What problem does it solve? Building authentication from scratch is error-prone and time-consuming, especially when supporting multiple sign-in providers, phone verification, and role-based access control across web and mobile platforms. ## Core Features & Use Cases - Social Authentication: Implement Google, Facebook, Apple, Twitter/X, GitHub, and Microsoft sign-in for Web, Flutter, iOS, and Android with proper error handling and account linking. - Phone Authentication: Add SMS-based verification with reCAPTCHA, E.164 formatting, and platform-specific flows including Android auto-verification. - Custom Claims & RBAC: Set role-based claims via Admin SDK, enforce them through Firestore and Storage Security Rules, and manage token refresh propagation. - Use Case: A team building a Flutter app with Google Sign-In and admin roles can follow the modules to wire up authentication, set custom claims via Cloud Functions, and secure Firestore data with claim-based rules. ## Quick Start Ask the AI to implement Google Sign-In with Firebase Authentication for your web or Flutter app, including session persistence and security rules.