React 19 + Vite + Firebase + GPT-5.1 | AI Leadership Coaching Platform

We are looking for an experienced full-stack developer to continue building Worksparks (app.worksparks.com), an AI-powered leadership coaching platform. Phase 1 is live. Phase 2 adds the features that take us from MVP to a scalable B2B product. Immediate Priority: Security Fixes Before anything else, we need two known vulnerabilities closed: • Firestore rules currently allow any logged-in user to read other users' private coaching conversations. This is a trust and reputational risk that must be fixed first. • AI endpoints are publicly accessible with no authentication, exposing us to uncapped OpenAI API cost blowout. Needs auth protection immediately. Both are well-scoped fixes. We want them done quickly as a separate, fixed-price piece of work before Phase 2 features begin. Phase 2 Feature Scope 1. User Profile & Onboarding • Collect name, role, team size, and top leadership challenge on first login • Save profile data to Firestore users collection • Display profile summary on the dashboard 2. B2B Enterprise Layer • Organisation accounts with admin and employee seat management • HR/L&D dashboard showing session counts, challenge categories, and coaching uptake by team • CSV bulk employee upload • Anonymised org-level analytics • Exportable reports (PDF or CSV) 3. Stripe Payments Integration • Individual plan: $29/month • Team plan (5–20 seats): $199/month • Enterprise plan (20+ seats): $25/user/month • Advise on whether an enterprise setup/onboarding fee is appropriate and how to implement it 4. PWA / Mobile • Add manifest.json and service worker to enable 'Add to Home Screen' on iOS • Later phase: React Native app for App Store (not in scope now, but architecture should support it) Tech Stack • React 19 + Vite 7 • Firebase (Auth, Firestore, Hosting, Functions) • OpenAI GPT-5.1 • React Router v7 • React Firebase Hooks • React Toastify • React Icons What We're Looking For • Strong experience with React 19 and Firebase (especially Firestore security rules and Functions) • Stripe integration experience — subscriptions, seat-based billing, and multi-tier plans • Comfortable working in an existing codebase and picking up context from handover documentation • Can advise on architecture decisions, not just execute tickets • Responsive communication — this is an active build, not a slow burn To Apply Please include: • Brief overview of your experience with React + Firebase projects • Any Stripe multi-tier billing work you have done • Your approach to fixing the Firestore security rules issue described above • Hourly rate or project-based quote Fixed-price proposals are welcome for the security fix scope. Hourly preferred for Phase 2 feature work. Please do not contact us outside upwork please and we are open to suggestions and enhancements on the app. HR Saas experience preferred.