Contract-First Frontend: Scaling Reliable UIs with OpenAPI and AI

For years, our web and mobile apps were consuming separate backend endpoints with inconsistent responses, creating friction, bugs, and duplicate work as the system grew. Even though our apps already used TypeScript, API types were manually maintained and frequently drifted from real backend behaviour, making onboarding harder and slowing down feature delivery. We stopped fighting the API and adopted a contract-first, schema-driven workflow using OpenAPI. Treating the API as a single source of truth changed everything. Even early in the migration, we began generating fully type-safe TypeScript clients for both web and mobile, catching frontend–backend mismatches before they reached production and significantly reducing runtime errors. OpenAPI also became the foundation for AI-assisted development. With reliable contracts in place, tools like Claude and Cursor can generate React hooks, components, mocks, and tests that actually work — because they understand the system boundary, not just the syntax.