Frappe HRMS is a full-featured Human Resource and Payroll management system built as a Frappe/ERPNext application. It covers the complete employee lifecycle including recruitment, onboarding, attendance and shift management, leave administration, payroll processing, expense claims, performance appraisals, and separation. The system provides both a desktop interface via the Frappe framework and a mobile-first Progressive Web App (PWA) built with Vue.js and Ionic for employee self-service. A separate roster application handles shift scheduling and assignment. The architecture follows Frappe's monolithic pattern with custom DocTypes, server-side Python controllers, client-side JavaScript, and extensive reporting. Payroll processing is a key strength, supporting salary structures with formula-based components, tax slabs, multi-currency, gratuity, and benefit claims. The codebase demonstrates strong engineering practices with comprehensive test coverage, data migration patches across versions, and reusable patterns such as safe formula evaluation, immutable leave ledger entries, and push notification mixins. It integrates tightly with ERPNext for accounting entries and payment processing.