Frontend Developer — Next.js / React / TypeScript (Existing Production App)

You'll be joining an existing, live production web application — not a greenfield build. The stack is Next.js 14 (App Router), React 18, and TypeScript. Styling is a hand-rolled design-token system — no Tailwind, no component library (this is a deliberate constraint, not something open to debate). The product operates in a regulated, data-sensitive business domain, so accuracy and honesty in what the UI displays matters more than usual — nothing may look more certain or complete than it actually is. What you'll be doing Building and modifying screens inside an existing codebase, following an established architecture and a written set of UI rules you'll be given after you're hired. Working strictly within existing patterns — no new npm packages, no framework upgrades, no swapping in your own preferred component library, without explicit sign-off first. Every change goes through a gate before it's considered done: a clean TypeScript check, automated tests passing, and a written summary of what changed — reviewed before anything merges. Requirements Strong, recent experience with Next.js App Router and TypeScript — comfortable reasoning about Server vs. Client Components correctly. Experience working inside someone else's strict technical constraints, not introducing your own tooling preferences. Careful, low-ego written communication — most collaboration is async and review-based, not live pairing. Basic accessibility competence (keyboard navigation, semantic HTML, focus management). Nice-to-have Experience with OpenAPI-generated TypeScript types. Experience on a product with strict "don't show this" UI rules (e.g. no fabricated data, no overstated certainty). Playwright test-writing experience. How to apply — read carefully, this affects whether you're considered Do not submit an AI-generated proposal. Proposals are screened for generic AI-written cover letters, and those are auto-deprioritized. Write your own words, and reference something specific from this post to prove you actually read it. Show your work instead of just describing it. Include a link to a short (3–5 minute) video — a YouTube link (can be unlisted) or a Loom — where you walk through a real Next.js + TypeScript project you've built: show the code, explain one decision you made and why, and show it actually running. This matters more than your written proposal. To prove you read this far: start your proposal with the word "App Router" as the first word. Proposals that skip this are not reviewed. Screening questions (add these in Upwork's job post settings) Describe a project where you had to work within someone else's strict architectural rules — no new dependencies, no framework upgrades, a hand-rolled design system — instead of using your own preferred tools. How did that go? Walk through how you'd verify a TypeScript/Next.js change didn't break anything before handing it off for review — what's your actual checklist? Paste the link to your video walkthrough here as well (see "How to apply").