✅	Fri, 10 Apr 2026 23:20:02 UTC
Edge Functions	✅	Fri, 10 Apr 2026 23:20:02 UTC

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