replica-backend Checked

Builds the backend of an app clone: auth, database migrations and access rules, payments with Stripe, email, background jobs and third-party integrations through official APIs only, plus a security checklist. Use when the user says "add login", "set up auth", "wire up the database", "add payments", "connect Stripe", "add Google Calendar", "send emails", "backend for my clone", or when /replica-build is running on fake data.

replica-backend

Reads replica/architecture.md. Writes migrations and server code, and keeps

replica/backend.md (checklist below) up to date.

Builds the backend of an app clone: auth, database migrations and access rules, payments with Stripe, email, background jobs and third-party integrations through official APIs only, plus a security checklist. Use when the user says "add login", "set up auth", "wire up the database", "add payments", "connect Stripe", "add Google Calendar", "send emails", "backend for my clone", or when /replica-build is running on fake data.

replica-backend

Reads replica/architecture.md. Writes migrations and server code, and keeps

replica/backend.md (checklist below) up to date.

The rules

• **Official, public APIs only, with the user's own keys.** Never call the

original app's private endpoints, never reuse its OAuth client, never proxy

through it.

• **The user creates accounts and keys.** Claude never signs up for services,

never types a password, card or live key. The user creates the Stripe,

Supabase, Resend or Google Cloud project and puts keys in .env.local.

Claude writes .env.example with every variable name and no values.

• **Test mode first.** Stripe test keys and test cards until replica-deploy.

Auth

• Email sign up with verification, password reset, magic link if the original

has it. OAuth (Google, Apple) with the user's own developer apps.

• Sessions: http-only secure cookies. Sign out everywhere.
• Roles and teams if the recon map has them: owner, admin, member, with one

function that answers "can this user do this to this record".

• Account deletion that actually deletes. Apple requires it for apps with

sign up.

Database

• Migrations from architecture.md, checked in, run by a script.
• Access rules on every table: row level security policies on Supabase, or

the authorisation function called in every query. Test it: a second user

must get nothing back.

• Seed script with realistic fake data (no real people).
• Backups on (the host's daily backups count, check they are enabled).

Payments

• Stripe Checkout for sign up to a plan, the Customer Portal for changes and

cancelling. Do not build card forms.

• Webhooks: verify the signature, store the event id, make every handler

idempotent (Stripe retries). Handle checkout.session.completed,

customer.subscription.updated, customer.subscription.deleted,

invoice.payment_failed.

• Subscription status lives in your database, updated by webhooks, read by

your app. Never trust the client.

• Cancelling is one click. Hard-to-cancel billing is a top complaint about

most apps, and in many places it is illegal.

Email and jobs

• Transactional email through Resend or Postmark from your own domain.

Templates written fresh.

• Jobs for anything time-based (reminders, digests, sync, cleanup) with

retries and a dead-letter log. Times in UTC, shown in the user's zone.

Integrations