Full Stack Developer

Full-stack developer needed to fix and harden an existing web application I have an existing web app (a comparison/recommendation tool for household services) that needs bug-fixing and improvement work on two core areas: an AI-powered document scanner and a recommendation engine. Tech stack: React + TypeScript (frontend) Node.js (backend) Supabase (Postgres + RLS) pnpm monorepo Important: the app was originally built using an AI coding agent, so this is fix-and-extend work on an existing codebase — not a build-from-scratch project. You must be comfortable reading, understanding, and debugging existing code (rather than wanting to rewrite it). What needs doing (approx. 30 hours): Document scanner (AI vision) — accuracy fixes. The scanner reads uploaded documents and extracts structured data, but it currently mis-reads or hallucinates certain fields. I need it diagnosed and fixed so it extracts the correct values reliably (and returns nothing, rather than inventing data, when a field is genuinely absent). Also needs to handle multiple documents uploaded in sequence. Sample documents and expected outputs will be provided for testing. Recommendation engine — logic audit. Verify the ranking logic is correct, that user-applied filters actually flow through and update the results, and that the underlying data is complete and correctly used. Fix any errors found. Stability & QA. Confirm the core user flows work end-to-end without crashing or freezing, and that the frontend and backend are correctly connected. Required skills: Strong React + TypeScript + Node.js (full-stack) Genuine Supabase experience (Postgres + RLS) — not just general SQL Comfortable debugging and extending an existing codebase Strong plus: Experience integrating LLM / AI vision APIs (the scanner is an AI feature) Product/SaaS experience (rather than agency/landing-page work) How I'd like to work: Hourly, capped at ~30 hours, with check-in points before any large fixes so we agree scope as we go I'd like to start with a small paid trial task (one bounded fix) before the full engagement Please tell me, in your reply: how would you approach picking up and debugging an unfamiliar codebase you didn't build? Looking for someone who's a strong problem-solver and communicator, comfortable working independently on defined tasks. Please don't apply if you're only interested in greenfield/rebuild work — this is targeted fixing and hardening of an existing product.