Next.js + Shopify app developer (AI-first workflow, spec-driven)

We are a Melbourne-based company building a commercial Shopify public app. It is a transactional product, not a theme and not a storefront build. You will build against an existing spec. The architecture and the decisions are already made. We need accurate implementation and clear flagging of genuine gaps, not system design. Spec is shared after a mutual NDA. Stack - Next.js 16 (App Router), React 19, TypeScript - Supabase - Postgres, Auth, RLS - Vercel, with a Postgres-backed work queue - Shopify app surfaces: embedded App Home using Polaris web components and App Bridge, Admin UI extensions, Theme App Extension, checkout and order status extensions - Shopify Functions, Admin GraphQL, App Proxy AI-first You run an agentic workflow daily and can show us how you use it. You feed specs to your tools as context rather than re-deriving requirements each session, you review and correct what comes back, and you write the concurrency-critical code yourself. Required - Production Next.js App Router and React 19 - Shopify public app work: OAuth, Admin GraphQL, webhooks, App Bridge, app extensions. Name the apps and say whether they were public or custom - Postgres under transactional load: row locking, isolation levels, idempotency keys - Distributed failure modes: retries, duplicate webhook delivery, partial failure, reconciliation To apply Skip the generic proposal. Answer these three questions and we will read every word: - Which agentic tools do you use, and what does your workflow look like? - A Shopify public app you have shipped. Tell us about it? - How soon could you start?