Senior Full-Stack Engineer — Finish a Multi-Tenant SaaS (React + Supabase + Stripe Connect)

IF YOU CALL MY PHONE OR EMAIL ME YOU WILL BE DISQUALIFIED. FIXED PRICE DELIVERABLES ONLY. SORRY. NO HOURLY. We run SWAGO (swago.com) — a custom-apparel/merch e-commerce storefront — and we're turning its platform into MerchOS (merchos.io), a multi-tenant SaaS where any brand can spin up their own branded merch storefront on a subdomain (brand.merchos.io). SWAGO becomes the flagship tenant; the same codebase serves unlimited tenants. This is not greenfield. A substantial foundation already exists — we need a senior engineer to take it across the finish line to a production, self-serve multi-tenant launch. What's already built Host-based tenant routing (flagship / SaaS / tenant subdomains), tenant context, per-host branding. Tenant data model + row-level-security isolation (Postgres RLS): tenants, members, invites, platform admins, orders/carts/leads scoped by tenant_id. Tenant signup + Stripe Connect onboarding; company-store checkout wired to destination charges + platform application fees. Per-tenant catalog overlay and per-tenant margin/MOQ pricing scaffolding; tenant theming data model + asset storage bucket. What we need you to do (the heavy lift) Finish self-serve tenant commerce — tenant storefront (browse → cart → checkout) fully wired to Stripe Connect + tenant-scoped orders; activation/go-live. Payments hardening — Connect refunds & dispute/chargeback handling, account.updated/payout.failed Connect webhooks, per-tenant tax, and SaaS subscription billing (tiered plans/monthly fees, dunning, upgrades/cancellations). White-label — tenant branding editor UI (logo/favicon/hero/colors/portfolio), custom domains (shop.brand.com w/ cert provisioning), and per-tenant transactional email sending domains (Resend). Isolation & lifecycle completeness — audit remaining tables/storage for tenant scoping, tenant suspension/offboarding/data-export, quotas/rate limits, and content moderation. Ops — per-tenant observability, platform-admin impersonation/support tooling, audit logging. Tech stack (you must be strong in these) React (React Router v7, framework/SPA mode, TypeScript), Supabase (Postgres, RLS, Edge Functions/Deno, Auth), Stripe Connect (destination charges, application fees, webhooks), Vercel (deploys, domains, edge/rewrites), Resend. Ideal candidate Has shipped a real multi-tenant SaaS (subdomain + custom-domain routing, tenant isolation). Deep Stripe Connect experience (marketplaces/platforms), including refunds/disputes/payouts. Fluent in Postgres RLS and secure multi-tenant data modeling. Comfortable owning ambiguous, cross-cutting infra work end-to-end. Screening questions (please answer to apply) Link a multi-tenant app you built. How did you handle tenant isolation and custom domains? In Stripe Connect, who bears the fee/liability on a refund and a chargeback, and how do you implement it? How would you enforce per-tenant data isolation in Postgres so one tenant can never read another's orders?