app.build is an open-source AI code generator initially focused on creating reliable CRUD web applications by prioritizing reliability over advanced features. The tool employs a finite state machine (FSM) for flow control, tree-based search for solution generation, and specialized actors for different tasks, ensuring that each component is validated before completion. Despite its initial limitations, app.build aims to enhance reliability through stateless design, concurrent execution, and a robust validation pipeline that includes TypeScript compilation and Playwright end-to-end tests. The tool emphasizes context engineering to avoid common pitfalls in AI code generation, utilizing encapsulation and feedback loops to refine its processes. Although initially constrained to a specific tech stack, app.build plans to expand its scope, allowing users to build more advanced applications with broader technological support, guided by insights gained from user interactions and error logs in its current iteration.