Senior Full-Stack Dev — Next.js/Firebase/Capacitor | Fixed-Price Packets | 30-40 hrs/wk | Start ASAP

⚠️ Read first: all communication stays on Upwork. Anyone who contacts me off-platform (email, WhatsApp, Telegram, LinkedIn, anything) is instantly blocked and reported as spam. No exceptions, no "just easier to chat there." US-based wellness brand with a live cross-platform app (Next.js 15, Firebase, Capacitor Android, PWA) in a launch push with hard deadlines — we need the final work done and we need it moving now. We're adding a senior developer alongside our build lead. The work comes as fixed-price work packets — written scope, acceptance checklist, milestone payments — not hourly billing. First packet is already scoped and ready to assign; a steady pipeline follows: a gamified vocabulary widget, a public assessment funnel, cognitive exercise revisions, a UI overhaul against a locked design system, ongoing features after launch. The non-negotiable: real capacity. We need more than 30 hours a week — ideally around 40 — for the coming weeks. If you're juggling several clients and can offer 5–10 hours, do not apply; we've seen enough of those proposals. A smaller honest number from someone else beats a big soft one from you. Who fits: 5+ years full-stack with deep React/Next.js. Real production Firebase (not "familiar with"). At least one shipped Capacitor or comparable hybrid app. Game mechanics / timed interactive UI a strong plus. Fluent written English, async-first. How we work: every packet has written scope and acceptance criteria before work starts — you quote it fixed, we approve, you build. A locked design + compliance canon you build against — you flag conflicts, you never improvise around them. Every "done" ships with screenshots/recordings and is independently verified before payment. Defects are fixed free; scope changes are priced in advance. Minimum-scope access per task. NDA + IP assignment before first commit. Daily three-line status during the push. If a mistake is yours, you say so — our current lead does, and it's why he leads. Process (fast): screening questions → paid fixed-price trial packet (real scoped ticket in our repo, own acceptance checklist, paid regardless of outcome) → immediate ongoing packets for whoever clears it. Screening questions (answer ALL in your proposal; generic or AI-boilerplate answers auto-declined): Link one shipped project using Next.js + Firebase together; your specific contribution in two sentences. A client's spec conflicted with itself. What did you do before writing code? Your honest, exact weekly availability for the coming weeks, your timezone, and your other active commitments in rough terms. This number is load-bearing — we plan against it. What breaks when a web feature that works in Chrome ships inside an Android webview? Two real examples you've personally hit. Have you built game mechanics or timed interactive UI? Link or describe the closest thing. Describe one fixed-price project you completed — how you scoped it, and what you did when something turned out bigger than quoted.